Adaptive Optics Lab Herzberg Institute Subaru Telescope Astronomical Institute. Final Optical Design

Transcription

1 Adaptive Optics Lab Herzberg Institute Subaru Telescope Astronomical Institute Final Optical Design Olivier Lardière Issue : 1.1 January 8, 2013

2 1 Raven Final Optical Design UVic AOLab Changelog Date Issue Comments Author Jun 29, First draft Olivier Lardière Nov 19, Throughput added Olivier Lardière "Raven is the `Trickster', bringing the moon, sun and stars to the world. Raven teaches us to be clever and creative." Doug Lafortune, Coast Salish

3 UVic AOLab Raven Final Optical Design 2 Acronym ' AG AO188 BS CCD CDM CL CU DM DOF EE EELT EMCCD FoV FoR FWHM GEO IMR INO IR IRCS LWP MOAO Na NCPA NGS NIR OAE OL PTV POS QE RMS SH subap SWP TBC TBD TT WFE WFS arcminute arcsecond AutoGuider Subaru 188actuator AO system Beam Splitter ChargeCoupled Device Calibration DM Closed Loop Calibration Unit Deformable Mirror Degree of Freedom Ensquared Energy European Extremely Large Telescope Electron Multiplying Charge Coupled Device Field of View Field of Regard full width at half the maximum Geometric Image Rotator Institut National d'optique Infrared Subaru Infrared Camera and Spectrograph long wave pass beam splitter MultiObject Adaptive Optics System Sodium NonCommon Path Aberrations Natural Guide Star near infrared OAxis Ellipsoid Openloop PeakToValley Picko System Quantum eciency root mean square ShackHartmann subaperture short wave pass beam splitter To be conrmed To be dened TipTilt Wavefront Error Wavefront Sensor

4 3 Raven Final Optical Design UVic AOLab Contents 1 Introduction 9 2 Related documents 9 3 Optical layout of Raven 9 4 Powered Entrance Window Prescription Performance Tolerancing Ghost image analysis Thermal analysis NGS OLWFS OL-WFS pick-o system OL-WFS optical layout Performance Collimating lens :1 relay lens Tolerancing Collimating lens :1 relay lens Ghost image analysis Thermal analysis LGSWFS Prescription Performance Tolerancing Ghost image analysis Thermal analysis Science pick-o arms Layout Prescription Science Pick-o arm Trombone Performance Tolerancing Science picko mirror Trombone Ghost image analysis Thermal analysis

5 UVic AOLab Raven Final Optical Design 4 8 Science Relay Layout Prescription OAE Science DMs LWP K-mirror Roof mirror eld stop Performance Tolerancing OAE Ghost image analysis Thermal analysis Beam Combiner Prescription Roof mirror Exit relay lens Performance Roof mirror Exit relay lens Overall performance of the science path with IRCS Tolerancing Roof mirror Exit relay lens Ghost image analysis Thermal analysis Figure and ClosedLoop WFSs Prescription Figure Source Trombone M Compensator plate CL-WFS path Performance Figure Source arm CL-WFS arm Tolerancing Ghost image analysis Thermal analysis Acquisition Camera Prescription Performance Tolerancing Ghost image analysis

6 5 Raven Final Optical Design UVic AOLab 11.5 Thermal analysis Design performance vs. requirements Performance summary Throughput

7 UVic AOLab Raven Final Optical Design 6 List of Figures 1 Top view of the Raven optical layout Side view of the Raven optical layout D shaded model of Raven Prescription of the Powered Entrance Window Lateral color and focal shift of the Powered Entrance Window Schematic of the Raven picko system Field coverage of the NGS OLWFS pickos NGS OL-WFS optical layout Decentration of the collimating lens to align the NGS OL-WFS arm RMS wavefront error vs. FoV on the LA plane of the NGS OL-WFS Field dependant aberration of the OL-WFS collimating lens Field dependant aberration of the OL-WFS collimating lens in terms of Zernike modes Prescription of the WFS relay lens doublet WFS 1:1 relay lens Spot diagram of the WFS 1:1 relay lens Image distortion of the WFS relay lens and induced WFE Field-dependant aberrations induced by the WFS relay lens distortion LGS WFS layout LGS WFS RMS wavefront Wavefront error seen by the LGS WFS at zenith LGS wavefront error variation vs. zenith angle and FoV Field coverage of the two science pickos Science picko mirror specications Trombone M2 specications Science path layout Parent ellipsoid of the OEA mirror Science DM actuator geometry Specications of the LWP Specications of the K-mirror Roof mirror eld stop Science relay spot diagram IRCS Oner relay Roof mirror prescription Air-spaced doublet Exit Relay Lens Exit relay lens singlet # Exit relay lens singlet # Exit relay lens ray fan Exit relay lens RMS wavefront versus eld Exit relay lens focal shift Science path spot diagrams at exit focus Science path Strehl eld map Footprint diagrams in the pupil stops of IRCS Spot diagram on the IRCS slit

8 7 Raven Final Optical Design UVic AOLab 44 Geometric ensquared energy in the slit plane of IRCS Spectrum of the Figure Source LED Wavefront error without and with the Figure source compensator plate Specication of the gure source compensator plate Alignment gure source compensator Spot diagram of the CL-WFS beam reducer RMS wavefront error versus eld of the CL-WFS beam reducer Field dependant aberration of the CL-WFS beam-reducer Acquisition camera path Acquisition camera fold mirror Prescription of the plano-convex lens of the Acquisition Camera Prescription of the cemented doublet of the Acquisition Camera Spot diagram of the Acquisition camera triplet Science path throughput curve OL-WFS throughput curve

9 UVic AOLab Raven Final Optical Design 8 List of Tables 1 Zemax le names Openloop NGS SHWFS specications Sodium notch lter specications Science picko mirror prescription Trombone M1 prescription OAE prescription Requirement compliance

10 9 Sec. 4 Raven Final Optical Design UVic AOLab Table 1: Names of the Zemax les used for optimizing (O), analyzing (A), tolerancing (T) or reporting (R) each subsystem. Subsystem Zemax le Use Entrance Window subaru+entrancewindowoptimized.zmx OAR tol3pupentrancewindowoptimized.zmx TR OL-WFS Coll. lens ngswfscolllensao40-13-forward.zmx AR OL-WFS Relay lens tolngswfsrelaylenscustomlessdistorohara.zmx OATR OLWFS (all) ngswfsfull-forward.zmx AR LGS-WFS lgswfsalonestagefoldedalldbtshifted25mm.zmx OA lgswfsalonestagefoldedalldbtshifted25mmtol.zmx TAR Science Relay sciencerelayoptimellipsolwpwedge.zmx OATR Exit Relay lens tolachromatoptimizedstop8airspaced40mmdiafnumbshorter.zmx ATR AchromatOptimizedStop8AirSpaced40mmDiaFnumbShorter.zmx OAR Science Path (all) sciencerelayoptimellipsolwpwedgebeamcomb2shorterfnumbwircsoffner.zmx AR Figure Source compensatorplate.zmx OAR CL-WFS FoldClWfsStockLensesRoss.zmx OAR Acq. Camera tolinvertedfieldlenstripletohara4final.zmx OATR Raven (all subsys.) ravenircsfullclwfsfoldtromb2.zmx AR 1 Introduction This document describes the nal optical design of Raven and completes the CoDR document. This document provides, for each sub-system of Raven, the prescription and the manufacture tolerances of its components, a stray light and thermal analysis, and the expected performance with the tolerances. The last two section presents the requirement compliance matrix and the NCPA budget error for each optical paths. 2 Related documents Please refer to the Optical DRD and to the CoDR documents to have a more general description of Raven and the requirements and concept of each subsystem. The assembly and alignment tolerances of the dierent subsystem are described in the Alignment plan document. Table 1 gives the name of the Zemax le used for the design of each subsystem. The Zemax les are available on Dropbox folder /raven/doc/opticaldesign/ and on the CD accompanying this report. 3 Optical layout of Raven Figures 1 to 3 depicts the full optical layout of Raven. The layout has been optimized with a merit function to try to balance the clearance between each components and t all the component in the available space. It's worth noting that there is now more clearance between the Acquisition Fold Mirror and the Roof Mirror. The optical design of the CU being subcontracted to INO, a simplied rstorder design of CU has been represented in these gures. The actual design of the CU will be added later once available.

11 UVic AOLab Raven Final Optical Design Sec OL-WFS Figure source DM Science pick-offs NGS pick-offs Lenslet array CL-WFS Entrance window Flip mirror Acq. Cam. LWP Roof mirror Relay lens AG/SH surface Trombone Rotator Compensator Common output pupil IRCS OAE LGS-WFS z y 200 mm Calibration Unit Bench size: L=1400, W=1200 mm Figure 1: Top view of the Raven optical layout. Both science and WFS paths are represented here, in addition to the calibration unit, the acquisition camera and the CL-WFSs. Beside the Calibration Unit, the design of Raven is fully symmetrical with respect to the vertical plane containing the telescope optical axis.

