Light modulation apparatus, image pickup apparatus, and drive methods therefor

• US 7,110,155 B2
• Filed: 04/14/2004
• Issued: 09/19/2006
• Est. Priority Date: 11/12/1999
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Udaka, Toru, Nito, Keiichi
• Primary Examiner(s): Mack, Ricky
• Assistant Examiner(s): CHOI, WILLIAM C
• Application Number:
  US10/824,101
• Publication Number:
  US 20040196523A1
• Time in Patent Office: 888 Days
• Field of Search: 359/239, 359/246, 359/251, 359/255, 359/253, 359/264, 315/149, 315/150, 315/156, 315/157, 315/291, 396/121, 396/147, 396/213, 396/235, 396/237, 396/246, 313/121, 345/84, 345/87, 345/89, 345/94, 345/98, 345/691
• US Class Current: 359/253
• CPC Class Codes: G02F 1/13312 Circuits comprising photodetectors for purposes other than feedback
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/13712 the liquid crystal having negative dielectric anisotropy
• CPC Class Codes: G02F 1/13725 based on guest-host interaction G02F1/13762, G02F1/13737, take precedence
• CPC Class Codes: G09G 2320/041 Temperature compensation

Abstract

Disclosed are a light modulation apparatus including a liquid crystal device; and a polarizing plate disposed in an optical path of light made incident on said liquid crystal device; wherein said liquid crystal device is of a guest-host type using a negative type liquid crystal as a host material, an image pickup apparatus using the light modulation apparatus, and methods of driving the light modulation apparatus and image pickup apparatus.

Claims

1. A light modulation apparatus comprising:

a liquid crystal device;

a pulse control unit for changing the transmittance of light made incident on said liquid crystal device from a current transmittance into a target transmittance by sequentially applying at least two distinct drive pulses to said liquid crystal device; and

a polarizing plate that is movable into and out of an optical path of light made incident on said liquid crystal device;

wherein said at least two drive pulses include a first drive pulse having a first pulse height and a first pulse width and a second drive pulse having a second pulse height and a second pulse width; and

wherein the first pulse height is greater than the second pulse height and/or the first pulse width is greater than the second pulse width.

2. A light modulation apparatus according to claim 1, further comprising a drive circuit unit, wherein the drive pulses are generated in synchronization with a clock generated by said drive circuit unit.

3. A light modulation apparatus according to claim 2, further comprising a control circuit unit, wherein luminance information of the light emerged from said liquid crystal device is fed back to said control circuit unit, and the drive pulses are generated in synchronization with said clock, which is generated by said drive circuit unit on the basis of a control signal supplied from said control circuit unit.

4. A light modulation apparatus according to claim 1, wherein said polarizing plate is disposed in a movable portion of a mechanical iris in such a manner as to be movable into and out of the optical path by operation of said movable portion of said mechanical iris.

5. A light modulation apparatus according to claim 1, wherein a drive electrode of said liquid crystal device is formed at least over the entire region of an effective light transmission portion.

6. An image pickup apparatus comprising:

a light modulation apparatus including a liquid crystal device and a pulse control unit for changing the transmittance of light made incident on said liquid crystal device from a current transmittance into a target transmittance by sequentially applying at least two distinct drive pulses to said liquid crystal device;

wherein said light modulation apparatus is disposed in an optical path of an optical system of said image pickup apparatus;

wherein said at least two drive pulses include a first drive pulse having a first pulse height and a first pulse width and a second drive pulse having a second pulse height and a second pulse width; and

wherein the first pulse height is greater than the second pulse height and/or the first pulse width is greater than the second pulse width.

7. An image pickup apparatus according to claim 6, further comprising a drive circuit unit, wherein the drive pulses are generated in synchronization with a clock generated by said drive circuit unit.

8. An image pickup apparatus according to claim 7, wherein said drive circuit unit is a drive circuit unit of an image pickup device disposed on a light outgoing side of said light modulation apparatus, and luminance information of the light emerged from said liquid crystal device is fed back to said control circuit unit, and the drive pulses are generated in synchronization with said clock, which is generated by said drive circuit unit on the basis of a control signal supplied from said control circuit unit.

9. An image pickup apparatus according to claim 6, wherein said liquid crystal device is a guest-host type liquid crystal device.

10. An image pickup apparatus according to claim 9, wherein a host material of said liquid crystal device is a negative or positive type liquid crystal having a negative or positive type dielectric constant anisotropy.

11. An image pickup apparatus according to claim 9, wherein a guest material of said liquid crystal device is a positive or negative type dichroic dye molecular material having a positive or negative type light absorption anisotropy.

