Beam Scanning Confocal Differential Heterodyne Interferometry

Song, Chang-Woo; Kim, Tae Joong; Gweon, Dae−Gab

doi:10.1080/15599610701261076

Cited by 4 publications

(1 citation statement)

References 10 publications

(12 reference statements)

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“…In many cases, two or more thin laser beams are simutaneously used in precision metrology and multiple-degree-of-freedom metrology [1][2][3][4][5][6][7][8][9][10][11][12]. Typically, two parallel thin beams are used to measure relative displacement and angle displacement, especially in multi-axis interferometer and differential interferometer systems [1][2][3][4][5][6][7][8][9]. The parallelism of two parallel beams is strictly limited to provide high measuring accuracy.…”

Section: Introductionmentioning

confidence: 99%

Measuring Parallelism for Two Thin Parallel Beams Based on Autocollimation Principle

Shen

Zheng

et al. 2014

KEM

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In order to measure the parallelism of two thin parallel beams in multi-axis interferometers and differential interferometers, the autocollimation principle was used by locating a CCD at the focal plane of collimation lens, the two beams converge on CCD image plane at different points when they are not parallel, and the distance between the two converging points is used to calculate the parallelism of the two beams. To achieve high accuracy and low system error, the CCD defocus and tilt should be strictly controlled according to the accuracy requirement. A centroid algorithm with grey threshold was used to reduce the influence of image noise. A beam-selected structure was designed to let the two beams converge to the CCD image plane in sequence to avoid superposition of beam spots. An experimental setup is built to verify the validity of the method. Experimental results show that the system has a centroid position resolution of 0.05 arcsec and a centroid position stability of 0.4 arcsec. It is therefore concluded that the method can be used to measure parallelism that is more than few arcsecs for two thin beams. Moreover, the measuring accuracy of this method can be improved when higher centroid position stability is achieved.

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