Semi-natural simulation of the angular matching of the axes of the working and marker laser beams in a high-precision laser ranging system

Abstract

This paper describes an automatic adjustment system designed to measure and automatically minimize the difference in angular mismatch between the optical axes of a working (probe) beam and a marker beam that simulates the optical axis of the detector channel in a laser ranging system. This paper is primarily focused on the specifications of the basic components of the measurement system (laser sources, controllable optomechanical components, and sensors used to measure the angular orientation of the laser beams) used to maintain precision angular matching of the working and marker laser beams in order to develop a process for semi-natural simulation of a precision laser ranging system to produce and study angular matching between the working and marker beam axes. This semi-natural simulation was used to model angular matching of the working and marker laser beams in a high-precision laser ranging system; the simulation was implemented using a laser system specifically developed for the purpose. The main results include a novel laser facility developed for semi-natural simulation of the angular matching of the probe (1064 nm) and marker (671 nm) beams in a laser ranging system where this difference in matching does not exceed 1″. The facility periodically relays images of the laser beams to a polarization-based unit for matching of the beams using spatial filters. The facility was used to obtain experimental data on the positional characteristics of a quadrant photodiode and CMOS-array digital camera used as a laser beam matching unit. We show that this type of digital camera is preferred since it does not require advance knowledge of the positional characteristic. Initially aligned laser beams were observed to randomly become misaligned due to angular instability in the laser beams. We have shown that the angular matching of the pulsed probe and CW marker beams can be automatically controlled using a motorized mirror installed outside the marker-beam optical system and also propose an algorithm for operation of the marker beam in this mode. The scientific value of this paper is based on the novel nature of the laser sensor facility, the experimentally measured characteristics of the hardware components used in the marker laser channel, and the fact that the matching of the pulsed and CW laser beams can be controlled by means of motorized mirrors. The paper has practical value in that a procedure has been developed for semi-natural simulation of the angular matching of probe and marker beams to support the design of high-precision laser ranging systems operating in the near-infrared spectrum.