GRINTECH GmbH. product information.

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1 GRINTECH GmbH product information

2 GRIN rod lenses Gradient index lenses for fiber coupling and beam shaping of laser diodes z l d s f Order example: GT-LFRL CC (670) Design wavelength Coating Code NA: 0.5 Pitch: 0.25 Diameter: 1.0 mm Laser Focusing Rod Lens GRINTECH Working distance and lens length deviating from these standards can also be produced; 8 angled facet available on request ZEMAX files can be DOWNLOADed from our website Pitch P Working distance s (mm) Numerical Aperture NA Lens length zl (mm) Focal length f (mm) Gradient constant g (mm -1 ) Refractive index at the center of the profile no wavelength λ (nm) Product code Diameter d: 0.5 mm GT-LFRL CC (670) GT-LFRL CC (670) GT-LFRL CC (810) GT-LFRL CC (810) GT-LFRL CC (1550) GT-LFRL CC (1550) * GT-LFRL CC * GT-LFRL CC Diameter d: 1.0 mm ,53 2,32 0,91 0, GT-LFRL CC (670) ,53 2,12 0,92 0, GT-LFRL CC (670) ,53 2,34 0,92 0, GT-LFRL CC (810) ,53 2,13 0,93 0, GT-LFRL CC (810) ,52 2,36 0,93 0, GT-LFRL CC (1550) ,52 2,16 0,94 0, GT-LFRL CC (1550) * GT-LFRL CC * GT-LFRL CC Diameter d: 1.8 mm ,52 4,27 1,67 0, GT-LFRL CC (670) ,52 3,88 1,69 0, GT-LFRL CC (670) ,51 4,30 1,69 0, GT-LFRL CC (810) ,51 3,91 1,71 0, GT-LFRL CC (810) ,51 4,35 1,72 0, GT-LFRL CC (1550) ,51 3,96 1,73 0, GT-LFRL CC (1550) * GT-LFRL CC * GT-LFRL CC Diameter d: 2.0 mm ,50 4,91 1,92 0, GT-LFRL CC (670) ,50 4,48 1,94 0, GT-LFRL CC (670) ,50 4,94 1,94 0, GT-LFRL CC (810) ,50 4,52 1,96 0, GT-LFRL CC (810) ,49 4,99 1,97 0, GT-LFRL CC (1550) ,49 4,57 1,99 0, GT-LFRL CC (1550) * Rod lenses with NA 0.2 for other wavelengths are available on request. GRIN rod lenses are offered with antireflection coatings (R < 0.5 % for the design wavelength and incidence angles of corresponding to measurements on a reference substrate) Coating Code: NC: no coating (reflection loss approx. 12 %) C1: λ = 670 nm C2: λ = nm C5: λ = nm Variations due to modifications of the production process are possible. It is the user s responsibility to determine suitability for the user s purpose. Tolerances: lens length zl: ± 5% due to variations of the gradient constant working distance s: ± 0.02 mm diameter d: + 0 / mm Please ask for tighter diameter tolerances Surface quality: 5 / 3 x 0.025; L 3 x 0.005; E 0 (defined by DIN ISO : ). The surface quality is defined within 90 % of the lens diameter. Outside of this area defects are allowed. Revision 04/2013

