<title>Low-cost monochrome CRT helmet display</title>

Abstract

The goal of the cathode ray tube (CRT) helmet-mounted display (HMD) project was development and demonstration of a low-cost monochrome display incorporating see-through optics. The HMD was also to be integrable with a variety of image generation systems and suitable for use with low-cost cockpit trainers and night vision goggles (NVG) training applications. A final goal for the HMD was to provide a full field of regard (FOR) using a head-tracker system. The resultant HMD design included two 1 inch CRTs used with a simple optical design of beam splitters and spherical mirrors. The design provides for approximately 50% transmission and reflectance capabilities for observing the 30 degree(s) vertical X 40 degree(s) horizontal biocular instantaneous field-of-view visual image from a graphic image generator system. This design provides for a theoretical maximum of 10.8% of the CRT image source intensity arriving at the eye. Initial tests of image intensity at the eye for an average out-the-window scene have yielded 12 to 13 Foot Lamberts with the capability of providing approximately 130 Foot Lamberts. Invoking a software 'own ship' mask to 'blackout' the visual image, the user can monitor 'in-cockpit' instrumentation utilizing the see- through characteristics of the optics. The CRTs are operated at a TV line rate with a modulation transfer function (MTF) of approximately 65%. The small beam spot size and the high MTF provide for an enhanced image display. The display electronics are designed to provide a monochrome video picture based on an RS170 video input.