Development of the micro displacement measurement system based on astigmatic method

A non-contact micro displacement measurement system with a long working distance is presented based on the astigmatic technology. The astigmatic method principle is to detect the shape change of the reflected laser beam on a four-quadrant photodiode. The laser beam shape changes with respect to the positions of the reflect mirror, because of the focal length difference of the astigmatic lens in sagittal and tangential planes. The test results of the implemented micro displacement measurement system show good performances of accuracy and reliability.