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Proceedings Paper

Three-dimensional surface profile measurement using a liquid crystal grating with a triangular intensity distribution
Author(s): Hiroo Fujita; Akira Suguro; Toru Yoshizawa
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Paper Abstract

This paper discusses a novel device for measuring 3D-surface profiles of objects using a grating pattern projection method. In particular, the configuration of a grating pattern generating and image processing system for calculating phase distribution from deformed grating images are described. In the grating pattern generating system, the grating is made from a liquid crystal (LC) with a stripe structure pattern which is driven by a pulse width modulation method. The intensity distribution made by the stripe LC grating is set to be triangular. The triangular distribution will be realized using low-bit gray levels. For instance, less than 11 gray levels will produce two patterns which is phase shifted by 1/4cycles; then, projection onto an object can be achieved twice. The deformed grating images posed by the object are detected by a CCD camera in the form of a two-phase image. The image processing system transforms the intensity distribution of the two-phase image into phase distribution which corresponds to the profile of the object. In this operation, linear regions are chosen where the intensities of the two-phase image change linearly by selecting the two-phase image alternately. The one cycle period is formed with four linear regions (quadrant), and the phase width in each quadrant is set to be π/2. Because the intensity distribution in the linear regions varies depending on the profile of the object, the phase distribution in each region is calculated using a simple linear operation using intensity variations or pixel number data.

Paper Details

Date Published: 18 October 2002
PDF: 8 pages
Proc. SPIE 4902, Optomechatronic Systems III, (18 October 2002); doi: 10.1117/12.467400
Show Author Affiliations
Hiroo Fujita, Citizen Watch Co., Ltd. (Japan)
Akira Suguro, Citizen Watch Co., Ltd. (Japan)
Toru Yoshizawa, Tokyo Univ. of Agriculture and Technology (Japan)

Published in SPIE Proceedings Vol. 4902:
Optomechatronic Systems III
Toru Yoshizawa, Editor(s)

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