Application of the astigmatic method to the thickness measurement of glass substrates

Jingchao Zhang; Rui Ding; Xi Yan

doi:10.1117/12.901221

22 August 2011 Application of the astigmatic method to the thickness measurement of glass substrates

Jingchao Zhang, Rui Ding, Xi Yan

Proceedings Volume 8192, International Symposium on Photoelectronic Detection and Imaging 2011: Laser Sensing and Imaging; and Biological and Medical Applications of Photonics Sensing and Imaging; 819245 (2011) https://doi.org/10.1117/12.901221
Event: International Symposium on Photoelectronic Detection and Imaging 2011, 2011, Beijing, China

Abstract

We developed a high accuracy thickness measurement system for glass substrates based on the optical design of the astigmatic method. Reflective optical measurement systems are the most widely used glass thickness measurement methods in current industrial production practice. The incline of glass in reflective optical measurement system is the main factor of inaccuracy of thickness data. Compared with reflective optical measurement system, we found our design could effectively eliminate errors of glass thickness caused by slightly shifts of glass tilt. The astigmatic optical system includes a laser diode, a cylindrical lens, and a quadrant detector. This method measures the astigmatic focusing error signal induced form the measured glass placed in the astigmatic optical system. The astigmatic focusing error signal is converted into the thickness of the glass substrate. The proposed glass thickness measurement system is verified by using a coordinate measuring machine (CMM). On the validation of our system using tri-ordinate measuring machine, the accuracy of the proposed system is 0.2 μm, with a standard deviation of 0.7μm within the thickness measuring range of 1.2mm.

Citation Download Citation

Jingchao Zhang, Rui Ding, and Xi Yan "Application of the astigmatic method to the thickness measurement of glass substrates", Proc. SPIE 8192, International Symposium on Photoelectronic Detection and Imaging 2011: Laser Sensing and Imaging; and Biological and Medical Applications of Photonics Sensing and Imaging, 819245 (22 August 2011); https://doi.org/10.1117/12.901221

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