Asap advanced stray light tutorial optical software. Nov 10, 2015 optimum baffle parameters to shield the direct rays of stray light are arrived at for a cassegrain telescope using the iterative method. Innovative software simulation techniques to design. According to the star that should be detected,the point source transmittancepstof the telescope was calculated and the maximum value beyond 30 were given. The stray light properties of the offaxis threemirror telescope was analyzed and the basic design principles of the light shade and baffle vanes were presented,then the design of them was discussed. The objects of interest can lie anywhere in the fov. The aim of this study is determination of the stray light performance of the ino 340 telescope system and. In the following image, we see that this focuser baffle has eliminated roughly 23rds of the stray light in a linear sense, getting rid of almost 90% of the stray light in a solid angle sense. The stray light short course is an intensive 3day instruction on the language. Simulation of polarization effects including birefringence. The program cbers china brasil earth resources satellite is a partnership between.
Black coatings to reduce stray light tutorial bernie outram opti 521optomechanical engineering, fall 2009 introduction this report is a tutorial on the use of black coatings to reduce stray light. Integral optical monitoring camera straylight design. Optimum baffle parameters to shield the direct rays of stray light are arrived at for a cassegrain telescope using the iterative method. Conceptual design of a stray light facility for earth. The design of vane structure on baffle surfaces is analyzed using the apartpade stray light software, and the asap optical analysis and stray light software. It is one of the most important factors that influence the highaccuracy photometry of optical astronomical telescopes, which would reduce the signal to noise ratio of astronomical objects.
Selfemission of infrared and longer wavelength systems. This stray light reduces image quality of the telescope system. Baffle design and stray light analysis of the offaxis three. The method finds the exact solution for baffle parameters of a modified ritcheychretien telescope by iteratively solving the analytical relations using the actual ray coordinates of the telescope computed with the aid of optical design software. The rejection of the baffle must be of the order of 10 for field angles above 20 degrees while the allocated mass is 19 kilograms. Id like to follow mitch alsups suggestion to baffle direct stray light at the focuser, but i dont know how to choose the id of the baffle. As a practical course on the theory and calculations involved in stray light analysis, no software programs are used during the class. The baffle is offered in white or black with a wide flange.
Second order, or twoscatter, stray light paths are found by connecting objects on the list of. Stray light will not correct itself and will get worse over time. I looked at mel bartels baffle calculator and it suggested essentially no baffle given the size of my. In the third part, by analyzing stray light, a suitable baffle is designed for it. Where stray light software departs from cad is in the specification of the specular and scatter properties of the. The baffle designed for the optical system is a tube with two baffles combined with each other fig. I need to install a light baffle to 100% prevent light from coming in while allowing air to freely flow into the cab. The position of the bevels on the vane varies with the location of the vanes in the system.
And a compact one with high performance is designed. Results show that stray lights can be completely eliminated at angles greater than 2. Multiple scatter stray light occurs when stray light sources indirectly illuminate the optics. Stray light analysis, baffle, and optical design of a highresolution. Design and analysis of optimum baffle for a cassegrain telescope. In a lowcost consumer camera, stray light may be only a minor annoyance, but in a spacebased telescope, it can result in the loss of data worth millions of dollars. Baffle design and stray light analysis of the offaxis. Tracepro can simulate many aspects of optical system performance, including. In the next step, stray light is analyzed and a baffle with internal vanes is designed. The program cbers china brasil earth resources satellite is a partnership between brazil and china in the space area. Design and analysis of optimum baffle for a cassegrain.
Stray light has a damaging effect on the contrast and image quality in optical system. Mastering stray light analysis short course photon. The main source for stray light is the radiations coming from the sun, the earth and the moon and care must be taken to avoid swamping starlight with these sources of stray light. This section will introduce the main sources of stray light common to imaging systems. The steps or groves of a baffle absorb stray light to reduce glare and minimize ceiling brightness. Osa iterative method of baffle design for modified. These paths cause stray light indirectly, by first scattering from the baffle surfaces and then illuminating the optics. Stray light calculation methods with optical ray trace software bro. Stray light control in newtonian telescopes optical theory. Minimizing stray light in everyday optical systems.
