Image formation method for forming electrostatic latent image on photosensitive belt with laser beam and image formation apparatus of the same

• US 6,195,108 B1
• Filed: 07/19/1999
• Issued: 02/27/2001
• Est. Priority Date: 07/17/1998
• Status: Expired due to Fees

• Current Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Original Assignee: NEC Corporation
• Inventors: Kanno, Hiromasa
• Primary Examiner(s): Brase, Sandra
• Application Number:
  US09/356,459
• Time in Patent Office: 589 Days
• Field of Search: 347/116, 347/129, 347/133, 347/134, 399/31, 399/130, 399/162, 399/301
• US Class Current: 347/116
• CPC Class Codes: B41J 2/473 using multiple light beams, wavelengths or colours
• CPC Class Codes: G03G 2215/00164 by electronic scan control
• CPC Class Codes: G03G 2215/017 single rotation of recording member to produce multicoloured copy
• CPC Class Codes: H04N 1/047 Detection, control or error compensation of scanning velocity or position H04N1/0402 and H04N1/17 take precedence
• 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 2201/02439 Positioning method
• CPC Class Codes: H04N 2201/0471 using dedicated detectors
• CPC Class Codes: H04N 2201/04712 using unbroken arrays of detectors, i.e. detectors mounted on the same substrate
• CPC Class Codes: H04N 2201/04722 on a photoconductive drum or belt
• CPC Class Codes: H04N 2201/04729 in the main-scan direction
• CPC Class Codes: H04N 2201/04731 in the sub-scan direction
• 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 2201/04741 by detecting the sheet support or the photoconductive surface directly
• CPC Class Codes: H04N 2201/04744 by detecting the scanned beam or a reference beam
• CPC Class Codes: H04N 2201/04751 Detecting position relative to a step, e.g. using L-shaped masks, marks or gratings
• CPC Class Codes: H04N 2201/04786 Controlling a start time, e.g. for output of a line of data H04N2201/04784 takes precedence
• CPC Class Codes: H04N 2201/04789 in the main-scan direction
• 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 image formation apparatus of the present invention forms an electrostatic latent image on a moving photosensitive belt by a laser beam produced by a laser device. A belt edge detector 1 detects an edge portion (belt edge) of a photosensitive belt 100 in a main scanning direction. A virtual edge detection circuit 2 generates a virtual edge detection signal 2A which changes a generation timing in accordance with a change of a detection timing of the belt edge detected by the belt edge detector 1. The generation timing of the virtual edge detection signal 2A does not almost follow the detection timing of the belt edge which changes by flaws and non-linearity of the belt edge, and changes in accordance with a slow change of the detection timing. A synchronizing signal generation circuit 3 and a driving circuit 4 drives the laser device so as to start a writing of an image data by the laser beam in synchronization with the virtual edge detection signal.

Claims

1. An image formation apparatus which forms an electrostatic latent image on a moving photosensitive belt by a laser beam of a laser device, comprising:

a belt edge detector for detecting an edge portion (belt edge) of said photosensitive belt in a main scanning direction by a main scanning for said photosensitive belt;

a virtual edge detection circuit for generating a virtual edge detection signal which change its generation timing in accordance with a change of a detection timing of said belt edge detected by said belt edge detector, the generation timing of said virtual edge detection signal following a slow change of said detection timing;

a driving circuit for driving said laser device so as to start a writing of an image data by said laser beam in synchronization with said virtual edge detection signal, and

wherein said virtual edge detection circuit includes a comparing circuit for a time difference between a detection timing of an actual belt edge detected by said belt edge detector and a generation timing of the virtual edge detection signal, and an integrator for performing a charge/discharge processing in accordance with the time difference.

2. The image formation apparatus according to claim 1, wherein the slow change of said detection timing is a change produced by a movement of said photosensitive belt in the main scanning direction, and a changing time is sufficiently longer than that by said flaws and non-linearity of said belt edge.

3. The image formation apparatus according to claim 1, wherein said belt edge detector detects said belt edge and a reference position which is somewhat apart from said belt edge.

4. The image formation apparatus according to claim 3, wherein said virtual edge detection circuit changes the generation timing of said virtual edge detection signal in accordance with a change of a time difference between the detection timing of said reference position and the detection timing of said belt edge.

5. The image formation apparatus according to claim 1, wherein said virtual edge detection circuit further includes an adjusting circuit for adjusting a level of an output signal of said integrator in response to the change of the timing of the detection of said belt edge.

6. The image formation apparatus according to claim 5, wherein said adjusting circuit is a charge pump for adjusting the level of the output signal of said integrator by charging/discharging a prescribed amount of charges in/from said integrator.

7. The image formation apparatus according to claim 6, wherein said photosensitive belt has a marking for indicating a belt jointing portion, a marking detector for detecting the marking is provided, and a charge/discharge processing switching circuit for switching a charge/discharge processing by said charge pump based on said marking detected by said marking detector is provided.

8. An image formation apparatus which forms an electrostatic latent image on a moving photosensitive belt by a laser beam of a laser device, comprising:

a belt edge detector for detecting an edge portion (belt edge) of said photosensitive belt in a main scanning direction by a main scanning for said photosensitive belt;

a lamp signal generator for generating a lamp signal for each main scanning by said laser beam, the lamp signal rising up to a predetermined level;

an integrator;

a comparator for generating a virtual edge detection signal when a level of said lamp signal and a level of an output signal of said integrator coincide with each other;

a phase comparator for comparing a detection time of said belt edge by said belt edge detector with a generation time of said virtual edge detection signal; and

an adjusting circuit for adjusting the level of the output signal of said integrator based on a comparison result,

wherein said adjusting circuit adjusts the level of the output signal of said integrator by a change of the detection timing of said belt edge, and the generation timing of said virtual edge detection signal from said comparator changes.

9. The image formation apparatus according to claim 8, wherein said adjusting circuit is a charge pump which adjusts the level of the output signal of said integrator by charging/discharging charges of a prescribed amount in/from said integrator.

10. The image formation apparatus according to claim 9, wherein said photosensitive belt has a marking for indicating a belt jointing portion, a marking detector for detecting the marking is provided, and a charge/discharge processing switching circuit for switching a charge/discharge processing by said charge pump based on said marking detected by said marking detector is provided.

11. An image formation method, comprising the steps of:

comparing a phase difference between an actual belt edge signal detected by a belt edge detector and a virtual edge detection signal indicating a virtual belt edge; and

performing a charge/discharge processing for an integrator in accordance with the phase difference to shift a writing position by a laser, thus preventing a printing shift on a recording paper.