Apparatus and method for bi-directionally sweeping an image beam in the vertical dimension and related apparati and methods

• US 20040004585A1
• Filed: 05/19/2003
• Published: 01/08/2004
• Est. Priority Date: 05/17/2002
• Status: Active Grant

• Current Assignee: Microvisin, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Lewis, John R., Freeman, Mark, Sprague, Randy, Brown, Margaret, Bovee, Jim
• Granted Patent: US 7,580,007 B2
• Time in Patent Office: Days
• US Class Current: 345/32
• CPC Class Codes: G02B 26/0816 by means of one or more reflecting elements
• CPC Class Codes: G09G 3/02 by tracing or scanning a light beam on a screen
• CPC Class Codes: H04N 3/08 having a moving reflector

Abstract

A scan assembly of an image generator sweeps an image beam in a first dimension at a first rate and bi-directionally in a second dimension at a slower rate. Sweeping the beam bi-directionally in the vertical dimension (generally the dimension of the lower sweep rate) can reduce the scanning power by eliminating the flyback period, and, where the scan assembly includes a mechanical reflector, can reduce the error in the beam position without a feedback loop by reducing the number of harmonics in the vertical sweep function. Furthermore, because the image beam is “on” longer due to the elimination of the flyback period, the scanned image is often brighter for a given beam intensity. The scan assembly may also sweep the image beam non-linearly in the vertical dimension, and this sweep may be bi-directional or uni-directional. Sweeping the beam non-linearly can also reduce the error in the beam position by reducing the number of harmonics in the vertical sweep function.

Claims

1. A scan assembly that is operable to:

sweep an image beam in a first dimension at a first frequency; and

sweep the image beam bi-directionally in a second dimension at a second frequency that is lower than the first frequency.

2. The scan assembly of claim 1 wherein the first dimension is substantially orthogonal to the second dimension.

3. The scan assembly of claim 1, further operable to sweep the image beam bi-directionally in the first dimension.

4. The scan assembly of claim 1 wherein:

the first dimension comprises a horizontal dimension; and

the second dimension comprises a vertical dimension.

5. The scan assembly of claim 1, further operable to:

sweep the image beam in the first dimension by resonating at the first frequency; and

sweep the image beam in the second dimension by resonating at the second frequency.

6. A scan assembly that is operable to:

sweep an image beam in a horizontal dimension; and

sweep the image beam bi-directionally in a vertical dimension.

7. The scan assembly of claim 6 further operable to:

sweep the image beam in the horizontal dimension at a horizontal frequency; and

sweep the image beam in the vertical dimension at a vertical frequency that is lower than the horizontal frequency.

8. The scan assembly of claim 6 further operable to sweep the image beam bi-directionally in the horizontal dimension.

9. The scan assembly of claim 6 wherein the horizontal dimension is substantially perpendicular to the vertical dimension.

10. The scan assembly of claim 6, comprising:

a first reflector operable to sweep the image beam in the horizontal dimension; and

a second reflector operable to sweep the image beam in the vertical dimension.

11. The scan assembly of claim 6, comprising a single reflector operable to simultaneously sweep the image beam in the horizontal and vertical dimensions.

12. The scan assembly of claim 6 further operable to:

sweep the image beam in the horizontal dimension by resonating at a horizontal frequency; and

sweep the image beam in the vertical dimension by resonating at a vertical frequency.

13. The scanning assembly of claim 6 having horizontal and vertical resonant frequencies and further operable to:

sweep the image beam in the horizontal dimension by resonating at the horizontal frequency; and

sweep the image beam in the vertical dimension by oscillating at a vertical frequency other than the vertical resonant frequency.

14. The scan assembly of claim 6 further operable to sweep the image beam onto a retina.

15. An image generator, comprising:

a beam generator operable to generate an image beam; and

a scan assembly operable to sweep the image beam in a horizontal dimension and bi-directionally in a vertical dimension.

