Development of an auto-focus system by the moiré method

Ju Yi Lee, Yu Ju Lin, Yung Hsing Wang, Chien-Sheng Liu

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

An auto-focus system based on the moiré effect and the P control method is presented. First, a collimated laser beam passes through a focusing lens and falls incident on the surface of the sample. The deviation of the angle of the light reflected back is proportional to the defocus distance from the sample. The reflected light then passes through two spiral gratings, where three types of moiré patterns are observed and received by a linear CCD. A new formula is derived for finding the focus value (FV) in order to calculate the spiral angle of the moiré pattern and to determine the defocus distance from the sample. The results show that auto-focus should be achieved in a very short time by means of the defocus distance calculation and P control method.

Original languageEnglish
Title of host publication10th International Symposium on Measurement and Quality Control 2010, ISMQC 2010
Pages485-488
Number of pages4
Publication statusPublished - 2010 Dec 1
Event10th International Symposium on Measurement and Quality Control 2010, ISMQC 2010 - Osaka, Japan
Duration: 2010 Sep 52010 Sep 9

Other

Other10th International Symposium on Measurement and Quality Control 2010, ISMQC 2010
CountryJapan
CityOsaka
Period10-09-0510-09-09

All Science Journal Classification (ASJC) codes

  • Safety, Risk, Reliability and Quality

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