Tracepro stary light

,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,1,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,100,杂散光课程,2024年9月10日,光源,格点光源,表面光源,档案光源,表面光源特性,格点光源,单位选择,照度,辐度,光线能量设定,每根光线能量,总能量,光照度,档案光源,单位选择,照度,辐度,n-th,Scale,flux,格点光源，档案光源的变动,I,格点光源，档案光源的变动,II,Surface,Source,Property,Generator,Example,DefineSpectrum,CoordinateSystem,EditSpectrumData,Add/Modify/Delete,Units,TracePro,canaccommodatephotometricunits(cd/m,2,orfootlambert)orradiometricunits(W/m,2,).,Data sheet from,Luxeon,Rebel,DefineRadiationPattern,Data sheet from,Luxeon,Rebel,CoordinateSystem,EditAngularDistribution,Add/Modify/Delete,Surface,Source,Property,Generator(,续,),Bitmap,Source,Bitmap,Source Step by Step,1,1,导入所需图片,2,点击,Conversion,Bitmap,Source Step by Step,2,设定取样图片特性,水平长宽，垂直高度,初始位置,方向特性,Bitmap,Source Step by Step,3,目标特性设置,目标位置,方向特性,几何外形,大小高低,Bitmap,Source Step by Step,4,取样设置,每像素取样光线数,总光线数,RGB,波长,Bitmap,Source Step by Step,5,保存设置,点击,Browse,选择保存路径,设定文件名,设定保存格式为,.txt,Bitmap,Source Step by Step,5,作为档案光源导入,TracePro,Bitmap,Source Step by Step,6,光线追迹后用,True,Color,Map,查看,Bitmap,Source,use,in,imagine system,Observer,光线追迹,Image,成像光学,?,Object,点对点成像,所有从物方的点在像方合适的位置成像点,物象共轭,这样是达到了非常接近，但是电脑受不了,But this is not a good approach!,我们需要简化问题,取样一些有特征的点,减少光线数目,仅考虑通过光学系统的光线,运用一些光学构造来简化,(,焦距, F/#, NA,etc.),如果可能的话使得表面有序化,为成像分析设定一些优化,feedback loop,1,2,3,4,成像光学,(,续,),为模型设定体材质和表面材质,让光线通过模型,让系统去判定光线怎么传播,?,忽略所有的光学构造,不做任何假设,建造,真正的,3D,模型,非成像光学,折射,Refract,反射,Reflect,吸收,Absorb,前向散射,Forward Scatter,后向散射,Backward Scatter,光线碰到物件表面时候会发生,5,种状况,而且每个面上都会, (not to mention volume effects),TracePro, keeps track of where all this flux is going and reports it!,非成像光学,(,续,),表面特性,: Scatter & BSDF,BSDF vs. Scattered Intensity,BSDF,是描述光散射的一种方法,.,其中有三种,BSDF,BRDF(Bidirectional Reflectance Distribution Function),BTDF(Bidirectional Transmittance Distribution Function),BDDF(Bidirectional Diffraction Distribution Function),Scattered Intensity,In the old days, people measured the scattering properties of a surface by measuring the scattered intensity (,w/sr,) normalized to the incident power (w). This differs from the BSDF by a factor of,cos,q,.,BSDF,The BSDF is defined as,where,dL,s,is the radiance scattered from an area,dA,s,on the sample,d,E,i,is the incident irradiance on the area,dA,s,r,i,is the incident direction,r,s,is the scattered direction.,To measure BSDF, one illuminates an area,dA,s, measures incident flux,i, scattered flux,s, and calculates the solid angle d,s,subtended by the measuring detector. One can then calculate,dL,dE, and thus BSDF.,In general, BSDF is a function of both the incident direction and the scattered direction (hence the name bidirectional) .,Scattered Intensity,Scattered Intensity is defined as,Notice that,this differs from the BSDF by a factor of,cos,because,dI,s,=d,s,/d,d,dS,d,n,dA,cos,dA,i = incident, 0 =,specular,In the plane of incidence, |,-,0,| =,sin,- sin,0,At normal incidence,0,=,0,and |,-,0,| =,sin,At normal incidence and small scattering angles, |,-,0,|,Harvey-Shack