Abstract: A method and apparatus which eliminates beat like artifacts that occur when an RF signal is mixed with a pulsed signal of similar, but not identical, frequency to the RF signal. A controller for synchronizing the phase of a RF carrier signal to a video signal provides beat elimination in a high pixel rate laser printer. The video signal and RF carrier signal are multiplied and sent to an acousto-optic modulator for pulsing a uniform burst of energy in the form of a laser beam to a photoconductor. The controller may include a synchronous gateable crystal oscillator with logic such as TTL, CMOS, ECL or equivalent logic functions using discrete transistors, where the synchronous gateable crystal oscillator is frequency dependent upon a laser printing speed. Eliminating imaging defects such as variable pixel width and density provides a sharper, uniform pixel printout.

Abstract: In a raster output scanner, a system for using one original beam and one facet of a rotating polygon to generate two consecutive scan lines. The original beam is first separated into two beams in a beam splitter. The resultant beams are polarized ninety degrees apart, and directed to the modulator. The beams are a sufficient distance apart so that the A/O modulator can modulate each beam with a minimum of crosstalk. The output beams are then brought together to within one scan line separation by a beam recombiner, which is a reversed beam splitter. The beams can be brought together to this close proximity without optical interference because the beams are plarized ninety degrees apart.

Abstract: A raster output scanner which can be instantly varied between the most common spot densities, such as 240, 300, 400 and 600 spots per inch in the slow scan direction. The scanner produces a plurality of scans per inch, either by scanning with one beam or several simultaneous beams, the number of scans per inch being a common denominator of all of the spot densities. For example, for the above spot densities, 1200 scans per inch would be required. Then each scan is independently modulated so that the correct number of spots per inch are generated. Thus, for example, if 4 consecutive scans are used to create one spot, then the spot density will be 300 spots per inch.

Abstract: A variable attenuator for controlling scanning beam intensity having a twisted nematic liquid crystal for rotating the beam, a polarization analyzer for detecting the degree of alteration in the polarization of the beam by the crystal comprising a polarizing beam splitting plate separating the beam into primary and secondary beams, a photocell providing a signal reflecting the intensity of the secondary beam, a control for adjusting power to the crystal in response to the signal, a glass plate at an angle of incidence equal to but opposite from that of the beam splitting plate for correcting aberrations to the primary beam, and an anti-reflective coating on the optical surfaces of the crystal.In a second embodiment, the plates are replaced by a polarizing cube. In a third embodiment, to obviate fluctuations in the attenuator output, the glass plate instead serves as the source of the beam component to the photocell.

Abstract: An acousto-optic deflector having a plurality of transducers formed on a planar surface of the acousto-optic medium wherein the incident laser beam is maintained at the Bragg angle as the deflection angle is changing by utilizing electronically introduced phase delays between adjacent transducer electrodes.