Torque while turn-around scan mirror assembly

Claim 1

A scan assembly comprising a housing, a scan member mounted by means of flexural pivots to said housing, a torquer device mounted between said scan member and said housing for providing in response to an applied electrical control signal, energy to said member so as to cause it to rotate on said flexural pivots, at least two spring means each of which are disposed for contacting said scan member near the end of its travel in one respective direction, for absorbing energy therefrom and for reapplying a portion of said energy to drive said member in the opposite direction, said spring means each include at least one leaf spring mounted so as to be in substantial engagement with said scan member during at least a portion of the turn-around period at the end of each scanning cycle, and wherein the improvement comprises circuit means for sensing the contact of said scan member with said spring means and for applying a control signal to said torquer so as to impart during the turn-around period of said scan member the energy required to maintain a substantially constant scan rate for said member with said control signal comprising first and second segments of opposite polarity and poled so as to drive said torquer device to add energy to the scan mirror assembly during the deflection and return travel portions of the movement of said leaf springs and said circuit means including means for comparing the scan angle sequence of said member to that of a reference signal pulse train and for controlling the duration of said control signal so as to substantially maintain a scan angle sequence which is determined by said reference signal pulse train.