Sub-pixel calibration of CCD in Moiré fringes measurement based on image processing

The measurement based on Talbot effect and Moir fringes is suitable for lens of long focal length. To get the focal length accurately, the width or slope coefficient of Moir fringes are essential parameters. The CCD calibration precision should be improved due to its significant impact on measurement accuracy. A CCD calibration is put forward. The grating is set as the self-reference to calibrate the equivalent length of CCD pixel. The calibration is presented based on image processing and Gauss curve fitting. The calibration accuracy is proved less than 0.1 pixel by calibrating the standard fringes generated by MATLAB. Finally, the CCD pixel is calibrated by grating and gauge block separately, the results show that the calibration method using grating is simple and precise.