CCD-area-based autocollimator for precision small-angle measurement

Abstract

An optical method for precision small-angle measurement based on CCD-area-based autocollimator is proposed in this article. The autocollimator utilizes CCD area—an interline CCD image sensor in a video camera as its detector. A collimated image is taken by the video camera and captured into the memory of a personal computer by an image board with high performance, then the image is transformed into a digital image and can be further processed by software with special arithmetic. A small angular displacement is magnified twice by the collimator objective with a long focal length and the camera lens of the video camera. By using a cold-light source and special data processing arithmetic, the measuring resolution of the autocollimator has been greatly improved. The method is proved to be reliable by a prototype experiment. Although some inexpensive materials were used in the experiment, two-axis angular displacement can be measured simultaneously and a measuring accuracy of 0.01 arcsec has been achieved. If some expensive materials with lower temperature expansion coefficient are used, a measuring accuracy of about 0.005 arcsec or a much higher measuring accuracy can be achieved. Until now, this has been the highest measuring accuracy.

Simultaneous multi-segmented mirror orientation test system using a digital aperture based on sheared Fourier analysis

“…For the normal application of an angular measurement, laser interferometers [10], and photoelectric autocollimators [11] are standard solutions. Their accuracy is state of the art, but they have limited capability when measuring multiple segments and surface shapes.…”

Roll angle measurement using a polarization scanning reference source

“…Currently available sensors, which include optical line of sight, inertial, RF antennas painted on the projectile, and magnetometers, do not satisfy the needs of an on-board roll angle, measurement system. Other techniques including the use of polarization 4 , and MEMS technology 5 , interferometry 6 , moiré technique 7 , vision based 8 , total internal reflection based 9 and autocollimators 10 also fall short.…”

High-precision technique for in-situ testing of the PZT scanner based on fringe analysis

“…Traditionally, optical methods for rotation angle measurement have been performed using interferometers [1][2][3], autocollimators [4][5][6] and methods based on the internal reflection [7][8][9][10]. In recent years, newer techniques, such as fringe-analysis techniques [11], Lau interferometry [12], fringe projection [13,14], and the circle Dammann grating [15], have been also developed for angle measurement.…”