Towards High Resolution Absolute Angle Sensing using Dual-Wavelength Laser Speckle

We present a two dimensional angle sensor with greater than 0.01 degrees resolution, using dual-wavelength laser speckle. The technique uses speckle correlation of a double speckle pattern, determining absolute surface tilt from a single frame. A constructed sensor was used to measure a grid of 2D angles between
$\pm 0.25^{\circ}$
rotating around both
$x$
and
$y$
axes. Sensor performance was limited by laser mode instability effects, however an analysis of measurements demonstrated that a stable mode output could achieve bias errors of less than 0.010°, and standard deviations of 0.003° around
$x$
and 0.021° around
$y$
.