BSDF,Shift-Invariant BSDF Representation,ABg,BSDF Model,The,ABg,BSDF model is a modified inverse-power-law model. It has the form,where the,b,and,b,0,vectors are from the Harvey-Shack BSDF model. In this model, the beta vector is the projection of a unit vector in the,scattering,direction onto the tangent plane, and the,b,0,vector is a projection of the unit vector in the,specular,direction onto the tangent plane. A, B, and g are fitting parameters.,In the,ABg,model, A determines the height of the curve, B determines the point where the curve transitions from flat to sloped (on a log-log plot as shown above) and g determines the slope (on a log-log plot). The roll-off value is equal to A/B.,ABg,BSDF Model where A=0.0025, B=0.001, and g=1.8,A typical,ABg,model BSDF, graphed on a log-log scale,Typical,BSDFs,光滑面,(,拋光面,),g,值由,1.5,到,3.5,一般介於,2,到,3,B is small,1e-6,to,1e-10, depending on surface statistics,散射面,(,粗造面,),If g =,0, BSDF is perfect,Lambertian,. Many baffle coatings come close to this.,If not,Lambertian, typically B is large,0.1,to 1, and g is large,2, 3, 4, 5, 6,Energy conservation,BSDF Wizard,The BSDF Wizard is a standalone program to help fitting the,ABg,model to measured data.,After opening an ASTM-standard or Schmitt Measurement BSDF file, move the control points (black squares) with the mouse to fit the green curve to the measured data.,The,ABg,values for the fitted green curve are shown at the right and can be used to define the BRDF or BTDF in a surface property.,孔径衍射,孔径衍射,Any surface can be made a diffracting surface.,You may need to insert a dummy object for diffraction, as in this example.,When a ray intersects a diffracting surface, it is “bent” or deviated.,Importance sampling can be used with diffracting surfaces.,Example,运用分析工具,Analysis Mode,Ray sorting:,For ray display to see the paths of stray rays.,For irradiance maps to see irradiance distributions for,specular,vs,scattered rays.,For irradiance maps to see the paths where stray rays for hot spots.,Incident ray table,Ray history table,Ray sorting for display,光线能量选择,显示某一块区域的光线,入射光线表格,光线历史表格,Smart Simulation,阈值,Thresholds,光通量阈值,Flux thresho,l,d,光线交叉的界限,Intercept limits,光线分裂,Ray splitting,随机光线,Random rays,随机因子,Random seed,重点取样,Important sampling,分析模式,Simulation mode,Exit surface setting,Simulation file manager,阈值,Thresholds,光通量阈值,Flux threshold,光线交叉的界限,Intercept limits,Monte Carlo,光线追迹,为何使用,Monte Carlo,光线追迹,在,TracePro,中蒙地卡罗光线追迹法在模拟光由发射源开始采随机数分布，到达物体表面会产生反射 折射 散射等现象，均采随机数生成继续做光线追迹,光经由一表面散射后仍持续会碰上其他介质持续做追迹,以此方式描述模拟可以接近现实世界光的行为,蒙地卡罗光线追迹为一采随机数分布计算模拟之方法,蒙地卡罗光线追迹,A crude Monte Carlo calculation is the simplest form of a probability experiment,Perform an experiment N times, count the number of times n that the event occurs,An estimate of the probability is:,p,e,= n / N,We can never get an exact value of,p,e, but we can make the uncertainty in,p,e,arbitrarily small by increasing N.,The absolute uncertainty in,p,e,is:,The relative uncertainty in,p,e,is: (where p denotes the true probability),Hence, the accuracy of the result is inversely proportional to the square root of the number of trials,降低方差,利用一些降低方差的技巧可以使实验的次数降低而又趋近真实结果,分裂,(Splitting),重点取样,(importance sample),光线分裂,当光线碰到物件的表面的时候会分裂成好几条光线，其中有被吸收的，反射的，折射的，透射散射，反射散射,.,同样入射光线的能量也会分裂，其分布由相关特性决定。