3 GRIN cylindrical lenses Gradient index lenses for the fast axis collimation of high power laser diode bars, high brightness diodes and other beam shaping purposes Plane surfaces z l d b s Order example: GT-LFRL CC (670) Design wavelength Coating Code NA: 0.5 Pitch: 0.25 Diameter: 1.0 mm Laser Focusing Rod Lens GRINTECH Working distance and lens length deviating from these standards can also be produced; different lens width available upon request ZEMAX files can be DOWNLOADed from our website Pitch P Working distance s (mm) Numerical Aperture NA Lens length zl (mm) Focal length f (mm) Gradient constant g (mm -1 ) Refractive index at the center of the profile no Width b (mm) Wavelength λ (nm) Product code Thickness d : 0.5 mm GT-LFCL CC (810) GT-LFCL CC (940) * GT-LFCL CC (670) Thickness d : 1.0 mm GT-LFCL CC (810) GT-LFCL CC (940) * GT-LFCL CC (670) Thickness d : 1.3 mm GT-LFCL CC (810) GT-LFCL CC (940) * GT-LFCL CC (670) * Cylindrical lenses with NA 0.2 for other wavelengths are available on request. GRIN cylindrical lenses are offered with antireflection coatings (R < 0.5 % for the design wavelength and incidence angles of corresponding to measurements on a reference substrate) Coating Code: NC: no coating (reflection loss approx. 12 %) C2: λ = nm Variations due to modifications of the production process are possible. It is the user s responsibility to determine suitability for the user s purpose. Tolerances: lens length zl: thickness d: working distance s: ± 6% due to variations of the gradient constant ± 0.02 mm ± 0.03 mm Surface quality: 5 / 3 x 0.025; L 3 x 0.005; E 0 (defined by DIN ISO : ). The surface quality is defined within 90 % of the thickness and within b 1 mm of the width. Outside of this area defects are allowed. Revision 05/2011

4 GRIN Objective Lenses for Endoscopy Gradient index lenses for endoscopic imaging optics Non-toxic silver-based glass material, view angle ϑ = ± 30 Plane surfaces, low chromatic aberration Combination with prisms and beam splitter cubes on request New feature: Aperture and field stops (black chromium coating ring on lens surface generated by photolithography) on request Certification: Biological safety toxicology (EN ISO ) Order example: GT-IFRL CC y O l ϑ z l y i d d A Coating Code NA: 0.5 Working distance: 10 mm Diameter: 1.0 mm Imaging Focusing Rod Lens GRINTECH Working distance and lens length deviating from these standards can also be produced ZEMAX files can be DOWNLOADed from our website Diameter Working distance Lens length 1 Parax. Magnification Refractive index at the Product code d (mm) l (mm) zl (mm) M = yi/yo center of the profile no 2.0 Infinity GT-IFRL-200-inf-50-CC : GT-IFRL CC : GT-IFRL CC : GT-IFRL CC 1.8 Infinity GT-IFRL-180-inf-50-CC : GT-IFRL CC : GT-IFRL CC : GT-IFRL CC 1.0 Infinity GT-IFRL-100-inf-50-CC : GT-IFRL CC : GT-IFRL CC : GT-IFRL CC 0.85 Infinity GT-IFRL-085-inf-50-CC : GT-IFRL CC : GT-IFRL CC 0.6 Infinity GT-IFRL-060-inf-50-CC : GT-IFRL CC : GT-IFRL CC 0.5 Infinity GT-IFRL-050-inf-50-CC : GT-IFRL CC : GT-IFRL CC : GT-IFRL CC : GT-IFRL CC 1 Design Wavelength 570 nm GRINTECH Objective lenses are available with AR coatings (R < 0.5 % for the design wavelength and incidence angles of corresponding to measurements on a reference substrate) Coating Code: NC: no coating (reflection loss approx. 12 %) C1: AR coating for VIS on both sides Variations due to modifications of the production process are possible. It is the user s responsibility to determine suitability for the user s purpose. Tolerances: lens length zl: ± 5% due to variations of the gradient constant diameter d: + 0 / mm Please ask for tighter diameter tolerances Surface quality: 5 / 3 x 0.025; L 3 x 0.005; E 0 (defined by DIN ISO : ). The surface quality is defined within 90 % of the lens diameter. Outside of this area defects are allowed. Note: GRINTECH objective lenses can be combined with GRIN relay lenses to complete endoscopic imaging systems by gluing the optical surfaces directly together. Prisms to change the direction of view can also be glued directly on the front surface of the objective lens. We are pleased to advise you. Revision 01/2013

