High-depth-resolution range imaging with multiple-wavelength superheterodyne interferometry using 1550-nm lasers.

Lasers and laser diodes are widely used as illumination sources for optical imaging techniques. Time-of-flight (ToF) cameras with laser diodes and range imaging based on optical interferometry systems using lasers are among these techniques, with various applications in fields such as metrology and machine vision. ToF cameras can have imaging ranges of several meters, but offer only centimeter-level depth resolution. On the other hand, range imaging based on optical interferometry has depth resolution on the micrometer and even nanometer scale, but offers very limited (sub-millimeter) imaging ranges. In this paper, we propose a range imaging system based on multi-wavelength superheterodyne interferometry to simultaneously provide sub-millimeter depth resolution and an imaging range of tens to hundreds of millimeters. The proposed setup uses two tunable III-V semiconductor lasers and offers leverage between imaging range and resolution. The system is composed entirely of fiber connections except the scanning head, which enables it to be made into a portable device. We believe our proposed system has the potential to tremendously benefit many fields, such as metrology and computer vision.