Bauer Associates (United States)

The display is a key element in the softcopy image chain. If the display is not optimized, information is lost. Studies seeking to assess the effects of bandwidth compression and image enhancement will reach false conclusions unless the display system is optimized. Although standards exist for the display of text and symbology, no such standards exist for continuous tone imagery. To help remedy this situation, a series of studies were conducted to help define guidelines for the effective display of continuous tone imagery, with emphasis on surveillance and reconnaissance imagery. Imagery of various types (visible, IR, multispectral, SAR) was displayed on cathode ray tube (CRT) and active matrix liquid crystal displays (AMLCD) that varied in luminance and spatial resolution performance. Over a series of eight studies, trained imagery analysts provided National Imagery Interpretability Ratings (NIIRS) and Briggs target ratings (a measure of minimum discriminable target size as a function of contrast) to assess the impact of display variations. From these studies, recommendations were derived for display pixel density, contrast modulation, and luminance measures including dynamic rang, ambient light level, color temperature, and perceptual linearization. This paper defines the display performance measures used, performance measurement procedures, and presents guidelines for display optimization. Results of studies supporting the guidelines are summarized. Use of the guidelines is recommended in any study involving softcopy display of continuous tone imagery.

The Space Interferometer Mission (SIM) will achieve important science objectives of NASA's Origins program by performing astrometric measurements of targets within and beyond our galaxy with a precision of the order of a few microarcseconds. This accuracy can only be attained by carefully balancing sources of astrometric error arising from the systematic accuracy of the interferometer, thermal distortions, vibration caused by spacecraft systems, and errors in knowledge of the spacecraft's altitude and velocity. A rigorous systems engineering approach must be applied to the conduct of trades between these different sources of error and the TRW SIM Study Team has developed a mathematical model of the performance of SIM to support these trades. This paper shows how the model is constructed using simple analytical relationships and then employed to determine the dependence of system performance on a wide range of configuration parameters, such as baseline length, aperture size, and attitude knowledge. These studies indicate where subsystem performance requirements are critical and where requirements may be relaxed with little degradation of overall astrometric accuracy.

The High Resolution Mirror Assembly (HRMA) of the Advanced X-ray Astrophysics Facility (Imaging) (AXAF-I) consists of four nested paraboloids and four nested hyperboloids, all of meter-class size, and all of which are to be assembled and aligned in a special 15 meter tower at Eastman Kodak Company in Rochester, NY. The goals of the alignment are (1) to make the images of the four telescopes coincident; (2) to remove coma from each individually; and (3) to control and determine the final position of the composite focus. This will be accomplished by the HRMA Alignment Test System (HATS), which is essentially a scanning Hartmann test system. The scanning laser source and the focal plane of the HATS are part of the Centroid Detector Assembly (CDA), which also includes processing electronics and software. In this paper we discuss the design and the measured performance of the CDA.

Pupil diffraction usually defines the achievable resolution in conventional optical systems. However, since diffraction-limited resolution is proportional to radiation wavelength (for a given aperture size), diffraction is usually ignored for x-ray systems with wavelengths in the angstrom regime. Nonetheless, high-resolution x-ray systems are arising which use very narrow annular apertures, relatively long x-ray wavelengths, or both. In a surprising number of these systems, pupil diffraction can have a non-negligible effect on resolution. There is excellent work in the literature describing the diffraction pattern from such apertures in terms of Airy rings and ring groups. It can be shown that this approach is equivalent in a wide range of conditions to considering an infinite 1-D slit with a width equal to the actual annular width. It can be shown that the energy enclosed in the focal plane dimension transverse to the slit is very close to the energy encircled in the true annular system focal plane. In short, the system designer can make an excellent first approximation of pupil diffraction effects in an x-ray system by applying standard single-slit diffraction formulas to the annular aperture width and x-ray wavelength.