Design of an image quality tester
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Helmet-mounted displays (HMDs) provide essential pilotage and fire control imagery information for pilots. However, image quality testers for HMD validation do not currently exist in the field. This research employed techniques from imaging analysis and interpretation, and computer-aided design/computer-aided manufacturing (CAD/CAM) to demonstrate that a portable image quality tester can be developed for HMD validation in the field. For this study, a charge coupled device (CCD) camera and lens were selected. Hardware characteristics such as viewing angles in horizontal and vertical positions, dynamic working range at day and night, pixel resolution, focal length, and aperture ratio were evaluated with respect to HMD functionality. Experiments to evaluate camera sensitivity and test pattern merits were conducted using a programmable micro-positioning system, CCD camera, optical fixtures and benches. Next, the relative ratio among features within the image profile, and an ideal image profile and evaluation criteria were established based on the experiment results. Third, image processing algorithms and techniques, such as edge detection, were developed and applied in test pattern feature detection. A software prototype including modules for image capture, image analysis and interpretation, and user manuals was developed. Finally, a hardware package design was proposed. The design incorporates a notebook computer with flat panel display to interface with the camera and software prototype; and fixtures for the HMD, camera, computer, and power supply. This design will allow the tester to be used in the field. Future work includes (1) fabrication and field evaluation of the tester; (2) development of an embedded intelligent algorithm to tune the tester image profile as more HMDs are evaluated; (3) addition of an on-line real time interactive adjusting and self-tuning capability based on a given environmental t scenario; and (4) self-diagnosis, built-in-test, and reliability testing capabilities to facilitate preventive maintenance. 2001 SPIE.
