A Compact Three Degrees-of-Freedom Motion Sensor Based on the Laser-Self-Mixing Effect

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The simultaneous measurement of the linear displacement and two rotation angles (yaw and pitch) of a moving object using a laser sensor based on the self-mixing effect is reported. The laser head includes three commercial diode lasers equipped with monitor photodiodes. The target is a plane mirror attached to the moving object. The linear and angular resolutions are 0.7 <emphasis><formula formulatype="inline"><tex>$\mu$</tex></formula></emphasis>m and <emphasis><formula formulatype="inline"><tex>$0.8\times 10^{-3\circ}$</tex></formula></emphasis> (2.7 arcsec), respectively. The linearity of the sensor response has been verified over a range of 1 m and <emphasis><formula><tex>$\pm$</tex></formula></emphasis>0.4<emphasis><formula formulatype="inline"><tex>$^{\circ}$</tex></formula></emphasis>. Using three retroreflector prisms with a diameter of 10 mm instead of the plane mirror, the angular range of yaw and pitch has been improved by one order of magnitude. </para>