Research On Key Technologies Of Laser Anti-counterfeit Pattern Detection And Development Of Its Sensor

The laser holographic anti-counterfeit patterns have been widely applied in the field of anti-counterfeit. Signal obtained from laser anti-counterfeit pattern is different from that from other patterns, therefore, in order to solve problems of quality control in the process of laser anti-counterfeit patterns, it is necessary to study on key technologies of laser anti-counterfeit pattern and develop a sensor for laser anti-counterfeit pattern detection, which has important theory significance and application significance, also has good economic efficiency and social efficiency.Research in this paper focus on the design of special-purpose lightsource, intelligent deviation rectifying controller based on detection of characteristic symbol, image capturing and its processing. Several aspects of work mainly to be done are as follows.(1) Through the comparason between quality of images of several embossing laser anti-counterfeit patterns under different conditions of different wave length, different incident angle and different luminous intensity, characteristics the embossing laser anti-counterfeit patterns are obtained and one kind of lightsource using the color light emitter diode with three basic color is designed, which the wave length and the illumination angle and the intensity can be adjusted.(2) Image signal captured by CCD are transported to FPGA and image parameters such as mean value, contrast gradient are calculated in real-time and transported to MCU as the feedback signal. Adjustment of parameters for light source are transported from MCU to FPGA and used to control PWM signal, which constitute closed-loop control for intelligent adjustment of parameters for light source.(3) In the production process of embossing laser anti-counterfeit patterns, CIS image sensor is used to detect position of the characteristic symbol. Deviation is obtained by comparing current position of the characteristic symbol with the equilibrium position and the step motor is drove to correct the deviation, which realizes the intelligent control of detection and correction.(4) The timing driving circuit and the integration time adjustment circuit areintegrated in a piece of programmable logical component CPLD, which realized the integration and miniaturization of image sensor. Integration time adjustment realized by that MCU exchanging data with CPLD through SPI interface.(5) Several kinds of images pre-processing algorithm are used to process image of embossing laser anti-counterfeit pattern captured by image sensor. A suitable image pre-processing algorithm is selected from those algorithms through the analysis and comparative of all the pre-processing results. Circuits of image pre-processing algorithm based on parallel computation and the assembly line technology in FPGA are presented.(6) The sensor which has detection and correction functions based on detection of characteristic symbolic line is applied in the production line of RFID card for deviation detection and correction of the antenna foundation plate successfully, and excellent application effect are obtained.