Image display device and optical low-pass filter

• US 5,755,501 A
• Filed: 08/25/1995
• Issued: 05/26/1998
• Est. Priority Date: 08/31/1994
• Status: Expired due to Fees

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Aoyama, Shigeru, Shinohara, Masayuki
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US08/519,167
• Time in Patent Office: 1,005 Days
• Field of Search: 353/20, 353/38, 353/69, 353/84, 349/105, 349/109, 349/117, 349/118, 359/567, 359/569, 359/570, 359/558, 359/559
• US Class Current: 353/31
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: G02B 5/1866 Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606

Abstract

An image display device is so adapted as to eliminate image roughness while the resolution of the image is kept as high as possible. The image display device includes an image display body having a plurality of pixels arranged periodically in two dimensions and an optical low-pass filter placed on the front surface of the image display body. The spatial frequency of the initial minimum value of an modulation transfer function in one direction of the optical low-pass filter is decided by two basic frequency vectors M, N for sampling frequencies determined by the arrangement of pixels in the image display body, and the spatial frequency of the initial minimum value of the modulation transfer function in the other direction of the optical low-pass filter is decided by differences ±(N-M) between the basic frequency vectors.

Claims

1. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

an initial minimum value of a modulation transfer function in one direction of said optical low-pass filter being decided by two basic frequency vectors for sampling frequencies determined by a pixel arrangement of said image display body, and an initial minimum value of the modulation transfer function in the other direction of said optical low-pass filter being decided by the difference between the basic frequency vectors.

2. The device according to claim 1, wherein said optical low-pass filter is one of a two-dimensional phase grating and a two-dimensional prism plate.

3. The device according to claim 2, wherein said two-dimensional phase grating is a sinusoidal phase grating.

4. The device according to claim 2, wherein said two-dimensional phase grating comprises two one-dimensional phase gratings formed on respective ones of two sides of a substrate, said two phase gratings having grating directions that differ from each other.

5. The device according to claim 2, wherein said two-dimensional phase grating comprises two one-dimensional phase gratings formed on respective substrates and having grating directions that differ from each other.

6. The device according to claim 1, wherein said optical low-pass filter is fixed on said image display body in a manner in intimate contact therewith.

7. The device according to claim 1, wherein said optical low-pass filter is secured to said image display body via a bonding layer or adhesive layer.

8. The device according to claim 1, wherein said optical low-pass filter is provided between said image display body and a lens.

9. The device according to claim 1, wherein said image display body is an image display component of one of a liquid-crystal display device, a plasma display device, an electroluminescent device and a CRT display device.

10. A viewfinder of a video camera having the image display device set forth in claim 1.

11. A TV projector having the image display device set forth in claim 1.

12. A television having the image display device set forth in claim 1.

13. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a delta arrangement comprising rows and columns perpendicular to each other, mutually adjacent rows being offset from each other by a half period;

said optical low-pass filter splitting incident light into four light rays which have point symmetry with respect to a central axis of these light rays;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

one of the following sets of Equations (41) through (44) and Equations (45) through (48) holding when relative positions of virtual images, which are formed on said image display body by the split light rays, with respect to the central axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement;

##EQU27##

14. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a delta arrangement comprising rows and columns perpendicular to each other, mutually adjacent rows being offset from each other by a half period;

said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

relative positions of virtual images, which are formed on said image display body by two sets of the split light rays, with respect to the central optic axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement;

one of the sets of following Equations (1) through (4) and Equations (5) through (8) holding when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU28##

15. The device according to claim 14, wherein said optical low-pass filter is one of a two-dimensional phase grating and a two-dimensional prism plate.

16. The device according to claim 14, wherein said image display body is a color image display body and is composed of an arrangement of pixels of a plurality of colors, said pixel periods Δ

x, Δ

y being decided by the arrangement of pixels of one color among said plurality of colors.

17. The device according to claim 14, wherein said optical low-pass filter has a characteristic determined using a wavelength in the vicinity of the central wavelength of displayed light.

18. The device according to claim 14, wherein an image is displayed using a plurality of colors, and said optical low-pass filter has a characteristic determined using a central wavelength.

