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1 32 11 Vol.32,No ACTAOPTICASINICA November,2012 (, ), 16 60, 200, -8D~ +10D (1D=1m -1 ), 120lp/mm (MTF) 0.2 5% LED,, λ/4, 99.5% ; ; ; TH744 A doi: /aos DesignofaNovelWideView-FieldAngleandAnti-Stray-LightFundusCamera YangJiaqiang ChengDewen WangQingfeng WangYongtian (SchoolofOptoelectronics,BeijingInstituteof Technology,Beijing100081,China) Abstract A novelportablefree-dilatedfunduscameras withlargefieldofview (FOV)isdesigned.Bytaking considerationofhumaneye saberrationandvergence,aswelasthesharingoftheeye-pieceobjectivelensbetween theiluminationsystemandtheimagingsystem,alenssystem with16configurationsissetupforoptimization.asa result,anfovof60 and2megapixelsresolutionhavebeenachieved.thecameracanbeadaptedtoeyesinwhich vergencerangesfrom -8Dto +10D;themodulationtransferfunction (MTF)valuesofalfieldsarehigherthan 0.2at120lp/mm withdistortionlessthan5%.inordertoeliminatethestraylightreflectedbycornea,ring-shaped LEDlightsourceisusedtoreplacetraditionalKohleriluminationsystem.Themethodnotonlyensuresilumination uniformityonfundus,butalsogreatlyimprovesiluminationeficiencyanddramaticalysimplifiesthesystem.a polarizingbeamspliter(pbs)andaquarter-waveretarderareusedtoreplacethetraditionalbeamspliterandthe blackdotboardforthefirsttimetoshieldthestraylight.99.5% ofthestraylightcausedbytheeye-pieceobjective lensesiseliminated. Keywords opticaldesign;funduscamera;anti-stray-lightdesign;polarizingbeamspliter;annularlightsource OCIScodes ; ,, [1],,, [2~4] : ; : : 973 (2011CB706701) ( ) : (1988 ), jiaqiang @163.com : (1982 ),,,, CAD/CAE 3D cdwlxk@bit.edu.cn( )

2 ,, 2), 1925, ; [5] 3) [6,7],, 2.1.2, 2~8 mm,,, CCD CCD 200, (MTF) 120lp/mm 0.2 [8], 60, 5%,, 90% [5] 2.2 (PBS) λ/4,,,, CODE V 16 ( 8 ), 1, 60 4,, 6 2 MTF 2, MTF 200 1/2inch(1inch=0.0254m) CCD, : 1), ; 120lp, MTF 0.2, MTF 1 Fig.1 Initialstructureopticalpathoftheimagingsystem

3 : 2 (a) (b) MTF Fig.2 MTFcurvesofimagingsystemfornormaleyesin (a)visibleand (b)near-infraredwavelength CODE V, MTF 3 3 Fig.3 Layoutoftheimagingsystemoffunduscamera 4-8D~+10D(1D=1m -1 ) MTF 120lp/mm MTF 0.2, 200 1/2inch CCD 5%, MTF lp/mm MTF 5 MTF 5 ±7, 120lp/mm,MTF MTF 6-8D~+10D, MTF 0.2, 0.5%, 120lp/mm MTF, CCD, -8D~+10D

4 4 (a)mtf (b) Fig.4 (a)mtfcurvesand (b)distortionoftheimagingsystem 5 (a)mtf (b) Fig.5 (a)mtfcurvesand (b)distortionoftheeye-pieceobjectivelens 6 (a) (b) 120 MTF Fig.6 MTFcurveswithdiferentdiopterΦin120lp/mmin (a)visibleand (b)near-infraredwavelength 2.3,

5 : 7, LED, ; LED [8] LED LED LED,,, Fig.7 Layoutoftheiluminationsystem Table1 Systemparametersofthedesignedexample Eyemodel Liou-Brennaneyemodel, Entrancepupildiameter 3mm View-fieldangle 60 Light-sourcediameter Inner8mm,outer12mm Ilumination-annulusdiameter Inner3mm,outer6mm 3.2 LightTools 100 W, , λ/4 8(a), 3 mm, 6 mm; λ/4 8(b) λ/4 20mm ; 8(c) 8(c),±4.47mm π [9] 30 (±15 ), P center, W/mm 2, [10] CODE V % P W/mm 2, P max W/mm 2 U [11] U =1- Pcenter-P85% P max 100%. (1) %

6 8 (a) ;(b) ;(c) Fig.8 Simulationofiluminationuniformityinfundus.(a)Iluminationannulusatthepupiloftheeye; (b)iluminationspotatfundus;(c)energydistributioncurveatfundus 3.3 LightTools, W, PBS 9 30, 100W, 4% 1%, PBS, PBS p 97%,s 100%, W W, W 3% PBS λ/4, 99.5% PBS ; 50%, 48.5% ,, PBS 92%, 2,,CCD W, 9 LightTools Fig.9 3DstructureoffunduscamerainLightTools 2, PBS PBS, 2 PBS PBS PBS Table2 Reflectedpowerofsurfaceswithand λ/4 0, PBS λ/4 withoutpbs WithPBS WithoutPBS Reflectionofthecornea/W PBS, Reflectionofthefundus/W Reflectionsoftheeye-piece, objectivelens/w LightTools,, 4 PBS, :, LED

7 : LED,, [J]. 2008,28(12):2245~2249 ;, PBS λ/4,,, LightTools [J]., 99.5% [J].Opt.Technol.,2000,26(2):139~141 ;, 60, -8D~+10D ,, [J].,2012,32(1): LingNing,ZhangYudong,RaoXuejunetal..Asmaladaptive opticalimagingsystemforcelsoflivinghumanretina[j].acta Optica Sinica,2004,24(9):1153~1158.,2004,24(9):1153~1158 4LiChao,JiangBaoguang,Xia Mingliangetal..Laserspeckle reductioninretinaimagingilumination[j].acta Optica Sinica,.,2008,28(12):2245~2249 5CuiGuihua.Controlofghostandscaterlightinretinalcamera. [J].,2000,26(2):139~141 6C.Riva,I.Ben-Sira.Two-pointfluorophotometerforthehuman ocularfundus[j].appl.opt.,1975,14(11):2691~2693 7J.Liang,D.R.Wiliams.Aberrationsandretinalimagequality ofthenormalhuman eye[j].j.opt.soc.am.a,1997, 14(11):2873~2883 1XiaoZexin.Opticssystem designofeyegroundtelevision[j]. 8Li Chun,Sun Qiang, Liu Yinget al..design of uniform Opt.Technol.,2005,31(2):170~172 iluminationsystemoffunduscameraanditsstraylightshield[j].. [J].,2005,31(2): ChineseJ.Opt.& Appl.Opt.,2010,3(4):363~ ~172,,. 2KongNingning,LiDayu,Xia Mingliangetal..Liquidcrystal [J].,2010,3(4):363~368 adaptiveopticssystemforretinalimagingoperatedonopen-loop 9JiJiarong. Advanced Optics Tutorial[M ].Beijing:Science anddouble-pulse mode[j].acta Optica Sinica,2012,32(1): Press, ~43. [M]. :, ~43. 10E. Dehoog,J. Schwiegerling. Fundus camera systems: a comparativeanalysis[j].appl.opt.,2009,48(2):221~228 11E.Dehoog,J.Schwiegerling.Optimalparametersforretinal iluminationandimaginginfunduscameras[j].appl.opt., 2008,47(36):6769~6777 :

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