12 11 Sec. 4 Raven Final Optical Design UVic AOLab AG/SH surface z x Calibration Unit Entrance window NGS pick-offs 200 mm OL-WFS Acq. Cam. DM OL-WFS FSM LGS-WFS Figure 2: Side view of the Raven optical layout. CL-WFS IRCS

13 Sec Raven Final Optical Design UVic AOLab Calibration Unit Phase screens CDM AG/SH surface Figure source OL-WFS Entrance window OAE LGS-WFS Acq. Cam. Flip mirror DM OL-WFS OAE Relay lens Lenslet array Roof mirror LWP Trombone Rotator CL-WFS Figure 3: 3D shaded model of Raven. Figure source CL-WFS IRCS DM

14 13 Sec. 5 Raven Final Optical Design UVic AOLab 4 Powered Entrance Window 4.1 Prescription The PEW is a plano-convex lens made in CaF2, 180mm diameter, 10mm thick. The plane surface shall be torward Raven to mitigate aberrations. As the PEW is not exactly located in a focal plane, it impacts slightly the F/# of the telescope beam, which is The PEW has been oversized in diameter as the PEW may be decentred up to 10mm to compensate possible bench misalignments in tilt. The specications and the drawings of the PEW are in Fig Performance Figure 5 shows the lateral color and the axial focal shift due to the PEW. Both error are lower than the diration limit. A 10mm decenter of the PEW steers the beam by 2 arcminutes without inducing noticeable aberrations, both on pupil and image planes. This sets the alignment tolerance in tilt for the Raven bench. 4.3 Tolerancing The PEW has very little impact on the image quality as the EW works as a eld lens, but has more impact on the pupil. The merit function for tolerancing was the RMS ray intercept radius in the pupil plane for the centre and the edge of the pupil and also the exit pupil distance. There is no focus compensator as we want the exit pupil at a specic distance. Commercial tolerances provides good enough performance. The lateral ray intercept spread is lower than 1.2% of a subaperture with 90% of condence. Fig. 4 species the tolerances. 4.4 Ghost image analysis The double-bounce on the faces of the PEW creates a defocused ghost image fainter than the principal image, which is beyond the dynamicrange of the WFS and science detectors. There is no ghost pupil image neither. 4.5 Thermal analysis A temperature variation from -5 to 25 o C has no or little impact on the performance. 5 NGS OLWFS 5.1 OL-WFS pick-o system Three OLWFSs are installed in a vertical plane, 15mm before the telescope focal plane. The three WFSs are located around the optical axis in a Yshape, respectively at 0 o +130 o and -130 o from the downward axis (Fig. 3). Each picko mirror and

15 UVic AOLab Raven Final Optical Design Sec PART/DRAWING REVISION tol3pupentrancewindowoptimized.zmx Configuration 1 of 1 Raven Powered Entrance Window PROJECT/TITLE 02/05/ :1 Olivier Lardière DATE SCALE DRAWN APPRV Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria ISO Element Drawing Indications According to ISO / - 6/ - 5/ - 2/ - 5/ - 4/ 5' 1/ - 4/ - 3/ µm 0/ - 3/ µm BBAR nm V = d BBAR nm Ø E 162 N = d Ø E 162 R CX GLASS: CAF2 R PLANO Left Surface Material Right Surface Dimensions in Millimeters Ø P P Figure 4: Prescription of the Powered Entrance Window.

16 15 Sec. 5 Raven Final Optical Design UVic AOLab Maximum Field: Deg Airy Airy µm Lateral Color Raven Powered Entrance Window 19/01/2012 Data Referenced to Wavelength µm Real rays used. Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria subaru+entrancewindowoptimized.zmx Configuration 1 of Wavelength in µm Focal Shift in µm Chromatic Focal Shift Raven Powered Entrance Window 19/01/2012 Maximum Focal Shift Range: µm Diffraction Limited Range: µm Pupil Zone: Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria subaru+entrancewindowoptimized.zmx Configuration 1 of 1 Figure 5: Lateral color and focal shift due to the Powered Entrance Window. The maximum FoV considered for the lateral color is 1.75 arcminutes on the sky.

17 UVic AOLab Raven Final Optical Design Sec Table 2: Openloop NGS SHWFS specications. Active pixels Pixel size µm Sensor area ( pupil size) mm Subaperture Pixels per subaperture Pixel scale 0.38"/pix WFS FoV 4.8 camera are mounted on x-y translating stages to avoid the pupil to rotate on the WFS LA. A schematic of the picko mechanism is shown in Fig. 6). It is worth noting that the CCD array grid of the two top cameras will be rotated by 40 o with respect to the science DM actuator grid. As this angle is permanent, this is not an issue for the interaction matrices. Figure 7 shows the eld coverage of the three OLWFS pickos with 100mmtravel stages. With such a travel, the OLWFS can observe any asterism within a 3.5' FoR. 5.2 OL-WFS optical layout Fig. 8 shows the optical layout of one OLWFS. Each OLWFS probe arm consists of a at picko mirror, located 15mm upstream of the telescope focal plane, reecting the rays 90 o toward a 2.5mm diameter eldstop located 15mm behind the picko mirror. As the outer size of the led stop need to be less than 5mm to avoid collision, another larger stop may be required few centimetres further (dimensions TBD). Then an achromat (stock lens from Ross Optical # L-AOC087/230, f=40.5mm, dia.=13mm) collimates the beam and forms a 3.0mm diameter pupil on a lenslet array (LA). A standard LA from SUSS MicroOptics (Ref. # , d=300µm, f=4.77mm) is perfectly suitable for Raven. A 589.3nm notch lter is mounted with the collimating lens to block the Rayleigh scattering of the sodium LGS. This is a custom lter made by Omega Optical, the specications are listed in Tab. 3 An achromatic 1:1 relay lens reimages the spots of the LA on the detector. This relay lens is made of two identical custom achromats arranged in a symmetric telecentric scheme (Fig. 14 and 13). It is worth noting there is no stop in-between the 2 lenses of the 1:1 relay. The detector is a pixel EMCCD ixon 860 camera from Andor Technology. The relay lens barrel is directly mounted on the C-mount ring of the camera. Table 2 lists the parameters of the OL NGSWFSs. 5.3 Performance Collimating lens It is worth noting that the decentrer of collimating lens may be adjusted to recenter the pupil on the LA. This can advantageously relax the mechanical tolerance on the tilt error of the whole WFS arm. A 1 o tilt error can be compensated with a 0.7mm

18 17 Sec. 5 Raven Final Optical Design UVic AOLab Rear view Top view Figure 6: Schematic of the Raven picko system. The OLWFS arms are represented in light grey, and the science pick-os in dark grey. A 100mmtravel would ideal for the OLWFSs, but 50mm is still acceptable to patrol a 2' diameter FoV.

19 UVic AOLab Raven Final Optical Design Sec (a) (b) Figure 7: Field coverage of the three NGS OLWFS pickos for 100mm travel XY stages. This travel can accommodate almost any asterism of 3 NGSs in a 3.5' diameter FoV (a). The central LGS can also be used with only 2 NGSs on the same side to increase the sky coverage (b). F/13.6 beam from Subaru + PEW Field stop Ø=5 (2.5mm) Collimating lens f=40.5mm, Ø=13mm Na notch filter Pick-off mirror 5x7.1mm Z Lenslet array d=300µm f=4.77mm 1:1 Relay f=35mm, Ø=12.5mm EMCCD camera 128x128px Y X 50 mm Figure 8: NGS OL-WFS optical layout.

20 19 Sec. 5 Raven Final Optical Design UVic AOLab Table 3: Sodium notch lter specications. Substrate BK7 Dimension /-0.25mm Thickness 2.0±0.2mm Clear aperture 12.5mm central diameter Transmitted wavefront error λ/8 Notch center wavelength (CWL) 589.3nm Notch FWHM 10nm Optical density at CWL 3.0 Transmission outside blocked band 94% Angle of incidence 0 o Beam 1/2 cone angle 2.2 o Scratch & Dig decenter of the collimating lens. The aberrations induced by the decentrer are lower than the diraction limit for the whole WFS FoV (Fig. 9 and 10). Figure 11 displays the wavefront on the LA plane for a source at 2.4" from the WFS optical axis minus the on-axis wavefront. This shows the variation of the WFE versus the whole WF FoV. The variation is 54nm PV or 12nm RMS. Figure 12 plots this eld-dependant wavefront error in terms of Zernike modes for two eld positions, 1.2" and 2.4". There is some focus and astigmatism, scaling as the square of the eld, and a bit of coma, scaling as the eld :1 relay lens As the LA "converts" the WFE into spot centroids, the merit function of the relay lens is not the WF but the spot radius and the image distortion. One wants the (geometric) spots as small as possible to get more photons on a single pixel of the detector, and the minimal distortion not to alter the spot positions and generate aberration after centroiding and phase reconstruction. To add some complexity, the image distortion of the relay lens varies with the incoming WF tilt, generating eld-dependant aberrations and non-linearity error in the tilt response of the WFS. Field-dependant aberrations and non-linearity of WFSs are usually not an issue in close-loop AO system, but can be critical in an open-loop system, such as Raven. The phase reconstructor indeed assumes the WFS linear over all its dynamic-range (i.e. its FoV) and the interaction matrix exercises the WFS only around 0. If the tilt response of the WFS is not calibrated and not linearized by software in the RTC, the tilt non-linearity error and eld-dependant aberrations will propagate on the science path. Figure 14 and 15 plots respectively the ray trace and the spot diagram of the 1:1 relay lens for dierent eld and subaperture locations. The spot radius is smaller than one detector pixel (24 24µm) for all congurations. The tilted WF case is simulated by a pupil stop decenter. The image distortion of the 1:1 relay is close to 0.00% for an on-axis WF, and reaches -0.06% for a 2.4 arcsec tilted incoming WF on the LA (Fig. 16). As the

21 UVic AOLab Raven Final Optical Design Sec (a) WFS arm aligned on optical axis (b) WFS arm misaligned (1 o tilt) (c) Misalignment compensated by lens decenter (0.7mm) Pick-off mirror Y Field stop Pupil on LA X Z 3D Layout Raven NGS OL-WFS Collimating lens 20/01/2012 Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria ngswfscolllenslao40-13-forward.zmx Configuration: All 3 Figure 9: The collimating lens can be decentred to compensate a tilt between the telescope optical axis and the WFS optical axis. (a) is the perfectly aligned WFS arm, (b) is the WFS arm tilted at 1 o from the telescope optical, (c) is the tilted WFS arm with the collatmating lens decentred by 0.7mm to recenter the pupil on the lenslet array (LA).