5 GRIN Endoscopic Rod Lens Systems GRIN endoscopic systems, which combine a GRIN objective lens, a GRIN relay lens and a GRIN eyepiece. Combining the system with a prism enables the change of the direction of view (see Fig. 2). Standard diameters are 0.5, 1.0 und 2.0 mm. We offer the systems in two different principle design options: A. The objective lens creates a reduced intermediate image at the exit surface of the objective lens, which will be imaged by the relay lens 1:1 (if the lens length of the relay lens is a multiple of the period) or - 1:1 (if the lens length of the relay lens is an odd multiple of the half period) to the exit surface of the relay lens. B. The objective lens creates a reduced intermediate image at the exit surface of the objective lens, which will be imaged by the relay lens (including the eyepiece in form of a ¼ pitch-lens (e.g pitch, 1.25 pitch, 1.75 pitch etc.) at infinity. Such a lens system is a complete endoscopic imaging system. It allows the direct observation with the human eye or the use of a conventional camera system (including camera lens). Schematic view of the two designs: Pitch 0.5 Pitch object 90 prism objective object objective lens relay lens 0.75 Pitch - intermediate image CCD eye Fig. 1: Examples of designs for GRINTECH endoscopic systems. The pitch length can be increased by a whole number of the half pitch length in dependence on the requested endoscope length. Details are shown in table 1. Fig. 2: Changing the direction of view of a GRIN lens by a 90 prism Table 1: Configurations of endoscopic systems (other on request) Design [Ø - pitch] Diameter [mm] Image orientation System length [mm] comment like Design B ca with eyepiece like Design A ca without eyepiece inverted to Design B ca with eyepiece inverted to Design A ca without eyepiece like Design B ca with eyepiece * 1.0 like Design B ca with eyepiece like Design A ca without eyepiece inverted to Design B ca with eyepiece inverted to Design A ca without eyepiece * 1.0 like Design B ca with eyepiece * 2.0 like Design B ca with eyepiece * 2.0 like Design A ca without eyepiece * 2.0 inverted to Design B ca with eyepiece inverted to Design A ca without eyepiece like Design B ca with eyepiece (* - These configurations are standard and are available in smaller quantities (5 pc) on request.) We will advise you. Please contact us. Revision 04/2011

6 High-NA Endomicroscopic Imaging Objective for Fluorescence Microscopy GRINTECH s high-na Endomicroscopic Imaging Objectives cascade the optical power of a plano-convex lens and a GRIN lens with aberration compensation to achieve an object NA of 0.8. Applications: In vivo endomicroscopy, fluorescence microscopy, tissue imaging, flexible fluorescence microscopy, NA conversion Product Code: GT-MO Features: Object NA = 0.80 Object working distance 80 µm (water) Image NA = 0.18 Magnification 4.65 x Recommended Excitation 488 nm Mounted in stainless steel holder Product Code: GT-MO Features: Object NA = 0.80 Object working distance 80 µm (water) Image NA = Magnification 1.92 x Recommended Excitation 488 nm Mounted in stainless steel holder Image NA = 0.18 Object NA = 0.8 Image NA = Object NA = 0.8 Image wd = 200 µm in air Object wd = 80 µm in water Image wd = 100 µm in air Object wd = 80 µm in water 1.4 mm 1.4 mm 7.00 mm 7.65 mm (+/-0.17mm) 3.30 mm 4.10 mm (+/-0.35 mm) Diffraction limited NA versus Field N.A. diffraction limited radial object field height [µm] (from optical design simulation according to Marechal 488 nm, wavefront RMS 0.07 λ) Chromatic Aberration in Object Space Diffraction limited NA versus Field N.A. diffraction limited radial object field height [µm] (from optical design simulation according to Marechal 488 nm, wavefront RMS 0.07 λ) Chromatic Aberration in Object Space working distance in water [µm] λ [nm] working distance in water [µm] λ [nm] Revision 05/2011 Variations due to modifications of the production process are possible. It is the user s responsibility to determine suitability for the user s purpose. Pat. US 7,511,891