Next, a program must be written to calculate the position of star on the. So if you do a lot of work in the uv, checking your spectrophotometers stray light is a necessity. Instrumental background jwst integrated science instrument module isim scott o. This article demonstrates stray light analysis techniques using the filter string functionality in nonsequential mode, as well as supporting features. If these baffles closely match the desired cone of incoming light, and are spaced properly, then most of the stray light coming from other directions will hit a baffle instead of finding its way to the eyepiece. The design can keeps the stray lights out of the system or been greatly absorbed on the condition of low absorption rate of the baffle. These are made to reduce the amount of stray light in the edges. Stray light analysis and control spie press pm229 eric. In the infrared optical system,due to the special infrared imaging system, the stray can have the very tremendous influence to the image formation,this article utilizes the solidworks 3d design software design, and use the extinction thread zemax optical analysis software on the extinction of a thread, the infrared lenses for analysis, through theoretical and. This light will often set a working limit on the dynamic range of the system. Stray light fundamentals in order to properly and effectively execute a stray light design, the sources and sensitivities of stray light must be well understood. Baffle design and analysis of straylight in multispectral camera of.
It is difficult to do optical and mechanical design concurrently, so the information required to perform a complete stray light analysis is rarely available early in the design cycle. To reduce these effects mechanical structures are needed to control stray light. Minimizing stray light in everyday optical systems features. Stray light analysis is an important validation step for both optical and mechanical assemblies. Students follow the apex workflow procedure to design and analyze a variety of illumination and imaging systems. The light may be from the intended source, but follow paths other than intended, or it may be from a source other than the intended source. In traditional way, stray light can be effectively suppressed with a long baffle, which is not suitable for microsatellites with limited space. Stray light control in newtonian telescopes optical. Im looking for a better understanding of the design criteria for a focuser baffle. The only place light is coming in is via the passive air intake hole at the bottom of the cab. Fov ufov definition the fov is defined by the science objectives of integral.
During navigation by star sensor, the image quality may be unexpectedly reduced by stray light sources. The baffle is offered in white or black with a wide flange to presents a smaller aperture at the ceiling line. When you need to analyze baffles for the suppression of stray light due to scattering, diffraction, ghost images, and self emission, tracepro is an invaluable tool. Skeltonc anasa goddard space flight center, 8800 greenbelt rd. Further, we have proposed here a design procedure that improves the performance of an optimum baffle arrived at in view of finite reflective nature of the practical blackened baffle structure. To limit this stray light, it is proposed to put the payload in a black box as large as possible. Baffle turbulence design and test about the stray light control equipments. Simulation of spectrometers and other multispectral systems. The goal of this work is the development of an optical baffle in order to reduce the disturbing light from the sun and the analysis of stray light in the optical system of the camera. These incoherent and discrete lights do not follow the normal optical path of the imaging system 25,26,27,28,29,30.
In the infrared optical system,due to the special infrared imaging system, the stray can have the very tremendous influence to the image formation,this article utilizes the solidworks 3d design software design, and use the extinction thread zemax optical analysis software on the extinction of a thread, the infrared lenses for analysis, through theoretical and practical study. Stray light results in image blur and the contrast reduction of the camera. Thus a basic goal of baffle design is to keep light from shining on the optics. The diffuse black painted straight vane baffle design was used as the baseline design to compare results to the other eight designs. The depth and angle of the vanes are variables that are evaluated for both a centrally obscured system and an unobscured. Tracepro, a stray light simulation software from lambda research corporation, was used to simulate and compare each of the nine baffle systems for stray light rejection. Stray light modeling of the james webb space telescope jwst integrated science instrument module isim scott o.
Hi instrument optical design university of birmingham. Zooming in at the eyepiece area, we can see that stray light from above and below the stray light shield can only arrive outside of the fully illuminated filed of view. The rear one rejects or attenuates the remaining stray light reflected into optical system from the front baffle walls. Stray light analysis and baffle design of remote sensing. Optical system design of star sensor and stray light. What is stray light and how to test for it fireflysci. Mastering stray light analysis short course photon engineering.
Does anyone know the design of an external baffle for a lens for. Stray light analysis and baffle design of remote sensing camera for microsatellite november 2009 proceedings of spie the international society for optical engineering. Thermal imaging analysis technology software by lambda. How to reduce stray light in optomechanical systems. Multiplescattered light even when stray light sources do not illuminate the optics directly, they can still cause. Photon engineerings mastering stray light analysis short course is an intensive 3day instruction on the language, science, theory, techniques, and calculations involved in all aspects of stray light. In cassegrain telescopes image plane is located behind the primary mirror so stray light directly reaches the image plane. Verification program has been set up to demonstrate experimentally. Stray light is light in an optical system, which was not intended in the design. Optical system design of star sensor and stray light analysis.
