Optical Design with Zemax

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1 Optical Design with Zemax Lecture : Correction II 3--9 Herbert Gross Summer term

2 Correction II Preliminary time schedule 6.. Introduction Introduction, Zemax interface, menues, file handling, preferences, Editors, updates, windows, Coordinate systems and notations, System description, Component reversal, system insertion, scaling, 3D geometry, aperture, field, wavelength 3.. Properties of optical systems I Properties of optical systems II Aberrations I Diameters, stop and pupil, vignetting, Layouts, Materials, Glass catalogs, Raytrace, Ray fans and sampling, Footprints Types of surfaces, Aspheres, Gratings and diffractive surfaces, Gradient media, Cardinal elements, Lens properties, Imaging, magnification, paraxial approximation and modelling Representation of geometrical aberrations, Spot diagram, Transverse aberration diagrams, Aberration expansions, Primary aberrations, Aberrations II Wave aberrations, Zernike polynomials, Point spread function, Optical transfer function Advanced handling 7.. Optimization I Telecentricity, infinity object distance and afocal image, Local/global coordinates, Add fold mirror, Vignetting, Diameter types, Ray aiming, Material index fit, Universal plot, Slider,IO of data, Multiconfiguration, Macro language, Lens catalogs Principles of nonlinear optimization, Optimization in optical design, Global optimization methods, Solves and pickups, variables, Sensitivity of variables in optical systems Optimization II Systematic methods and optimization process, Starting points, Optimization in Zemax 9 8. Imaging Fundamentals of Fourier optics, Physical optical image formation, Imaging in Zemax 5.. Illumination.. Correction I 9.. Correction II Introduction in illumination, Simple photometry of optical systems, Non-sequential raytrace, Illumination in Zemax Symmetry principle, Lens bending, Correcting spherical aberration, Coma, stop position, Astigmatism, Field flattening, Chromatical correction, Retrofocus and telephoto setup, Design method Field lenses, Stop position influence, Aspheres and higher orders, Principles of glass selection, Sensitivity of a system correction, Microscopic objective lens, Zoom system Physical optical modelling Gaussian beams, POP propagation, polarization raytrace, coatings

3 Correction II Contents 3. Field lenses. Stop position influence 3. Aspheres and higher orders 4. Principles of glass selection 5. Sensitivity of a system correction 6. Microscopic objective lens 7. Zoom system

4 Correction II Field Lenses 4 Field lens: in or near image planes Influences only the chief ray: pupil shifted Critical: conjugation to image plane, surface errors sharply seen marginal ray chief ray field lens in intermediate image plane lens L lens L shifted pupil original pupil

5 Correction II Field Lens im Endoscope 5 without field lenses with field lens with field lenses Ref : H. Zügge

6 Correction II Influence of Stop Position on Performance 6 Ray path of chief ray depends on stop position stop positions spot

7 Correction II Effect of Stop Position 7 Example photographic lens stop Small axial shift of stop changes tranverse aberrations In particular coma is strongly influenced Ref: H.Zügge

8 Correction II Higher Order Aberrations: Achromate, Aspheres 8 Splitted achromate achromat broken contact aspheric air space ray a zone Aspherical surface... zone zone Ref : H. Zügge

9 Correction II Higher Order Aberrations: Merte Surface 9 Merte surface: - low index step - strong bending - mainly higher aberrations generated Transverse spherical aberration O.5 (a) O.5 (b) Merte surface From : H. Zügge

10 Correction II Aspherical Surfaces Additional degrees of freedom for correction Exact correction of spherical aberration for a finite number of aperture rays Strong asphere: many coefficients with high orders, large oscillative residual deviations in zones Location of aspherical surfaces:. spherical aberration: near pupil. distortion and astigmatism: near image plane corrected points Use of more than asphere: critical, interaction and correlation of higher oders tan u' residual spherical aberration SPH

11 Correction II Coexistence of Aberrations : Balance Example: Achromate Balance :. zonal spherical. Spot 3. Secondary spectrum standard achromate axial color spherical aberration a) compromise : zonal and axial error sur sur sur 3 sum sur sur sur 3 sur 4 sum b) spot optimized c).6 3 secondary spectrum optimized sur sur sur 3 sur 4 sum -3 sur sur sur 3 sur 4 sum Ref : H. Zügge

12 Correction II Coexistence of Aberrations : Balance Example: Apochromate Balance :. zonal spherical. Spot 3. Secondary spectrum SSK CaF F3 r P 4 nm 45 nm 5 nm 55 nm 6 nm 65 nm 7 nm 4 nm 45 nm 5 nm 55 nm 6 nm 65 nm 7 nm axis z field.7 field.

Color correction: index n large dispersion difference desired positive lens field flattening

13 Correction II Principles of Glass Selection in Optimization 3 Design Rules for glass selection Different design goals:. Color correction: index n large dispersion difference desired positive lens field flattening Petzval curvature. Field flattening: large index difference + + desired negative lens color correction + - availability of glasses - - dispersion n Ref : H. Zügge

14 Correction II Sensitivity of a System 4 Sensitivity/relaxation: Average of weighted surface contributions of all aberrations Sp h Sph -3 Correctability: Average of all total aberration values Total refractive power Kom a Coma k F F F j j j Important weighting factor: ratio of marginal ray heights Ast Ast j h j h CH L 4 3 CHL Inz- Wi 3 incidence angle