7 High-NA Endomicroscopic Imaging Objective for 2-Photon Microscopy GRINTECH s high-na Endomicroscopic Imaging Objectives cascade the optical power of a plano-convex lens and a GRIN lens with aberration compensation to achieve an object NA of 0.8. Applications: In vivo endomicroscopy, 2-photon microscopy, deep brain and tissue imaging, flexible fluorescence microscopy, NA conversion Product Code: GT-MO Features: Object NA = 0.80 Object working distance 200 µm (water) Image NA = 0.18 Magnification 4.8 x Recommended Excitation nm Mounted in stainless steel holder Product Code: GT-MO Features: Object NA = 0.80 Object working distance 200 µm (water) Image NA = Magnification 1.92 x Recommended Excitation nm Mounted in stainless steel holder Image NA = 0.18 Object NA = 0.8 Image NA = Object NA = 0.8 Image wd = 200 µm in air Object wd = 200 µm in water Image wd = 100 µm in air Object wd = 200 µm in water 1.4 mm 1.4 mm 7.00 mm 7.50 mm (+/-0.17 mm) 3.30 mm 4.00 mm (+/-0.35 mm) Diffraction limited NA versus Field N.A. diffraction limited 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0, radial object field height [µm] (from optical design simulation according to Marechal 810 nm, wavefront RMS 0.07 λ) Chromatic Aberration in Object Space Diffraction limited NA versus Field N.A. diffraction limited radial object field height [µm] (from optical design simulation according to Marechal 810 nm, wavefront RMS 0.07 λ) Chromatic Aberration in Object Space working distance in water [µm] λ [nm] working distance in water [µm] λ [nm] Revision 05/2011 Variations due to modifications of the production process are possible. It is the user s responsibility to determine suitability for the user s purpose. Pat. US 7,511,891

8 GRIN Needle Endomicroscopes GRIN Needle Endomicroscopes are used for deep tissue imaging. They relay the micron-scale resolved image of the tissue over a longer length to a plane outside of the tissue at the other end of the needlescope. Most frequently they are used with multi-photon fluorescence imaging (Design Wavelength 860 nm) or with epi-fluorescence imaging (Design Wavelength 520 nm). The Endomicroscopes are fabricated as GRIN-singlets with NA = 0.50 on both sides or as GRIN-doublets with an object NA of 0.5 and an image NA of Working distances on object side are specified in water or tissue, on image side in air. The doublets are offered in different lengths resulting from adding 0.5 GRIN-pitches (periods) to the GRIN relay lens (NA = 0.19). Product Code Length (mm) Working distance in water (µm) object side Working distance in air (µm) image side Design Wavelength (nm) NA object side / image side Magnification Image / Object Diameter d: 0.5 mm NEM S / :1 S NEM S / :1 S NEM DS / : 1 D NEM DM / : 1 D NEM DL / : 1 D NEM DS / : 1 D NEM DM / : 1 D NEM DL / : 1 D Diameter d: 1.0 mm NEM S / :1 S NEM S / :1 S NEM S / :1 S NEM DS / : 1 D NEM DL / : 1 D NEM DS / : 1 D NEM DL / : 1 D Singlet / Doublet Notes: Diameters are sole GRIN-optics diameters Optionally the Endomicroscopes can be delivered in medical-grade stainless steel tubes (1.4301), with outer diameters of 0.70 mm for 0.5 mm optics and 1.2 mm for 1.0 mm optics. The tubes are mounted flush on the object side (tissue, high NA). On the image side, the optics sticks out of the tube by µm. Please add ST to the product code if desired. The lengths can have a tolerance of +/- 3 %. The lenses are non-coated. For customized projects, the lenses can be AR-coated. A side-viewing scope using microprisms may be also possible on a customized basis.

