RESONANT SCANNING APPARATUS FOR DEFLECTING A MIRROR

1,152,730. Mirror mountings. TEXAS INSTRUMENTS Inc. Aug. 18, 1966 [Sept. 1, 1965], No.37084/66. Heading G2J. [Also in Division H4] Relates to an optical scanning device in which a mirror is moved to cause reflected light to trace a curved line e.g. a circle or spiral. In a first embodiment, Fig. 1, a mirror 10 is attached to a glass or quartz resonant fibre 50 itself attached to a Piezo-electric transducer 52 having two pairs of poles spaced 90 degrees apart to which the alternating current from a source 22 is applied directly and via a phase-shifting circuit 40. The length of the fibre is adjusted so that it resonates at the frequency at which the scanner is to operate i.e. the frequency of the alternating current. The fibre amplifies the deflection (stresses) of the transducer, causing mirror 10 (preferably concave) to move and thus reflect light in a circular scan if the phase-shift is 90 degrees, or a spiral scan if the sine waves are ramp-modulated. In further embodiments the mirror is attached to a resonant fibre itself attached to the ends of two Piezo-electric length expander bars to which the alternating currents are applied, Fig. 2 (not shown); or the mirror is secured to a resonant fibre made of magnetic material which is clamped at its other end, the mirror-fibre-clamp combination being magnetized by a direct current biasing coil, and the resonant fibre being surrounded by electromagnetic driving elements to which the alternating currents are applied, Fig. 3 (not shown).