In order to measure the geometry of a micro-hole with high aspect ratio, we made the light coming out from the laser to
transmit in the reversal direction by double optical fibers coupling, modeled both the energy distribution at the end of an
optical fiber and the output of CCD, used zernike moment subpixel algorithm to locate the edge of an image and a
compensation algorithm to improve the precision of edge location. The effectiveness of the method newly developed is
verified through experiments. Experimental results indicate that the newly developed method can be used to measure the
geometry of a blind hole of 2.0mm depth with a diameter of about 0.2mm using a double frequency interferometer with a
repeatability uncertainty of less than 0.4m.