9 Small Size Laser-optic Line Generator GRINTECH s Gradient-Index Micro-Optic Components with plane optical surfaces generate a homogeneous laser line from a Gaussian beam of a single-mode laser diode. The extraordinary small module size of 6.43 mm x 10.5 mm and a weight of only 0.9 g are combined with a line uniformity of approx. ± 8% and a diffraction-limited focus size. Applications: 3D contour mapping Optical alignment Machine vision Biomedical Standard Options: Line divergence (Fan angle): ± 10, ± 15, ± 20 (see ordering information below) Line focus position can be specified between 80 mm and infinity (collimation) when ordering. Please see remarks below for focus size and depth of focus. Red laser diode: Sanyo DL , λ = 658 nm, PLD = 40 mw, TO 5.6 mm package (no driver) Mechanical Specifications: Weight: 0.9 g Dimensions: 6.43 mm x 10.5 mm Package material: anodised aluminium y x I I y x LASER RADIATION AVOID EXPOSURE TO THE BEAM CLASS 3B LASER PRODUCT Environmental Specifications: Operating temperature: 0 50 C Storage temperature: -20 C +70 C Resistance to vibrations: 2 g / Hz (acc. IEC68-2-6) Resistance to mechanical shock: 15 g / 6 ms (acc. IEC ) Laser safety class: depending on application and additional optics up to class 3B Optical Specifications: Fan divergence angles : ± 10, ± 15, ± 20 Focus distance: 80 mm infinity, Gaussian shape Line width in focus: FWHM/Distance = 0.60 µm/mm, Example: approx. 120 µm line width (FWHM) in 200 mm distance Far field divergence depending on line widths, approx. according to Gaussian beam laws Squint angle: 2 Transmission efficiency: Pout / PLD = 90 95% Example: Line width: 75 µm FWHM in focus distance 123 mm Relative Intensity 1,0 0,8 0,6 0,4 0,2 0,0 Example: Line profile +/- 10 Module Divergence angle in Variations due to modifications of the production process are possible. It is the user s responsibility to determine suitability for the user s purpose. Order example: GT-LLGM-643-DA-FD Focus distance in mm (between 80 mm and infinity) Divergence angle: 10 for ± for ± 15 Diameter: 6.43 mm 20 for ± 20 Laser Line Generator Modul GRINTECH Revision 04/2011

10 In Vivo Medical Confocal Imaging and Optical Coherence Tomography GRIN Imaging systems Diameter: 0.5 mm / 1.0 mm / 1.8 mm / 2.0 mm Prisms to change the direction of view can be assembled Combination with optical fibers and imaging fiber bundles on request Optical design for customized solutions AR- and splitter (dichroic, polarizing, non-polarizing) coatings on request Mounted in stainless steel tubes on request Colonic tissue of the rat imaged by an endoscopic confocal laser scanning probe using GRIN front optics In Vivo Microendoscopy In Vivo OCT Endoscopy Prism GRIN rod lens Glass ferrule Single Mode Fiber J. Neurosci. 26(41): Standard diameters: 0.5, 1.0, 1.8, 2.0 mm Standard magnifications: 1:4.9 and 1:2.6 Object NA: 0.5, new: 0.8 (system) Resolution limit < 0.7 µm Diameters: 1.0, 1.8, (0.5) mm working distance, spot size and divergence can be designed to customized specifications Diffraction-limited Gaussian spots Generation of internal reference signal within probe possible Example: typical amplitude modulation of back reflected interference signal in the fiber about 80 % (moving mirror as reflector) Tolerances GRIN lens: lens length zl: ± 5% due to variations of the gradient constant diameter d: + 0 / mm working distance s: ± 0.01 mm Variations due to modifications of the production process are possible. It is the user s responsibility to determine suitability for the user s purpose. Surface quality: 5 / 3 x 0.025; L 3 x 0.005; E 0 (defined by DIN ISO : ). The surface quality is defined within 90 % of the lens diameter. Outside of this area defects are allowed Revision 04/2011

