Abstract
This paper describes a new approach for passive measurements of transparent glass plate surfaces, in which the position distributions of the surfaces are obtained from virtual images of pattern boards taken with a camera. In the approach, structured patterns displayed on two boards are acquired with a camera through the surface and reflection points on the front and rear surfaces are located geometrically using the triangulation principle without any prior knowledge of the coordinates of other reflection points. This feature enables us to obtain a high spatial resolution of detection with high accuracy. In real-image experiments, reflection point position distributions on the planar glass plates of 3- to 10-mm in thickness were detected. The overall averages of position errors from the true are below 0.2 and 0.5mm along the lateral and vertical directions, respectively. The average of the error absolutes is less than 1mm and the standard deviation is less than 1.12mm for the lateral and vertical directions. Furthermore, it is made clear that the detection errors are caused by the quantization errors. The detection principle and system are simple, and the detection accuracy and spatial resolution, as well as the reliability, seem to be satisfactory enough for use in the inspection and production fields.