16. The image generator of claim 15 wherein the image beam comprises a beam of electromagnetic energy.

17. The image generator of claim 15 wherein the image beam comprises a beam of electromagnetic energy having at least one wavelength in the visible spectrum.

18. The image generator of claim 15, further comprising an exit-pupil expander operable to convert the swept image beam into multiple exit pupils.

19. A scan assembly that is operable to:

sweep an image beam in a first dimension at a first frequency; and

sweep the image beam non-linearly in a second dimension at a second frequency that is lower than the first frequency.

20. The scan assembly of claim 19, further operable to sweep the image beam non-linearly in the first dimension.

21. The scan assembly of claim 19, further operable to sweep the image beam bi-directionally in the second dimension.

22. The scan assembly of claim 19, further operable to sweep the image beam sinusoidally in the first and second dimensions.

23. The scan assembly of claim 19, further operable to sweep the image beam in the second dimension according to a function of the second frequency and a harmonic of the second frequency.

24. A scan assembly that is operable to:

sweep an image beam in a horizontal dimension; and

sweep the image beam non-linearly in a vertical dimension.

25. The scan assembly of claim 24, further operable to sweep the image beam non-linearly in the horizontal dimension.

26. The scan assembly of claim 24, further operable to sweep the image beam bi-directionally in the vertical dimension.

27. The scan assembly of claim 24, further operable to sweep the image beam sinusoidally in the horizontal and vertical dimensions.

28. The scan assembly of claim 24, further operable to sweep the image beam in the vertical dimension according to a function of a fundamental frequency and a harmonic of the fundamental frequency.

29. An image-display system, comprising:

a display screen; and

an image generator, comprising,

a beam generator operable to generate an image beam, and

a scan assembly operable to sweep the image beam onto the display screen in a horizontal dimension and bi-directionally in a vertical dimension.

30. A method, comprising:

sweeping an image beam in a first dimension at a first frequency; and

sweeping the image beam back and forth in a second dimension at a second frequency that is lower than the first frequency.

31. The method of claim 30 wherein sweeping the image beam in the first dimension comprises sweeping the image beam back and forth in the first dimension.

32. A method, comprising:

sweeping an image beam in a horizontal dimension; and

sweeping the image beam back and forth in a vertical dimension.

33. The method of claim 32 wherein sweeping the image beam in the horizontal dimension comprises sweeping the image beam back and forth in the horizontal dimension.

34. The method of claim 32 wherein:

sweeping the beam in the horizontal dimension comprises sinusoidally sweeping the beam in the horizontal dimension at a horizontal frequency; and

sweeping the beam in the vertical dimension comprises sinusoidally sweeping the beam back and forth in the vertical dimension at a vertical frequency that is lower than the horizontal frequency.

35. The method of claim 32 wherein sweeping the beam back and forth in the vertical dimension comprises sweeping the beam along a path that is a function of a fundamental vertical frequency and a harmonic of the fundamental vertical frequency.

36. The method of claim 32 wherein:

sweeping the beam in the horizontal dimension comprises sweeping the beam in the horizontal dimension according to a horizontal sinusoid having a phase; and

sweeping the beam in the vertical dimension comprises sinusoidally sweeping the beam back and forth in the vertical dimension according to a vertical sinusoid such that the beam traverses a pattern that repeats every n_h periods of the horizontal sinusoid, the vertical sinusoid having a phase equal to

$-\frac{\mathrm{\pi <br><br>}}{2}+\frac{\mathrm{\pi <br><br>}}{n_h}<br><br>\left[k+\frac{1}{2}\right]$

when the phase of the horizontal sinusoid equals

$\pm <br><br>\frac{\mathrm{\pi <br><br>}}{2}$

and where k=0, 1, . . . , (2n_h−

1).

