Tachistoscope

A tachistoscope is a device that displays a picture, text, or an object for a specific amount of time. It can be used for various purposes such as to increase recognition speed, to show something too fast to be consciously recognized, or to test which elements of a display are memorable.

Early tachistoscopes were mechanical, using a flat masking screen that containing a window. The screen concealed the picture or text until the sceen moved, at a known speed, the window over the picture or text, revealing it. The screen continued to move until it hid the picture or text again. Later tachistoscopes used a shutter system typical of a camera in conjunction with a slide or transparency projector. Even later, tachistoscopes used brief illumination, such as from fast-onset and fast-offset fluorescent lamps, of the material to be displayed. By the late 1990s, tachistoscopes had largely been replaced by computers for displaying pictures and text.^[1]