Techniques to improve source modeling are presented: filament flux weighing, depositions on the arc envelope interior, and electrode degradation. Filament sources provide more light from the center in comparison to the ends. Additionally, the helix interior is hotter due to increased absorption, and thus the flux emission is greatest here. These effects for linear filaments are modeled in software with the ancillary use of camera images of lit appearance. The result is that the source luminance is more accurately modeled. This technique, called flux weighting, is described and software examples using reflectors are presented and compared to those that do not use flux weighting. Software models of arc sources that employ camera images of the arc provide accurate representations of the source radiance. However, these models do not include arc source aging. Aging effects include degradation of the electrodes and the depositions on the interior of the envelope. These phenomena lead to a decrease typically in the luminance from the source. Camera images of the lit and unlit appearance of arc sources are presented and their effect on the arc output is discussed. Additionally, software examples using reflectors are presented and compared to those that do not use these techniques.
This paper discusses the reverse engineering of filament-based light sources for computerized optical analysis purposes, especially problems raised by source tolerances. The H12 automotive headlamp bulb is used as a case study. Notes on reverse engineering sources consist of: a statement of the challenges involved, our source-modeling methodology, and useful values and procedures pertaining to simulated sources and optical ray-tracing software. A multi-model approach is outlined and consists of: gathering tolerance information from specification sheets, modeling for source tolerances with eight key models, and output comparisons between nominal and toleranced versions of the H12 source. Recommendations for including source tolerances in non-imaging illumination designs conclude.
KEYWORDS: Monte Carlo methods, Photography, Raster graphics, RGB color model, Diffraction, Modulation transfer functions, Distortion, Cameras, Imaging systems, Computer simulations
Advances in computer technology have dramatically increased raytrace speeds in optical engineering software. Increases in raytrace speed have, in turn, led to new methods for evaluating optical system performance. Designers traditionally evaluate imaging system performance with spot diagrams, MTF plots, ray aberration plots, and distortion plots. These tools are invaluable for two reasons: (1) they provide the information experienced designers need to make design decisions, and (2) they require only a coarse sampling of rays. However, these tools are an indirect representation of imaging system performance. The designer must `wait and see' how the lens performs in situ. With today's computers and optical engineering software, it is now possible to evaluate imaging system performance visually as well as numerically--prior to lens fabrication. This paper will discuss the benefits of visual characterization for various practical optical systems. Distortion, diffraction, imagery with 3D objects, and other optical phenomenon will be evaluated.
Various simulations of volume-based sources are explored, beginning with an overview of optical design software, the industry that utilizes it, and a procedural outline for source simulation. These simulations are explained from the simplest to most complex methodologies to date. Two basic approximations of the volume-emitter, (1) a tubular surface distribution and (2) a cylindrical volume distribution, that cannot model the asymmetry of the original emitting-volume are considered. Simulation methodologies that rely on mathematical tools are investigated. Using a CCD image of the emission and the inverse Abel transform, a 2D irradiance distribution is transformed into a 3D emitting volume. An algorithm developed to handle asymmetric volume-emitters is discussed, and the results of the simulated arc are compared to its original CCD image. In addition, the geometry of the arc source is modeled into a CAD (Computer Aided Design) program, and optical properties are assigned to its components in the optical/illumination design program. Using the most detailed emitter simulation, an assessment of the source geometry's influence on system output is made. The need for a detailed volume-emitter simulation is demonstrated through system output comparison between those utilizing the most complicated simulation and those using basic surface and volume approximations of the actual emitting-volume.
Software packages capable of simulating complex optical systems have the power to shorten the design process for non-imaging illumination, projection display, and other imaging illumination systems, Breault Research Organization's Advanced Systems Analysis Program (ASAP) and Robert McNeel and Associates' Rhinoceros computer aided design software, together, allow complicated optical systems to be simulated and analyzed. Through the use of Rhinoceros, an optical system can be accurately modeled in a 3D design environment. ASAP is then used to assign optical properties to the Rhinoceros CAD model. After the optical system has been characterized, it can be analyzed and optimized, by way of features specific to the ASAP optical analysis engine. Using this simulation technique, an HID arc source manufactured by Ushio America, Inc. is accurately represented. 2D CCD images are gathered for the source's emitting-volume across its spectral bandwidth. The images are processed within ASAP, via the inverse Abel command, to produce a 3D emitting-volume. This emitting-volume is combined with an accurate model of the source geometry and its optical properties, to finalize a functioning virtual source model. The characterized source is then joined with a simulated optical system for detailed performance analysis: namely, a projection display system.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.