11 Customized GRIN Lens Assemblies GRIN Fiber Pigtails Applications: fiber optical sensors, biophotonic probes, optical switches, fiber coupling Fiber Pigtails using Gradient Index Rod Lenses Focussing, collimating and imaging GRIN lenses Use of special fibers on request AR and beam splitting coatings on request 8 angled facet of fiber and optics possible Please ask for customized solutions GRIN Arrays Linear Lens Arrays for collimation / imaging of fiber bundles Application: telecom components, optical switches, sensor arrays 1x8, 1x12, 1x16 GRIN Rod Lens Arrays Pitches 250 (± 1) µm / 500 (± 1) µm Lens diameter: 240 (± 1) µm / 480 (± 1) µm Lens NA: 0.35 / 0.5 / 0.2 Please ask for customized solutions Example: Fiber Spacer GRIN Lens Prism lens diameter: 0.48 mm pitch: 0.50 mm v-groove array made by dicing in glass Examples: Fiber optic sensor mounted in stainless steel tube GRIN lens diameter: 0.5 / 1.0 / 1.8 mm Tube diameter: 0.7 / 1.2 / 2.0 mm Side opening for prism exit possible SMF Pigtail using glass ferrule and capillary GRIN lens diameter: 1.8 mm Capillary diameter: 2.8 mm 2-D Lens Arrays Application: multi-imaging sensors, read-out of biochips Examples: 4x5 GRIN Rod Lens Array Pitch: 1.60 (± 0.01) mm Lens diameter: 1.0 mm Lens NA: 0.5 Mount: machinable ceramic Pitch: 4.50 (± 0.02) mm Lens diameter: 1.8 mm Lens NA: 0.5 Mount: brass SMF Pigtail using glass ferrule, mounted in stainless steel tube GRIN lens diameter: 0.5 / 1.0 / 1.8 mm Tube diameter: 0.7 / 1.2 / 2.0 mm Multimode Fiber Pigtail using customized SMA 905 connector and integrated GRIN lens Cylindrical Lens Arrays Application: line pattern generation, 1:1 imaging, slow axis divergence reduction of HPDL-bars (SAC arrays) Pitch: 0.5 / 1.0 / 1.3 mm NA of single lens: 0.2 / 0.5 Suppression of crosstalk by absorber layers possible Beam homogenization Variations due to modifications of the production process are possible. It is the user s responsibility to determine suitability for the user s purpose. Revision 04/2011

12 Gradient Index (GRIN) Lenses GRIN rod lenses for fiber coupling GRIN cylindrical lenses for beam shaping of high power laser diode bars and high brightness diodes easy to assemble due to the plane surfaces good off- and on-axis performance non-toxic silver and lithium ion exchange Gradient Index Optics GRIN lenses represent an interesting alternative to conventional spherical lenses since the lens performance depends on a continuous change of the refractive index within the lens material. Instead of curved shaped surfaces only plane optical surfaces are used. The light rays are continuously bent within the lens until finally they are focussed on a spot. A half-pitch lens images an object on the entrance surface inverted to the exit surface of the lens. A quarter-pitch lens images a point source on the entrance surface of the lens into infinity or collimates it, respectively. This configuration is usually applied to the collimation of single-mode and multi-mode optical fibers and laser diodes. For high-power laser diodes, GRIN cylindrical lenses are used for the Fast-Axis- Collimation. A 0.23-pitch lens images a point source placed in the working distance s into infinity or collimates it (see Fig. 3). d s f z l Fig. 3. GRIN rod lens Fig. 1 GRIN lens Conventional spherical lens The GRIN lenses are produced by silver ion exchange in a special glass. The composition of the glass is protected by a patent. In contrast to the conventionally used technology this is a non-toxic process and bears no health and environmental risks for both the producer as well as the user of these products. This process is performed in rods and slabs resulting in rod lenses and cylindrical lenses with plane optical surfaces. A radial refractive index profile of nearly parabolic shape n(r) = n0 sech(gr) realizes a continuos cosine ray trace within a GRIN focussing lens, the period length z1-p of the lens is given by 2π z = 1 p g and does not depend on the entrance height and the entrance angle of the light ray (see Fig 2). n0 represents the refractive index at the center of the profile, r the radius and g the gradient constant. Fig. 2. Ray traces within a GRIN focussing lens of different pitch lengths The geometrical length of the particular lens zl is calculated from the characteristic pitch of the lens P, 2π zl = P g Various imaging designs can be realized using the same index profile by choosing different lens lengths: A 1- (2, 3, or more, respectively)-pitch lens reproduces an object placed in the entrance surface of the lens identically into the exit surface. The geometrical gradient constant g and the lens length zl determines the focal length f and the working distance s of the lens, 1 1 f =, s = n gsin(gz ) n gtan(gz ) 0 l 0 Various imaging problems can be solved by choosing different lens lengths zl (see Fig.4). O l 2 s Fig. 4. Image formation by a GRIN focusing lens f The maximum acceptance angle of a GRIN collimating lens ϑ is determined by the numerical aperture NA. As in fiber optics, it is derived from the maximum index change of the GRIN profile, R 0 sin( ϑ ) = NA = n n = n 1 sech (gd / 2). z l P 1 P 2 nr is the refractive index at the margin of the profile, and d is the lens diameter or the lens thickness, respectively. GRIN lenses with a high numerical aperture (NA 0.5) are produced by silver ion exchange in a special glass which avoids any coloration in the visible spectral range. The absorption edge of the silver containing glass occurs at a wavelength of λ0.5 = 370 nm. GRIN lenses with low numerical aperture (NA 0.2) are fabricated via lithium ion exchange. The absorption edge of the glass being used is at a wavelength of λ0.5 = 235 nm. l f s 2 y, r l z I Revision 04/2011

