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Proceedings Paper

High-resolution dimensional measurement apparatus using optical scale with different grating pitches
Author(s): Hiroo Fujita
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Paper Abstract

This paper discuses an apparatus used in industrial inspection for optically detecting dimensions. In particular, the configuration of optical unit with compact in size and simpler in construction, and signal processing unit with resolution to be better than 0.1 micrometers are described. The key devices of the new optical unit are optical scale and light source. The optical scale consists of one moving and two stationary gratings. Both of these gratings have different pitch lengths. For example, the pitch of the moving and stationary gratings are 50 micrometers and 10 micrometers , respectively. These pitches are set to odd integer multiples. The optical scale, directly irradiated by a divergent light emitted from a laser diode, generates two sinusoidal signals with a 10 micrometers period. By using the divergent light, the need for a collimating lens is eliminated. This reduces the overall size of the optical unit. The signal processing unit operates on the two signals for detecting the signal phase at the stop position of the moving grating. The basis of this phase detection is a simpler linear operation. By using the linear operation, high resolution detection of the signal phase is accomplished by segmenting an interval of one cycle period of the signal into more than 300 parts.

Paper Details

Date Published: 23 October 2001
PDF: 8 pages
Proc. SPIE 4398, Optical Measurement Systems for Industrial Inspection II: Application in Industrial Design, (23 October 2001); doi: 10.1117/12.445539
Show Author Affiliations
Hiroo Fujita, Citizen Watch Co. Ltd. (Japan)

Published in SPIE Proceedings Vol. 4398:
Optical Measurement Systems for Industrial Inspection II: Application in Industrial Design

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