The amplifier input is a voltage proportional to the photocurrent signal produced by a photodiode, which is irradiated by a modulated light beam at the same chopper frequency.
Using the optical chopper to modulate the detected light to make it related to the reference squarewave signal is a common method of locking phase detection of weak signals.
其中利用光学斩光器对被测光进行调制使其与方波参考信号相关是对微弱光信号进行锁相检测的一种常用方法。
3
Here comes a candle to light you to bed, here comes a chopper to chop off your head.