READING METHOD OF MARK INFORMATION

摘要

PURPOSE:To detect the stable signal in response to the form of a mark and the variation of the light irradiating angle to the mark surface by irradiating parallel light beams to the mark surface from the oblique direction and receiving only the light dispersed from the mark surface by a photodetecting element to transduce the dispersed light into an electric signal. CONSTITUTION:A light source 3 and a projecting lens system 4 are provided with inclination to a mark surface 2. The light of the source 3 is turned into approximately parallel beams through the system 4. These parallel beams are made incident to the surface 2 at an incident angle alpha from the direction parallel to the mark 1 and at an incident angle beta from the direction vertical to the mark 1 respectively. At the same time, a photodetecting element 5 and a photodetecting lens system 6 are set approximately parallel to the surface 2. Thus the light reflected directly from the surface 2 is avoided, and only the dispersed light is received by the element 5 and transduced into electric signal. Then the signal level is stabilized in response to the form of the mark 1 and the variation of light irradiating angle to the surface 2. Thus the information on the mark 1 is always read assuredly.