Measuring the power of scanning lasers, such bar code scanners, presents a problem. A bar code laser beam scans back and forth at a very high frequency so any ordinary photodiode power meter will not measure the power in the beam but rather the average power impinging on it, i.e. the power times the fraction of time the beam is on the detector. Therefore, when exposed to a scanned beam, the reading will be much lower than the actual power in the beam. For example, if a scanning laser delivers 2mW to a photodiode sensor and the beam is on the sensor only 1% of the time, the instrument will read only 0.02mW.

Aligning an invisible laser beam with a visible pointer beam may sound simple but to do it right with everything lined up is not so obvious. Here is how it is done:

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