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1、CODE V Introductory Seminar:Day 1“Optics 101”Digital Camera Design Study,3280 East Foothill BoulevardPasadena,California 91107 USA(626)795-9101 Fax(626)795-0184e-mail:World Wide Web:http:/,Section 1Optics 101(on a Budget),Goals and“Not Goals”,Goals:Brief overview of basic imaging conceptsIntroduce s
2、ome lingo of lens designersProvide resources for quick reference or further studyNot Goals:Derivation of equationsExplain all there is to know about optical designExplain how CODE V works,Sign Conventions,Distances:positive to rightCurvatures:positive if center of curvature lies to right of vertexAn
3、gles:positive measured counterclockwiseHeights:positive above the axis,Light from Physics 102,Light travels in straight lines(homogeneous media)Snells Law:n sin q=n sin qParaxial approximation:Small angles:sin q tan q q;and cos q 1Optical surfaces represented by tangent plane at vertexignore sag in
4、computing ray heightthickness is always center thicknessPower of a spherical refracting surface:1/f=f=(n-n)*cUseful for tracing rays quickly and developing aberration theory,Cardinal Points,6 important points along the axis of an optical system2 focal points(front and back):input light parallel to t
5、he axis crosses the axis at focal points F and F2 principal points(primary and secondary):extend lines along input ray and exiting focal ray;where they intersect defines principal“planes”which intersect the axis at the principal points2 nodal points(first and second):rays aimed at the first appear t
6、o emerge from the second at the same angle.“first”points defined by parallel rays entering from the right;“second”points defined by parallel rays entering from the left,Cardinal Points Illustrated,Effective Focal Length(EFL)=distance from principal point to focal point,Aperture Stop,Aperture stop:de
7、termines how much light enters the system2 special raysMarginal ray:from on-axis object point through the edge of the stopChief ray:from maximum extent of object through the center of the stop,Pupils and the Aperture Stop,PupilsEntrance pupil:image of aperture stop viewed from object spaceExit pupil
8、:image of aperture stop viewed from image space,Specifying the Aperture,EPD=Entrance pupil diameterNAO=Numerical aperture in object space(finite object)NA=Numerical aperture in image spacef/#=EFL/EPDNote:some NAO systems will not fill a physical aperture stop(common in photonics systems.)You still m
9、ust specify a stop surface.,Specifying the Pupil,Infinite object:/#=EFL/EPDNAO not valid,Same Triplet,Different f/#s,Field Definition,Field definition describes how much of the object you image.Specify object angle,object height(finite object),image height.,Aberrations,Perfect imaging:point on objec
10、t maps to point on the image,for all points on object and all rays through the aperture stop.Aberrations:deviations from this“1st order”aberrations:Defocus:wrong image locationTilt:wrong image orientation,Third-Order Aberrations,Spherical:focal length f varies with aperture height only aberration on
11、-axisComa:magnification varies with aperturerays through edge of aperture hit image at different height than rays through center of apertureAstigmatism:sagittal(x-axis)and tangential(y-axis)ray fans have different foci.Field curvature:planar object forms curved imagedepends on index of lenses and th
12、eir powerDistortion:image magnification depends on image heightimage is misshapen,but focus isnt changed,Ray Aberration Curves,Vertical axis:distance on image plane between chief ray and current rayHorizontal axis:relative height of ray in aperture stop(or entrance/exit pupil),Ray Aberration Curves(
13、cont.),Chromatic Aberration,Index is function of wavelength:n=n(l)Abbe number describes the dispersion:Vd=(nd 1)/(nF nc)ld=587.6 nm(yellow)lF=486.1 nm(blue)lc=656.3 nm(red)Small Vd(Vd 20-50):very dispersive,colors spread a lotLarge Vd(Vd 55-90):less dispersion,Rays and Waves,Rays are normal to wavef
14、rontWaves diffract at apertures and can interfereRays can image perfectly;waves cant due to diffraction at aperturesA point images to Airy disk Diffraction-limited spot size(diameter)=2.44 l f/#(microns),Modulation Transfer Function(MTF),Start with black and white bars(or sinusoid)with specified fre
15、quency.Frequency in“lines/mm”,where“lines”=“line pairs”(1 black line+1 white line)=cycleModulation=contrast Imax=maximum intensityImin=minimum intensityfor object,contrast=1(pure black and white),MTF,MTF(cont.),Image is not perfect;contrast drops due to:AberrationDiffractionVignettingVaries with:fie
16、ld point considered orientation of target(radial or tangential),Gaussian Beams,w0 is 1/e2 spot radius at waistw(z)is 1/e2 spot radius at distance z from the waistBeam wavefront is planar at waistq is laser divergence angle=l/pw0,References for Optics Library,Classics W.Smith Modern Optical Engineeri
17、ngW.Smith Modern Lens DesignD.MalacaraOptical Shop TestingImportant components Rudolf KingslakeVol.1-5 Applied Optics andOptical EngineeringR.Shannon and J.WyantVol.6-10 Applied Optics and Optical EngineeringR.KingslakeOptical Design MethodsW.WelfordSymmetrical Optical SystemsU.S.GovernmentMil.Handbook 141,
