  Speckle correlation based optical levers SC OptLev possess attractive
characteristics suitable for sensing small changes in the angular orientations
of surfaces. In this study, we propose and demonstrate a spatial multiplexing
technique for improving the dynamic range of SC OptLev. When the surface is in
its initial position, a synthetic speckle intensity pattern, larger than the
area of the image sensor is created by transversely shifting the image sensor
and recording different sections of a larger speckle pattern. Then, the
acquired images are stitched together by a computer program into one relatively
large synthetic speckle pattern. Following the calibration stage, the synthetic
speckle intensity pattern is used to sense changes in the surfaces angular
orientation. The surface is monitored in realtime by recording part of the
speckle pattern which lies within the sensor area. Next, the recorded speckle
pattern is a cross correlated with the synthetic speckle pattern in the
computer. The resulting shift of the correlation peak indicates the angular
orientations of the reflective surface under test. This spatial multiplexing
technique enables sensing changes in the angular orientation of the surface
beyond the limit imposed by the physical size of the image sensor.
