Abstract
The purpose of this study is to measure no-contact three-dimensional surface profile by a focus method. A liquid varifocal lens is utilized to change a focal length by liquid pressure. Contrast images along the focal length are obtained by 4-step phase shifting technique using a liquid crystal grating. A distance can be determined by the relation between the pressure of varifocal lens and the peak position of contrast by the Gaussian fitting . An accuracy check of this measurement is conducted by moving a motor stage. The experiment values are in good agreement with calibrated values in the measurement range from 0 to 60mm with ±0.3 mm of accuracy. Surface profiles of a screw and a deep hole with 40mm have been measured to demonstrate for this method.
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