MARK READING METHOD OF MICROFILM DRIVING DEVICE

• Main Authors: ICHIZUKA AKIRA, YAMATO YOUICHI
• Format: Patent
• Language: English
• Published: 28.06.1985
• Subjects: ACCESSORIES THEREFOR; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USINGWAVES OTHER THAN OPTICAL WAVES; APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FORPROJECTING OR VIEWING THEM; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY; PHOTOGRAPHY; PHYSICS

PURPOSE:To read a mark accurately by changing a set reference value in accordance with the illuminance of a light source and variance of the density of a film base. CONSTITUTION:Before a microfilm 1 is loaded, the light of the light source is received directly by a photo sensor 9, and light source illuminance information passing an A/D converter 20 is inputted to a CPU, and one of switches S1-S3 is turned on in accordance with the level of this information, and an amplification factor is selected to prevent saturation of an operational amplifier 21. A transmitted light from a base part of the film 1 is received by the sensor 9, and the light reception signal is supplied to the CPU through the converter 20, and then, a threshold reference value corresponding to the illuminance of the light source and variance of the density of the film base based on the direct light and the transmitted light is determined by the CPU and is set to a binarizing circuit 22 through a D/A converter 23. A mark read output which corresponds accurately to presence/absence of a blip mark 12 is generated by the circuit 22.