IP Library › Granted Patent US 6,999,212
Granted Patent B2
US 6,999,212 · App. 09/900,865 · Granted Feb 14, 2006

Back-light module for image scanning device and method for calibrating illumination with the back-light module

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Quick Facts
Patent No.
US 6,999,212
App. No.
09/900,865
Granted
Feb 14, 2006
Kind
B2
Abstract

A back-light module for an image scanning device includes a casing, a pair of tubular lamps, a light guide plate, and a frosted transparent plate. The image scanning device includes a document supporting plate and an optical scanning module movable in a longitudinal direction. A calibration of illumination with the back-light module is done by (1) activating the back-light module to project light onto the optical scanning module, (2) driving the optical scanning module in the longitudinal direction, (3) obtaining illumination signals associated with selected pixels of a longitudinally-extending calibration zone formed on the document supporting plate, (4) comparing each illumination signal with a reference to obtain a result and manipulating the result to obtain a calibration parameter, and (5) calibrating the illumination of pixels of an image with the corresponding calibration parameters in scanning a transmissive original document.

Claims (11)

1. A method of calibrating illumination of a back-light module of an image scanning device by employing a longitudinally-extending calibration zone to obtain a back-light source with a uniform distribution of illumination in a longitudinal direction of the image scanning device, comprising the following steps:

(a) activating the back-light module to form a light source and project light onto an optical scanning module of the image scanning device;

(b) driving the optical scanning module in the longitudinal direction;

(c) obtaining a signal representing illumination of at least one selected pixel of the calibration zone in the longitudinal direction with the optical scanning module;

(d) comparing the signal with a pre-set reference to obtain a comparison result to determine a calibration parameter; and

(e) calibrating the illumination of an image with the calibration parameters in scanning an original document.

2. The method as claimed in claim 1 , wherein the illumination signal of each selected pixel comprises signals associated with red, green and blue colors.

3. The method as claimed in claim 1 , wherein the calibration parameter comprises parameters for red, green and blue colors.

4. The method as claimed in claim 1 , wherein the selected pixels comprise all pixels of the calibration zone in the longitudinal direction.

5. The method as claimed in claim 1 , wherein the selected pixels comprise pixels of every given number of pixels of the calibration zone in the longitudinal direction.

6. The method as claimed in claim 1 , wherein the reference is stored in a memory unit of the image scanning device in advance.