Patent ID: 6646736
Filing Date: 2003-11-11
Classification: G01N

Abstract:
A method for calibrating equipment for detecting impurities in transparent material, said detecting equipment including a light source to illuminate the material, a camera to detect light transmitted through the material and a signal processing apparatus for processing and analyzing signals from the camera representing the light transmission through the material, said method comprising the steps of:(a) displaying dark areas on a film of transparent material with a predetermined size larger than sizes desired for the calibration; (b) subsequent to step (a), reducing the dark areas to the desired sizes for the calibration using a repro- or microfilm camera to form a calibration film; (c) determining the actual sizes of the reduced dark areas; (d) determining the size of the dark areas on the calibration film using the detecting equipment; and (e) comparing the sizes of the dark areas of step (d) and the actual sizes of the dark areas of step (c) for calibration of the detecting equipment.