method and device for lateral registration of consecutive frames with an often led zeilendrucksystem in a single pass

摘要

An image bar recording system. which, in a preferred embodiment, utilizes a plurality of LED image bars to form a plurality of latent images. which may subsequently be developed in different colors. The print bars are initially aligned so that each color image is in precise lateral registration on the surface of a photoreceptor belt. The registration is accomplished by means of a Z-shaped pattern (30) of slot-like apertures (30A,30B,30C) along the non-image edge of a photoreceptor belt (17), the pattern extending in the direction of the belt motion (process direction). Each print bar is positioned adjacent the belt surface and the elements of the LED array are selectively energized to form the desired image. An array of non-imaging elements (52) is contiguous to the image-forming pixels (50) and positioned along the belt so as to be periodically visible through the apertures of the Z-shaped pattern by photosensors positioned beneath each of the print bars. By an iterative energization process, and by timing the periods between the detection of the energised element through the apertures, one of the end pixels of each array is identified as a fiduciary pixel lying at the center trace line of the Z-shaped pattern. Upon recognition of the fiduciary pixel (e.g. p4), the system controller establishes a #1 write pixel at the other end of the array. Each bar is initially laterally aligned by enabling fiduciary and #1 pixels in the same manner. A predetermined tolerance is stored in system memory and in circuitry associated with detecting the position of the fiduciary pixel. During operation, if the tolerance is found to be exceeded (the fiduciary pixel is detected as no longer along the center trace line of the Z-shaped pattern), correction signals are generated which select a new fiduciary pixel which is within the tolerance range, the new fiduciary pixel also establishing a new #1 write pixel. The detection circuitry is designed to discriminate between the exceeding of tolerance conditions caused by lateral motion of a print bar or by lateral motion of the photoreceptor belt, and to generate the appropriate correction signals. IMAGE