New type of autocollimator based on the normal tracing method and Risley prisms

Abstract

In the present study, we proposed a new type of autocollimator for high-accuracy angular measurement within a large angle range. The new system comprises a traditional autocollimator and Risley prisms, and it employs the normal tracing method to measure the angle. By rotating the Risley prisms, the outgoing beam of the autocollimator can be deflected close to the normal direction of the reflecting mirror and then reflected back to the system by the mirror along the near normal direction to realize normal tracing. Based on the angle measured by the autocollimator and the rotation angles of Risley prisms, we can calculate the tilt angle of the mirror. Since the beam returns to the system close to the original path, the angle error caused by aberration, optical component processing defects, nonuniform refractive index, and so on, can be ignored. Due to the normal tracing measurement method, theoretically, the angle error is not affected by the working distance. ZEMAX non-sequential simulation shows that the angle error caused by aberration in the new system can be significantly reduced.

Research on achromatic Risley prism in normal tracing angle measurement system

“…The direction ðα x ; α y Þ of the light emitted from the RPs is calculated from the respective rotation angles r 1 and r 2 of the two prisms. 3 According to the centroid algorithm, the centroid position ðx; ȳÞ of the light spot Q is obtained as 16 Fig. 5 Normal tracing angle measurement system.…”

“…5 Normal tracing angle measurement system. 3 Fig. 4 Deflection angle errors, in which the prism adopts the parameters in Table 2.…”

“…It has a wide range of applications in various fields of scientific research, such as measuring the flatness of the large plane of the machine tool, the straightness of the long guide rail, the angle between the optical planes, the perpendicularity between the vertical planes, the initial orientation of the calibration of the inertial reference of the aircraft, and the monitoring of the attitude of the rocket launcher 1 – 3 At present, the photoelectric autocollimator with the highest measurement accuracy on the market is ELCOMAT HR, which can only guarantee a measurement accuracy of 0.01″ in the range of ±10″ and a measurement accuracy of 0.03″ in the full-scale range (±300″) 4 …”

“…Due to the influence of aberrations, process defects, response consistency errors in various areas of the CCD, it is difficult to improve the measurement range and measurement accuracy at the same time. Our team introduced the Risley prisms (RPs) into the traditional autocollimator system and used the normal tracing method 3 , 5 to measure the angle with a large range and high precision. In the measurement of the new system, by rotating the RPs, the measurement beam direction can be precisely adjusted 6 – 9 and the measuring beam can be reflected near the normal direction of the tested mirror to realize the paraxial propagation of the measuring beam.…”

An Ultracompact Angular Displacement Sensor Based on the Talbot Effect of Optical Microgratings

“…For photoelectric autocollimation [ 10 ], the collimated light beam is detected by a photodetector after being reflected by a plane mirror [ 11 , 12 , 13 , 14 , 15 ]. A change in the pitch angle leads to a rotation of the mirror, which results in a change in the reflection direction of the reflected beam.…”