37. The method of claim 32 wherein:

sweeping the beam in the vertical dimension comprises sweeping the beam in the vertical dimension according to a vertical sinusoid having a phase; and

sweeping the beam in the horizontal dimension comprises sinusoidally sweeping the beam back and forth in the horizontal dimension according to a horizontal sinusoid such that the beam traverses a pattern that repeats every n_v periods of the vertical sinusoid, the horizontal sinusoid having a phase equal to

$-\frac{\mathrm{\pi <br><br>}}{2}+\frac{\mathrm{\pi <br><br>}}{n_h}<br><br>\left[k+\frac{1}{2}\right]$

when the phase of the horizontal sinusoid equals

$\pm <br><br>\frac{\mathrm{\pi <br><br>}}{2}$

and where k=0, 1, . . . , (2n_v−

1).

38. An image generator, comprising:

a beam generator operable to generate an image beam that forms pixels of sequential scanned images from pixels of corresponding source images and that is operable to switch the beam from one of the source images to a subsequent source image at a switch frequency; and

a scan assembly operable to,

sweep the image beam in a first dimension, and

sweep the image beam bi-directionally in a second dimension at a sweep frequency that differs from the switch frequency.

39. The image generator of claim 38 wherein the sweep frequency differs from half the switch frequency.

40. An image generator, comprising:

a beam generator operable to generate an image beam that forms pixels of sequential scanned images from pixels of corresponding source images and that is operable to switch the beam from one of the source images to a subsequent source image at a switch frequency; and

a scan assembly operable to,

sweep the image beam in a horizontal dimension, and

sweep the image beam bi-directionally in a vertical dimension at a vertical sweep frequency that differs from the switch frequency.

41. The image generator of claim 40 wherein the vertical sweep frequency differs from half the switch frequency.

42. The image generator of claim 40 wherein:

at a first time the beam generator is operable to form the image beam from a first pixel at a first relative location of a first source image and switch to forming the image beam from a second pixel at a second relative location of a second source image;

at a second time the beam generator is operable to from the image beam from a third pixel at the first relative location of a third source image and switch to forming the image beam from a fourth pixel at the second relative location of a fourth source image;

the difference between the first and second times being greater than or equal to a predetermined time.

43. The image generator of claim 40 wherein:

at a first time the beam generator is operable to form the image beam from a first pixel at a first relative location of a first source image and switch to forming the image beam from a second pixel at a second relative location of a second source image;

at a second time the beam generator is operable to form the image beam from a third pixel at the first relative location of a third source image and switch to forming the image beam from a fourth pixel at the second relative location of a fourth source image;

the difference between the first and second times being greater than or substantially equal to a persistence time of a human eye.

44. The image generator of claim 40 wherein the vertical sweep frequency equals any frequency other than k/2 times the switch frequency, where k=1, 2, 3, . . . +∞

.

45. The image generator of claim 40, further comprising:

a buffer having a first section operable to sequentially store first source images and having a second section that is operable to sequentially store second source images; and

wherein the beam generator is operable to switch the beam from being formed from a pixel at a relative location of the first section of the buffer to being formed from a pixel at a next relative location of the second section of the buffer at the switch frequency.

46. A method, comprising:

switching formation of an image beam from a pixel of one source image to a pixel of another source image at a switch frequency;

sweeping the image beam in a first dimension; and

sweeping the image beam bi-directionally in a second dimension at a sweep frequency that differs from the switch frequency.

47. The method of claim 46 wherein the switching comprises:

at a first time, switching the formation of the image beam from a first pixel at a first relative location of a first source image to a second pixel at a second relative location of a second source image; and

at a second time, switching the formation of the image beam from a third pixel at the first relative location of a third source image to a fourth pixel at the second relative location of a fourth source image such that a difference between the first and second times is greater than or equal to a predetermined time.

48. A method, comprising:

switching formation of an image beam from a pixel of one source image to a pixel of another source image at a switch frequency;

sweeping the image beam in a horizontal dimension; and

sweeping the image beam bi-directionally in a vertical dimension at a vertical sweep frequency that differs from the switch frequency.

