Three-dimensional visual stimulator

We describe a newly developed three-dimensional visual stimulator (TVS) that can change independently the directions, distances, sizes, luminance, and varieties of two sets of targets for both eyes. It consists of liquid crystal projectors (LCP's) that generate the flexible images of targets, Badal otometers that change target distances without changing the visual angles, and relay-lens systems that change target directions. A special control program is developed for real-time control of six motors and two LCP's in the TVS together with a three-dimensional optometer III that simultaneously measures eye movement, accommodation, pupil diameter, and head movement. The TVS measurement ranges are as follows: distance, 0 to -20 D; direction, ±16° horizontally and ±15° vertically; size, 0-2° visual angle; and luminance, 10(-2)-10(2) cd/m(2). The target images are refreshed at 60 Hz and speeds with which the target makes a smooth change (ramp stimuli) are as follows: distance, 5 D/s; direction, 30°/s, size, 10°/s. A simple application demonstrates the performance.