Color image reader for use in image forming apparatus

• US 6,747,766 B1
• Filed: 09/13/2000
• Issued: 06/08/2004
• Est. Priority Date: 09/13/2000
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Inventors: Kamisuwa, Yoshikatsu, Tanimoto, Koji, Nakane, Rintaro
• Primary Examiner(s): Williams, Kimberly
• Assistant Examiner(s): Worku, Negussie
• Application Number:
  US09/661,406
• Time in Patent Office: 1,364 Days
• Field of Search: 358/1.9, 358/475, 358/509, 358/505, 358/514, 358/513, 358/518, 358/515, 358/517, 358/538, 358/406, 358/494, 358/504
• US Class Current: 358/505
• CPC Class Codes: H04N 1/486 with separate detectors, each detector being used for one specific colour component

Abstract

A color image reader according to the present invention has a reading object holder which is plate shape and which can transmit light and holds the subject to be read, a lighting device for illuminating the subject to be read on the reading object holder a reducing lens for providing convergence to the image light from the reading object, a 3-line CCD sensor for receiving the image light with convergence given by the reducing lens and outputting three electrical signals corresponding to the image light, and a lateral chromatic aberration correction circuit for designating one output signal of the three output signals outputted from the 3-line CCD sensor to the reference, comparing the two remaining output signals with the output signal used for the reference, and providing a predetermined correction to the two remaining output signals, and can suppress generation of image color deviation which depends on the distance between the 3-line CCD sensor and the optical axis of the reducing lens.

Claims

1. A color image reader comprising:

a reading object holder, having plate shape and which can transmit light, for holding a subject to be read;

a lighting device for illuminating the subject to be read on the reading object holder;

a reducing lens for providing convergence to the image light from the reading object;

a 3-line CCD sensor for receiving the image light with convergence given by the reducing lens and outputting three electrical signals corresponding to the image light; and

a lateral chromatic aberration correction circuit for storing only parameters representing an approximate expression or linear expression for correcting color deviation in all pixel positions in a main scanning direction, for designating one output signal of the three output signals outputted from the 3-line CCD sensor to the reference, for comparing the two remaining output signals with the output signal used for the reference, and for providing a predetermined correction to the two remaining output signals,

wherein the 3-line CCD sensor contains three sets of line sensors arranged on the same plane in parallel to one another, and are positioned in such a manner that the image light passing through the center of the reducing lens impinges on the line sensor located at the center of the three sets of the line sensors, and

wherein the lateral chromatic aberration correction circuit finds the difference of the outputs corresponding to the optional pixel in each of the two remaining outputs with respect to the output of the center line sensor to the optional pixel for the three outputs outputted by the 3-line CCD sensor.

2. The color image reader according to claim 1, wherein the lateral chromatic aberration correction circuit determines the difference of outputs of the remaining two outputs corresponding to the optional pixels with respect to the output used for the reference to the optional pixel for the three outputs outputted by the 3-line CCD sensor.

3. The color image reader according to claim 1, wherein the lateral chromatic aberration correction circuit finds the difference of the outputs corresponding to optional pixels in each of the two remaining outputs with respect to the output used for the reference to the optional pixel for the three outputs outputted by the 3-line CCD sensor.

4. The color image reader according to claim 1, wherein the lateral chromatic aberration correction circuit corrects the lateral chromatic aberration with respect to the output of the center line sensor by D₂ and D₃ defined by the second signal output at the i-th pixel:

i₂ expressed by

5. The color image reader according to claim 1, wherein the image signal outputted by the center line sensor of the three outputs outputted by the 3-line CCD sensor is green (G), the image signal outputted by the second line sensor deviated in the first direction with respect to the light passing through the center of the reducing lens is red (R), and the image signal outputted by the third line sensor deviated in the second direction opposite to the first direction with respect to the center of the reducing lens is blue (B).

6. The color image reader according to claim 5, wherein the lateral chromatic aberration correction circuit finds the centers of balance P_R, P_G, and P_B of image signals of respective colors, by

7. The color image reader according to claim 5, wherein the lateral chromatic aberration correction circuit corrects the lateral chromatic aberration with respect to the output of the center line sensor by D_R and D_B defined by the following linear expressions

8. The color image reader according to claim 7, wherein in the lateral chromatic aberration correction circuit, the individual parameters K_R, L_R, K_B and L_B are predetermined with respect to the change portion that changes in accordance with the frequency for the 3-line CCD sensor to read the chart image when the black-and-white pair line image contained in the chart for the 3-line CCD sensor to read the image has a predetermined angle with respect to the direction in which the 3-line CCD sensor reads the chart image.

9. The color image reader according to claim 1, wherein the lateral chromatic aberration circuit does not store patterns for correction.

10. A color image forming apparatus comprising:

a color image reader including;

a reading object holder, having plate shape and which can transmit light, for holding a reading object;

a lighting device for illuminating the reading object on the reading object holder;

a reducing lens for giving convergence to the image light from the reading object;

a 3-line CCD sensor for receiving the image light with convergence given by the reducing lens and outputting three electrical signals corresponding to the image light; and

a lateral chromatic aberration correction circuit for storing only parameters representing an approximate expression or linear expression for correcting color deviation in all pixel positions in a main scanning direction, for designating one output signal of the three output signals outputted from the 3-line CCD sensor to the reference, for comparing the two remaining output signals with the output signal used for the reference, and for providing a predetermined correction to the two remaining output signals;

an exposure device for irradiating the exposed light with the light intensity varied in correspondence with the output image signal generated by the color image reader to a predetermined position;

the first and the second image forming apparatus in which each of the image forming apparatuses comprises a photosensitive material which is a light receptor, a developing apparatus for selectively supplying the visualized material to the photosensitive material, a transcription apparatus for transcribing the visualized material from the photosensitive material to the transferred material, wherein individual image forming apparatus which supply the visualized material by the developing apparatus to the latent image formed on the photosensitive material by the exposed light irradiated from the exposure apparatus to visualize the image and form the visualized image are disposed in a predetermined arrangement, and form a plurality of toner images for each color component in correspondence with the output image signals for each color component supplied from the color image reader in conformity to time series;

a transferred material conveying mechanism located at a predetermined position with respect to each of the transcription apparatus of the first and the second image forming apparatus and conveying the visualized image formed by the first and the second image forming apparatus transcribably onto the transferred material while the transferred material fed from the storage section is being conveyed; and

a fixing apparatus including a heating mechanism and pressurizing mechanism, for fixing the visualized image transferred on the transferred material to the transferred material being conveyed by the transferred material conveying mechanism.

11. The color image forming apparatus according to claim 10, wherein the lateral chromatic aberration circuit does not store patterns for correction.