Tilt angle measurement with a Gaussian-shaped laser beam tracking

TL;DR

This paper presents a high-precision tilt measurement instrument for laser guiding mirrors using Gaussian beam triangulation, achieving sub-microradian accuracy and a large dynamic range through numerical and experimental validation.

Contribution

The authors developed a novel Gaussian beam triangulation method for precise tilt measurement with high accuracy and stability, validated by numerical and experimental results.

Findings

Achieved a measurement error of 0.13 microradian.

Demonstrated a measurement range of ±0.65 degrees.

Validated the method's feasibility through numerical modeling and experiments.

Abstract

We have addressed the challenge to carry out the angular tilt stabilization of a laser guiding mirror which is intended to route a laser beam with a high energy density. Such an application requires good angular accuracy as well as large operating range, long term stability and absolute positioning. We have designed an instrument for such a high precision angular tilt measurement based on a triangulation method where a laser beam with Gaussian profile is reflected off the stabilized mirror and detected by an image sensor. As the angular deflection of the mirror causes a change of the beam spot position, the principal task is to measure the position on the image chip surface. We have employed a numerical analysis of the Gaussian intensity pattern which uses the nonlinear regression algorithm. The feasibility and performance of the method were tested by numeric modeling as well as experimentally. The experimental results indicate that the assembled instrument achieves a measurement error of 0.13 microradian in the range +-0.65 degrees over the period of one hour. This corresponds to the dynamic range of 1:170 000.