Frequency modulator for modulating image data based on frequency data of scan lines of an image carrier

• US 7,170,544 B2
• Filed: 04/29/2004
• Issued: 01/30/2007
• Est. Priority Date: 05/16/2003
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Horiuchi, Izuru
• Primary Examiner(s): Pham; Hai
• Assistant Examiner(s): Martinez, Jr.; Carlos
• Application Number:
  US10/835,745
• Publication Number:
  US 20040227807A1
• Time in Patent Office: 1,006 Days
• Field of Search: 347/247, 347/249, 347/250, 347/261, 359/201
• US Class Current: 347/247
• CPC Class Codes: H04N 1/053 in main scanning direction, e.g. synchronisation of line start or picture elements in a line
• CPC Class Codes: H04N 1/1135 for the main-scan only
• CPC Class Codes: H04N 1/12 using the sheet-feed movement or the medium-advance or the drum-rotation movement as the slow scanning component, e.g. arrangements for the main-scanningsheet-feed movement by translatory movement of a flat picture-bearing surface H04N1/1008; main-scanning using oscillating or rotating mirrors H04N1/113; using multi-element arrays H04N1/19
• CPC Class Codes: H04N 1/506 Reproducing the colour component signals picture-sequentially, e.g. with reproducing heads spaced apart from one another in the subscanning direction
• CPC Class Codes: H04N 2201/02443 using adhesive
• CPC Class Codes: H04N 2201/04768 Controlling the frequency of the signals
• CPC Class Codes: H04N 2201/04798 Varying the main-scan control during the main-scan, e.g. facet tracking

Abstract

A frequency modulation device for use in an image forming apparatus. The image formation apparatus includes an image carrier and a laser device for scanning the image carrier along a plurality of scan lines. Each scan line is divided into segments having segment boundaries in which the same segment boundary in adjacent scan lines are offset. The frequency modulation device generates frequency data for use in modulating the input image data, which is utilized by the laser device to scan the image carrier, which permits output of an electrophotograph of high image quality by suppressing segment boundaries caused by moiré fringes or color shifting to below a level at which such boundaries are not visually detectable.

Claims

1. A frequency modulation device incorporated in an image forming apparatus having an image carrier and a laser device, the frequency modulation device modulating input image data, and the laser device scanning the image carrier along a plurality of scan lines responsive to the modulated image data, the frequency modulation device comprising:

means for storing frequency information on each of the plurality of scan lines in a format in which each scan line is divided into segments having segment boundaries and the segment boundaries of adjacent scan lines are offset with each other; and

means for generating frequency data based on the stored frequency information;

wherein the frequency modulation device modulates the input image data based on the frequency data,

wherein said generating means includes a counter generating data including line phase data and segment data and a frequency calculator calculating the frequency data based on the frequency information and the data from the counter.

2. A frequency modulation device according to claim 1, wherein said storing means is a register.

3. A frequency modulation device according to claim 2, wherein the register stores frequency information in a format in which the plurality of scan lines are divided having a same number of segments.

4. A frequency modulation device according to claim 2, wherein the register stores frequency information in a format in which adjacent scan lines are divided having a different number of segments.

5. A frequency modulation device according to claim 2, wherein the register stores frequency information including frequencies at the segment boundaries.

6. A frequency modulation device according to claim 5, wherein the counter generates the data including phase data for each segment of a scan line.

7. A frequency modulation device according to claim 6, wherein the frequency calculator calculates the frequency data based on the segment boundary information and the phase data.

8. A frequency modulation device according to claim 2, wherein the register stores the frequency information including frequency within each segment of a scan line.

9. A frequency modulation device according to claim 8, wherein the register stores the frequency information including average value of amount of correction within each segment of a scan line.

10. A frequency modulation device according to claim 9, wherein the frequency calculator calculates the frequency data by adding the frequency information from the register and the data from the counter to a basic frequency.

11. A method for scanning an image carrier with input image data using a laser device, the method comprising the following steps:

generating a plurality of scan lines of image data;

dividing each scan line into a plurality of segments having segment boundaries such that for adjacent scan lines, the segment boundaries are offset;

providing and storing frequency information for each segment;

generating frequency data based on the stored frequency information;

modulating the image data based on the frequency data; and

scanning the image carrier using the laser device along the plurality of scan lines based on the modulated image data,

wherein said frequency generating step further includes a step of providing data including line phase data and segment data and a step of calculating the frequency data based on the frequency information, the line phase data and the segment data.

12. A method of claim 11, wherein the step of providing data includes providing phase data for each segment of a scan line.

13. A method of claim 12, wherein the frequency information within each segment includes information on average value of amount of correction within each segment.