Tachistoscope
（重定向自Tachistoscopic）
A tachistoscope is a device that displays an image for a specific amount of time. It can be used to increase recognition speed, to show something too fast to be consciously recognized, or to test which elements of an image are memorable. Projection tachistoscopes use a slide or transparency projector equipped with the mechanical shutter system typical of a camera. The slide is loaded, the shutter locked open, and focusing and alignment are adjusted, then the shutter is closed. When ready for the test, a shutter speed is selected, and the shutter is tripped normally.