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Browse Prior Art Database

BAD PIXEL DELETION TECHNIOUE FOR LED PRINTERS

IP.com Disclosure Number: IPCOM000025229D
Original Publication Date: 1984-Feb-29
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 160K

Publishing Venue

Xerox Disclosure Journal

Abstract

In Image Input Terminals, the technique of "bad pixel deletion" has been used in the past to eliminate the effects of pixels which are non-functional on solid state image sensors. A small number of bad pixels are compensated for in the following manner. During calibration, bad pixels are identified by isolating those which fail to meet certain minimum standards. These can be isolated single pixels, preferably a small number per solid state sensor. During operation then, the pixels identified as being "badt1 are deleted by replacing their value with the value of the pixel immediately preceding the bad pixel. The result is that solid state imaging sensors which have a small number of bad pixels after fabrication can be used, thereby improving the yield considerably. Also, bad pixels which develop after installation in systems can also be compensated in the same way, eliminating service calls for single isolated malfunctions.

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XEROX DISCLOSURE JOURNAL

----c

BAD PIXEL DELETION TECHNIOUE FOR LED PRINTERS
Ronald G. Matteson

Proposed Classification
U.S. Cl. 358/240 Int. C1. H04n 3/12

-b -L

BINARY DATA(VIDE0) SCAN LINE

TRANSFER

7 I

STORPGE SHIFT. REG ARRAY

* REG 1 : DRIVERS 8

B I NARY DATA (VIDEO) FIG 20

FOR EVERY SCAN LINE

LIGHT COLLECTOR

SHIFT- STORAGE

.

L

/- --

1 lp

TEST

~c)% BAD PIXELS

Volume 9 Number 1 January/February 1984 69

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BAD PIXEL DELETION TECHNIQUE FOR LED PRINTERS (Cont'd)

In Image Input Terminals, the technique of "bad pixel deletion" has been used in the past to eliminate the effects of pixels which are non-functional on solid state image sensors. A small number of bad pixels are compensated for in the following manner. During calibration, bad pixels are identified by isolating those which fail to meet certain minimum standards. These can be isolated single pixels, preferably a small number per solid state sensor. During operation then, the pixels identified as being "badt1 are deleted by replacing their value with the value of the pixel immediately preceding the bad pixel. The result is that solid state imaging sensors which have a small number of bad pixels after fabrication can be used, thereby improving the yield considerably. Also, bad pixels which develop after installation in systems can also be compensated in the same way, eliminating service calls for single isolated malfunctions.

It would be an advantage to be able to apply the same philosophy to electronic printers which also use arrays of printing elements such as ink jet printers, LED printers and electrostatic printers. Unfortunately, the dual of the image input terminal case cannot be used since each discrete element of the output transducer must be used and must be operable. A way of compensating for bad pixels has been devised however, and is explained below.

70

    XEROX DISCLOSURE JOURNAL Volume 9 Number 1 January/February 1984

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BAD PIXEL DELETION TECHNIQUE FOR LED PRINTERS (Con t'd)

As an example and referring to drawing Figure I, an LED array 1 exposes a photoreceptor 5 by means of a row of closely spaced light emitting diodes. Each diode is either on or off for a given line of the output image, representinq 1's or 0's in the output data. Typically, video data in binary form is applied to a shift register 6 which accepts a complete scanline of data. The data is then transferred to a storage register and driver stage 7 which stores the scanline of data and drives the LED array 1. Bits which have the value of "one" are used to illuminate an LET), those having a value of "0" retain the LED in the off configuration. While the LED array 1 is being controlled for one scanline, the next scanline is being serially supplied to the shift register 6 for transfer at the end of the exposure of the preceding scanline. In this way, scanlines are sequentially...