Positional correction for apparatus having a plurality of drawing systems

• US 7,102,661 B2
• Filed: 09/23/2003
• Issued: 09/05/2006
• Est. Priority Date: 09/24/2002
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Satoh, Nobuyuki
• Primary Examiner(s): PHAM, HAI CHI
• Application Number:
  US10/667,305
• Publication Number:
  US 20040125195A1
• Time in Patent Office: 1,078 Days
• Field of Search: 347116-117, 347233-235, 347/240, 347251-254, 347/19, 347248-250, 356603-605, 356618-620, 356/242, 399/72, 399/301, 399394-396, 355/41
• US Class Current: 347/234
• CPC Class Codes: G02B 26/123 Multibeam scanners, e.g. using multiple light sources or beam splitters
• 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 1/192 Simultaneously or substantially simultaneously scanning picture elements on one main scanning line
• CPC Class Codes: H04N 2201/02439 Positioning method
• CPC Class Codes: H04N 2201/0471 using dedicated detectors
• CPC Class Codes: H04N 2201/04717 on the scanned sheet, e.g. a reference sheet
• CPC Class Codes: H04N 2201/04722 on a photoconductive drum or belt
• CPC Class Codes: H04N 2201/04732 Detecting at infrequent intervals, e.g. once or twice per line for main-scan control
• CPC Class Codes: H04N 2201/04734 Detecting at frequent intervals, e.g. once per line for sub-scan control
• CPC Class Codes: H04N 2201/04758 by controlling the position of the scanned image area H04N2201/04755, H04N2201/04756 take precedence
• CPC Class Codes: H04N 2201/04794 Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line

Abstract

An apparatus for forming an image by use of a plurality of light beams, which are simultaneously modulated according to image signals and joined together on a photoconductive surface to form the image. The apparatus includes a photoconductive drum having a photoconductive surface and a reference mark, a pattern supplying unit which supplies image data in synchronization with a detection of the reference mark associated with a rotation of the photoconductive drum, and drawing systems which (i) create moiré stripes on the photoconductive surface by simultaneously drawing overlapping sets of slanted lines with the respective light beams according to the image data, and (ii) draw a reference position mark alongside the moiré stripes on the photoconductive surface according to the image data.

Claims

1. An apparatus for forming an image by use of a plurality of light beams, which are simultaneously modulated according to image signals and joined together on a photoconductive surface to form the image, comprising:

a photoconductive drum having a photoconductive surface and a reference mark;

a pattern supplying unit configured to supply image data in synchronization with detection of the reference mark associated with rotation of the photoconductive drum; and

drawing systems configured to create moiré

stripes on the photoconductive surface by simultaneously drawing overlapping sets of slanted lines with the respective light beams according to the image data, and draw reference position marks alongside the moiré

stripes, on the photoconductive surface according to the image data.

2. The apparatus as claimed in claim 1, further comprising a computing unit which computes an amount of correction of position of the light beams on the photoconductive surface in a main scan direction in response to a comparison between positions of the moiré

stripes and positions of the reference position marks, the main scan direction being substantially parallel to an axis of the photoconductive drum.

3. The apparatus as claimed in claim 2, further comprising a sensor which detects the position of the moiré

stripes.

4. The apparatus as claimed in claim 2, wherein said computing unit computes the amount of correction of position of the light beams by interpolating data that are obtained for at least three positions along a circumference of the photoconductive drum.

5. The apparatus as claimed in claim 2, wherein said comparison is made either on the photoconductive surface or on a sheet of paper on which a toner image of the moiré

stripes and the reference position marks are created.

6. The apparatus as claimed in claim 1, further comprising a circuit which adjusts position of the light beams on the photoconductive surface in a main scan direction according to comparison between positions of the moiré

stripes and positions of the reference position marks, the main scan direction being substantially parallel to an axis of the photoconductive drum.

7. The apparatus as claimed in claim 1, wherein said drawing systems include:

a first drawing system which uses a first one of the light beams to draw a first set of lines slanted at a predetermined angle; and

a second drawing system which uses a second one of the light beams to draw a second set of lines slanted at an angle opposite to the predetermined angle, said first set of lines and said second set of lines having an identical line pitch and an identical line width.

8. An apparatus for adjusting positions of a plurality of light beams, which are simultaneously modulated according to image signals and joined together on a photoconductive surface to form an image, comprising:

a photoconductive drum having the photoconductive surface and a reference mark;

a pattern supplying unit configured to supply image data in synchronization with a detection of a reference mark associated with a rotation of the photoconductive drum;

drawing systems configured to create moiré

stripes on the photoconductive surface by simultaneously drawing overlapping sets of slanted lines with the respective light beams according to the image data, and draw reference position marks alongside the moiré

stripes, on the photoconductive surface according to the image data; and

a circuit configured to adjust positions of the light beams on the photoconductive surface in a main scan direction according to a comparison between a position of the moiré

stripes and a position of the reference position marks, the main scan direction being substantially parallel to an axis of the photoconductive drum.

9. An apparatus for forming an image by use of a plurality of light beams, which are simultaneously modulated according to image signals and joined together on a photoconductive drum to form the image, comprising:

means for forming reference position marks on the photoconductive drum; and

means for forming moiré

stripes alongside the reference position marks on the photoconductive drum by simultaneously drawing overlapping sets of slanted lines with the respective light beams.

10. The apparatus as claimed in claim 9, further comprising computing means for computing an amount of correction of position of the light beams on the photoconductive drum in a main scan direction in response to a comparison between positions of the moiré

stripes and positions of the reference position marks, the main scan direction being substantially parallel to an axis of the photoconductive drum.

11. The apparatus as claimed in claim 10, further comprising means for detecting the position of the moiré

stripes.

12. The apparatus as claimed in claim 10, wherein said computing means computes the amount of correction of position of the light beams by interpolating data that are obtained for at least three positions along a circumference of the photoconductive drum.

13. The apparatus as claimed in claim 10, wherein said comparison is made either on the photoconductive surface or on a sheet of paper on which a toner image of the moiré

stripes and the reference position marks are created.

14. The apparatus as claimed in claim 9, further comprising means for adjusting position of the light beams on the photoconductive drum in a main scan direction according to a comparison between positions of the moiré

stripes and positions of the reference position mark, the main scan direction being substantially parallel to an axis of the photoconductive drum.

15. The apparatus as claimed in claim 9, wherein said means for forming moiré

stripes include;

a first drawing system which uses a first one of the light beams to draw a first set of lines slanted at a predetermined angle; and

a second drawing system which uses a second one of the light beams to draw a second set of lines slanted at an angle opposite to the predetermined angle, said first set of lines and said second set of lines having an identical line pitch and an identical line width.

16. An apparatus for adjusting positions of a plurality of light beams, which are simultaneously modulated according to image signals and joined together on a photoconductive drum to form an image, comprising:

means for forming reference position marks on the photoconductive drum;

means for forming moiré

stripes alongside the reference position marks on the photoconductive drum by simultaneously drawing overlapping sets of slanted lines with the respective light beams; and

means for adjusting the positions of the light beams on the photoconductive drum in a main scan direction according to a comparison between a position of the moiré

stripes and a position of the reference position marks, the main scan direction being substantially parallel to an axis of the photoconductive drum.