22 21 Sec. 5 Raven Final Optical Design UVic AOLab RMS Wavefront Error in Waves Diffraction Limit RMS Wavefront Error in Waves Diffraction Limit Y Field in Millimeters RMS Wavefront Error vs Field Raven NGS OL-WFS Collimating lens Olivier Lardière (lardiere@uvic.ca) 20/01/2012 Poly Adaptive Optics Lab University of Victoria Reference: Centroid (a) ngswfscolllenslao40-13-forward.zmx Configuration 1 of Y Field in Millimeters RMS Wavefront Error vs Field Raven NGS OL-WFS Collimating lens Olivier Lardière (lardiere@uvic.ca) 20/01/2012 Poly Adaptive Optics Lab University of Victoria Reference: Centroid (b) ngswfscolllenslao40-13-forward.zmx Configuration 3 of 3 Figure 10: RMS wavefront error vs. FoV on the LA plane of the NGS OL-WFS. The FoV ranges from 0 to 2.4 arcsec on sky, i.e. the whole WFS FoV. (a) is for the perfectly aligned case, (b) is for a WFS arm tilted at 1 o from the telescope optical axis and the collatmating lens decentred by 0.7mm to recenter the pupil on the lenslet array (LA). In both cases the RMS error is lower than the diraction limit for most of the WFS FoV. The aberrations of the telescope are not shown here. distortion varies with the incoming WF tilt, eld-dependant aberrations are generated (Fig. 17). The relay lens has been optimized to provide minimal distortion on-axis and at 2.4" on-sky (i.e. the edge of the WFS FOV). This improves the linearity of relay-lens tilt response (Fig. 17a) and minimize the high-order aberrations, like astigmatism and coma (Fig. 17b). The maximum non-linearity error in tilt reaches -210nm PTV at 1.4" ( i.e. -0.4% of the incoming WF tilt). If this tilt error is propagated to the science path, it will cause an image motion of 6mas in the slit of IRCS. This motion is signicantly smaller than the slit half-width (70mas) and does not impact the ensquared energy. Thus, a linearization of the WFS tilt response by software may be desirable but not mandatory. Moreover, it is worth noting that the closed-loop tracking with the pick-o mirror up to 10Hz will keep the incoming WF tilt low, which should help. The high-order aberrations are more critical for the ensquared energy. Fortunately, the designed relay lens generates no more than 20nm rms of wavefront error at 2.4", and this error scale as the cube of the eld (Fig. 17b). Hopefully, these eld-dependant aberrations are small enough compared to the overall error budget of Raven and do not need to be calibrated (TBC). The cubic t expression mentioned in the gures are for the nominal design. On the system, one recommends a proper calibration of the WFS in tilt on the central CU source by moving the picko.

23 UVic AOLab Raven Final Optical Design Sec OL WFS field dependant WF error on LA at 2.4" from centre [nm] y [mm] x [mm] PTV = 54.02nm RMS = 12.00nm Figure 11: Field dependant aberration of the OL-WFS collimating lens.

24 23 Sec. 5 Raven Final Optical Design UVic AOLab 20 OL WFS field dependant WFE on LA WF tilt = 2.4" WF tilt = 1.2" WFE [nm PV] Zernike Modes Figure 12: Field dependant aberration of the OL-WFS collimating lens in terms of Zernike modes for 2 eld locations.

25 UVic AOLab Raven Final Optical Design Sec Figure 13: Prescription of the WFS relay lens doublet. PART/DRAWING REVISION tolngswfsrelaylenscustomlessdistorohara.zmx Configuration 2 of 2 Raven WFS 1:1 Relay Lens PROJECT/TITLE 20/03/ :1 Olivier Lardiere DATE SCALE DRAWN APPRV Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria ISO Element Drawing Indications According to ISO / - 6/ - 6/ - 5/ - 2/ - 5/ - 2/ - 5/ - 4/ 3' 1/ - 4/ 3' 1/ - 4/ 3' 3/ µm 0/ - 3/ µm 0/ - 3/ µm nm V = d V = d nm Ø E 9 N = d Ø E 9 N = d Ø E 9 R CX GLASS: S-TIM25 R GLASS: S-BAL41 R CX Left Surface Material Middle Surface Material Right Surface Dimensions in Millimeters Ø P P

26 25 Sec. 5 Raven Final Optical Design UVic AOLab (a) (b) Y X Z Raven WFS 1:1 Relay Lens 21/03/2012 (a) On-axis WF (b) Tilted WF (2.4 on sky) 3D Layout Central spot Outermost spots Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria tolngswfsrelaylenscustomlessdistorohara.zmx Configuration: All 2 Figure 14: WFS 1:1 relay lens layout for an onaxis incoming wavefront (a) and titled WF at 2.4 arcsec on sky (b). 5.4 Tolerancing Collimating lens The collimating lens is a stock lens from Ross Optical with standard tolerance. Surface irregularities is accounted for in the OL-WFS oset calibration. The positions of the collimating lens and the LA can be adjusted to keep the beam collimated and the pupil plane on the LA. This relaxes the constrain on the focal lenght. The standard focal length tolerance is ±2%, meaning that the pupil diameter on the LA may also vary within ±2%, which should be acceptable as this error is permanent and is accounted for in the interaction matrix :1 relay lens Manufacture and alignment errors have been considered for the tolerancing of the relay lens. It turned out that the tolerance are driven by the distortion requirement rather than by the spot radius requirement. The back focus is used as a compensator (in reality the compensator will be the "front" focus, i.e. the distance between the LA and the relay lens, but this is equivalent as the relay lens is symmetrical). The worst oender are the tilt and decenter of the whole barrel holding the two achromats and the individual tilt and decenter of each achromat with respect to the barrel. To keep the distortion lower than 0.12% (i.e. eld-dependant aberrations lower than 50nm rms) with 90% of condence, the tilt and decenter of the barrel shall be less than ±0.2 o and ±0.2mm respectively. The individual tilt and decenter of each achromat shall

27 UVic AOLab Raven Final Optical Design Sec Config 1 On-axis WF Config 2 Tilted WF (2.4 on sky) , mm , mm , mm , mm , mm Surface IMA: CCD Raven WFS 1:1 Relay Lens 21/03/2012 Units are µm. Box width : 24 Configuration Matrix Spot Diagram Reference : Centroid 589nm 700nm 900nm Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria tolngswfsrelaylenscustomlessdistorohara.zmx Configuration: All 2 Figure 15: Spot diagram of the WFS 1:1 relay lens for an onaxis WF and tilted star at 2.4 arcsec. on sky. For each case there is a spot diagram for a central spot and the two outermost spots. The square corresponds to the size of one detector pixel.

28 27 Sec. 5 Raven Final Optical Design UVic AOLab WFS relay lens Subaperture centres Polychromatic spot centroids (100x scale) 0.5 y [mm] x [mm] (a) Measured WF Actual WF [nm PV] WF aberrations induced by the relay lens 2.4" RMS = 19.87nm Zernike Modes (b) Figure 16: (a) Image distortion of the WFS relay-lens WF for an incoming WF tilted at 2.4" on sky. The distortion reaches -0.06%. The distortion is exaggerated 100. (b) Aberrations induced by the WFS relay lens distortion after computation of the centroids. The tip-tilt-removed RMS error is 20nm. The main modes generated are tip/tilt (Z 2 or Z 3 ), astigmatism (Z 5 or Z 6 ) and coma (Z 7 or Z 8 ).

29 UVic AOLab Raven Final Optical Design Sec Measured WF Tilt Actual WF Tilt [nm PTV] y = 43 x x x Tilt response of the WFS (polychromatic) Zemax data Cubic fit Actual WF Tilt [arcsec. on sky] (a) WF Aberrations [nm PTV] Field dependant aberrations induced by the WFS relay lens (polychromatic) Z6 (astigmatism) Zemax data Z6 cubic fit Z8 (coma) Zemax data Z8 cubic fit Z6 = 2.3 x x x Z8 = 0.79 x x x WF Tilt [arcsec. on sky] (b) Figure 17: Field-dependant aberrations induced by the WFS relay lens distortion shown in Fig. 16. The main modes are tip/tilt (a), astigmatism and coma (b).

30 29 Sec. 6 Raven Final Optical Design UVic AOLab be ±0.2 o and ±0.1mm respectively. To guarantee a good centering, the achromat diameter matches perfectly the lens holder inner diameter, and each lens holder will be screw on a C-mount tube (i.e. the barrel). The mechanical tolerance of the C-mount tubes made by Edmund Optics are typically lower than ±0.1mm (TBC). As for the manufacture of the lenses, the centering error of the lens surface has little impacta standard precision lens centering at ±3 is good enough. The achromats are made by BMV Optical. Decentrations and tilts of one doublet relatively to the other are acceptable up to ±0.5mm and ±0.5 o respectively. To mitigate the alignment errors, the two doublets are mounted on the same barrel (C-mount tube). 5.5 Ghost image analysis There is no detectable ghost image or pupil on the WFS camera. 5.6 Thermal analysis The OL-WFS path has been optimised for a temperature of 5 o C and an atmospheric pressure of 0.6 bar. However, a temperature variation from -5 to 25 o C has no or little impact on the performance. 6 LGSWFS 6.1 Prescription An onaxis LGS is available at Subaru for Raven. The LGS focus location ranges from 76.6 to 153.9mm behind the NGS focus for a zenith angle of 60 o and 0 o respectively. Figure 18 displays the optical layout of the LGS WFS. The LGS WFS path lies underneath the bench top surface and is bent sideways at 90 o to ease access. First, the LGS beam pass through a hole the Acquisition fold Mirror (Sec. 11) located 100mm behind the NGS focus. Right behind this mirror, there is another fold mirror (LGS fold) sending the LGS beam downward. Then, an achromat (OptoSigma # A30, f=170.4mm, dia.=25mm) forms a pupil plane on the FSM (PI S-330-8SL) used for windshake correction up to ±1.5 on sky. A beam reducer made of two achromats (Edmund Optics # and , f=101.6 and 25mm, and dia.=25.4 and 12.5mm respectively) forms a 3mm diameter pupil on the LA. A motorized variable iris (or a removable 1.6mm diameter eld stop) is located in the focus formed by the rst lens of the beam reducer. The iris shall be wide open (dia. 13.5mm) during the acquisition of the LGS spot, and closed to a 1.6mm diameter during AO correction. A 1:1 relay lens reimages the LA spots on an Andor Xion 860 EMCCD camera. The same LA and relay lens is used for the NGS WFS and LGS WFS, except the coating which is optimized for 589nm. The whole LGS WFS path is mounted on a 10mm travel x-y motorized stage to acquire the LGS spot and track the slow lateral motion of the spot due to mechanical exions of the telescope and a residual alignment error of the tertiary mirror. This travel corresponds to ±10 on sky.

