Tachistoscopic display using color-lookup-table display devices

In this article, I describe a method for presenting multiple bit-mapped images on video displays under precise temporal control. The method makes use of the color-table animation technique that can be used with color-lookup-table display devices. The principal challenge in applying this technique to the display of multiple stimuli lies in dealing efficiently with the problem of overlapping displays. The solution described here is to allocate separate bit slices of screen memory to stimuli that overlap and to allocate sequential color-table indices to stimuli that are disjoint. Software is described that automatically computes the location of a stimulus on the screen, allocates color indices appropriately, transfers bit images to screen memory efficiently, and manipulates the color lookup table to present a given stimulus to the viewer. These operations are handled transparently; the user simply draws the stimuli and then turns them on or off under program control.