49. The method of claim 48 wherein the switch frequency differs from twice the vertical sweep frequency.

50. The method of claim 48 wherein the switching comprises:

at a first time, switching the formation of the image beam from a first pixel at a first relative location of a first source image to a second pixel at a second relative location of a second source image; and

at a second time, switching the formation of the image beam from a third pixel at the first relative location of a third source image to a fourth pixel at the second relative location of a fourth source image such that a difference between the first and second times is greater than or equal to a predetermined time.

51. The method of claim 48 wherein the switching comprises:

at a first time, switching the formation of the image beam from a first pixel at a first relative location of a first source image to a second pixel at a second relative location of a second source image; and

at a second time, switching the formation of the image beam from a third pixel at the first relative location of a third source image to a fourth pixel at the second relative location of a fourth source image such that a difference between the first and second times is greater than or equal to a persistence time of a human eye.

52. The method of claim 48 wherein the switch frequency equals any frequency other than 2/k times the vertical frequency, where k=1, 2, 3, . . . , +∞

.

53. The method of claim 48, further comprising:

sequentially loading first source images into a first buffer;

sequentially loading second source images into a second buffer; and

wherein switching the formation of the image beam comprises switching the formation of the image beam from a relative location of the first buffer to a next relative location of the second buffer at the switch frequency.

54. An image generator, comprising:

a scan assembly operable to sweep an image beam in a first dimension at a first frequency and non-linearly in a second dimension at a second frequency that is lower than the first frequency, the image beam having an intensity; and

a beam generator operable to modulate the intensity of the image beam as a function of a position of the swept beam in the second dimension.

55. An image generator, comprising:

a scan assembly operable to sweep an image beam in a horizontal dimension and non-linearly in a vertical dimension, the image beam having an intensity; and

a beam generator operable to modulate the intensity of the image beam as a function of a position of the swept beam in the vertical dimension.

56. The image generator of claim 55 wherein:

the scan assembly is further operable to non-linearly sweep the image beam in the horizontal dimension; and

the beam generator is operable to modulate the intensity of the image beam as a function of the position of the swept beam in the horizontal dimension.

57. The image generator of claim 55 wherein the scan assembly is further operable to sweep the image beam bi-directionally in the vertical dimension.

58. The image generator of claim 55 wherein the scan assembly is further operable to sweep the image beam bi-directionally in the horizontal dimension.

59. The image generator of claim 55 wherein the scan assembly is further operable to sweep the image beam sinusoidally in the horizontal and vertical dimensions.

60. The image generator of claim 55 wherein the scan assembly is further operable to sweep the image beam in the vertical dimension according to a function of a fundamental frequency and a harmonic of the fundamental frequency.

61. The image generator of claim 55 wherein the beam generator is further operable to modulate the intensity of the image beam in proportion to a derivative of the position of the swept beam in the vertical dimension.

62. A method, comprising:

sweeping an image beam in a first dimension at a first frequency, the image beam having an intensity;

sweeping the image beam non-linearly in a second dimension at a second frequency that is lower than the first frequency; and

modulating the intensity of the image beam as a function of a phase angle of the swept beam in the second dimension.

63. The method of claim 62 wherein sweeping the image beam in the second dimension comprises sweeping the image beam bi-directionally in the second dimension.

64. A method, comprising:

sweeping an image beam in a horizontal dimension, the image beam having an intensity;

sweeping the image beam non-linearly in a vertical dimension; and

modulating the intensity of the image beam as a function of a phase angle of the swept beam in the vertical dimension.

65. The method of claim 64 wherein:

sweeping the image beam in the horizontal dimension comprises sweeping the image beam non-linearly in the horizontal dimension; and

wherein modulating the intensity of the beam comprises modulating the intensity of the image beam as a function of the position of the swept beam in the horizontal dimension.