31 UVic AOLab Raven Final Optical Design Sec NGS focal plane Acq. Fold Mirror to Acquisition Camera LGS Fold Y-Z-stage (10mm travel) Collimating lens Z-stage (45mm travel) Beam reducer 1:1 Relay Z 100 mm Y X FSM Iris Lenslet array d=300µm f=4.77mm EMCCD camera Figure 18: LGS WFS layout. The whole optical train is mounted on a 2axis horizontal stage (YZ stage) to track the slow lateral drift of the LGS spot due to mechanical exures of the telescope or a misalignment of the tertiary mirror. A linear stage (Z stage), holding the components from the iris to the camera, tracks the axial motion of the LGS focus due to the zenith angle variation. The red and blue beams are for zenith angle 0 and 60 o respectively. For clarity purpose, the path is unfolded (the FSM is actually fold at 90 o around X-axis) and the blue beam is not shown after the iris. Also, all the components behind the rst lens of the beam reducer are mounted on a 50mm travel focus stage to accommodate LGS range from 80 to 180km. A sodium line pass-band lter blocks all the wavelengths outside the band ±10nm to reduced the background due to the sky and the nearby stars. 6.2 Performance The LGS WFS has been designed to mitigate as much as possible the aberrations varying with the eld or the LGS range. The motorized two-axis stage ensures that the LGS spot is always close to the optical axis of the collimating lens. Similarly, the FSM ensures that the LGS beam is on the optical axis of the beam reducer and the rest of the WFS path. The LGSWFS itself is diractionlimited over the whole FoV and the whole

32 31 Sec. 6 Raven Final Optical Design UVic AOLab 0.1 RMS Wavefront Error in Waves Diffraction Limit Z=60 o Z=0 o Y Field in Millimeters RMS Wavefront Error vs Field Raven LGS WFS with FSM Olivier Lardière (lardiere@uvic.ca) 26/01/ Adaptive Optics Lab λ=589nm University of Victoria lgswfsalonestagefoldedalldbtshifted25mmghost.zmx Reference: Centroid Configuration 21 of 2 Figure 19: RMS wavefront error of the LGS WFS alone (without the telescope) versus the eld position for zenith angles 0 o and 60 o. sodium layer range (Fig. 19), and there is no noticeable pupil shift when sodium layer range varies. The performance of the whole system will be limited only by the spherical aberration of the telescope due to the nite distance of the sodium layer (the telescope is designed for objects at innity). The actual wavefront seen by the LGS- WFS with no turbulence is displayed in Fig. 20 for the worst case, when the telescope is at zenith. The wavefront slope is maximum on the pupil edge and corresponds to a shift of 1/10 th pixel for the spot centroids, which is negligible compared to the pixel subaperture FoV. Consequently, there is no need to add a spherical aberration corrector in the LGS WFS path, this aberration will be accounted for in the NCPA calibration. The variation of this residual aberration with respect the zenith angle and the FoV are shown on the interferograms in Fig. 21a and b respectively. The wavefront dierence reaches 0.14 waves PTV between 0 and 60 o zenith angles, and 0.54 waves PTV from the centre to the edge of the WFS FoV (2.4 arcsec radius). The eld-dependant aberration may be calibrated (TBD), however this error is quiet small and should not be an issue as the FSM, working in close-loop, will keep each spot near its subaperture centre.

33 UVic AOLab Raven Final Optical Design Sec E E E E E E E E E E E+000 Wavefront Function Raven LGS WFS with FSM 24/01/ µm at , (deg) Peak to valley = waves, RMS = waves. Surface: 33 (LA back) Exit Pupil Diameter: E+000 Millimeters Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria lgswfsalonestagefoldedalldbtshifted25mm.zmx Configuration 1 of 4 Figure 20: Wavefront error seen by the LGS WFS at zenith, this includes the spherical aberration of the telescope. Raven LGS WFS with FSM 24/01/ Interferogram between Configurations 1 and 3 Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria µm at , (deg). Peak to Valley = waves, Fringes/Wave = Surface: 33 (LA back) Exit Pupil Diameter: E+000 Millimeters Xtilt = 3.00, Ytilt = (a) lgswfsalonestagefoldedalldbtshifted25mm.zmx Raven LGS WFS with FSM 26/01/ Interferogram between Configurations 1 and 2 Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria µm at , mm. Peak to Valley = waves, Fringes/Wave = Surface: 14 (LA back) Exit Pupil Diameter: E+000 Millimeters Xtilt = 3.00, Ytilt = (b) lgswfsalonestagefoldedalldbtshifted25mmghost.zmx Figure 21: LGS wavefront error variation vs. zenith angle (a) and FoV (b). Interferogram (a) shows the wavefront dierence between zenith angles 0 o and 60 o. Interferogram (b) shows the wavefront dierence between eld centre and eld edge (2.4" arsec on sky).

34 33 Sec. 7 Raven Final Optical Design UVic AOLab 6.3 Tolerancing The LGSWFS involves only stock lenses. It has been checked that the lens manufacturer tolerances do no degrade the performance of the WFS, both for the pupil and the wavefront. Each lens of the beam reducer will have adjustments in X,Y, Z, which gives lot of freedom to compensate lens fabrication errors. 6.4 Ghost image analysis A ghost analysis have been made for both conguration (0 and 60 o zenih angles) and for source from 0 to 2.4 arcsec from the optical axis. Thanks to the iris and the anti-reection coating there is no ghost reections detectable on the camera. 6.5 Thermal analysis The LGS-WFS path has been optimised for a temperature of 5 o C and an atmospheric pressure of 0.6 bar. However, a temperature change from -5 to 25 o C and a pressure change from 0.6 to 1 bar has no impact on the performance. This only assumes that the position of the sled holding the WFS camera is adjusted, which will be done in closed-loop. 7 Science pick-o arms 7.1 Layout The science pick-o mirrors are located in a vertical plane 20mm behind the telescope focal plane, i.e. 35mm behind the OLWFS pickos to avoid collisions. Each picko mirror is mounted at the tip of a rotating telescopic arm. A fold mirror, refereed to as Elbow Mirror, is located at the joint of the arm and is parallel to the pick-o mirror to provide a xed optical axis (Fig. 6). This periscopic scheme does not rotate the pupil when the arm turns around its joint. After the Elbow Mirror, a trombone, made of two fold mirrors at 90 o from each other, keeps the optical path length constant. Figure 25 displays the optical layout of the whole science path for one channel, including the science picko arm and the trombone. The required translation range for the picko arm and for the trombone are ±50mm and ±25mm respectively in order to patrol a 2 arcmin diameter FoR with no constraint. A 32mm overlap (±30 on the sky around the center) is required to be able to observe two science targets on the same side of the FoR when one LGS and two NGS are used for the wavefront sensing. Figure 22 shows the eld coverage of the two science pickos for a 50mm 32 o travel.

35 UVic AOLab Raven Final Optical Design Sec o S +30 Figure 22: Field coverage of the two science pickos for a 50mm 32 o travel, and a 32mm overlap.

36 35 Sec. 7 Raven Final Optical Design UVic AOLab 8.8mm 0.00E E E R y R x 6.25mm 6.25mm -3.22E E E E E mm 45 o ±0.25 o -8.60E E E mm 6.25mm Surface Sag Map RAVEN Science Relay Optimized Ellipsoid 04/10/2011 Surface 14: pickoff2 Units are Millimeters. Width = 8.8, Decenter x = 0, y = 0 Millimeters. University of Victoria Adaptive Optics Lab Olivier Lardière (lardiere@uvic.ca) tolsciencepickoff4ellipso.zmx Configuration 1 of 1 Figure 23: Science picko mirror specications. 7.2 Prescription Science Pick-o arm The picko mirror is not at but toroidal in order to conjugate the pupil on the science DM with no pupil astigmatism. Figure 23 and table 4 give the manufacture specications for the science picko mirrors with tolerances. The science picko mirrors have been made by BMV Optical and they exceed the requirements. The actual radii of curvature are R x = 1802mm, R y = mm with 9nm rms of surface irregularity and no noticeable surface decenter. A 4.3mm-diameter eld stop is located just behind the science picko mirror ( 4 5mm from the mirror centre) to block straylight. As the outer dimension is limited by the arm width a second larger eld stop is required closer to the Elbow mirror (dimensions TBD). The Elbow mirror is an o-the-shelf mm right-angle mirror, 1/10 wave, protected silver, from Thorlabs, part #MRA25-P Trombone The rst mirror of the trombone is a custom due to its dimensions. A 51.5mm diameter mirror with a 48mm diameter clear aperture is required to both transmit the whole beam with no vignetting and still t in a standard Newport 1-inch mirror mount with tilt adjustments. The specication for the manufacture of trombone M1 are listed in table 5. Figure 24 gives the manufacture specication for the second mirror (M2) of the trombone. This is actually a partial mirror reecting more than 94% of the science beam, and transmitting at least 3% of the gure source emitting in the nm band (Sec. 10). Trombone M2 has been made by BMV Optical following the "metal coated partial mirror" approach.

