Characteristics and use of APD in optical rangefinders

Photodiodes are commonly used as detectors in optical rangefinders. However, one drawback is that good accuracy cannot be obtained when the distance is relatively long. This has in turn led to the occasional use of the APD (avalanche photodiode) because of the long distance accuracy its internal gain mechanism provides. One of the most essential characteristics required in this application is the time response property. Since the photodiode is more stable in operation, its time response tends to be less affected by the type of operating environments. APD time response, on the other hand, is more vulnerable, tending to be easily affected by the environment. This has to be taken into account during APD operation and handling. In studying ways to make the APD more resistant to different operating environments we mainly concentrated on the time pickoff technique. Results of that study are related here