Specular signal return through a range-compensating lens.

Abstract

A range-compensating lens has been developed which alleviates, to a certain degree, the one-over-range-squared attenuation in the signal (laser) return for active optical systems [Appl. Opt.58, 7921 (2019)APOPAI0003-693510.1364/AO.58.007921]. This compensation applies to the diffuse return and, in particular, the perfectly diffuse return that is an assumption used to develop the equations. However, there is another component of the return that is equally important, and that is the specular signal return. Often this return is a result of a very shiny and close target, since the return needs to closely follow the outgoing beam path in order for the light to be returned to the detector. This implies a high sensitivity to target orientation. For this reason, specular returns are not counted on as a signal return, and the sensor is generally not designed to use this type of return, which can lead to an undesired detector saturation, should a high reflectivity specular return occur. This return, with respect to a range-compensation lens, was only discussed briefly and qualitatively. The work here means to address this specular signal return quantitatively as it applies to a range-compensating lens as compared to that of a traditional lens and considers the specular performance on the sensor-level.