37 UVic AOLab Raven Final Optical Design Sec Substrate Dimension Aperture Clear aperture Bevels Radius of curvature along x-axis (long side) Radius of curvature along y-axis (short side) Surface irregularity Surface decenter Coating Table 4: Science picko mirror prescription. Fused silica Right-angle prism 6.25 ± 0.5mm side Rectangular ±0.5mm Elliptical, central mm 0.5mm R x = 1791mm ± 3% Convex R y = 896mm ± 3% Convex 30nm rms for Zernikes beyond astigmatism (focus and astigmatism are already accounted for in R x and R y tolerances) ±0.5mm along y-axis (decenter along x-axis is not an issue as the mirror tilt can be adjusted) Protected silver on hypotenuse Table 5: Trombone M1 prescription. Substrate Fused silica Dimension Circular / 0.1mm diameter Thickness 12.5±1.0mm Clear aperture 48mm central diameter Surface atness Edges Ground, 0.2mm max bevel Coating Protected silver Scratch & Dig 40-20

38 37 Sec. 7 Raven Final Optical Design UVic AOLab Substrate BK7 or fused silica Dimension Rectangular, 50.8x /-0.25mm Thickness 6±0.2mm Clear aperture 40x62mm elliptical Parallelism <1 arcmin Reflected wavefront distorsion λ/10 over clear aperture Transmitted wavefront distorsion λ/10 over clear aperture R Coating on front surface avg 93% nm T avg 3% nm (1) Coating on back surface Anti-Reflection, R avg 1% nm Angle of incidence 45 o Beam cone angle ±2.2 o Scratch & Dig Notes: 1. There might be two possible approaches: (i) a metal coated partial mirror, or (ii) a short-wavepass dichroic. Option (ii) is preferred to increase the transmission of the nm beam and mitigate straylight from the reflection on the front surface. 2. Unpolarized light source 3. Temperature range -25 to 60 o C 4. Humidity range 0 to 100% 5. Coating resistant to humidity per MIL-C-14806A PAR Illustration of intended use: Figure 24: Trombone M2 specications. The material is fused silica.

39 UVic AOLab Raven Final Optical Design Sec Performance As the science picko arm cannot work without the science relay, only the performance of the whole science path have been analysed (Sec. 8). 7.4 Tolerancing Science picko mirror As the science picko has little impact on the image plane, but lot of impact on the pupil, the merit function used for the tolerancing is the transverse ray intersect in the pupil plane (DM) for the center and four edge points of the pupil, this for 5 sources evenly located in the science FoV (4 arcsec. diameter). The merit function is zero for a perfectly circular 25mm diameter pupil centred on the DM for all sources inside the science FoV. The compensators used are the tip and tilt of the picko and Elbow mirrors, and the distance between the OEA and the DM, in order to recenter and refocus the pupil on the DM. Even if the picko mirror has very little impact on the image, the spot radius in the image plane near the roof mirror was also monitored during the tolerancing process to make sure that the image quality remains diraction limited. The tolerances listed in table 4 correspond to a pupil distortion lower than 0.6% of the pupil diameter Trombone A precisiongrade surface quality has been specied for all fold mirrors (i.e. λ/10 ptv). 7.5 Ghost image analysis A 4.3mm diameter eld stop is located just behind the science picko mirror to mitigate straylight. As the science picko arm and trombone involve only mirrors, there is no ghost images. Refer to Sec. 10 for possible ghost images of the gure source generated by a double-bounce in trombone M Thermal analysis No proper thermal analysis has been done for the science picko arm as an isotropic thermal expansion as no impact on the angles. Only variation of the distance between trombone M1 and M2 may rise concerns. However, the thermal expansion of the trombone assembly is negligible compared to the ±1mm tolerance for the OAE decenter (Sec. 8).

40 39 Sec. 8 Raven Final Optical Design UVic AOLab Table 6: O-Axis Ellipsoid (OAE) mirror prescription. Substrate Pyrex or equivalent Dimension Circular 70±0.5mm diameter Thickness 20±0.5mm Clear aperture 56mm central diameter Radius of curvature mm Concave, at ellipsoid apex Conic Surface irregularity (PTV) Decenter ±1mm Edges Ground, 0.5mm max bevel w/ ats or marks to locate x and y axis Coating Protected silver 8 Science Relay 8.1 Layout Behind the science picko arm and the trombone, there is an o-axis ellipsoid (OAE) mirror, a DM, a long-wave-pass (LWP) beam-splitter, a K-mirror and a roof mirror (Fig. 25). Basically, the science path is nothing but a 1:2 image relay with one eld lens at each end (picko and roof mirrors). The telescope focus is at one focus on the OAE, and the roof mirror is near the second focus of the OAE. Both picko and roof mirrors are near an image plane and can be powered to put the pupil at the right spot as does a eld lens. The pick-o and roof mirror are indeed both toroidal to put the pupil on the DM and at innity (for IRCS) respectively. A LWP beamsplitter has been added in the path in order to feed a CL-WFS (Sec. 10). Also a Kmirror allows elongated science targets to be rotated and aligned with the IRCS slit during long exposures. As the roof mirror belongs to the beam combiner subsystem, the prescription of the roof mirror is detailed in Sec Prescription OAE The prescription of the OAE are listed in table 6. The geometry of the parent ellipse is dened in Fig. 26. The OAE has been manufactured by Precision Asphere Inc Science DMs The science DM located in a pupil plane is a custom magnetic DM from ALPAO featuring actuators (145 in total) over 30mm clear aperture, but only 11 11

41 UVic AOLab Raven Final Optical Design Sec OAE Telescope focus Figure source BS Trombone Science pick-offs Roof mirror Field stops d=4 Compensator LWP Rotator DM Lensletarray d=300µm f=4.77mm Common output pupil Figure 25: Science path layout. Z Relay lens X Y 100 mm IRCS input focus

42 41 Sec. 8 Raven Final Optical Design UVic AOLab Focus F 2 (622.60, ) M ( , 0) o Mirror o Source F 1 (0,0) Apex S Figure 26: Geometry of the parent ellipsoid of the OEA mirror. The OAE is a small portion of a giant ellipsoid of foci F 1 and F 2. F 1 is the telescope focus near the science picko (or the gure source), and F 2 is the focus near the roof mirror.

43 UVic AOLab Raven Final Optical Design Sec Science DM (ALPAO DM145 25) Actuator Clear aperture Beam footprint 5 y[mm] x[mm] Figure 27: Science DM actuator geometry. actuators will be in the beam as the telescope pupil diameter is 25mm on the DM (Fig. 27). This provides a 1-actuator safety ring useful to mitigate edge eects and increase the stroke of the DM in tip/tilt. The total number of actuators to control is still LWP A long-wave pass (LWP) beam-splitter is required to reect the visible light to the CL-WFS (Sec. 10) and transmit the IR light to IRCS. The specications of the LWP are listed in Fig. 28. The LWP is in fused silica, 5mm thick with a wedge of 10.5 arcminutes, thicker edge toward the CLWFS. The purpose of this small wedge is (i), to send the ghost image out of the science FoV, and (ii), to reduce the lateral color from 13µm to 4µmin the output focus (Fig. 31). The lateral color induced by the LWP in the exit pupil is only 0.17% of the pupil diameter K-mirror The image rotator is made of three gold coated at mirror arranged in a K conguration (Fig. 25). Due to their specic dimensions, those mirrors are custom-made by BMV

44 43 Sec. 8 Raven Final Optical Design UVic AOLab Substrate Fused silica Dimension Circular, /-0.25mm diameter Thickness 5±0.2mm Wedge angle /-0.5 arcmin. Clear aperture 15mm diameter Reflected wavefront distorsion λ/10 over clear aperture Transmitted wavefront distorsion λ/10 over clear aperture Coating on front surface R avg 70% nm R avg 90% nm T avg 93% nm Coating on back surface Anti-Reflection, R avg 3% nm Angle of incidence 15 o Beam cone angle ±1.1 o Scratch & Dig Notes: 1. Unpolarized light source 2. Temperature range -25 to 60 o C 3. Humidity range 0 to 100% 4. Coating resistant to humidity per MIL-C-14806A PAR A mark on the side of the plate shall locate the thinner edge of the wedge 6. Illustration of the intended use: Figure 28: Specications of the LWP. The mark on the edge of the manufactured LWP indicates the location of the thicker side of the wedge, not the thinner side. The mark shall be toward the CLWFS.

45 UVic AOLab Raven Final Optical Design Sec Optical. The specications for their manufacture are listed in Fig Roof mirror eld stop Each science channel is equipped with a eld stop in the image plane near the roof mirror. The eld stop is mm square to limit each single science FoV to 4 4 arcsec (Fig. 30) After combination by the roof mirror, the two science beam forms a 4 8 arcsec rectangular eld with no overlap and matching the extent of the IRCS slits (Fig: 41). 8.3 Performance The overall performance of the science relay, including the picko arm, are diraction limited in the NIR (Fig. 31. The pupil shift or distortion on the DM is less than 0.23% ptv of the pupil diameter, for all sources within the science FoV and all wavelengths within 0.9 and 2.5µm. A more detailed performance analysis is done in the output focal plane of Raven in order to include the aberrations due to the beam combiner (Sec. 9). 8.4 Tolerancing Only the custom OAE mirrors required a special attention for tolerancing. mirror are o-the-shelves at mirrors with precision-grade quality. Other OAE As the OAE is located a similar distances from an image plane and pupil plane, this mirror impacts both planes. Consequently, the criterion for the tolerancing of the OAE are both the image quality in the image plane near the roof mirror, and the pupil formed on the DM. The compensators used are the OAE tip, tilt and decenters, the distance between the OAE and the DM, and the back focus. The tolerances listed in Table 6 lead to a pupil shift or distortion on th DM less than ±0.6% for any sources in the FoV, and a diraction limited image quality in the output focus. 8.5 Ghost image analysis As the science relay is mainly made of mirrors, the only component deserving concerns about ghost images is the LWP due to the possible double-bounce of the light between the two faces of the LWP. The LWP features a 10.5 arcminutes wedge to move the ghost image in the output focal plane 4mm away from the main image, i.e. 4" on sky, so that the ghost falls outside the useful FoV and is blocked by the roof mirror eld stop. At last, the design of the K-mirror barrel is made so that the light cannot pass directly through the K-mirror without hitting the three mirrors.