66. The method of claim 64 wherein sweeping the image beam in the vertical dimension comprises sweeping the image beam bi-directionally in the vertical dimension.

67. The method of claim 64 wherein sweeping the image beam in the horizontal and vertical dimensions comprises sweeping the image beam sinusoidally in the horizontal and vertical dimensions.

68. The method of claim 64 wherein sweeping the image beam in the vertical dimension comprises sweeping the image beam in the vertical dimension according to a sinusoid and a harmonic of the sinusoid.

69. The method of claim 64 wherein modulating the intensity of the image beam comprises modulating the intensity of the image beam in proportion to a velocity of the swept beam in the vertical dimension.

70. A method, comprising:

sweeping an image beam in a first dimension;

sweeping the image beam bi-directionally in a second dimension according to a function of a fundamental sweeping frequency and a harmonic of the fundamental frequency.

71. A method, comprising:

sweeping an image beam in a horizontal dimension;

sweeping the image beam bi-directionally in a vertical dimension according to a function of a fundamental vertical sweeping frequency and a harmonic of the fundamental frequency.

72. An image generator, comprising:

a scan assembly operable to scan an image by sweeping an image beam in a first dimension and non-linearly in a second dimension, the image beam having an intensity and operable to generate scanned pixels of the scanned image;

a clock generator operable to generate a pixel clock; and

a beam generator coupled to the clock generator and, in response to each cycle of the pixel clock, operable to interpolate a respective scanned pixel of the scanned image by interpolating the intensity of the image beam from a respective original pixel of an original image upon which the scanned image is based.

73. The image generator of claim 72 wherein:

the first dimension comprises a vertical dimension; and

the second dimension comprises a horizontal dimension.

74. The image generator of claim 72 wherein:

the first dimension comprises a horizontal dimension; and

the second dimension comprises a vertical dimension.

75. The image generator of claim 72 wherein the scan assembly is operable to sweep the image beam sinusoidally in the second dimension.

76. The image generator of claim 72 wherein the scan assembly is operable to sweep the image beam in the second dimension according to a sinusoid of a fundamental frequency and a sinusoid of a harmonic of the fundamental frequency.

77. The image generator of claim 72 wherein the clock generator is operable to generate the pixel clock such that the scanned pixels are substantially evenly spaced in the second dimension.

78. The image generator of claim 72 wherein the clock generator is operable to generate the pixel clock such that the scanned pixels are unevenly spaced in the second dimension.

79. The image generator of claim 72 wherein:

the first and second dimensions respectively comprise vertical and horizontal dimensions;

the clock generator is operable to generate the pixel clock such that the scanned pixels are substantially aligned with the respective original pixels in the vertical dimension; and

the beam generator is operable to interpolate the respective scanned pixel by interpolating the intensity of the image beam from a respective original pixel that is substantially aligned with the scanned pixel in the vertical dimension.

80. The image generator of claim 72 wherein:

the first and second dimensions respectively comprise vertical and horizontal dimensions;

the scan assembly is operable to sweep the image beam non-linearly in the vertical dimension;

the clock generator is operable to generate the pixel clock such that the scanned pixels are substantially aligned with the respective original pixels in the vertical dimension; and

the beam generator is operable to interpolate each scanned pixel by interpolating the intensity of the image beam from a respective original pixel that is substantially aligned with the scanned pixel in the vertical dimension.

81. The image generator of claim 72 wherein:

the first and second dimensions respectively comprise vertical and horizontal dimensions;

the clock generator is operable to generate the pixel clock such that the scanned pixels are substantially aligned with the respective original pixels in the vertical dimension and that some of the scanned pixels are misaligned with the respective original pixels in the horizontal dimension; and

the beam generator is operable to interpolate each of misaligned scanned pixel by interpolating the intensity of the image beam from two respective original pixels that are substantially aligned with and that are on opposite sides of the misaligned scanned pixel in the vertical dimension.

