Laser scanner for thickness measurements on the production line

Thomas C.Y. Leung; Rong-shing Shu; Jiunn-Shyong Wu

doi:10.1117/12.20239

1 August 1990 Laser scanner for thickness measurements on the production line

Thomas C.Y. Leung, Rong-shing Shu, Jiunn-Shyong Wu

Proceedings Volume 1265, Industrial Inspection II; (1990) https://doi.org/10.1117/12.20239
Event: The International Congress on Optical Science and Engineering, 1990, The Hague, Netherlands

Abstract

In the manufacturing of continuously formed products such as metal plates and plastic sheets, on-line monitoring of thickness is important for quality control. Most cases require noncontact measurements. The most widely used optical technique is "optical triangulation" in which a lateral effect position-sensing detector is used. However, the technique has a limited measurement range to resolution ratio making it not suitable for some on-line applications. In this paper we propose a new approach to measure thickness in which the position of a scanning laser beam is timed. It eliminates the restriction of measurement range by the dimension of the detector as in traditional optical triangulation. Also, because small area silicon photodiodes are used, signal-to-noise ratio is largely enhanced thus improving the resolution. The probe we built demonstrates a 47 % measurement range-to-standoff distance ratio and a 2.8x104 measurement range-to-resolution ratio. Also, its performance is not influenced by large changes in object reflectivity.

Citation Download Citation

Thomas C.Y. Leung, Rong-shing Shu, and Jiunn-Shyong Wu "Laser scanner for thickness measurements on the production line", Proc. SPIE 1265, Industrial Inspection II, (1 August 1990); https://doi.org/10.1117/12.20239

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KEYWORDS

Sensors

Signal detection

Optics manufacturing

Photodiodes

Laser scanners

Silicon

Control systems

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