46 45 Sec. 8 Raven Final Optical Design UVic AOLab Substrate Fused silica Dimension Rectangular, 21x33±0.25mm Thickness 5.0±0.25mm Clear aperture 10x17.5mm off-centre rectangle (1) Surface flatness λ/10 over clear aperture Edge The short side close to clear aperture must be beveled at 30 o ±2.5 o from normal to the front surface (1) Ground, 0.25mm max bevel Coating Protected Gold Scratch & Dig Test report Interferogram with achieved flatness Notes: 1. Refer to this drawing for detailed shape and location of the clear aperture. Dimensions are in millimeters: Front surface (coated) 30 o 5 Clear aperture 10x17.5mm rectangular (a) Substrate Fused silica Dimension Rectangular, 21x30±0.25mm Thickness 5.0±0.25mm Clear aperture 10x10mm square, centred on the mirror Surface flatness λ/10 over clear aperture Edge Ground, 0.25mm max bevel Coating Protected Gold Scratch & Dig Test report Interferogram with achieved flatness (b) Figure 29: Specications of the K-mirror for M1 & M3 (a) and M2 (b).

47 UVic AOLab Raven Final Optical Design Sec B Scale: Millimeters A Aperture Full X Width : Aperture Full Y Height: Footprint Diagram Raven with Calibration Unit, OL and CL WFSs 12/04/2012 Surface 156: field stop Ray X Min = Ray X Max = Ray Y Min = Ray Y Max = Max Radius= Wavelength= Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria ravenircsfullclwfsfoldtromb.zmx Configurations 1,2,5 Figure 30: Top view of the square eld stop of the roof mirror (left) and beam footprint in the eld stop plane (right). Dimensions are in millimetres. An adjustment in X of the eld stop is highly desirable to line up the edge of the eld-stop (point B) with the apex of the roof (point A).

48 47 Sec. 8 Raven Final Optical Design UVic AOLab OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) IMA: 0.229, mm IMA: 2.382, mm IMA: 4.542, mm OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) IMA: 0.229, mm IMA: 2.383, mm IMA: 4.542, mm OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) Surface IMA: roof IMA: focus 0.229, mm IMA: 2.382, mm Spot Diagram RAVEN Science Relay Optimized Ellipsoid 09/02/2012 Units are µm. Airy Radius: µm Field : RMS radius : GEO radius : Scale bar : 120 Reference : Centroid IMA: 4.542, mm Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria sciencerelayoptimellipsolwpwedge.zmx Configuration 1 of 1 Figure 31: Spot diagram of the science relay at the focus of the OAE near the roof mirror. This spot diagram includes the aberrations of the telescope for an on-axis source. The circles are the Airy disc is H band. The FoV is ±2 arcsec.

49 UVic AOLab Raven Final Optical Design Sec Thermal analysis The whole science path has been optimised for a temperature of 5 o C and an atmospheric pressure of 0.6 bar. Aluminium TCE has been used for all spacers to assess the impact of a 20 o C temperature variation. There is no noticeable change on both the pupil and image planes. 9 Beam Combiner 9.1 Prescription At last there is a beam combiner to feed IRCS. A roof mirror rearranges the two science channel side by side, and a 2:1 exit relay lens re-images the focus of the OAE to a more accessible location for IRCS and restore the initial (or close to initial) F/# of the beam Roof mirror The purpose of the roof mirror is to (i), re-arrange the two science beam side by side 4 arcsec apart in the image plane to feed the slit of IRCS with both science targets simultaneously, and (ii), superimpose the exit pupils of both beams to pretend there is only one beam (Fig. 32). The roof mirror is actually made of two distinct rectangular mirrors almost in contact on one side. The tilt and tip of each mirror is adjusted to superimpose the exit pupil of both beams. The distance between the image plane and the roof mirror is 17.5mm. The two mirrors form a concave roof, rather than a convex roof, and are located just behind the intersection of the optical axis of the two channels. This geometry makes right-angle edge mirrors suitable and minimise the gap between the two mirrors (Fig. 25). Each mirror is toroidal to conjugate the exit pupil of Raven to innity. This maximise the throughput in IRCS, as the cold stop of IRCS is on the secondary mirror of an Oner relay. The exit pupil of Raven is formed by the exit relay lens. In order to get the exit pupil of Raven at innity, the roof mirror shall form an intermediary pupil plane at about 200mm in front of the exit relay lens, which can be handy for aligning the roof mirror. This intermediate pupil plane is refereed to as common output pupil on Fig. 25. The prescription for the manufacture of the roof mirrors are listed in Fig. 33. The roof mirror has been made by BMV Optical Exit relay lens The last optical component of Raven is a 2:1 relay lens made of a 42mm diameter air-spaced doublet (Fig. 34) providing diraction-limited images from 0.9 to 2.5µm(Fig. 38). The air gap is 5.0mm thick at the centre of the lenses. The doublet is located at mm from the roof mirror (i.e mm from the input focus). The rst lens is made in S-FTM16 glass from Ohara (Fig. 35), and the

50 49 Sec. 9 Raven Final Optical Design UVic AOLab Roof mirror Raven exit relay lens Slit IRCS entrance window IRCS Offner relay M2 Z Y M1 X 3D Layout RAVEN science beam combiner w/ IRCS Offner relay 08/03/2012 Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria sciencerelayoptimellipsolwpwedgebeamcomb2shorterfnumbwircsoffner.zmx Configuration 1 of 1 Figure 32: Optical interface of Raven with IRCS. The foreoptic of IRCS consists in an Oner relay. The Raven exit beam shall pass through the cold pupil stop (M2) and the slit. second lens in IR-grade CaF 2 (Fig. 36). Both glasses have a transmission greater than 95% up to 2.4µm. The relay lens forms a F/12.45 beam. This F/number is a good trade-o minimizing the vignetting on both echelle and grism modes of IRCS (Fig. 42). The exit relay lens can be decentred to steer the output beam to ease the alignment of IRCS with respect to Raven. A 2mm decenter induces a 30 arcmin tilt on the outgoing beam with no aberrations. A focus can be generated by moving this relay lens along the axis for doing phase diversity with the IRCS imaging mode. A ±5mm axial shift induces negligible impact on the pupil conjugation. 9.2 Performance Roof mirror The roof mirror has very little impact on the image as it acts as a eld lens. Moreover, the requirement on the pupil distortion is much looser than 0.6% of the pupil diameter as there is no adaptive optics system behind the roof mirror. Consequently, no proper performance analysis has been done for the roof mirror.

51 UVic AOLab Raven Final Optical Design Sec Substrate Fused silica Dimension Rectangular, 32x /-0.25mm Thickness 5.0±0.25mm Clear aperture 5x5mm square at 0.2mm max from one short edge (2) Radius of Curvature along x-axis R x = 613.5±10mm Concave (long side) Radius of Curvature along y-axis R y = 518.8±15mm Concave (short side) Surface Decenter ±1.0mm along y-axis (1) Surface irregularities λ/10 over clear aperture from the theoretical shape Edge Edge close to clear aperture: Cut or ground, 0.1mm max bevel (2) Other edges: Ground, 0.5mm max bevel Coating Protected Gold Scratch & Dig or better (mirror near an image plane) Test report Interferogram with actual radii of curvature and surface irregularities Notes: 1. Decenter along x-axis is not an issue, so both mirrors can be made from a single blank and cut down after polishing. 2. Refer to this drawing for definition of the axis and accurate location of the clear aperture. Dimensions are in millimeters. Curvatures are exaggerated. R y is not shown: Coated surface R x = mm y Clear aperture 5x5mm square x Figure 33: Roof mirror prescription. The actual radii of curvature made by BMV Optical are R y =515.6mm and R x =614.2mm.

52 51 Sec. 9 Raven Final Optical Design UVic AOLab Figure 34: Air-spaced doublet Exit Relay Lens. Light comes from left-hand side. The air gap is 5.0mm thick at the centre Exit relay lens Figure 37, 38 and 39 show respectively the transverse ray fan plot of the exit relay lens for a ±2 arcsec FoV on sky, the RMS wavefront error versus eld, and the focal shift from 1.1 to 2.4µm. The performance of this relay lens is by far limited by the diraction Overall performance of the science path with IRCS Figure 40 shows the spot diagrams for one science channel (4 4 arcsec on sky) at the exit focus of Raven, i.e. the entrance focus of IRCS. It is worth noting that the beam combiner does not degrade the image quality obtained in the focus near the roof mirror (Fig. 31). Figure 41 displays the Strehl ratio eld map in the exit focus for both science channels. The displayed eld is the eld limited by the square eld stop near the roof mirror. The position of the slits of IRCS planned to be used with Raven are overlaid to gure out which part of the eld will be more useful for spectroscopy. It is worth noting that the whole 4 8 arcsec FoV is potentially usable in the imaging mode of IRCS. The IRCS Zemax model provided by Subaru has been added downstream Raven to check that all the rays pass properly through the pupil stops (Fig. 42) and the slit of IRCS. Also, this allows use to analyze the science performance of Raven with IRCS in terms of ensquared energy, assuming no turbulence. Figure 43 displays the spot diagram in the slit plane for J, H and K bands. Perfor-

53 UVic AOLab Raven Final Optical Design Sec Figure 35: Exit relay lens singlet #1. First singlet 1 PART/DRAWING REVISION tolachromatoptimizedstop8airspaced40mmdiafnumbshorter.zmx Configuration 2 of 2 Raven exit relay lens PROJECT/TITLE 04/04/ :1 Olivier Lardière DATE SCALE DRAWN APPRV Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria ISO Element Drawing Indications According to ISO / - 6/ - 5/ - 2/ - 5/ - 4/ 3' 1/ - 4/ 2' 3/ µm 0/ - 3/ µm AR nm V = d AR nm Ø E 35 N = d Ø E 35 R CX GLASS: S-FTM16 R CC Left Surface Material Right Surface Dimensions in Millimeters Ø Ø P P

54 53 Sec. 9 Raven Final Optical Design UVic AOLab P P Ø Dimensions in Millimeters Left Surface Material Right Surface R CX GLASS: CAF2 R CX Ø E 35 N = d Ø E 35 AR nm V = d AR nm 3/ µm 0/ - 3/ µm 4/ 5' 1/ - 4/ 2' 5/ - 2/ - 5/ - 6/ - 6/ - ISO Element Drawing Indications According to ISO Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria APPRV DRAWN SCALE DATE Olivier Lardiere :1 04/04/2012 PROJECT/TITLE Raven exit relay lens tolachromatoptimizedstop8airspaced40mmdiafnumbshorter.zmx Configuration 2 of 2 REVISION PART/DRAWING 1 Second singlet Figure 36: Exit relay lens singlet #2.