82. The image generator of claim 72 wherein:

the first and second dimensions respectively comprise vertical and horizontal dimensions;

the clock generator is operable to generate the pixel clock such that some of the scanned pixels are misaligned with the respective original pixels in the vertical and horizontal dimensions; and

the beam generator is operable to interpolate each misaligned scanned pixel by interpolating the intensity of the image beam from three respective original pixels that together define a region in which the misaligned scanned pixel is located.

83. The image generator of claim 72 wherein:

the first and second dimensions respectively comprise vertical and horizontal dimensions;

the scan assembly is operable to sweep the image beam non-linearly in the vertical dimension;

the clock generator is operable to generate the pixel clock such that some of the scanned pixels are misaligned with the respective original pixels in the vertical and horizontal dimensions; and

the beam generator is operable to interpolate each misaligned scanned pixel by interpolating the intensity of the image beam from four respective original pixels that together define a region in which the misaligned scanned pixel is located.

84. A method, comprising:

generating pixels of a scanned image by sweeping an image beam in a first dimension and non-linearly in a second dimension; and

interpolating an intensity of the image beam for each scanned pixel from a respective original pixel of an original image upon which the scanned image is based.

85. The method of claim 84 wherein generating the pixels of the scanned image comprises sweeping the image beam sinusoidally in the second dimension.

86. The method of claim 84 wherein generating the pixels of the scanned image comprises sweeping the image beam in the second dimension according to a sinusoid of a fundamental frequency and a sinusoid of a harmonic of the fundamental frequency.

87. The method of claim 84 wherein interpolating the intensity of the image beam comprises interpolating the intensity at respective times that cause the scanned pixels to be substantially evenly spaced in the second dimension.

88. The method of claim 84 wherein interpolating the intensity of the image beam comprises interpolating the intensity at respective times that cause the scanned pixels to be unevenly spaced in the second dimension.

89. The method of claim 84 wherein interpolating the intensity of the image beam comprises:

interpolating the intensity at respective times that cause the scanned pixels to be substantially aligned with the original pixels in the first dimension; and

interpolating the intensity for each scanned pixel from a respective original pixel that is substantially aligned with the scanned pixel in the first dimension.

90. The method of claim 84 wherein:

generating the pixels of the scanned image comprises sweeping the image beam non-linearly in the first dimension; and

interpolating the intensity of the image beam comprises, interpolating the intensity at respective times that cause the scanned pixels to be substantially aligned with the original pixels in the first dimension; and

interpolating the intensity for each scanned pixel from a respective original pixel that is substantially aligned with the scanned pixel in the first dimension.

91. The method of claim 84 wherein interpolating the intensity of the image beam comprises:

interpolating the intensity at respective times that cause the scanned pixels to be substantially aligned with the original pixels in the first dimension and that cause at least some of the scanned pixels to be misaligned with the respective original pixels in the horizontal direction; and

interpolating the intensity for each misaligned scanned pixel from two respective original pixels that are substantially aligned with and that are on opposite sides of the misaligned scanned pixel in the vertical dimension.

92. The method of claim 84 wherein interpolating the intensity of the image beam comprises:

interpolating the intensity at respective times that cause at least some of the scanned pixels to be misaligned with the respective original pixels in the first and second dimensions; and

interpolating the intensity for each misaligned scanned pixel from three respective original pixels that together define a region in which the misaligned scanned pixel is located.

93. The method of claim 84 wherein:

generating the pixels of the scanned image comprises sweeping the image beam non-linearly in the first dimension; and

interpolating the intensity of the image beam comprises,

interpolating the intensity at respective times that cause at least some of the scanned pixels to be misaligned with the respective original pixels in the first and second dimensions, and

interpolating the intensity for each misaligned scanned pixel from four respective original pixels that together define a region in which the misaligned scanned pixel is located.