Automatic collimation system by Talbot interferometry

This study concerns the automatic high precision beam collimation system using the Talbot interferometry. When the collimation beam is obtained placed point-source of light in focal position of the collimation lens, the defocus value is calculated from a moire fringe width in the Talbot interferometry using only two grating. With the advance of collimation, the moire fringe cannot be confirmed. Using the movement of moire fringe when one of grating shifts, the expanded moire fringe width is measured high-precisely from the phase difference of intensity change of two detecting points, using peak position of the cross-correlation coefficient. With the result of the defocus value, the collimator lens is positioned by motor controller.