Measuring shape and position change of micro targets based on speckle correlation and polarization

To solve the quantitative measuring problem of shape and position changes in micronano-scale, a method based onspeckle correlation and polarization is proposed. This method divides 650nm laser into S and P plane polarized light beams, which are focused on micro targets, incident and reflect near the normal line of surfaces. After passingthrough a polarizer, the reflected beams is directly recorded by a digital imaging chip as a two-dimensional specklepattern with polarization characteristics. This speckle pattern is the convolution of the reflection lights caused by therandom fluctuation of the target object's surface, be knew as complex interference pattern. Therefore, it can beregarded as a stationary two-dimensional random signal, and the correlation is used to calculate parameters of spatial domain. According to the principle of superposition, when there are multiple micro targets, the total correlation peak can be regarded as the superposition of the sub cross-correlation factors from multiple microtargets. That is, when the shape and position changes from multiple micro targets are consistent, the total cross- correlation peak is high and steep. Otherwise, it will divide into multiple sub cross-correlation peaks. Todistinguish the shape and position changes of targets corresponding to the deviation of different sub cross- correlation peaks, two polarization beams S and P, are currently used to correspond to two detection channels. This experiment used Sony IMX179 CMOS to achieve 0.08~1.41μm/pixel in-plane displacement sensitivity. Thermal expansion of the metal wires are used to achieve the shape and position changes, and the results met expectations.