Tools for evaluation of candidate stereoscopic camera systems, including subjective impression are invaluable during the development of the system architecture. Ray tracing has long been used to predict the performance of optical elements used in camera systems. Stray light ray tracing analysis software utilizing a Monte Carlo method for generating random rays provides ray-intercept maps for two stereoscopic camera image planes that are used to build a random dot stereogram (RDS). The visual fusion of the RDS produced by random rays traced through a model of the candidate system provides an impression of the system quality. The impact of system parameters as well as imperfections in the optical design can thus be visualized and even quantified by the observer's ability to separate objects modeled at different distances from the stereoscopic camera(s). This paper describes the technique for generating an RDS using Lambda Research Corporation's TracePro software and provides examples of system performance with and without the introduction of optical imperfections.
Evaluation of infrared sensor performance begins with integration on an optical test station and initial acquisition of a source target image. Preliminary performance evaluation includes sensor radiant response, image performance, and sensor alignment. Integration and preliminary performance evaluation may be expedited by the use of an innovative target consisting of a cold background surrounding a hot extended source with a thin, cold wire obscuration. This paper describes an appropriate target geometry and provides a nomogram that allows estimation of sensor focal error based on an observed ratio of target image response between two detector elements.
The determination of the radiant power distribution at the focal plane is necessary for the numerical prediction of sensor radiometric performance. In a diffraction limited system with a circular pupil and central obscuration, the energy distribution can be calculated by numerical integration of the appropriate Bessel function(s). However, not all optical systems are that simple. The determination of the energy distribution for non-diffraction limited systems and systems having arbitrary pupil shapes is of practical importance but requires a more complicated analysis. The paper provides, in a 'cookbook' fashion, the algorithms necessary for the prediction of the focal plane power distribution in diffraction and non-diffraction limited optical systems with arbitrarily shaped pupils. The sensor pupil function, comprised of amplitude and phase, may be defined by the optical design or may be obtained by interferometric measurements performed on an existing system. The pupil function, expressed in complex notation, is processed through a two-dimensional fast Fourier transform, interpolated and scaled to provide the focal plane energy distribution. In addition to an algebraic description of the necessary algorithms, the paper includes code written in the C- language and numerical examples suitable for validation.
The U.S. Army Strategic Defense Command facility for the characterization of advanced low- background mosaics (CALM) is operated by Rockwell International Corporation. The facility supports a cryogenic test chamber with controlled background (flood) and target sources. The test chamber allows the measurement of focal plane array response to a moving point image in the presence of a radiant background that may be controlled over a range from less than 109 to over 1014 photons/second-square centimeter. An ancillary data acquisition system is capable of performing a 15-bit analog-to-digital conversion of focal plane array output data and storing processed digital data at 2 megabytes per second. This paper describes the facility and its use in the evaluation of a solid state photomultiplier (SSPM) focal plane array. The SSPM is a back illuminated, impurity band conduction device capable of detecting individual photons over infrared wavelengths extending from 1 to 28 micrometers. A description of the test configuration, test conduct, and data analysis are presented along with results of the SSPM evaluation.