Study on method of radiometric calibration for precision measurement of micro size damage site

摘要

Large aperture optical have high risk of damage when woke on high flux laser. For avoid lethal damages breakdown the expensive large aperture optical, replace the optical that damaged before damage site increase to can't repaired, we need precision measurement of optical surface damage sites size. The size of the optics which be detected is 400μm ×400μm, and the size of CCD array pixel is 4Kx4K which we selected, so pixel resolution only 100μm of the Optical Damage Online Inspection system, it hard to measurement damage sites which size less than 100μm. This paper describes a method of radiometric calibration to measure online optical damage site that greater than 50μm by Optical Damage Online Inspection system. Numerical statement gray on CCD of different size damage sites by select a fixed variable of illumination intensity, shutter and numerical aperture of image-forming system. Fitting a curve with suitable function of gray and actual size, precision measure optical damage sites that greater than 50um by the curve. Test rersults indicate that, the deviation less than 20% which measure size and actual size .This method settle problems of micro size damage site hard to measure online under the condition of long working distance and low optical resolution. At present, this method have used on Optical Damage Online Inspection system of high flux laser installation, it important significance for observation damage site size grown and accurately appraise the optical damage.