Galvanometer-type tilting-mirror scanning system and circuit therefor

DETAILED DESCRIPTION What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims: 1.
In a scanning system of the type which scans originals by shifting an image of an original projected onto the photodiode row of a charge-coupled device in a direction transverse to the photodiode row, in combination, a galvanometric tilting-mirror mechanism including a mirror mounted for tilting motion and used to shift the projected image of an original to be scanned, and including an oil-filled structure operative for damping the motion of the tilting-mirror mechanism; heating means operative for stabilizing the temperature of the oil in the oil-filled structure; control circuit means generating a control signal which determines the tilting motion of the mirror and is comprised of plural control-signal components, including a sawtooth-waveform component which determines the forwards-direction scanning sweep speed of the tilting mirror, a tiltback component in the form of a pulse of a polarity causing the tilting mirror to perform a rapid tiltback motion, a forwards-accelerating component in the form of a pulse of a polarity which brakes the rapid tiltback motion and accelerates the mirror back up to its forwards-direction scanning speed, the sum of the durations of the tiltback component and the forwards-accelerating component not exceeding the vertical blanking interval of the standard T.
V.
scanning schedule employed, and a corrective component in the form of a pulse which compensates for the loss of linearity as between the sawtooth-waveform component and the motion of the mirror which would occur in the absence of the corrective component.
2.
A scanning system as defined in claim 1, the control circuit means including adjusting means operable for adjusting the amplitudes of the sawtooth-waveform component, the tiltback component and the forwards-accelerating component independently of one another.
3.
A scanning system as defined in claim 1, the control circuit means including means generating rectangular pulses synchronized with the sweep flanks of the sawtooth waveform component and differentiating circuit means deriving the corrective component from the rectangular pulses by differentiating the latter, the differentiating circuit means having a time-constant corresponding to the time interval during which said loss of linearity would occur in the absence of the corrective component