Liquid crystal exposure device

• US 7,271,798 B2
• Filed: 08/14/2003
• Issued: 09/18/2007
• Est. Priority Date: 08/14/2002
• Status: Active Grant

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Holdings Co., Ltd.
• Inventors: Yokoyama, Masafumi, Masubuchi, Sadao, Yasunaga, Makoto, Matsunaga, Masaaki
• Primary Examiner(s): Shalwala; Bipin
• Assistant Examiner(s): DHARIA, PRABODH M
• Application Number:
  US10/492,354
• Publication Number:
  US 20050200614A1
• Time in Patent Office: 1,496 Days
• Field of Search: 345/87, 345/89, 345/102, 345/147, 345/7, 345/212, 345/204, 345/211, 345/44, 345/76, 345/77, 345/47, 359/2, 359/35, 359/567, 359/13, 359/14, 359/34, 250/330, 348/333.01, 355/40, 349/2
• US Class Current: 345/204
• CPC Class Codes: B41J 2/447 using arrays of radiation sources B41J2/475 takes precedence
• CPC Class Codes: B41J 2/465 using masks, e.g. light-switching masks

Abstract

A color liquid crystal exposure apparatus includes a color light source for emitting a plurality of colored light beams, a liquid crystal shutter having a plurality of liquid crystal pixels arrayed in a direction orthogonal to the direction of the relative movement, and a driving circuit for switching the color light source from one color to another, and for driving the plurality of liquid crystal pixels. The plurality of liquid crystal pixels are divided into a plurality of pixel groups. The liquid crystal pixels in each pixel group are arrayed, one displaced from another by a prescribed distance, in the direction orthogonal to the direction of the relative movement. The driving circuit drives the plurality of liquid crystal pixels in time-division fashion so that the liquid crystal pixels having the same displaced position in the plurality of pixel groups are driven at one time.

Claims

1. A liquid crystal exposure apparatus for exposing a photosensitive member during a relative movement thereof, comprising:

a color light source for emitting a plurality of colored lights;

a liquid crystal shutter having a plurality of liquid crystal pixels arrayed in a direction orthogonal to the direction of said relative movement; and

a driving circuit for switching said color light source from one colored light to another, and for driving said plurality of liquid crystal pixels, wherein

said plurality of liquid crystal pixels are divided into a plurality of pixel groups of N liquid crystal pixels each, said N liquid crystal pixels in each pixel group being arrayed, one displaced from another by a prescribed distance, in the direction orthogonal to the direction of said relative movement, and

said driving circuit drives a plurality of liquid crystal pixels having the same displaced position in said plurality of pixel groups at a time in time-division fashion.

2. The liquid crystal exposure apparatus according to claim 1, wherein

each of said plurality of liquid crystal pixels has a first electrode and a second electrode,

the first electrodes of said plurality of liquid crystal pixels are connected in common to said driving circuit,

the second electrodes of said liquid crystal pixels having the same displaced position in said plurality of pixel groups are all connected to a corresponding one of N time-division lines, and

said driving circuit drives said plurality of liquid crystal pixels in time-division fashion by switching between said N time-division lines.

3. The liquid crystal exposure apparatus according to claim 2, wherein said driving circuit switches between said time-division lines while any particular one of said colored lights of said color light source is selected.

4. The liquid crystal exposure apparatus according to claim 3, wherein a write period WF required to complete the exposure of said photosensitive member by all of liquid crystal pixels of said pixel groups is determined by the product of a division period F, during which said time-division lines are switched from one line to another, and the number, M, of colored lights that said color light source emits.

5. The liquid crystal exposure apparatus according to claim 4, wherein the distance H by which said liquid crystal pixels are displaced from each other satisfies the relation H=h/NM, where h denotes the distance over which said photosensitive member relatively moves during said write period WF, N the number of liquid crystal pixels in each of said pixel groups, and the number, M, of colored lights that said color light source emits.

6. The liquid crystal exposure apparatus according to claim 4, wherein the direction in which said liquid crystal pixels are displaced in each of said pixel groups is a downstream direction when viewed along the direction of said relative movement of said photosensitive member.

7. The liquid crystal exposure apparatus according to claim 4, wherein the length of each of said liquid crystal pixels in said liquid crystal pixel array, as measured along the direction of said relative movement, is equal to the distance h over which said photosensitive member relatively moves during said write period WF.

8. The liquid crystal exposure apparatus according to claim 4, wherein the number, M, of colored lights is 3, and the number, N, of liquid crystal pixels in each of said pixel groups is 3.

9. The liquid crystal exposure apparatus according to claim 4, wherein the number, M, of colored lights is 3, and the number, N, of liquid crystal pixels in each of said pixel groups is 2.

10. The liquid crystal exposure apparatus according to claim 4, wherein the number, M, of colored lights is 3, and the number, N, of liquid crystal pixels in each of said pixel groups is 4.

11. The liquid crystal exposure apparatus according to claim 2, wherein said driving circuit switches said color light source between said plurality of colored lights while any particular one of said time-division lines is selected.

12. The liquid crystal exposure apparatus according to claim 11, wherein a write period WF required to complete the exposure of said photosensitive member by all of said liquid crystal pixels of said pixel groups is equal to the sum of selection periods of all of said time-division lines.

13. The liquid crystal exposure apparatus according to claim 12, wherein said driving circuit switches said color light source from one color to another in a time equal to an Mth submultiple of the selection period of each of said time-division lines, where M denotes the number of colored lights that said color light source emits.

14. The liquid crystal exposure apparatus according to claim 13, wherein the distance H by which said liquid crystal pixels are displaced in each of said pixel groups satisfies the relation H=h/N, where h denotes the distance over which said photosensitive member relatively moves during said write period, and N the number of liquid crystal pixels in each of said pixel groups.

15. The liquid crystal exposure apparatus according to claim 13, wherein the direction in which said liquid crystal pixels are displaced in each of said pixel groups is a downstream direction when viewed along the direction of said relative movement of said photosensitive member.

16. The liquid crystal exposure apparatus according to claim 13, wherein the length of each of said liquid crystal pixels in said liquid crystal pixel array, as measured along the direction of said relative movement, is equal to the distance h over which said photosensitive member relatively moves during said write period.

17. The liquid crystal exposure apparatus according to claim 11, wherein the number, M, of colored lights is 3, and the number, N, of liquid crystal pixels in each of said pixel groups is 3.

18. The liquid crystal exposure apparatus according to claim 11, wherein the number, M, of colored lights is 3, and the number, N, of liquid crystal pixels in each of said pixel groups is 2.

19. The liquid crystal exposure apparatus according to claim 11, wherein the number, M, of colored lights is 3, and the number, N, of liquid crystal pixels in each of said pixel groups is 4.