15 Correction II Sensitivity of a System 5 Quantitative measure for relaxation with normalization A k j j A j j F j F h j h F j F Non-relaxed surfaces:. Large incidence angles. Large ray bending 3. Large surface contributions of aberrations 4. Significant occurence of higher aberration orders 5. Large sensitivity for centering Internal relaxation can not be easily recognized in the total performance Large sensitivities can be avoided by incorporating surface contribution of aberrations into merit function during optimization

16 Sum Correction II Sensitivity of a System 6 Double Gauss.4/ Representation of wave Seidel coefficients [l] , ,8 5,6-5,4 -, -5 - surfaces Ref: H.Zügge Verz Sph Koma Ast Petz Verz

17 Correction II Photographic lens 7 Incidence angles for chief and marginal ray Photographic lens Field dominant system Primary goal is to control and correct field related aberrations: coma, astigmatism, field curvature, lateral color chief ray 6 incidence angle marginal ray

18 Correction II Microscopic Objective Lens 8 Incidence angles for chief and marginal ray marginal ray microscope objective lens Aperture dominant system Primary problem is to correct spherical aberration chief ray incidence angle

19 Correction II Microscope Objective Lens 9 Possible setups for flattening the field Goal: - reduction of Petzval sum - keeping astigmatism corrected a) single meniscus lense b) two meniscus lenses c) symmetrical triplet d) achromatized meniscus lens e) two meniscus lenses achromatized f) modified achromatized triplet solution

20 Correction II Aplanatic Surfaces Aplanatic surfaces: zero spherical aberration:. Ray through vertex. concentric 3. Aplanatic Condition for aplanatic surface: r ns n' s' ss' n n ' n n' s s' Virtual image location Applications:. Microscopic objective lens. Interferometer objective lens s' s s' s und u u' ns n' s' hyperboloid oblate ellipsoid oblate ellipsoid prolate ellipsoid + power series + power series + power series + power series s' vertex sphere concentric sphere aplanatic S

21 Correction II Aplanatic Lenses Aplanatic lenses Combination of one concentric and one aplanatic surface: zero contribution of the whole lens to spherical aberration Not useful:. aplanatic-aplanatic. concentric-concentric bended plane parallel plate, nearly vanishing effect on rays A-A : parallel offset A-C : convergence enhanced C-A : convergence reduced C-C : no effect

22 Correction II Development of Microscopic Lens. Step : Generation of high-na on axis a ) without meniscus lens numerical aperture : NA =.9 b) a-c meniscus lens NA =.4 c ) a-c meniscus lenses NA =.37 d) 3 a-c meniscus lenses NA =.589 e) 3 a-c meniscus lenses and c-c meniscus lens NA =.589

23 Correction II Development of Microscopic Lens 3. Step : Optimization on axis Correcting thickness Introducing free working distance Inserting finite field axis correction. version :. and 4. lens to thin, field m. version : free working distance to short, field 5 m 3. version : field m

24 Correction II Development of Microscopic Lens 4 3. Step : Improvements Additional degrees of freedom Material changes Avoiding strong bendings Optimization of lens-thickness Comparison of variants Fine-tuning

25 Correction II Development of Microscopic Lens 5 Overview of the steps of development. Correction on axis, quality good. Correction with field, compact, quality not sufficient 3. Correction with triplet, some surfaces obsolet, quality not sufficient 4. Correction with one doublet and larger air distances, quality not sufficient 5. Correction with two doublets, quality nearly good enough 6. Further optimization with glass choices, better field uniformity 7. with working distance and telecentricity

26 Correction II Basic Principle 6 Two thin lenses in a certain distance t: Focal length f f f f f t Refractive power t h h Kinds of zoom systems a) Finite-finite (F-F) b) Infinite-finite (I-F) c) Infinite-infinite (I-I)

27 Correction II Change of Focal Length 7 Distance t increased First lens fixed changed distance t moved lens changed focal length f

28 Correction II Change of Focal Length 8 Distance t increased Image plane fixed two lenses moved t f image plane

29 Correction II Mechanical Compensated Zoom Systems 9 Simple explanation of variator and compensator Movement of variator arbitrary Compensator movement depends on variator Perfect invariance of image plane possible compensator nonlinear variator linear relay lens objective lens image plane P P P

30 Correction II Optical Compensated Zoom Systems 3 Combined movement of two rigid coupled lenses Image plane location only approximately constant Only one moving part fixed group coupled moved lenses relay lens fixed image with defocus P P P

31 Correction II Three-Component Zoom System 3 Setup:. lens fixed first lens fixed second lens third lens image plane f f f 3 Given : M, L Arbitrary but recommended : Calculation : central position s' 3 M M ( s' s 3 f t t s' M ) M M L M M ( M ) M L 3 M M M t ( M ) M ( M ) 3 t

32 Correction II Symmetrical Afocal Setup 3 Telescope angle magnification : f f f w' w h h first last asymmetric > t max Major positions symmetric Magnification First Second distance distance = max > t max = t m t m = asymmetric t m t m = / max < t min < Symmetrical layout t min

33 Correction II Example 33 Professional factor 5 zoom lens with 5 moving groups Very smooth and excellent correction Ref: Tokumaru, USP (988) f = 46 mm f = 5 mm spherical coma astigma curvature distortion ax chrom la chrom st group f = 7 mm nd group 3rd group f = 5 mm 4th group f = 35 mm 5th group f = 9 mm sum

Lens Design I. Lecture 10: Optimization II Herbert Gross. Summer term

Lens Design I. Lecture 10: Optimization II Herbert Gross. Summer term Lens Design I Lecture : Optimization II 5-6- Herbert Gross Summer term 5 www.iap.uni-jena.de Preliminary Schedule 3.. Basics.. Properties of optical systrems I 3 7.5..5. Properties of optical systrems