55 UVic AOLab Raven Final Optical Design Sec ey OBJ: (deg) ex ey OBJ: (deg) ex Py Px Py Px ey OBJ: (deg) ex Py Px Raven to IRCS relay lens 15/02/2012 Maximum Scale: ± µm Surface: Image Transverse Ray Fan Plot Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria achromatoptimizedstop8airspaced40mmdiafnumbshorter.zmx Configuration 1 of 1 Figure 37: Transverse ray fan plot of the air-spaced doublet optimized to relay the exit image plane of Raven with the input image plane of IRCS. The lateral errors are lower than 4µm for J, H and K bands, i.e. 8 mas on the sky (to be compared to the 22 mas/pixel resolution of the IRCS imaging mode).

56 55 Sec. 9 Raven Final Optical Design UVic AOLab 0.08 RMS Wavefront Error in Waves Diffraction Limit Y Field in Degrees Raven to IRCS relay lens 10/04/2012 Poly Reference: Centroid RMS Wavefront Error vs Field Figure 38: Exit relay lens RMS wavefront versus eld Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria tolachromatoptimizedstop8airspaced40mmdiafnumbshorter.zmx Configuration 2 of 2

57 UVic AOLab Raven Final Optical Design Sec Wavelength in µm Focal Shift in µm Chromatic Focal Shift Raven to IRCS relay lens 15/02/2012 Maximum Focal Shift Range: µm Diffraction Limited Range: µm Pupil Zone: Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria tolachromatoptimizedstop8airspaced40mmdiafnumbshorter.zmx Configuration 1 of 1 Figure 39: Exit relay lens focal shift.

58 57 Sec. 9 Raven Final Optical Design UVic AOLab OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) IMA: , mm IMA: , mm IMA: , mm OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) IMA: , mm IMA: , mm IMA: , mm OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) Surface: IMA IMA: , mm IMA: , mm Spot Diagram RAVEN Science Relay Optimized Ellipsoid 14/02/2012 Units are µm. Airy Radius: µm Field : RMS radius : GEO radius : Scale bar : 60 Reference : Centroid IMA: , mm Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria sciencerelayoptimellipsolwpwedgebeamcomb2.zmx Configuration 1 of 1 Figure 40: Science path spot diagrams at exit focus for one science channel (±2" FoV) for J, H and K bands. The spot diagrams of the other channel are a mirrored copy. Only the elds #4 to 6 (central row) go through the slit of IRCS. Circles show the Airy disc in H band. mances are very similar to those obtained in the output pupil plane of Raven (Fig. 40), meaning that the Raven output relay lens and the IRCS Oner relay add negligible aberrations in the system. All spots are well smaller than the slit width (75µmfor the Echelle mode). Note that the slit is horizontal, thus only the spot #4, 5 and 6 can possibly pass through the slit. Actually, only the central spot pass through the slit if we consider the blind zone between the 2 FoV and the exact length of the slit, so spots #4 and 6 have to be considered as a worst case scenario for the spectroscopic mode. In addition, for pointlike source the science image rotator can be turned such as only the best spots (#2, 5 and 8) pass through the slit. The spots in the corners must be considered only for the imaging mode of IRCS. Figure 44 plots the geometric ensquared energy (EE) in the slit plane of IRCS used with Raven and no atmospheric turbulence. The static aberrations of the system have no impact on the EE beyond 18µmfrom the centroid. The slit halfwidth is 27µm in Grism mode and 37.5µm in Echelle mode. Consequently, the EE in the slits will be only limited by the diraction and/or the residual turbulence.

59 UVic AOLab Raven Final Optical Design Sec y [arcsec on sky] Strehl ratio field map on exit focus Min Strehl = Max Strehl = Slit#2, Ech. K Slit#3, Ech. H Slit#4, Ech. IzJ Slit#14, Grism x [arcsec on sky] 0.86 Figure 41: Strehl ratio eld map at the output focal plane of Raven for both science channels (science pickos on telescope optical axis, no turbulence). The position of the slits of IRCS planned to be used with Raven are overlaid. 9.3 Tolerancing Roof mirror As the roof mirror is near an image plan, it has almost no impact on the image quality. The main criterion for tolerancing the roof mirror is actually the pupil image. The goal is to keep the pupil aberration or distortion less the 0.6% of the pupil diameter (this requirement could be signicantly relaxed as there is no AO component after the roof mirror, but we want to keep the possibility to use a SH-WFS at the output of Raven for characterising the overall performance of Raven). The compensator are the tilt of the roof mirror and the distance between the roof mirror and the exit relay lens, to recenter and refocus the pupil image. The resulting tolerances for the roof mirror are listed in Fig. 33. This kind of tolerance are easy to make Exit relay lens The criterion for the tolerancing of the relay lens is the image quality (RMS spot radius) at the output focus and the exit pupil distance. The compensators are the distance between the roof mirror and the exit relay lens (±10mm) and the back focus (±20mm). The tolerances specied on the ISO drawings of the lenses (Fig. 35 and 36) provide a RMS spot radius lower than 5.2µmwith 90% of condence. The worst oenders are the lens surface tilts (±2 to ±5 arcmin), and the element

60 59 Sec. 9 Raven Final Optical Design UVic AOLab Scale: Millimeters Aperture Diameter: Footprint Diagram RAVEN Science Relay Optimized Ellipsoid 08/03/2012 Surface 80: OFFNER(SECO) Ray X Min = Ray X Max = Ray Y Min = Ray Y Max = Max Radius= Wavelength= All (a) % rays through = 97.16% Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria sciencerelayoptimellipsolwpwedgebeamcomb2shorterfnumbwircsoffner.zmx Configuration 1 of 1 (b) Figure 42: Footprint diagrams of the rays coming from Raven at F/12.45 in the pupil stops of IRCS: (a) cold stop on the secondary mirror of the Oner relay (common to both Echelle and Grism modes), (b) Pupil stop of the Grism mode.

61 UVic AOLab Raven Final Optical Design Sec OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) IMA: 1.952, mm IMA: 0.998, mm IMA: 0.046, mm OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) IMA: 1.952, mm IMA: 0.998, mm IMA: 0.046, mm OBJ: , (deg) OBJ: , (deg) OBJ: , (deg) Surface: IMA IMA: 1.952, mm IMA: 0.998, mm Spot Diagram RAVEN Science Relay Optimized Ellipsoid 08/03/2012 Units are µm. Field : RMS radius : GEO radius : Box width : 75 Reference : Chief Ray IMA: 0.046, mm Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria sciencerelayoptimellipsolwpwedgebeamcomb2shorterfnumbwircsoffner.zmx Configuration 1 of 1 Figure 43: Spot diagram on the IRCS slit plane for one science FoV (±2, i.e. ±1.06mm object height) for J, H and K bands. Square boxes represents the slit width in Echelle mode (75µm, i.e on sky).

62 61 Sec. 9 Raven Final Optical Design UVic AOLab , (deg) , (deg) , (deg) , (deg) , (deg) , (deg) , (deg) , (deg) , (deg) Fraction of Enclosed Energy Half Width From Centroid in µm Geometric Ensquared Energy RAVEN Science Relay Optimized Ellipsoid 08/03/2012 Wavelength: Polychromatic Data has not been scaled by diffraction limit. Surface: Image Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria sciencerelayoptimellipsolwpwedgebeamcomb2shorterfnumbwircsoffner.zmx Configuration 1 of 1 Figure 44: Geometric ensquared energy in the slit plane of IRCS in H band for all the 9 sources of Fig. 43. The slit halfwidth is 27µm in Grism mode and 37.5µm in Echelle mode.

63 UVic AOLab Raven Final Optical Design Sec tilt (±3arcmin) and decenter (±0.05mm). A 3-arcmin tilt corresponds to a thickness variation of ±18µm on the edge of the spacer separating the 2 lenses. The tolerance on the spacer thickness is 5.0mm±0.2mm. 9.4 Ghost image analysis A stop will be installed in the common output pupil plane to mitigate straylight. Ghost images may be caused by the double-bounce in the thin air gap between the two elements of the exit relay lens. The ghost image analysis shows that there is no detectable ghost images, as the background intensity due to the ghost is fainter than the main image. 9.5 Thermal analysis The roof mirror and exit relay lens have been optimised for a temperature of 5 o C and an atmospheric pressure of 0.6 bar. However, a temperature and pressure variation from -5 to 25 o C and from 0.6 to 1 bar, has no impact on the performance of the beam combiner. This assumes that the back focus is adjusted by 0.6mm, which is not an issue considering the 25mm travel of the motorized focus stage of the exit relay lens. 10 Figure and ClosedLoop WFSs 10.1 Prescription The DM of each science arm is followed by a WFS (CLWFS) to allow the DM to be calibrated and also to be controlled in closedloop on bright targets. In addition, an internal source, refereed to as Figure source, can be turned on to check the DM shape during openloop operations on faint targets. In that case the WFS is used as a Figure WFS. The Figure source and CL-WFS paths are highlighted in green on Fig. 25. Two beam splitters are required, one to combine the gure source beam with the science beam (Trombone M2), and another one to feed the CLWFS with the visible part of the science beam (LWP, which has been described in Sec. 8) Figure Source The gure source is a green LED emitting between 500 and 550nm (Fig. 45) stacked with a 400µmdiameter pinhole and 220 grit ground glass diuser (Edmund Optics #45-652). This pinhole size corresponds to 0.76" on-sky, i.e. 2 pixels on the CL-WFS. Then, an iris limits the extend of the beam footprint in order to match the F/# of the science beam. At last, a 50mm diameter fold mirror reect the beam toward the trombone where the Figure source is combined with the science beam Trombone M2 The beam combiner is actually the second mirror of the trombone (Trombone M2). The specications of this beam-splitter are listed in Fig. 24. Basically, this is a metal-

64 63 Sec. 10 Raven Final Optical Design UVic AOLab Figure 45: Spectrum of the Figure Source LED. This is a green LED from CREE #C503B-GAS-CB0F0791.