The requirements are very stringent from the optical point of view as well as from the mechanical point of view. A rough, very flat black surface inside the tube walls will also help to soak up stray light. Very often when optical engineers hear stray light or see a requirement for some. For its development, it is necessary to control the stray light inside of the optical system, so that the degradation of the image quality can not occur. Stray light is defined as unwanted light in an optical system, a familiar concept for anyone who has taken a photograph with the sun in or near their cameras field of view. Thus, the stray light shield prevents stray light from washing out the image formed by the optics. Next, stray lights from offaxis sources like the sun, are analyzed. At this time there is enough information to make design changes that will reduce the stray. As we shall see later, the ultimate stray light baffle is a complete tube. Stray light is reduced by either moving the object or surface so it is no longer seen from the detector or directly illuminated, or by inserting a baffle that blocks the detectors view of the object or blocks illumination of the object. Analysis of stray light due to scattering, aperture diffraction, and ghost images. I am designing a baffle for stray light suppression for a lens which is going to used in a small imaging payload.
You do not need to be very experienced in stray light suppression to design basic features into the system, or to consider alternative designs that may signi. One of the most critical parts in the design of the stray light facility is to get rid of all internal stray light coming from reflection of the wall of the chamber or retro reflection from the tested item. Stray light is the unwanted light reaching the detector and reducing the image quality. Unlike lens design software that typically describes systems with, say, fewer than 100 surfaces, stray light analysis software may need to describe hundreds of thousands of surfaces literally modeling each nut and bolt. Asap advanced stray light tutorial this tutorial provides an introduction to using the apex optical design and analysis program, with handson exercises, demonstrations, and lectures. Optical and mechanical design of a straylight rejection. Vane structure is used to block direct propagation paths from the baffle walls to other objects in the system.
The level of stray light due to the dispersed radiation inside a monochromator or spectrograph is affected by the design of the instrument, its baffles and interior finish. So if you havent checked the stray light in your machine, now is the time to do so. I looked at mel bartels baffle calculator and it suggested essentially no baffle given the. This article is accompanied by a sample file available for download. The front baffle is a shield against direct sunlight. For example, the baffle parameters in the iranian national observatory ino340 telescope are calculated. An optical system that is designed to produce an image of an object or scene is limited by three main aspects. So, it is better than the baffle placed in region a but not. Comparison of baffle and vanes in open truss telescope. Stray light, scatter, optical analysis software, ray trace software.
Its presence may be caused by a wide variety of design and manufacturing factors. Opticaldesign software also extends to the design and analysis of nonimaging optics such as illumination systems, as well as to straylight analysis. In the front section of a baffle system the bevel should be on the object side of vanes, the side that will receive direct radiation from the offaxis sources. The level of stray light due to the dispersed radiation inside a monochromator or spectrograph is affected by the design of. Optimum baffle design of star sensor, proceedings of spie. The crisp lines and classic look of the baffle have made it the most popular of all recessed trims.
Stray light becomes more of an issue as you approach the uv range 190300 nm. Further, we have proposed here a design procedure that improves the performance of an optimum baffle arrived at in view of finite reflective nature of the practical blackenedbaffle structure. The baffle system so designed not only blocks the direct rays of stray light reaching the image. Innovative software simulation techniques to design specular. Microsoft powerpoint stray light presentation july 2017. Optical design software also extends to the design and analysis of nonimaging optics such as illumination systems, as well as to stray light analysis. After designing mechanical structures, it is necessary to detect effect of the structures in stray light of the system. Although stray light can never be completely eliminated, but it can be reduced to a level which it is negligible for most pointing directions. Optical and mechanical design of a straylight rejection baffle for corot j.
It has the advantage on a onestage baffle that the total straylight is attenuated in two different optimised elements. We will show you the evidences of calculation, and gave you the basis of the design. However, the awareness of ubiquitous stray light mechanisms and physical limitations, as well as good stray light control practices, can go a long way in. Founded in 1992, lambda research corporation offers stray light analysis, optical system design and analysis, optical testing, process. To reach the stringent straylight attenuation requirements, the omc is equipped with an optical baffle. The stray light properties of the offaxis threemirror telescope was analyzed and the basic design principles of the light shade and baffle vanes were presented, then the design of them was. Stray light modeling of the james webb space telescope jwst. To maintain image excellence from an optical system, stray light must be detected and eliminated. Stray light analysis, baffle, and optical design of a high. So, it need an external baffle to avoid the stray light. Baffle design and evaluation of the effect of different. Baffle design and analysis of straylight in multispectral. Vane structure design tradeoff and performance analysis. Minimizing stray light in everyday optical systems features aug.