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REFLEX SCAN IN PRINTERS Disclosure Number: IPCOM000025985D
Original Publication Date: 1989-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 181K

Publishing Venue

Xerox Disclosure Journal


The relative motion requirements for successful printing of images is physiologically/ sychologically based on the viewer's perception. Thus, in

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Proposed Robert M. Lofthus U.S. C1.358/260 Classification

Int. C1. H04n1/40

The relative motion requirements for successful printing of images is physiologically/ sychologically based on the viewer's perception. Thus, in

total relative motion, considering both input and output devices, not exceed a particular '%bathtub" curve in which spatial frequency is given as a function of the variation in pixel-to-pixel placement. For the more difficult task of printing half and continuous tones, other "bathtub" curves, much below the aforementioned curve for text printing, are specified. The maximum relative displacement allowed between pixels for this latter case is fractions of a micron. Clearly, it is a significant, if not monumental challenge to design the electrical/mechanical systems that will satisfy these relative motion requirements in a cost efficient manner. This proposal describes a method of meeting these strenuous motion requirements.

TKree basics assumptions are at the heart of this proposal:

1.Most printers possess an asynchronous relationship between input and output.

2.A high resolution, rotary, incremental encoder (up to 20,000 lineslrev) that is software controllable is available.

order to success

P ully design a text printer, it is necessary to guarantee that the

3.A high resolution belt photoreceptor encoder is available.

A macroscopic full width read bar is used to scan the document. This read bar has a resolution of 600 pixeldin and will "deliver" information at a clocked rate of 7,200 bits per 110 microseconds, i.e., a full 12 inch long read bar can dump its line, serially, in a clocked fashion, in 110 microseconds. Let us further assume that this time of 110 microseconds includes "overhead" and thus, after 110 microseconds, the next line can be scanned. With these assumptions, the fastest document processed speed (slow scan speed) is then
15.152 idsec. Assumin an intercopy gap of 1 inch for A4 documents fed long

The device controlling document motion in the slow scan direction is a vacuum drum with a circumference of 10 inches and this device firmly "grasps" the document in the scan region so that document motion past the read bar can be inferred from measurements of the rotary motion of the drum. An incremental encoder with a resolution of 6,000 Ip/rev is mounted directly on the drum.

edge first, we'll potentia B ly see an input document throughput of 95.7 cpm.

Volume 14 Number 3 May/June 1989 157

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The device receiving information from the full width read bar system will, of course, accept information at the same instantaneous rate as that already mentioned, i.e., 7,200 bits per 110 microseconds. It will be required, however, to accept this information in asynchronous fashion, i.e., it will be sent a packet of information, containing 7,200 bits, serially fed at a co...