Importance

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Abstract

In those high speed laser scanning systems, particularly those used in printing, employing an acousto-optical modulator driven at two or more carrier frequencies for scanning with a plurality of focussed beams simultaneously in order to reduce the required deflection scan rate and to better the rise and fall times of the waveforms, unwanted intermodulation effects arise. These undesirable intermodulation effects can be reduced or largely eliminated by increasing the difference in the carrier frequencies such that the diffracted beam spacing is increased considerably and utilizing either a scan line interlace scheme or a staggered beam scheme to maintain the required scan line spacing. In the latter case, the modulator is situated with the direction of propogation of the acousto-waves between zero and 90 degrees to the direction of image pattern scanning. The angle is made sufficiently large as to make one light beam spot in one scanning line lag a corresponding spot in the adjacent line. In a further approach the two techniques are combined.

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First Claim