Improvement Of CCD Dynamic Range With Image Fusion For Laser Spot Detection

Collection and analysis of laser spots is a practical task in laser applications. With the wide use of CCD in image capture and photoelectric measurement, the laser parameter test method using two-dimensional CCD detectors has many special advantages. For example, it can quickly detect spatial irradiance map of laser spots and pulse laser beam's parameters. But its intrinsic dynamic range cannot meet many practices. Increasing CCD dynamic range is one key to extend the field of CCD application.The characteristics of a laser spot are high power and high dynamic range. The principle and method of extending dynamic range of CCD by means of taking and then fusing multiple pictures of the same scene with various exposure times is presented in this paper. Both high and low intensity information are obtained respectively with short and long exposure time. The combined response curve is gotten with least square method. Then the effective pixel values of these multiple image are fused using weighting function and the extended high dynamic range image is achieved. We test the mentioned method through the measurement of the Fraunhofer diffraction pattern of a 100μm diameter pinhole illuminated by He-Ne laser and successfully get its high effective dynamic range image with diffraction details. Further, through the measurement of He-Ne laser beam and Gaussian fitting, the mentioned method is validated.This paper utilizes two programming languages synthetically to carry out the spot images collection and the spot parameter analysis. Visual C++ is used for image capturing, displaying and controlling for its high efficiency and work speed, while Matlab is used for image fusion and processing for its powerful data processing ability, so that their superiority are fully used. And good results are obtained.