Parallel beam-scanning system for flatness measurements of thin plates

Kuang-Chao Fan; John H. Wu

doi:10.1117/12.156468

22 September 1993 Parallel beam scanning system for flatness measurements of thin plates

Kuang-Chao Fan, John H. Wu

Proceedings Volume 2101, Measurement Technology and Intelligent Instruments; (1993) https://doi.org/10.1117/12.156468
Event: Measurement Technology and Intelligent Instruments, 1993, Wuhan, China

Abstract

This paper describes the work to develop a Parallel Beam Scanning System (PBSS) for the non-contact measurement of surface flatness of thin plates. The PBSS consists of a He-Ne laser source having good pointing stability a scanner to create divergent scanning beams a large aplanatic meniscus lens to convert the divergent beams to parallel beams a linear stage to drive the testpiece to each sampling position a screen for the projection of reflected beams from the tested surface and an image processing unit to analyze the projected image. Due to the out-of-flatness of the surface the straight line formed by the incident parallel beams will be distorted and magnified on the screen as it is reflected from the tested surface. The stage then positions the testpiece step-by-step to carry out measurements in the line-by-line sequence. A CCD camera is employed to capture the image of the distorted line on the screen each time. With the proposed mathematical model the flatness data of the testpiece can be computed from the input image data. Experimental results by the use of this system have shown in good agreement with the results obtained from the coordinate measuring machine. This system can be applied to the flatness measurements of thin plates such as sheet metals sheet moulding compound (SMC) plates glass plates etc. which are difficult to measure by traditional methods.

Citation Download Citation

Kuang-Chao Fan and John H. Wu "Parallel beam scanning system for flatness measurements of thin plates", Proc. SPIE 2101, Measurement Technology and Intelligent Instruments, (22 September 1993); https://doi.org/10.1117/12.156468

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KEYWORDS

Image processing

Inspection

Image analysis

Mathematical modeling

Binary data

Calibration

Data modeling

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