Multiplexing of transient image bar

Claim 1

An improved liquid crystal image bar for use in an electrophotographic printer of the type having a moving photoconductive member, means for pre-charging the photoconductive member prior to the formation of latent electrostatic images, means for developing the latent images with toner particles, means for transferring the developed images to permanent record sheets, means for fusing the developed images to the record sheets and means for cleaning the photoconductive member before it is pre-charged, the image bar being used to form the latent images on the photoconductive member one line at a time in response to digitized data signals during the operating mode of the printer, including: a liquid crystal material; first and second parallel, elongated glass substrates enclosing the liquid crystal material, each of the glass substrates having inner and outer surfaces, the inner surfaces confronting each other and being spaced a predetermined distance from each other; a first plurality of transparent electrodes being located on the inner surface of the first glass substrate and a predetermined, equally spaced second plurality of transparent mutually parallel electrodes being located on the inner surface of the second glass substrate, the electrodes on the second glass substrate being perpendicular to the electrode on the first glass substrate; a transparent film being coated over the electrodes on each of the inner surfaces of the first and second glass substrates; parallel polarizers being positioned on each of the outer surfaces of the glass substrates; an illuminating means for directing light towards a one of the polarizers from a location spaced therefrom; an alternating voltage source; means for energizing the electrodes by connecting them to the voltage source to prevent the passage of light through the image bar during the operating mode of the printer; means for de-energizing selected ones of the second plurality of electrodes on said one glass substrate for a predetermined time period followed by immediate energization thereof in response to receipt of digitized data signals, de-energization of each selected electrode for the predetermined time period followed by energization thereof being a cycle which causes a momentary passage of light through the image bar in the vicinity of said cycled electrode, the momentarily passed light being a burst of light which impinges on the moving photoconductive member to discharge a precharged region on the photoconductive representing a pixel thereon, thus, forming one line of a latent electrostatic image by the discharge of pixels representing the background regions of the latent image, the improvement comprising: a shift register, one portion of said digitized data signals representing one portion of said one line being clocked into the shift register while another portion of said digitized data signals forms a latent electrostatic image of another portion of said one line.