Abstract
A resolution-enhanced roll-angle measurement system based on a transmission grating autocollimator is proposed. The measurement principle is analyzed in detail. The system uses a transmission grating and a mirror group to produce a pair of central symmetric differential measurement beams that enable the measurement of roll angle. Because the measurement beams transmit through the rotating grating twice, the resolution is enhanced compared to conventional grating autocollimation methods with the same device. The roll-angle resolution reached 0.1 arcsec. Additionally, the effect of laser beam drift on the stability of angular measurement is effectively suppressed by using differential measurement method, the stability of the proposed grating autocollimator after the differential measurement is 0.11 arcsec.
Highlights
Precision angle measurement systems play an important role in precision manufacturing and equipment [1], precision motion control [2], [3], surface metrology [4], precision instrument calibration [5], and other precision measurement areas
Same angle change, the output of positionsensitive detectors (PSD) in proposed system is doubled compares to the typical grating autocollimator
Because the transmission grating and the reflector was aligned orthogonally, the roll angle γ, which is detected by the proposed grating autocollimator, and the yaw angle β which is detected by the commercial autocollimator are consistent, and they can be read out simultaneously
Summary
Precision angle measurement systems play an important role in precision manufacturing and equipment [1], precision motion control [2], [3], surface metrology [4], precision instrument calibration [5], and other precision measurement areas. Substantial research of angle measurement systems has been performed, including autocollimation [6]–[8], laser interference [9]–[12], total internal reflection [13]–[15], and fiber optic sensors [16], [17] These methods can accurately determine both pitch and yaw by measuring beam-path- or beam-direction-changes. The first category, diffraction-grating-based autocollimation [18]–[20], use diffraction gratings as reflectors, and converts roll to a directional change of the ±1st order diffraction beam. They are converted into a phase shift, and the roll is obtained by detecting the phase shift Most of these methods are difficult to combine with twodimensional angle measurements system to enable threedimensional angle measurement – with one exception: the grating-based autocollimator proposed by Gao et al [19]. This method improves the roll angle measurement resolution, and it makes the measurement system more compact
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