19. The device according to claim 15, wherein said two-dimensional phase grating is a sinusoidal phase grating.

20. The device according to claim 15, wherein said two-dimensional phase grating is comprised of two one-dimensional phase gratings formed on respective ones of two sides of a substrate, said two phase gratings having grating directions that differ from each other.

21. The device according to claim 15, wherein said two-dimensional phase grating comprises two one-dimensional phase gratings formed on respective substrates and having grating directions that differ from each other.

22. The device according to claim 14, wherein said optical low-pass filter is fixed on said image display body in a manner in intimate contact therewith.

23. The device according to claim 14, wherein said optical low-pass filter is secured to said image display body via a bonding layer or adhesive layer.

24. The device according to claim 14, wherein said optical low-pass filter is provided between said image display body and a lens.

25. The device according to claim 14, wherein said image display body is an image display component of one of a liquid-crystal display device, a plasma display device, an electroluminescent device and a CRT display device.

26. A viewfinder of a video camera having the image display device set forth in claim 14.

27. A TV projector having the image display device set forth in claim 14.

28. A television having the image display device set forth in claim 14.

29. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a delta arrangement comprising rows and columns perpendicular to each other, mutually adjacent rows being offset from each other by a half period;

said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

said two sets of optic axes forming angles of α

₁, α

₂, respectively, with the central optic axis;

said optical low-pass filter and said image display body having an optical distance of L between them;

a plane formed by one set of the optic axes having an inclination angle θ

₁ with respect to the row direction and a plane formed by the other set of the optic axes having an inclination angle θ

₂ with respect to the row direction;

disposition of said optical low-pass filter with respect to said image display body being decided in such a manner that one of the following sets of Equations (21) through (24) and Equations (25) through (28) holds when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU29##

30. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a mosaic arrangement comprising rows and columns perpendicular to each other, basic rows being arranged in the column direction and staggered by one-third period in the row direction;

said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

relative positions of virtual images, which are formed on said image display body by two sets of the split light rays, with respect to the central optic axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement;

the following Equations (9) through (12) holding when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU30##

31. The device according to claim 30, wherein said optical low-pass filter is one of a two-dimensional phase grating and a two-dimensional prism plate.

32. The device according to claim 30, wherein said image display body is a color image display body and is composed of an arrangement of pixels of a plurality of colors, said pixel periods Δ

x, Δ

y being decided by the arrangement of pixels of one color among said plurality of colors.

33. The device according to claim 30, wherein said optical low-pass filter has a characteristic determined using a wavelength in the vicinity of the central wavelength of displayed light.

34. The device according to claim 30, wherein an image is displayed using a plurality of colors, and said optical low-pass filter has a characteristic determined using a central wavelength.

35. The device according to claim 31, wherein said two-dimensional phase grating is a sinusoidal phase grating.

36. The device according to claim 31, wherein said two-dimensional phase grating comprises two one-dimensional phase gratings formed on respective ones of two sides of a substrate, said two phase gratings having grating directions that differ from each other.

37. The device according to claim 31, wherein said two-dimensional phase grating is comprised of two one-dimensional phase gratings formed on respective substrates and having grating directions that differ from each other.

38. The device according to claim 30, wherein said optical low-pass filter is fixed on said image display body in a manner in intimate contact therewith.

39. The device according to claim 30, wherein said optical low-pass filter is secured to said image display body via a bonding layer or adhesive layer.

40. The device according to claim 30, wherein said optical low-pass filter is provided between said image display body and a lens.

41. The device according to claim 30, wherein said image display body is an image display component of one of a liquid-crystal display device, a plasma display device, an electroluminescent device and a CRT display device.

42. A viewfinder of a video camera having the image display device set forth in claim 30.

43. A TV projector having the image display device set forth in claim 30.

44. A television having the image display device set forth in claim 30.

45. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

an initial minimum value of a modulation transfer function in one direction of said optical low-pass filter being decided by the sum and difference of two basic frequency vectors for sampling frequencies determined by a pixel arrangement of said image display body, and an initial minimum value of the modulation transfer function in the other direction of said optical low-pass filter being decided by one of the two basic frequency vectors.

46. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a delta arrangement comprising rows and columns perpendicular to each other, mutually adjacent rows being offset from each other by a half period;

said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

relative positions of virtual images, which are formed on said image display body by two sets of the split light rays, with respect to the central optic axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement;

the following Equations (13) through (16) holding when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU31##

47. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a mosaic arrangement comprising rows and columns perpendicular to each other, basic rows being arranged in the column direction and staggered by one-third period in the row direction;

said optical low-pass filter splitting incident light into four light rays which have point symmetry with respect to a central axis of these light rays;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

the following Equations (49) through (52) holding when relative positions of virtual images, which are formed on said image display body by the split light rays, with respect to the central axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement;

##EQU32##

48. The device according to claim 47, wherein said optical low-pass filter is constituted by two quartz plates that are superimposed in such a manner that directions in which light is split is perpendicular to each other.

49. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a delta arrangement comprising rows and columns perpendicular to each other, mutually adjacent rows being offset from each other by a half period;

said optical low-pass filter splitting incident light into four light rays which have point symmetry with respect to a central axis of these light rays;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

the following Equations (53) through (56) holding when relative positions of virtual images, which are formed on said image display body by the split light rays, with respect to the central axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement;

##EQU33##

50. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a mosaic arrangement comprising rows and columns perpendicular to each other, basic rows being arranged in the column direction and staggered by one-third period in the row direction;

said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

said two sets of optic axes forming angles of α

₁, α

₂, respectively, with the central optic axis;

said optical low-pass filter and said image display body having an optical distance of L between them;

a plane formed by one set of the optic axes having an inclination angle θ

₁ with respect to the row direction and a plane formed by the other set of the optic axes having an inclination angle θ

₂ with respect to the row direction;

disposition of said optical low-pass filter with respect to said image display body being decided in such a manner that the following Equations (29) through (32) hold when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU34##

51. The device according to claim 50, wherein said optical low-pass filter is a two-dimensional phase grating or a two-dimensional prism plate.

52. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a mosaic arrangement comprising rows and columns perpendicular to each other, basic rows being arranged in the column direction and staggered by one-third period in the row direction;

said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

relative positions of virtual images, which are formed on said image display body by two sets of the split light rays, with respect to the central optic axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement;

the following Equations (17) through (20) holding when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU35##

53. The device according to claim 52, wherein said optical low-pass filter is one of a two-dimensional phase grating and a two-dimensional prism plate.

54. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a mosaic arrangement comprising rows and columns perpendicular to each other, basic rows being arranged in the column direction and staggered by one-third period in the row direction;

said optical low-pass filter splitting incident light into four light rays which have point symmetry with respect to a central axis of these light rays;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

the following Equations (57) through (60) holding when relative positions of virtual images, which are formed on said image display body by the split light rays, with respect to the central axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement;

##EQU36##

55. The device according to claim 54, wherein said optical low-pass filter comprises two quartz plates that are superimposed in such a manner that directions in which light is split is perpendicular to each other.

56. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a delta arrangement comprising rows and columns perpendicular to each other, mutually adjacent rows being offset from each other by a half period;

said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

said two sets of optic axes forming angles of α

₁, α

₂, respectively, with the central optic axis;

said optical low-pass filter and said image display body having an optical distance of L between them;

a plane formed by one set of the optic axes having an inclination angle θ

₁ with respect to the row direction and a plane formed by the other set of the optic axes having an inclination angle θ

₂ with respect to the row direction;

disposition of said optical low-pass filter with respect to said image display body being decided in such a manner that the following Equations (33) through (36) hold when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU37##

57. An image display device comprising:

an image display body having a plurality of pixels arranged periodically in two dimensions; and

an optical low-pass filter placed on a front surface of said image display body;

said image display body having a pixel arrangement which is a mosaic arrangement comprising rows and columns perpendicular to each other, basic rows being arranged in the column direction and staggered by one-third period in the row direction;

said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis;

said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y;

said two sets of optic axes forming angles of α

₁, α

₂, respectively, with the central optic axis;

said optical low-pass filter and said image display body having an optical distance of L between them;

a plane formed by one set of the optic axes having an inclination angle θ

₁ with respect to the row direction and a plane formed by the other set of the optic axes having an inclination angle θ

₂ with respect to the row direction;

disposition of said optical low-pass filter with respect to said image display body being decided in such a manner that the following Equations (37) through (40) hold when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU38##

58. The device according to claim 57, wherein said optical low-pass filter is one of a two-dimensional phase grating and a two-dimensional prism plate.

