Surface condition measurement using optical heterodyne method

Hiroo Fujita

doi:10.1117/12.132158

20 October 1992 Surface condition measurement using optical heterodyne method

Hiroo Fujita

Proceedings Volume 1720, Intl Symp on Optical Fabrication, Testing, and Surface Evaluation; (1992) https://doi.org/10.1117/12.132158
Event: International Symposium on Optical Fabrication, Testing, and Surface Evaluation, 1992, Tokyo, Japan

Abstract

A surface height variation measurement device based on the differential heterodyne interferometric scheme using new optical beam scanning techniques is described. An acousto- optic deflector (AOD) is driven by a signal which has two frequency components to generate two first-order diffraction beams at different frequencies for the probing light beams. The two beams, which have only a slight separation, are deflected by the AOD. The scanning distance of the two beams via the AOD can be extended using a Galvano mirror, which is driven synchronized with the AOD and scans the two beams in the same direction. The scanning direction of the two beams can be changed in various directions in the two-dimensional plane using a specially made rotating prism. The difference in surface height between the points where the two beams are incident is detected from the phase change of a beat signal with accuracies on the order of 1 nm. We applied this device to surface condition measurements, such as surface roughness, shape, and fine angle.

Citation Download Citation

Hiroo Fujita "Surface condition measurement using optical heterodyne method", Proc. SPIE 1720, Intl Symp on Optical Fabrication, Testing, and Surface Evaluation, (20 October 1992); https://doi.org/10.1117/12.132158

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