Trial Production of Critical-fusion Frequency (CFF) Equipment by Using High-speed Liquid Crystal

A new device to measure the critical-fusion frequency (CFF) has been developed. In conventional methods, a light-source is set in a proper background and is made on-and-off. By such a type of equipment, measurement during work is difficult, since the examinee have to look into a dark box. The equipment is large in size, because the equipment includes some mechanical moving parts. In the proposed equipment, natural light is used as a source, which is modulated by a liquid crystal. This new equipment is small in size and makes possible the measurement of CFF during work, since a flickering spot appears in the open visual field of the examinee. A liquid crystal has been developed for this purpose with the response times of 1ms from clear to dark state and Sms from dark to clear state, which is enough to measure ordinary CFF ranging up to 50Hz.