Recording apparatus with double frequency driven liquid crystal shutter

Claim 1

Recording apparatus for optically writing on a photoreceptor in correspondence with image signals to be recorded comprising: (a) a light source for producing light; (b) a liquid crystal shutter for selectively transmitting light from said source; (c) means for focusing light transmitted by said liquid crystal shutter onto the photoreceptor; (d) said liquid crystal shutter being composed of a first transparent substrate provided with n-units of write selecting electrodes, a second transparent substrate provided with a plurality of recording signal electrodes which cross and are opposite the n-units of the write selecting electrodes, and a liquid crystal agent sealed between both substrates and whose dielectric anisotrophy becomes zero at a specified frequency f C , said write selecting and recording signal electrodes being provided with micro-shutters at the crossings therebetween; (e) a first supply means for supplying to the n units of the write selecting electrodes, write selecting signals having a frequency f H higher than said specified frequency f C , and a frequency f L lower than said specified frequency f C such that the phase of successive write selecting signals reverses after a time period Tw/n which is 1/n of the write cycle time Tw; and (f) a second supply means, responsive to said image signals, for supplying to the recording signal electrodes, recording signals of frequencies f H and f L having amplitudes that are the same as the amplitudes of said write selecting signals; (g) said first and second supply means being constructed and arranged such that during a selection period, in which a micro-shutter is selected by the write selecting signals, superposed driver signals are applied to the selected micro-shutter, said driver signals having either (i) the frequencies f L and F H throughout the selection period, or (ii) the frequency f H near the start of a selection period and of the frequencies f L and f H near the end of a selection period for establishing the on-off state of the selected micro-shutter; (h) said first and second supply means being further constructed and arranged such that, during a non-selection period in which a micro-shutter is not selected by the write selecting signals, said driver signals applied to a non-selected micro-shutter have the frequency f L near the end of a non-selection period and either (i) the frequencies f L and f H near the beginning of of a non-selection period, or (ii) no frequency near the beginning of a non-selection period for establishing the on-off state of the non-selected micro-shutter during a preceeding selection period.