13 Gradient Index Imaging Optics GRIN rod lenses and systems endoscopic and other miniaturized imaging applications easy to assemble due to the plane surfaces good off- and on-axis performance AR-coating on both sides possible non-toxic silver and lithium ion exchange low chromatic aberration GRIN Objective Design GRINTECH objective lenses are produced by non-toxic silver ion exchange in glass and are suited for medical applications. The large view angle of 60 degrees (± 30 ) is obtained by a strong index change within the glass material. The objective lenses image the object plane in a working distance l (see Fig. 1) into the end surface of the lens on a reduced scale. y O Fig. 1 Image formation by a GRIN objective lens The lenses are specified by the rod diameter d and the working distance l (see the respective data sheet). The corresponding magnification M and the necessary lens length zl are calculated by 1 arctan( n0 M = ; zl = n g l + 1 g 0 l ϑ z l l g) + π, where n0 is the center index of the lens, and g is the gradient constant of the lens. For each diameter, g can be calculated by using the lens length of the respective lens type with infinite working distance, π g =. inf 2z l y i d d A Beside standard working distances, customized lens designs can be provided on request. The dispersion of the index gradient causes a relative change of the focal length as function of the wavelength. In the visible range, the focal length of lenses with NA of 0.5 increases by approx % per nm with rising wavelength. For objective lenses of 1.0 mm diameter, the image plane of the blue light part (440 nm) is located approx. 18 µm inside the lens. The image plane of the red light part (650 nm) is located approx. 18 µm outside the lens exit plane. For lenses of 0.5 mm diameter for example, half of these image shift values is valid. GRINTECH objective lenses are characterized by a small field curvature. The image field is slightly bent inwards. For lenses of 1.0 mm diameter the field curvature is 40 µm maximum at 90 % of the aperture, for 0.5 mm diameter 20 µm maximum. The barrel shaped distortion of the image increases up to approx. 14 % of the image height at the lens margin (see CCD-image above). The resolution limit of the objective lenses is on-axis approx. 400 lines per mm in white light. GRIN Imaging Systems Complete imaging systems for endoscopes and other applications are fabricated by combining GRINTECH objective lenses, GRIN relay lenses of customized pitch lengths, and prisms. Please contact GRINTECH for customized solutions. Revision 04/2011

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