频闪观测器（Stroboscope）又称同步定时仪，可测量反复运动所需的时间。

频闪观测器是一个可以转动的圆盘，圆盘上有狭缝，能发出脉冲光。频闪观测器大多用来量度水波、脑波的频率。

A stroboscope also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces brief repetitive flashes of light. Usually the rate of the stroboscope is adjustable to different frequencies. When a rotating or vibrating object is observed with the stroboscope at its vibration frequency (or a submultiple of it), it appears stationary. Thus stroboscopes are also used to measure frequency.