Laser Spot Detection System Based On CMOS Digital Image Sensor

The laser spot detection is a key technology in the optical measurement. This paper aims to locate the center of the laser spot after long-distance transmission, with the methods of vision inspection. The system has very high practical value and is widely used in laser spot drift detection,laser simulation shooting performance testing and alignment degree detection of rail and so on. Typical visual inspection systems are simulated by the CCD camera,frame grabber and a computer. The processing of the digital images is completed within the computer.Because of the defects of the traditional visual inspection,such as high cost, big volume, low level of integration and low security,a new system of spot detection using CMOS digital image sensor as acquisition front-end and using programmable logic device FPGA as the core control chip is presented. This program with all-digital acquisition and transmission has high reliability and anti-jamming capability. Single-chip acquisition module composed of CMOS image sensor improves the integration of system and effectively reduces the system's size and cost,being easy to install and carry. Image algorithms processing by FPGA hardware have greatly increased calculation speed and meet the requirements of embedded systems.For the hardware and the circuit of the system,the FPGA chip EP3C16F484C8 is selected as the processor and the image sensor chip MT9T001 is used for designing image acquisition module. After correct configuration for CMOS by I2C bus,under the proper light conditions,the clear spot image will be got. At the same time,the control module of SDRAM has been designed in FPGA,with which the image data can be stored into SDRAM. Through a series of image processing such as distortion correction, filtering, binarization and center extraction,the center coordinates of the laser spot have been extracted successfully.In this paper,circuit debugging and program changes have been done to the new system and the result coincided with our expectation. On this basis,the experiment of precision measurement shows that system error is less in 1mm,meeting the design requirements.