12. An image pickup apparatus according to claim 6, further comprising a polarizing plate disposed in an optical path of light made incident on said liquid crystal device.

13. An image pickup apparatus according to claim 6, further comprising a polarizing plate that is movable into and out of an optical path of light made incident on said liquid crystal device.

14. An image pickup apparatus according to claim 13, wherein said polarizing plate is disposed in a movable portion of a mechanical iris in such a manner as to be movable into and out of the optical path by operation of said movable portion of said mechanical iris.

15. An image pickup apparatus according to claim 6, wherein a drive electrode of said liquid crystal device is formed at least over the entire region of an effective light transmission portion.

16. A method of driving a light modulation apparatus including a liquid crystal device, comprising the step of:

changing the transmittance of light made incident on said liquid crystal device from a current transmittance into a target transmittance by sequentially applying at least two distinct drive pulses to said liquid crystal device;

wherein the light modulation apparatus includes a polarizing plate that is movable into and out of an optical path of light made incident on said liquid crystal device;

wherein the at least two drive pulses include a first drive pulse having a first pulse height and a first pulse width and a second drive pulse having a second pulse height and a second pulse width; and

wherein the first pulse height is greater than the second pulse height and/or the first pulse width is greater than the second pulse width.

17. A method of driving a light modulation apparatus according to claim 16, wherein the drive pulses are generated in synchronization with a clock generated by a drive circuit unit provided in said light modulation apparatus.

18. A method of driving a light modulation apparatus according to claim 17, wherein luminance information of the light emerged from said liquid crystal device is fed back to a control circuit unit provided in said light modulation apparatus, and the drive pulses are generated in synchronization with the clock, which is generated by said drive circuit unit on the basis of a control signal supplied from said control circuit unit.

19. A method of driving a light modulation apparatus according to claim 16, further comprising selectively moving said polarizing plate into and out of said optical path of light made incident on said liquid crystal device.

20. A method of driving a light modulation apparatus according to claim 19, wherein said polarizing plate is disposed in a movable portion of a mechanical iris in such a manner as to be movable into and out of the optical path by operation of said movable portion of said mechanical iris.

21. A method of driving a light modulation apparatus according to claim 16, wherein a drive electrode of said liquid crystal device is formed at least over the entire region of an effective light transmission portion.

22. A method of driving an image pickup apparatus in which a liquid crystal device of a light modulation apparatus is disposed in an optical path of an optical system of said image pickup apparatus, comprising the step of:

changing the transmittance of light made incident on said liquid crystal device from a current transmittance into a target transmittance by sequentially applying at least two distinct drive pulses to said liquid crystal device;

wherein the at least two drive pulses include a first drive pulse having a first pulse height and a first pulse width and a second drive pulse having a second pulse height and a second pulse width; and

wherein the first pulse height is greater than the second pulse height and/or the first pulse width is greater than the second pulse width.

23. A method of driving an image pickup apparatus according to claim 22, wherein the drive pulses are generated in synchronization with a clock generated by a drive circuit unit provided in said light modulation apparatus.

24. A method of driving an image pickup apparatus according to claim 22, wherein a drive circuit unit is disposed on a light outgoing side of said light modulation apparatus, luminance information of the light emerged from said liquid crystal device is fed back to a control circuit unit provided in said light modulation apparatus, and the drive pulses are generated in synchronization with a clock generated by said drive circuit unit on the basis of a control signal supplied from said control circuit unit.

25. A method of driving an image pickup apparatus according to claim 22, wherein said liquid crystal device is a guest-host type liquid crystal device.

26. A method of driving an image pickup apparatus according to claim 25, wherein a host material of said liquid crystal device is a negative or positive type liquid crystal having a negative or positive type dielectric constant anisotropy.

27. A method of driving an image pickup apparatus according to claim 25, wherein a guest material of said liquid crystal device is a positive or negative type dichroic dye molecular material having a positive or negative type light absorption anisotropy.

28. A method of driving an image pickup apparatus according to claim 22, wherein a polarizing plate is disposed in an optical path of light made incident on said liquid crystal device.

29. A method of driving an image pickup apparatus according to claim 22, further comprising selectively moving a polarizing plate into and out of an optical path of light made incident on said liquid crystal device.

30. A method of driving an image pickup apparatus according to claim 29, wherein said polarizing plate is disposed in a movable portion of a mechanical iris in such a manner as to be movable into and out of the optical path by operation of said movable portion of said mechanical iris.

31. A method of driving an image pickup apparatus according to claim 22, wherein a drive electrode of said liquid crystal device is formed at least over the entire region of an effective light transmission portion.