Browse Prior Art Database

"BAD" CCD PHOTOSITE DETECTION AND COMPENSATION TN AN ELECTRONIC SCANNING ENVIRONMENT

IP.com Disclosure Number: IPCOM000027230D
Original Publication Date: 1995-Oct-31
Included in the Prior Art Database: 2004-Apr-07
Document File: 4 page(s) / 197K

Publishing Venue

Xerox Disclosure Journal

Abstract

There is believed to be a shortage of techniaues for Droviding: a critical customer and/or input from recei;ing "streak$7 areas *in a crirical image processing application. To eliminate such streakiness, in one example, a field replacement of a CCD module with a replacement CCD that has been previously selected for its uniformly responding photosites is provided. This is a costly and time consuming process due to low production yields of these so-called perfect CCD components. The numbers of these CCD modules are small and therefore cannot be utilized across a product line for these aforementioned constraints.

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

Proposed Classification
U.S. C1.358/443 Int. C1. H04n 1/40

"BAD" CCD PHOTOSITE DETECTION AND COMPENSATION TN AN ELECTRONIC SCANNING
__ -~~
ENVIRONMENT
William A. Blitz
Roger L. Triplett
Robert L. Traister

START

ci

'es

10

Sum Pixel Data 12

Divide Data Into

16 Small Areas

Get Average

'6 Store Location Pixel, "Bad" 1 I

I

Yes -qo

Areas Done

No

- e

XEROX DISCLOSURE JOURNAL Vol. 20 No. 5 September/October 1995 467

2o

Area of Value 4 I

A I

Get Pixel

22 Area in Value 4

[This page contains 1 picture or other non-text object]

Page 2 of 4

"BAD" CCD PHOTOSITE DETECTION AND COMPENSATION IN AN ELECTRONIC SCANNING ENVIRONMENT (Cont'd)

Background

There is believed to be a shortage of techniaues for Droviding: a critical customer and/or input from recei;ing "streak$7 areas *in a crirical image processing application. To eliminate such streakiness, in one example, a field replacement of a CCD module with a replacement CCD that has been previously selected for its uniformly responding photosites is provided. This is a costly and time consuming process due to low production yields of these so- called perfect CCD components. The numbers of these CCD modules are small and therefore cannot be utilized across a product line for these aforementioned constraints.

Description

Referring to FIGS. 1 and 2 a process for identifying "out of spec" CCD photosites in an electronic scanning system is shown. By placing known uniform density target(s) in an image plane of a CCD array, responses of every pixel in that CCD array can be characterized and evaluated against all/or any other pixel by a test criteria. Referring specifically to Step 10 of FIG. 1 a first scan line of a scanning system under examination is obtained. Each scan line consists of N pixels whose data is a digital representation of the target density. At step 12, pixel data, which can be either uncorrected or corrected, is summed as follows:

pixelN-1 = pixel ~-1

       + newpixelN-1 pixelN = pixelN + newpixelN pixel N + 1 = pixelN+ 1 + newpixelN+ 1 etc.

Through Step 14, a preselected number of Y scanlines are sampled for the present algorithm. It will be appreciated that deterministic noise and localized non-uniformities in a target are integrated by sampling a sufficient area of the target. Once a sufficient area has been obtained through use of steps 10, 12
and 14, data in localized groupings is analyzed at step 16 to negate spatial non- uniformities along the fast scan direction. In one example, a grouping would represent 1% to 10% of the total data. At step 20, the cumulated data of N pixels is summed and then divided by N to obtain a specified site average. The cumulated data for a specified pixel within the area is via step 22, obtained. With step 24, each pixel within the area is compared with the average of the area. If the pixel is outside X%, then that pixel is designated as "bad" (step 26)
and its location is stored for future reference and control. By way of steps 30 and...