Development of a three-axis angle sensor - Proposal of the measurement principle and identification experiments

This paper describes a 3-axes angle sensor based on laser autocollimation for simultaneous measurement of small tilt angles about X, Y and Z-axes. The sensor consists of a laser diode as the light source and quadrant photodiodes (QPDs) as the optical position-sensing device. Differing from a conventional 2-axis autocollimator, the sensor uses a diffractive grating as the target mirror. It is verified that the sensitivity of the sensor in the θ_x (rolling) direction is determined by the pitch of the diffractive grating and the diameter of the laser beam. The sensitivities in the θ_y (pitching) and the 1 (yawing) direction are determined by the wavelength and the beam diameter of the laser beam. It is confirmed that the resolution of θ_x is about 0.2 arc-seconds, and those of θ_y and θ, are about 0.02 arc-seconds. Optical design and experimental results are presented.