,光线分裂会在碰到的每个物件面上都会发生，上一个面发生后碰到下一个面后还会发生分裂。这就有点像树长出枝干，枝干又长出分枝干，最后长叶子。,在一定容忍度范围内使用重点取样可以提高效率,.,Ray splitting,Raytrace,Options,Options,Specular,rays,Random rays,Thresholds,Ray splitting,改变随机分裂数目？,改变阈值？,重点取样,重点取样是用来提高随机事件的抽样而不必通过显著提高事件发生的次数，比如增加光线数。,运用散射分布函数,Uses the scattering distribution function as a probability density to apportion a fraction of the scattered ray flux into a desired direction.,重点取样可以用在表面光源，散射材质表面，衍射，体散射物件,重点取样,(,表面光源,),重点取样,(,散射面,),Surface Example,Flux Threshold 0.00005,Simulation mode,Simulation mode,设定,exit,surface(s,),设定,Analysis Mode/Simulation Mode,资料收集,Simulation mode,设定,exit,surface(s,),设定,Analysis Mode/Simulation Mode,资料收集,Simulation file manager,Opened from the Tools menu,Select ray files saved during Simulation mode,raytrace,for viewing in the Irradiance Viewer,Analysis options,杂散光种类,Straight-Shots,在,Cassegrain,型的系统中，当中心遮拦太大或者望远镜的镜筒太短时，会出现,Straight,Shot.,视场外的光线也可以进入到望远镜，穿过第二个反射镜，通过主反射镜 的小孔，直接照射到焦平面上成为漫射光。如果太阳光线允许进入望远镜，则这类型的散射光式一种灾难,。,鬼像,Ghost Images,鬼像之所以这么称是因为它们不在焦点上，或者看起来像亮光源的光线的像的幽灵。鬼像是由透镜表面的反射所引起的。要产生鬼像，光线必须从透镜表面反射偶数次。所以会有二次反射鬼像，四次反射鬼像等。,单次散射光,Singly-Scattered light,当光源，如太阳，直接 照射到系统中的光学组件时候，会出现一次 散射的光。有一部分光的散射的方向会使它能到达像面。我们说这部分的光散射到视场里面了。一但光线散射到视场里面它就会成为漫射光，如果不产生渐晕，则没有办法消除它。因此挡光板的主要目的是光线使不能直接散射到光学组件上 。,多次散射光,Multi-Scattered Light,即使 漫反射光源不直接照射到光学组件上，但是首先通过挡光板表面进行散射，然后照射到光学组件上，它们也可以间接的产生漫反射光线。这种漫反射光线一般比直接散射的情况小，但仍然要重点考虑。,边缘衍射,Edge Diffraction,当孔径的直径和波长的比值相对较小的时候,(10,或更小,),时，视场外的光源通过孔径的直径和波长的比值相对较小的时候，视场外的光源通过孔径光阑的边缘衍射就会成为很厉害的散射光源,.,红外系统中的自发辐射,Self-Emission of Infrared Systems,热红外或热成像系统也会有散射光，它是由仪器本身的热辐射引起的。这些系统用来探测叠加在一个大背景上的小信号。在室温下黑体发射曲线的峰值大约是,10um,。因此这个波长的,World Glow,和这个辉光的小变化表明温度或者辐射率不同。在红外情景中，热像系统常常通过减去背景来提高对比度，当背景不均匀时候，就会产生漫射光,。,Combinations Of Above,自动重点取样,在大多数杂散光分析中，重点取样是必不可少的,定义重点的对象是关键步骤,TracePro,允许,手动设定或自动设定,在光学成像系统中自动重点取样,Auto importance sampling (AIS),显得方便易用,光学系统中的重点取样,你应该给每个光学表面定义重点取样，其目标应该为其像平面。实像面,(L3 and L4 above),的方向选择指向，虚像面,(L1 and L2 above).,的方向选择背向。自动重点取样就是这样做的。,借助两条重要光线,I,主光线,(Chief Ray),：,通过入瞳中心的光线,边缘光线,(Marginal),：,通过入瞳边缘的光线,出瞳,入瞳,孔阑,Optical Axis,Object,Image,Chief Ray,Marginal Ray,借助两条重要光线,II,像的位置由边缘光线来判定,像高由主光线来判定,自动重点取样,Double,Gauss,Step,by,Step,1,描述,打开,DBLGAUSS.OML (lens data from OSLO),应用特性,/,描述,/,物面编号,TracePro,将会按编号来追迹光线，像面必须完全吸收光线,Step by,Step 2 - Verify Prescription,检查系统树，确定物面编号顺序正确,确定胶合面处不重合,.,Step by,Step 3 - Trace Marginal Ray,按照经验判定边缘光线的初始位置并追迹测试,Y,坐标将会被设定为后续光线追迹光束的大小,Note,：,记住相关参数，后续中会使用到,Step by,Step 4 - Trace Chief Ray,按照经验判定主光线的初始位置并追迹测试,在这个例子中假定光阑的位置是在,Z=20.4,的地方,主光线会过光阑中心而成像视场边缘,Step by,Step 5 - Setup AIS from Dialog,设定中心光线，边缘光线，外部光线,点选,OK,，,TracePro,将会作下一步处理。