Focus-Induced Photoresponse: a novel optoelectronic distance measurement technique

We present the Focus-Induced Photoresponse (FIP) technique, a novel approach to optical distance measurement. It takes advantage of a widely-observed phenomenon in photodetector devices: a nonlinear, irradiance-dependent photoresponse. This means that the output from a sensor is dependent on the total number of photons incident and the size of the area in which they fall. With a certain arrangement of sensor and lens, this phenomenon will cause the output of the sensor to change based on how far in or out of focus an object is. We call this the FIP effect. Here we demonstrate how to use the FIP effect for distance measurements. We show that this technique works with different sensor materials, device types, as well as visible and near infrared light. In principle, any sensor exhibiting a photoresponse that depends nonlinearly on irradiance could be used with the FIP technique. It is our belief that the FIP technique can become an important method for measuring distance.