Stroboscopic Measurement Method

In the stroboscopic method of measurement, a rotating or vibrating body is illuminated by short light pulses that recur at a known frequency, and special markings on the body are observed during such illumination. Since the response of the retinal cells to a stimulus lasts approximately 0.1 sec, a continuous response results when the light reflected from a marking strikes the eye with a frequency greater than 16 times/sec. When the frequency of the light pulses is synchronized with the motion of the body, the marking appears to be stationary. Otherwise, the marking appears to move. If the frequency of the light flashes is known, the speed of rotation or frequency of vibration of the body can be calculated. The devices used in the stroboscopic method are known as stroboscopes.