Programmed Control of Optical Grating Scales for Visual Research

摘要

This report documents the design of a microprocessor based device which controls the brightness and contrast levels of video signals to be used by scientists in vision research to control laboratory monitors. Contrast control in a standard CRT monitor is obtained through the use of a commercial video chip linear circuit, and brightness control via a straight forward transistor amplifier. The transistor is inserted into the monitor's existing manual control circuit. The linear circuit and transistor are regulated by the microprocessor through digital-to-analog converters. A feedback network reports the actual brightness and contrast produced on the monitor's screen. This network is comprised of a 1024 element photodiode array and an analog-to-digital converter. The photodiode array measures the luminance directly off the monitor and the analog-to-digital converter digitizes the information for use by the microprocessor. The report also contains the results of an investigation into the use of digitally generated video and color monitors for vision research.