59. An optical low-pass filter for placement on a front surface of an image display body, an initial minimum value of a modulation transfer function in one direction of said optical low-pass filter being decided by two basic frequency vectors for sampling frequencies determined by a pixel arrangement of said image display body, and an initial minimum value of the modulation transfer function in the other direction of said optical low-pass filter being decided by the difference between the basic frequency vectors.

60. The device according to claim 59, wherein said optical low-pass filter is one of a two-dimensional phase grating and a two-dimensional prism plate.

61. The device according to claim 60, wherein said two-dimensional phase grating is a sinusoidal phase grating.

62. The device according to claim 60, wherein said two-dimensional phase grating comprises two one-dimensional phase gratings formed on respective ones of two sides of a substrate, said two phase gratings having grating directions that differ from each other.

63. The device according to claim 60, wherein said two-dimensional phase grating comprises two one-dimensional phase gratings formed on respective substrates and having grating directions that differ from each other.

64. An optical low-pass filter for placement on a front surface of an image display body having a pixel arrangement which is a delta arrangement comprising rows and columns perpendicular to each other, mutually adjacent rows being offset from each other by a half period, said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y, relative positions of virtual images formed on said image display body by two sets of split light rays with respect to a central optic axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y2 of the pixel arrangement, said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis, one of the following sets of Equations (1) through (4) or Equations (5) through (8) holding when the light-intensity ratio of light on the central optic axis to incident light and light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU39##

65. The device according to claim 64, wherein said optical low-pass filter is one of a two-dimensional phase grating and a two-dimensional prism plate.

66. The device according to claim 64, wherein said optical low-pass filter has a characteristic determined using a wavelength in the vicinity of the central wavelength of displayed light.

67. The device according to claim 64, wherein said optical low-pass filter has a characteristic determined using a central wavelength an image displayed using a plurality of colors.

68. The device according to claim 65, wherein said two-dimensional phase grating is a sinusoidal phase grating.

69. The device according to claim 65, wherein said two-dimensional phase grating is comprised of two one-dimensional phase gratings formed on respective ones of two sides of a substrate, said two phase gratings having grating directions that differ from each other.

70. The device according to claim 65, wherein said two-dimensional phase grating comprises two one-dimensional phase gratings formed on respective substrates and having grating directions that differ from each other.

71. An optical low-pass filter for placement on a front surface of an image display body having a plurality of pixels arranged periodically in two dimensions, said image display body having a pixel arrangement which is a mosaic arrangement comprising rows and columns perpendicular to each other, basic rows being arranged in the column direction and staggered by one-third period in the row direction, said image display body having a pixel period in the row direction which is Δ

x and a pixel period in the column direction which is Δ

y, relative positions of virtual images formed on said image display body by two sets of split light rays with respect to a central optic axis being represented by row-direction components X₁, X₂ of the pixel arrangement and column-direction components Y₁, Y₂ of the pixel arrangement, said optical low-pass filter splitting incident light into a plurality of light rays, the optic axis of any of these split light rays serving as a central optic axis, and there being at least two sets of optic axes having point symmetry with respect to this central optic axis, the following Equations (9) through (12) holding when the light-intensity ratio of light on the central optic axis to incident light and the light-intensity ratios of the two sets of split light rays to incident light are represented by P₀, P₁ and P₂, respectively;

##EQU40##

72. The device according to claim 71, wherein said optical low-pass filter is one of a two-dimensional phase grating and a two-dimensional prism plate.

73. The device according to claim 71, wherein said optical low-pass filter has a characteristic determined using a wavelength in the vicinity of the central wavelength of displayed light.

74. The device according to claim 71, wherein said optical low-pass filter has a characteristic determined using a central wavelength of an image displayed using a plurality of colors.

75. The device according to claim 72, wherein said two-dimensional phase grating is a sinusoidal phase grating.

76. The device according to claim 72, wherein said two-dimensional phase grating comprises two one-dimensional phase gratings formed on respective ones of two sides of a substrate, said two phase gratings having grating directions that differ from each other.

77. The device according to claim 72, wherein said two-dimensional phase grating is comprised of two one-dimensional phase gratings formed on respective substrates and having grating directions that differ from each other.