Patent ID: 6326606
Filing Date: 2001-12-04
Classification: G01N

Abstract:
A light-permeable portion shape checking apparatus comprising a light source for emitting checking light illuminating an object to be checked, the object having light-permeable areas transmitting light and light-blocking areas blocking light, a first sensor for photoelectrically converting light emitted from the light source and transmitted through the light-permeable portions of the object, a second sensor for photoelectrically converting the illuminated light from the light source, correcting means for correcting the output of the first sensor on the basis of the output of the second sensor, an analog-to-digital converter for converting the corrected sensor output from the correcting means to digital data, and computing means for shape checking the object according to the digital data from the analog-to-digital converter,the correcting means including a ratio signal supplying means for supplying a ratio signal representing the ratio between the output signals of the first and second sensors, and an amplifying means for amplifying the waveform of the first sensor output signal such that the maximum and minimum levels of the ratio signal are above the upper limit and below the lower limit of the analog-to-digital converter, respectively.