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Laser triangulation sensors suffer from the varied reflected light intensity which is due to the different object surface reflection characteristics. This varied reflected light intensity causes asymmetry of light spot shape, shifting of light spot center, and so on. This condition decreases the accuracy of measurement. Furthermore, it causes the linear CCD inside the sensor to go out of dynamic range, which is called blooming. Unlike plane CCD, linear CCD shows an asymmetry overflow phenomenon when blooming occurs. This phenomenon will limit the dynamic range and decrease the accuracy of laser triangulation sensor that is based on the linear CCD. However, we found the leading edge of light spot image on CCD array kept stable while scattering light intensity varied and the center of the light spot image shifted. Thus we designed a novel triangulation sensor which used the leading edge to indicate the location of light spot on the CCD, rather than using the center of light spot.

A self-calibrating phase-shifting technique using a Michelson Interferometer is presented to measure phase distribution more accurately in Digital Speckle Pattern Interferometry (DSPI). DSPI is a well-established technique for the determination of whole field deformation via quantitatively measuring the phase distribution of speckle interferograms that use the phase shifting technique. In the phase shifting technique, the phase distribution in a speckle interferogram is quantitatively determined by recording multiple intensity images (usually four images) in which a constant phase shift, e.g. 90 degrees, is introduced between each consecutive image. A precise phase determination is greatly dependent on the accuracy of the phase shift introduced. The popular methods to minimize the error resulting from inaccurate phase shift use various algorithms and need to record five or eight images (rather than four images).