,Step by,Step 6 - Verify AIS Target Definitions,验证是否成功设定,AIS,：,Message/Macro,Window,打开系统树,设定属性中进一步查看,Lensdemo,镜头 光源,成像面,蓝色为,Ghost,光线,Step,by,Step,1,打开,Lensdemo.oml,查看轮廓图及着色图,确定各物件见没有重合,Step,by,Step,2,设定光源,选取格点光源,格点图形：十字行,Y Points& X Points,Step,by,Step,3,光线追击选项,阈值,光线交叉界限,仿真与输出设定,Step,by,Step,4,光线追击,分析,/,光线筛选,选择表面,Step,by,Step,5,光线筛选,单次散射,多次散射,Step,by,Step,6,直接在光照度图上选择,Hot,Spot,来分析光线,Step,by,Step,7,通过入射光线表格分析光线,Step,by,Step,8,通过光线历史表格分析光线,Step,by,Step,9,光通量报告,可观察每个对象的表面所造成的损失，并分析不同状况之损失,Step,by,Step,10,光线路径分,类,可将光线分类并找出偶次反射之,Ghost,光线其能量及路径,让透镜的反射低,。,镜筒使用高吸收低反射的表面。,小结 改善,Ghost,方法,7m,2m,杂光分析,(,续,),非近轴情况下,杂光分析,(,续,),非近轴情况下,杂光分析,(,续,),非近轴情况下,杂光分析,(,续,),非近轴情况下,杂光分析,(,续,),非近轴情况下,Cassegrain Telescope,光路图,In,TracePro,The,Forststernwarte,耶拿,50cm,卡塞格林望远镜,.,Cassegrain Telescope,Use a Rectangular ray grid with y points = 1000, x points = 1. On the Beam tab of the Grid Raytrace dialog box, set Half angle R = 0.25. Set the Flux Threshold high (say 0.5) to suppress tracing of ghost rays. You should get a picture that looks something like the figure,above,.,Secondary Conical Baffle,Make a conical baffle around the secondary by inserting a tube. Use the,Insert|Tube,dialog and make a conical tube. This will necessarily vignette the beam slightly, either at the obscuration (light from the object) or at the outside of the stop (light from the primary) or both.,Apply black paint and re-trace the rays.,Primary Cylindrical Baffle,Make a tube in the center of the primary to block stray light from going through the hole in the primary. Make it so that it does not interfere with image-forming light, with a little space for tolerance. Apply black paint.,Apply black paint and re-trace the rays.,Main Baffle Tube,Make a tube around the telescope, large enough in diameter to leave room for baffle vanes, long enough for good stray light suppression, or as long as you think is permissible by other design considerations. The longer the tube, the better the stray light suppression. Try a tube with base at z=-100, length=400, radius=110.,Apply black paint and re-trace the rays.,Add Vanes,Add some baffles, with I.D. large enough that they dont vignette. In the figure below the aperture is 85mm and they are spaced 40mm apart.,Hint: make one baffle vane, apply names and properties, then do,Edit_ObjectMove_Copy,. The names and properties will be copied along with the geometry.,Complete the Telescope,Importance Sampling,Define importance sampling for the primary and secondary mirrors.,Determine the optimal location of the importance sampling target for the primary:,Set the half angle of the beam to zero and trace a y fan of rays using the,Grid,Raytrace,dialog box.,Exclude the secondary mirror and support struts from the ray-trace using the,Apply Properties,dialog box,Raytrace,Flag,tab.,Using the,Grid,Raytrace,dialog box,Beam Setup,tab, select,Beam orientation method: Euler angles (degrees),. Enter (-0.25, 0, 0) for the,Direction angles,.,The point where these rays come to a focus is the edge of the importance sampling target. Measure this point with the mouse: (0, 1.75, -105). Place the importance sampling target at (0, 0, -105). The rays do not come to a sharp focus because of the aberrations of the primary mirror, so make the target a little oversize, or about 2. The ray-trace is shown below.,利用以上,TracePro,的各項功能，即可很快速的分析出雜散光所需分析的,Ghost,，,Straight shot,，,single scatter,，,muti,-scatter,的分析項目。