Comparing flash lidar detector options

Abstract

Lidar (light detection and ranging) is a method of surveying based on pulsed laser light that is becoming very common. It is used by the military and by many commercial applications, such as 3D mapping and navigation in autonomous cars and unmanned air vehicles. For these applications, sensitive lidar detectors are essential. But there are different types of lidar detection schemes, with corresponding strengths and weaknesses. Here, we compare three lidar receiver technologies using the total laser energy required to perform a set of imaging tasks (a more detailed description is available elsewhere1). The tasks are combinations of two collection types (3D mapping from near and far), two scene types (foliated and unobscured), and three types of data products (geometry only, geometry plus 3-bit intensity, and geometry plus 6-bit intensity). The receiver technologies are based on indium gallium arsenide (InGaAs) Geiger mode avalanche photodiodes (GMAPDs) (see Figure 1), both InGaAs and mercury cadmium telluride (HgCdTe) linear mode avalanche photodiodes (LMAPDs), and optical time-of-flight (OTOF) lidar using commercial 2D cameras. This last method combines rapid polarization rotation of the image and dual lowbandwidth cameras to generate a 3D image. We chose scenarios to highlight the strengths and weaknesses of the various lidars. Table 1 summarizes the energy required for various imaging modalities. For the case of the InGaAs LMAPDs, we actually carried two bandwidth settings, but in the table we list only the bandwidth setting that required lower energy. GMAPD cameras operate with a low probability of return (i.e., reflection) on a single pulse, but require multiple coincident returns from the same range. The GMAPD cameras do well with bare-earth 3D mapping and 3D imaging through trees. In grayscale situations, the GMAPD cameras use somewhat more energy. The advantages of the GMAPDs are the following: they are thermoelectrically (TE) cooled; they are low energy per pulse, high-rep-rate lasers, Figure 1. Schematic illustration of a diffused-junction planar-geometry avalanche diode structure. This is the structure for one of our detector options, the Geiger mode avalanche photodiode (GMAPD). The electric field (E) profiles at right show that the peak field intensity is lower in the peripheral region of the diffused p-n junction than it is in the center of the device. SiNx: Silicon nitride. i-InP: Indium phosphide p-i-n diode. i-InGaAsP: Intrinsic (i.e., this region of the semiconductor wafer is not intentionally doped either por n-type) indium gallium arsenide phosphide.