The axial resolution of parallel confocal measurement can be improved as the laser source added into the system, but extreme monochromaticity of laser beam will produce the Talbot effect, which is an effect of many images of point light array appear along the optical path direction, and it causes to distinguish the true in-focus image from lots of Talbot images difficultly, which means the confocal measurement can’t be carried on. The author researched factors of the influences for Talbot distance, and developed some methods to weaken the impact of the Talbot effect. A LED was added into the laser parallel confocal measurement system to find the in-focus image, and there were no Talbot images nearby to impede positioning, and then the laser beam was lead into the system to measure with high precision. The difference of location of the two in-focus images with laser and LED was about 11μm in the experiment, which was shorter than one Talbot distance in the system, and the result indicated that the in-focal could be distinguished with this method.

Date Published: 31 January 2013
PDF: 6 pages
Proc. SPIE 8759, Eighth International Symposium on Precision Engineering Measurement and Instrumentation, 87593T (31 January 2013); doi: 10.1117/12.2014723

Published in SPIE Proceedings Vol. 8759:
Eighth International Symposium on Precision Engineering Measurement and Instrumentation
Jie Lin, Editor(s)