,结论,参考文献,General Stray Light,Proc. SPIE vol. 107,Stray-Light Problems in Optical Systems,(1977).,Proc. SPIE vol. 257,Radiation Scattering in Optical Systems,(1980).,Proc. SPIE vol. 384,Generation, Measurement, and Control of Stray Radiation III,(1983).,Proc. SPIE vol. 511,Stray Radiation IV,(1984).,Proc. SPIE vol. 675,Stray Radiation V,(1986).,Proc. SPIE vol. 967,Stray Light and Contamination in Optical Systems,(1988).,Proc. SPIE vol. 1331,Stray Radiation in Optical Systems,(1990).,Proc. SPIE vol. 1753,Stray Radiation in Optical Systems II,(1992).,Proc. SPIE vol. 2260,Stray Radiation in Optical Systems III,(1994).,Radiometry,The Infrared & Electro-Optical Systems Handbook, Volume 1: Sources of Radiation, Chapter 1, Radiation Theory, W.L. Wolfe, ERIM/SPIE Press, Bellingham, WA (1993).,Selected Papers on Radiometry, SPIE Milestone Series Vol. MS 14, SPIE Press (1990).,参考文献,General Scattering,M. Nieto-,Vesperinas,Scattering and Diffraction in Physical Optics, Wiley, New York (1991).,J.C. Stover,Optical Scattering: Measurement and Analysis, McGraw-Hill, New York (1990). Second Edition SPIE Press Bellingham, WA (1995).,Proc. SPIE vol. 1165,Scatter from Optical Components,(1989).,Proc. SPIE vol. 1753,Optical Scatter: Applications, Measurement, and Theory,(1991).,Proc. SPIE vol. 1995,Optical Scatter: Applications, Measurement, and Theory II,(1993).,Rough Surface Scattering,P. Beckmann and A.,Spizzichino,The Scattering of Electromagnetic Waves from Rough Surfaces,Pergamon, Oxford (1963).,Proc. SPIE vol. 3141,Scattering and Surface Roughness,(1997).,Proc. SPIE vol. 3246,Scattering and Surface Roughness II,(1998).,参考文献,Contamination in Optical Systems,R.P. Young,The Degradation of Mirror Bidirectional Reflectance Distribution Function (BRDF) by Particulate Contamination, Arnold Eng. Dev.,Ctr, Technical Report No. AEDC-TR-76-177 (1976).,Proc. SPIE vol. 2261,Optical System Contamination: Effects, Measurements, and Control IV,(1994).,Proc. SPIE vol. 4774,Optical System Contamination: Effects, Measurements, and Control IV,(2002).,Proc. SPIE vol. 3427,Optical Systems Contamination and Degradation,(1998).,Optical Engineering Vol. 31, No. 8 (August 1992).,Scattering from Particles,C.F.,Bohren,and D.R. Huffman,Absorption and Scattering of Light by Small Particles, Wiley, New York (1983).,H.C. van de,Hulst,Light Scattering by Small Particles, Dover, New York (1981).,Monte Carlo Techniques,J.M.,Hammersly,and D.C.,Handscomb,Monte Carlo Methods, Methuen and Co. (1965).,M.H.,Kalos,and P.A. Whitlock,Monte Carlo Methods Volume I: Basics, John Wiley & Sons, New York (1986).,B.J.T. Morgan.,Elements of Simulation, Chapman and Hall, London (1984).,