Clock control apparatus and method and image forming apparatus using clock control apparatus

• US 20020003568A1
• Filed: 02/07/2001
• Published: 01/10/2002
• Est. Priority Date: 02/08/2000
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Koga, Katsuhide
• Granted Patent: US 6,512,534 B2
• Time in Patent Office: Days
• US Class Current: 347/249
• CPC Class Codes: G06K 15/1219 Detection, control or error compensation of scanning velocity or position, e.g. synchronisation G06K15/1223 takes precedence

Abstract

A clock control apparatus which generates a clock for laser drive in latent image formation in an image forming apparatus. A main-scanning synchronizing clock generation unit 603 generates a synchronizing clock synchronized with a main-scanning synchronizing signal based on the main-scanning synchronizing signal and an original clock. A delay unit 604 delays the synchronizing clock so as to correct a mechanical shift upon latent image drawing by laser drive. A pseudo main-scanning synchronizing signal generation unit 103 generates a pseudo main-scanning synchronizing signal based on the synchronizing clock delayed by the delay unit 604, and supplies the pseudo main-scanning synchronizing signal to the main-scanning synchronizing clock generation unit 603. The main-scanning synchronizing clock generation unit 603 generates a clock synchronized with the pseudo main-scanning synchronizing signal. The clock is supplied via a clock selection unit 102 to a PWM generation unit 605, and is used for the laser drive.

Claims

1. A control apparatus for controlling a clock for drawing drive in an image forming apparatus, comprising:

a first synchronizing clock generation unit that generates a first synchronizing clock synchronized with a main-scanning synchronizing signal based on said main-scanning synchronizing signal and an original clock;

a delay unit that generates a delayed clock by delaying said first synchronizing clock in accordance with a designated correction amount;

a pseudo synchronizing signal generation unit that generates a pseudo synchronizing signal based on said delayed clock generated by said delay unit; and

a second synchronizing clock generation unit that generates a second synchronizing clock synchronized with said pseudo synchronizing signal based on said pseudo synchronizing signal and said original clock.

2. The apparatus according to claim 1, wherein said pseudo synchronizing signal generation unit counts said delayed clock and outputs a one-shot pulse.

3. The apparatus according to claim 1, wherein said first synchronizing clock generation unit and said second synchronizing clock generation unit are realized as one clock generation circuit,

and wherein said apparatus further comprising a selection unit that outputs said first synchronizing clock to said delay unit while said clock generation circuit outputs said first synchronizing clock, and outputs said second synchronizing clock for drawing drive while said clock generation circuit outputs said second synchronizing clock.

4. The apparatus according to claim 3, wherein said selection unit provides an output from said clock generation circuit as said first synchronizing clock to said delay unit from a point where said unit inputs said main-scanning synchronizing signal to a point where said unit inputs said pseudo synchronizing signal, and provides the output from said clock generation circuit as second synchronizing clock to the drawing drive from the point where said unit inputs said pseudo synchronizing signal to a point where said unit inputs a next main-scanning synchronizing signal.

5. The apparatus according to claim 1, wherein said drawing drive includes latent image drawing by laser, and wherein said correction amount is designated so as to correct a mechanical shift upon said latent image drawing.

6. A control method for controlling a clock for drawing drive in an image forming apparatus, comprising the steps of:

generating a first synchronizing clock synchronized with a main-scanning synchronizing signal based on said main-scanning synchronizing signal and an original clock;

generating a delayed clock by delaying said first synchronizing clock in accordance with a designated correction amount;

generating a pseudo synchronizing signal based on said delayed clock; and

generating a second synchronizing clock synchronized with said pseudo synchronizing signal based on said pseudo synchronizing signal and said original clock.

7. The method according to claim 6, wherein said pseudo synchronizing signal is a one-shot pulse outputted by counting said delayed clock.

8. The method according to claim 6, wherein said first synchronizing clock and said second synchronizing clock are generated by one clock generation circuit,

and wherein said method further comprising a selection step of determining an output destination so as to delay said first synchronizing clock to generate said pseudo synchronizing signal while said clock generation circuit outputs said first synchronizing clock, and changing the output destination so as to use said second synchronizing clock in the drawing drive while said clock generation circuit outputs said second synchronizing clock.

9. The method according to claim 8, wherein at said selection step, an output from said clock generation circuit is used as said first synchronizing clock from a point where said main-scanning synchronizing signal is inputted to a point where said pseudo synchronizing signal is inputted, and the output from said clock generation circuit is used in the drawing drive as said second synchronizing clock from the point where said pseudo synchronizing signal is inputted to a point where a next main-scanning synchronizing signal is inputted.

10. The method according to claim 6, wherein said drawing drive includes latent image drawing by laser, and wherein said correction amount is designated so as to correct a mechanical shift upon said latent image drawing.

11. An image forming apparatus comprising:

a first synchronizing clock generation unit that generates a first synchronizing clock synchronized with a main-scanning synchronizing signal based on said main-scanning synchronizing signal and an original clock;

a delay unit that generates a delayed clock by delaying said first synchronizing clock in accordance with a designated correction amount;

a pseudo synchronizing signal generation unit that generates a pseudo synchronizing signal based on said delayed clock generated by said delay unit;

a second synchronizing clock generation unit that generates a second synchronizing clock synchronized with said pseudo synchronizing signal based on said pseudo synchronizing signal and said original clock; and

drawing means for performing a drawing operation based on said second synchronizing clock and image data to be used in image formation.

12. The apparatus according to claim 11, wherein said pseudo synchronizing signal generation unit counts said delayed clock and outputs a one-shot pulse.

13. The apparatus according to claim 11, wherein said first synchronizing clock generation unit and said second synchronizing clock generation unit are realized as one clock generation circuit,

and wherein said apparatus further comprising a selection unit that outputs said first synchronizing clock to said delay unit while said clock generation circuit outputs said first synchronizing clock, and outputs said second synchronizing clock for drawing drive while said clock generation circuit outputs said second synchronizing clock.

14. The apparatus according to claim 13, wherein said selection unit provides an output from said clock generation circuit as said first synchronizing clock to said delay unit from a point where said unit inputs said main-scanning synchronizing signal to a point where said unit inputs said pseudo synchronizing signal, and provides the output from said clock generation circuit as said second synchronizing clock to the drawing drive from the point where said unit inputs said pseudo synchronizing signal to a point where said unit inputs a next main-scanning synchronizing signal.

15. The apparatus according to claim 11, wherein said drawing means performs laser drive for latent image formation, and forms a visible image on a print sheet.

16. The apparatus according to claim 15, wherein said drawing drive includes latent image drawing by laser,

and wherein said apparatus further comprises designation means for designating said correction amount so as to correct a mechanical shift upon said latent image drawing.

17. The apparatus according to claim 15, wherein said drawing means includes means for introducing optically-modulated laser light from a laser light source on an image holder, writing image information and forming a visible image, and said drawing means transfers the visible image onto a transfer medium thereby forming an image.

18. The apparatus according to claim 15, wherein said drawing means performs PWM modulation by using said second synchronizing clock.