FSM-300 or FSM-320 Fast Steering Mirror & FSM-CD300B ...
FSM-300 or FSM-320 Fast Steering Mirror & FSM-CD300B ...
FSM-300 or FSM-320 Fast Steering Mirror & FSM-CD300B ...
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12 <strong>Fast</strong> <strong>Steering</strong> Mirr<strong>or</strong> Technology<br />
Figure 2: <strong>FSM</strong> mirr<strong>or</strong> head showing the eight basic components.<br />
The voice coil actuat<strong>or</strong>s 1 provide the t<strong>or</strong>que necessary to tilt the mirr<strong>or</strong> substrate.<br />
Four actuat<strong>or</strong>s are mounted behind the mirr<strong>or</strong>, one in each quadrant.<br />
Voice coils are connected in pairs along the diameter of the mirr<strong>or</strong> and<br />
operate in a push/pull manner, rotating the mirr<strong>or</strong> about the axis that bisects<br />
them. Two actuat<strong>or</strong> pairs (four coils) plus a co<strong>or</strong>dinate transf<strong>or</strong>mation are<br />
used to produce two <strong>or</strong>thogonal rotations θx and θy about the X and Y axes.<br />
The high f<strong>or</strong>ce generated by four distributed actuat<strong>or</strong>s rotates large mirr<strong>or</strong>s<br />
m<strong>or</strong>e effectively than the one actuat<strong>or</strong> used in galvanometer scanners. The<br />
distributed f<strong>or</strong>ce combined with thick optics enables the <strong>FSM</strong> mirr<strong>or</strong> head to<br />
preserve static and dynamic surface flatness, excellent positional resolution,<br />
large angular range and rapid motion. The coil p<strong>or</strong>tion of the actuat<strong>or</strong>s is<br />
placed within the supp<strong>or</strong>t structure and contacted to a heat sink such that heat<br />
produced in the actuat<strong>or</strong> is dissipated far from the mirr<strong>or</strong> surface, thus<br />
minimizing thermal dist<strong>or</strong>tions.<br />
A flexure suspension system is used to supp<strong>or</strong>t the mirr<strong>or</strong> carrier that holds<br />
the mirr<strong>or</strong>. This system allows free rotation about <strong>or</strong>thogonal X and Y-axes<br />
while constraining side-to-side motion, rotation about the n<strong>or</strong>mal (Z) axis<br />
and “pogo” motion along the Z-axis. Different types of flexure systems are<br />
used f<strong>or</strong> different <strong>FSM</strong> applications. Some flexure systems are stiff (large<br />
spring constant) and offer a relatively stable and repeatable power-off mirr<strong>or</strong><br />
1 Hist<strong>or</strong>ically, voice coils were first used in loudspeakers, from which they derive their name. A linear<br />
voice coil consists of a tubular coil of wire situated within the radially <strong>or</strong>iented magnetic field of a<br />
permanent magnet. When current flows through the coil, a f<strong>or</strong>ce is generated that causes axial (linear)<br />
motion. This linear motion is then used to move the mirr<strong>or</strong>.
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