A sequence pulse counting method for shape measurement in dual-beam speckle interferometry

A temporal approach to fast shape measurement is presented. In principle, the rotational object method is used in combination with the sequence pulse counting method (SPCM) to determine the height of the object through calculating the related phase. Two specimens are tested to demonstrate the validity of the approach. One is an object covered by a Chinese character (tea) with a height variety of 0.3 mm, and the other is an object surface with a relatively large fluctuation of 3.5 mm. The experimental results are compared with mechanical measurements. An axis shifting method is also proposed to determine shapes with relatively large fluctuations. Effects of such parameters on the height measurement as incident angle of the dual light beams, tilting angle of the object, and azimuth angle of the measured point are discussed as well.