Note: Autocollimation with ultra-high resolution and stability using telephoto objective together with optical enlargement and beam drift compensation

Abstract

An autocollimation (AC) setup with ultra-high resolution and stability for micro-angle measurement is presented. The telephoto objective, which is characterized in long focal length at a compact structure size, and the optical enlargement unit, which can magnify the image displacement to improve its measurement resolution and accuracy, are used to obtain an ultra-high measurement resolution of the AC. The common-path beam drift compensation is used to suppress the drift of measurement results, which is evident in the high-resolution AC, thus to obtain a high measurement stability. Experimental results indicate that an effective resolution of better than 0.0005 arc sec (2.42 nrad) over a measurement range of ±30 arc sec and a 2-h stability of 0.0061 arc sec (29.57 nrad) can be achieved.

Automated calibration of multiple long gauge blocks using the KRISS linear measurement system

“…The angle sensor was implemented based on an autocollimator configuration [10] and operated as a null detector during automatic tip-tilt alignment of the LGBs. A collimated laser beam delivered through a single-mode fiber and a fiber collimator was incident on one of the measuring faces of an LGB using two alignment mirrors, as shown in figures 1 and 3.…”

High-precision two-dimensional angle sensor using a dot array of a diffractive optical element

“…In the autocollimation principle, angular displacement is obtained by measuring positional shift of a reticle image or a focused spot on an image plane of an imaging lens. Therefore, to obtain higher resolution, focal length of the image lens should be increased or some techniques enhancing the resolution of positional shift detection should be introduced [4][5][6][7]. Several commercial * Author to whom any correspondence should be addressed.…”

“…Some works on increasing resolution even with a short focal length imaging lens were reported. These include the optical enlargement technique [4], or techniques using a specially designed phase grating [5], a reticle having multiple slits [6], or a double-slit [7]. The averaging effect reduced random errors from digitization and photon noise, and achieved higher resolution than conventional autocollimators [6,7].…”

“…In this article, a high-precision two-dimensional (2D) angle sensor is presented, which employs a diffractive optical element (DOE) generating a 2D dot array. Comparing with the prior researches [4][5][6][7], originalities of this paper are to expand the high-resolution angle measurement strategy to two-axis case and reduce nonlinearity error effectively, using a DOE rather than a multiple-slit reticle or a double-slit plate. They also can be implemented as a small-sized sensor module with a simple configuration.…”