《日本大阪大学光学设计课件.ppt》由会员分享，可在线阅读，更多相关《日本大阪大学光学设计课件.ppt（33页珍藏版）》请在三一文库上搜索。
1、Design of photographic lens,Shinsaku Hiura Osaka University,The five Seidel aberrations,Parallel rays do not meet one point Spherical aberration Coma The image is not flat Astigmatism Curvature of field Image of a line is not a line Distortion,Spherical aberration(1),The source of the degradation at
2、 the center of the image (monochromatic) Lenses with spherical surface always have(Aspherical lens solves) Has effect to whole of the image, but usuallymeasured at the center only,Spherical aberration (longitudinal),h,Function of ray height h measured on the optical axis,Representation of sphericala
3、berration,Spherical aberration curve,Ray height,Paraxial focus,Longitudinal aberration is symmetric around optica axis; half of the curve is sufficient.,Near object,Appearance of spherical aberration,Object at infinity,Control of spherical aberration(1),Bending Balance of thickness and index of glas
4、s Divide one thick lens to two thin lenses Combination of conversing and diverging lens,Shape modification with constant thickness and focal length (spherical aberration is changing),1/500 of focal length 0.05mm each for front and back, F1.4 Diameter of circle of confusion is 0.036mm(as small as per
5、missible circle of confusion),Example of spherical aberration (1),Spherical aberration of standard 50mm F1.4 lens,Distortion,Function of object height (angle) measured on the image plane Ray height 0(principal ray only) For photography, 2% is permissible Barrel shape is better than pin-cushion shape
6、,Distortion (Transversal),Distortion (2),Positive(pin-cushion),Negative(barrel),Field curvature,function of Object height measured to the direction of optical axis Causing defocus at the corner of the image Ray height 0(independent to the spherical aberration)Direction of approaching the limit is ve
7、ry important (because lens is 3D),Field curvature （Longitudinal）,Astigmatism,Difference of the field curvature for different direction of approaching limit（also 0 , measured to optical axis) Object height / ray height : meridional image Object heightray height : Sagittal image,Astigmatism (longitudi
8、nal),M,S,Astigmatism (2),Meridional : (Meteorology) (chiefly of winds and air flow) aligned with lines of longitude. Sagittal : relating to or denoting the suture on top of the skull that runs between the parietal bones in a front to back direction.,Object sagittal image meridional image,Astigmatism
9、 (3),M image,middle image,Object,S image,Astigmatic difference,From the aesthetic point of view, M and S image must be close Or we would feel “flow” on the image,Astigmatic curve,Object height (angle),Astigmatic difference,Types of astigmatism,Coma,Function of ray height measured on the image Object
10、 height / ray height : meridional coma Object heightray height : sagittal coma,Coma (Transversal),(Meridional coma),Coma,Typical coma : causes asymmetric blur,Principal ray,Principal ray,Transversal,Object height,Coma is Transversal aberration,Case of no Coma (field curvature only),Image of coma,Lon
11、gitudinal chromatic aberration,Focal length varies caused by dispersion (variation of refractive index for wavelength) Causing degradation of the center of the image,Longitudinal chromatic aberration,h,Transversal chromatic aberration,Variation of focal length also causes the difference of image siz
12、e,Transversal chromaticaberration,Correction of chromatic aberration,Balanced out by using two different dispersion Non-linear dispersion can not be corrected,White light,Red light,Blue light,Crown,flint,Low disp.,High disp.,Parameters of optical glass,Basically two parameters (index, dispersion),Di
13、spersion,Optical glass chart,Abbe number,Optical glasses,Various materials (elements)Lead, silicon, potassium, Barium, Lanthanum, .,Dense flint Flint Light flint Barium flint Barium crown Dense crown Borosilicate crown Special short flint Lanthanum flint Lanthanum crown,Name symbol example index nd
14、abbe num. vd constituent,Optical glasses,Why we need many elements?,For correcting monochromatic aberration Thin lens with high index glass Thick lens with low index glass For correcting chromatic aberration,There are some differences for aberration even if the focal length is same,White light,F spe
15、ctrum(blue),d spectrum(green),C spectrum(red),Longitudinal chromatic aberration of single lens,Making of optical glass(1),Clay pot method : traditional but still good,Making Clay pots,Making of optical glass (2),To avoid the coloring the glass, very pure materials are used,Clay pot in a furnace,Maki
16、ng of optical glass (3),Cooling, annealing Cooling for two weeks Formed and keep heated for a long time (for uniformity and remove internal strain),Glass is picked out by breaking clay pot Glass is also broken, but also non-uniform part (babble, striae) is easily removed. Yielding : 50%,Making of op
17、tical glass (4),Corrosive materials are melted in platinum pot,Quality of glass Reflactive index : 0.00050 Dispersion : 0.8% Cost of special glass is up to thirty dollars / 1g,Platinum pot and glass,Correction of second order chromatic aberration,Abnormal (extraordinary) dispersion,Ordinary high ind
18、ex glass,Ordinary low index glass,AD(Kurz : short),AD(Lang : long),wavelength,Refractive index,Correction of chromatic aberration,Correction of chromatic aberration,Single(BK7),Doublet (achromat),apochromat,wavelength,IR,Longitudinal chromatic aberration,The five Seidel aberration,Longitudinal,Trans
19、versal,Spherical,Field curvature,Astigmatism,Coma,Distortion,L.C.A.,T. C. A,Monochromatic chromatic,parameter,Ray Height (thickness of incoming light),Object height (angle),Image of aberrations (1),Image of a point light source (PSF),Longitudinal chromatic aberration,Coma,Coma,Spherical aberration,Images of aberrations(2),Sagittal image,Meridional image (w/ TCA),Central image,Astigmatism,Graphs shown in OSLO,Graphs shown in OSLO,Coma (transversal aberration with respect to ray height),Field curvature,Similar to spherical aberration,Graphs shown in OSLO,