65 UVic AOLab Raven Final Optical Design Sec E E E E E E E E E E E E E E E E E E E E E E-002 Wavefront Function 17/02/ µm at , (deg) Peak to valley = waves, RMS = waves. Surface: Image Exit Pupil Diameter: E+001 Millimeters Tilt Removed: X = , Y = waves Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria compensatorplate.zmx Configuration 1 of 2 Wavefront Function 17/02/ µm at , (deg) Peak to valley = waves, RMS = waves. Surface: Image Exit Pupil Diameter: E+001 Millimeters Tilt Removed: X = , Y = waves Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria compensatorplate.zmx Configuration 2 of 2 (a) (b) Figure 46: Wavefront error without (a) and with (b) the Figure source compensator plate. Without compensator plate the wavefront error is dominated by astigmatism (0.86µm PTV). With compensator the residual wavefront error is very low (30nm PTV or 6nm RMS of coma. coated partial mirror reecting more than 93% of the whole spectrum and transmitting at least 3%, as the Figure source can easily be as bright as needed (special care must be taken to reduce stray light). A partial mirror is much cheaper and give better performance than a shortwave pass (SWP) dichroic. Moreover, a partial mirror does not restrict the wavelength of the gure source. Trombone M2 is made by BMV Optical Compensator plate A compensator plate in fused silica tilted at 45 o is added in the gure source path to cancel the aberrations due to the tilted partial mirror and then, minimise the NCPA (Fig. 46). The manufacture specications of the compensator are listed in Fig. 47. It has the same thickness and same glass than trombone M2. The compensator plate is made by BMV Optical and will be mounted on the translation stage of the trombone surrounded by baes to block straylight. A thicker compensator plate may be used temporarily to mimic the lateral shift of the beam induced by the compensator and trombone M2 when the trombone is absent. This allow us to align the gure source before the installation of the trombone. This temporary compensator is a 12.7mm-thick fused silica optical at from Edmund Optics (part #43-438). Figure 48 shows how this compensator shall be positioned CL-WFS path In each CLWFS path, there is a beam reducer, a lenslet array (LA) in a pupil plane and a 1:1 relay lens (Fig. 25. The parameters of the CLWFS are identical to those of the OLWFS (Tab. 2).

66 65 Sec. 10 Raven Final Optical Design UVic AOLab Substrate Same as A3 Dimension Rectangular, 40x65+0.0/-0.25mm Thickness 6±0.2mm Clear aperture 33x47mm elliptical Parallelism <1 arcmin Transmitted wavefront distorsion λ/10 over clear aperture Coating on front surface Anti-Reflection, R avg 1% nm Coating on back surface Anti-Reflection, R avg 1% nm Angle of incidence 45 o Beam cone angle ±2.2 o Scratch & Dig Notes: 1. Unpolarized light source 2. Temperature range -25 to 60 o C 3. Humidity range 0 to 100% 4. Coating resistant to humidity per MIL-C-14806A PAR Figure 47: Specication of the gure source compensator plate. Trombone M2 Compensator Figure Source (a) Alignment compensator Figure Source (b) Figure 48: Alignment gure source compensator. The compensator and trombone M2 shift the chief ray of the gure source laterally in x and y (a). In order to align the gure source without the trombone and compensator, a temporary thicker compensator plate can be used as shown (tilted at o around the vertical axis, and at 45 o around the optical axis) to reproduce the same beam shift (b).

67 UVic AOLab Raven Final Optical Design Sec The goal of the beam reducer is to collimate the beam and form a 3mm diameter pupil on the LA. The beam reducer is made of two stock lenses. The rst lens is a 128mm focal length 20.6mm diameter achromat from Ross Optical (part # L- AOC153/230), and the second lens is a 35mm focal length 12.5mm diameter achromat from Edmund Optics (part #49-325). The 1:1 relay lens imaging the LA spots on the camera is stricly identical to the relay lens used in the OL-WFS Performance Figure Source arm Thanks to the compensator plate the residual wavefront distortion of the Figure source path should be pretty low, 6nm RMS of coma (Fig. 46) CL-WFS arm The beam reducer of the CL-WFS is diraction-limited, as shown on the spot diagram (Fig. 49). However, the RMS wavefront error varies slightly with the eld (Fig. 50). There is 72nm PTV (14nm RMS) of coma at 2 arcsec from the centre (Fig. 51). This eld-dependant aberration is not a static error and cannot be removed by changing the osets of the CL-WFS, but it may be ltered out as it is correlated with the tip and tilt Tolerancing As there is no custom powered optical component to be manufactured, no proper tolerance analysis has been done. A precision-grade atness has been requested for the compensator plate and trombone M Ghost image analysis A ghost image of the gure source is formed by a double-bounce inside trombone M2. Due to the low transmission of trombone M2 for the gure source, this ghost image is only 54 times fainter than the main image, and its chief ray is shifted by 3.69mm from the axis. Fortunately this beam shift corresponds to 6.94" on-sky, which is well outside the 4.8" diameter FoV of the CL-WFS. However, a xed 2.0mm diameter eld stop is required in the focal plane located between the two lenses of the beam reducer of the CL-WFS to block the ghost image and transmit only the useful FoV Thermal analysis The gure source and CL-WFS path have been optimised for a temperature of 5 o C and an atmospheric pressure of 0.6 bar. However, a temperature and pressure variation from -5 to 25 o C and from 0.6 to 1 bar, has no impact on the performance with all spacers made of aluminium. This is no need to adjust the back focus distance. Consequently, the CL-WFS oset slopes should not vary with the temperature.

68 67 Sec. 11 Raven Final Optical Design UVic AOLab OBJ: , (deg) OBJ: , (deg) 1.00 IMA: , rad IMA: , rad Surface: IMA Spot Diagram Raven Close-Loop WFS beam reducer 17/02/2012 Units are mr. Airy Radius: mr Field : 1 2 RMS radius : GEO radius : Scale bar : 1 Reference : Chief Ray Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria FoldClWfsStockLensesRoss.ZMX Configuration 1 of 1 Figure 49: Spot diagram of the CL-WFS beam reducer. As the beam reducer is an afocal system, this diagram plots the angular spot radius in mrad.

69 UVic AOLab Raven Final Optical Design Sec RMS Wavefront Error in Waves Diffraction Limit Y Field in Degrees Raven Close-Loop WFS beam reducer 17/02/2012 Poly Reference: Centroid RMS Wavefront Error vs Field Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria FoldClWfsStockLensesRoss.ZMX Configuration 1 of 1 Figure 50: RMS wavefront error versus eld of the CL-WFS beam reducer. A eld radius of o on the bean reducer corresponds to 2" on the sky.

70 69 Sec. 11 Raven Final Optical Design UVic AOLab CL WFS field dependant WF error at 2" from centre [nm] y [mm] x [mm] PTV = 71.68nm RMS = 14.44nm Figure 51: Field dependant aberration of the CL-WFS beam-reducer. 0

71 UVic AOLab Raven Final Optical Design Sec Acquisition Camera 11.1 Prescription A camera looking at the whole focal plane of the telescope is planned to ease the acquisition of the targets with the pickos. The shadows of the picko arm should be visible against the sky background. The expected spectral range for the acquisition camera is µm. A xed octagonal fold mirror located behind the science pickos reect the beam towards the acquisition camera located above the science arm plane (Fig. 52). A 14mm diameter central hole lets the LGS beam going through the LGS WFS (Fig. 53). The hole creates a 14" diameter central blind zone for targets. The acquisition camera can help acquire the LGS spot if the LGS laser beacon is misaligned by more than 10" from the telescope optical axis. The defocused LGS spot is 400µm wide on the CCD, which is small enough. A motorized focus stage is not necessary. After the fold mirror, there is a custom triplet acting as a eld lens and a collimator and an o-the-shelves C-mount imaging lens from Schneider Optics (17mm f/0.95 XENON lens, part # ). The exit pupil of the triplet matches the entrance pupil of the imaging lens. The triplet is made of a plano-convex lens in S-BSL7 and a cemented doublet in S-LAL7 and S-TIH6 glasses from Ohara (Figs. 54 and 55). The prescription of the Schneider lens is not available. Only the imaging performance of this lens in terms of MTF, distortion, transmittance and vignetting are available on the manufacturer's website. The selected camera is a Dalsa Pantera 1M30 featuring µm side pixels. The exposure time, the gain and the binning can be adjusted. This camera is not cooled, but dissipates 17W and can get warm. A water cooling may be desirable to evacuate the heat outside the bench enclosure Performance Zemax models or black boxes are not available for the C-mount Schneider lens. Only the performance of the custom triplet are presented here. We assume that the imaging lens does not degrade signicantly the image quality. The triplet has been optimized and characterized in reverse path, shining the light from the exit pupil (object at innity) towards the telescope focal plane (curved image plane to take in account the eld curvature of the telescope). Figure 56a plots the spot diagram of the triplet in the telescope focal plane. As the acquistion path is equivalent to a 10.26:1 relay lens, the image of a 12µm-wide pixel of the detector is 123.1µm-wide in the telescope focal plane. The outer square of the spot diagrams corresponds to 2 pixels. The inner circle corresponds to the diraction limit of the telescope at 600nm. Obviously, the acquisition camera is not diraction limited, but for most of the eld, the PSF are contained in one pixel (2 pixels for the edge of the FoR). Figure 56b plots the RMS spot radius versus the eld. The spot are roughly 3 times bigger than the diraction limit up to 1' on sky from the axis.

72 71 Sec. 11 Raven Final Optical Design UVic AOLab Camera Imaging lens Field lens Exit pupil Field lens LGS WFS X Y Telescope focal plane 3D Layout Raven Acquisition Camera Field Lens 22/03/2012 Figure 52: Acquisition camera path. Olivier Lardière (lardiere@uvic.ca) Adaptive Optics Lab University of Victoria TolinvertedFieldLensTripletOhara4Final.ZMX Configuration 1 of 1 Z