Rigid Disk Contaminant Detector
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
If a laser beam is aimed at a disk so as to form a very small angle with its surface, a small particle on the disk will be seen to reflect a portion of the beam. This article describes a method of detecting and counting the particles on a disk by utilizing a TV camera to pick up the light from the particles. The video signal output from the camera can be used to detect the presence of a particle. The background reflection from the disk is now not as large a factor because only a small portion of the disk is being sensed at one time. This eliminates the problem of background noise. Several characteristics of a TV camera must be taken into account for this system to work properly. The first is that a bright spot can activate several adjacent scan lines. This is taken care of with the circuit of Fig. 1.