Efficiently focusing light

• US 20070262246A1
• Filed: 05/04/2006
• Published: 11/15/2007
• Est. Priority Date: 05/04/2006
• Status: Active Grant

• Current Assignee: Candledragon, Inc.
• Original Assignee: Candledragon, Inc.
• Inventors: Goldman, Andrew, Liberman, Sergey, Pittel, Arkady, Elektrov, Stanislav
• Granted Patent: US 7,755,026 B2
• Time in Patent Office: Days
• US Class Current: 250/227.130
• CPC Class Codes: B23K 26/042 Automatically aligning the laser beam
• CPC Class Codes: B23K 26/705 Beam measuring device
• CPC Class Codes: G06F 3/0428 by sensing at the edges of the touch surface the interruption of optical paths, e.g. an illumination plane, parallel to the touch surface which may be virtual sensing beam interruptions in a planar beam grid of an optical touch-screen G06F3/0421

Abstract

An array of sensitive pixel elements is configured to generate signals representative of sensed light that is associated with writing being done by a user, and an optical system concentrates light from a light source across a section of the array of sensitive pixel elements, the signals being useful to compute a subpixel measurement of a position of the light source.

Claims

1. An apparatus comprising

an array of sensitive pixel elements configured to generate signals representative of sensed light that is associated with writing being done by a user, and

an optical system to concentrate light from a light source across a section of the array of sensitive pixel elements,

the signals being useful to compute a subpixel measurement of a position of the light source.

2. The apparatus of claim 1 in which the array comprises a row of pixels along a length of the array.

3. The apparatus of claim 1 in which the sensitive pixel elements are sensitive to infrared light.

4. The apparatus of claim 1 in which the array of sensitive pixel elements comprises a lateral position measurement detector.

5. The apparatus of claim 4 in which the lateral position measurement detector comprises a CMOS linear array.

6. The apparatus of claim 4 in which the lateral position measurement detector comprises a CMOS 2D array.

7. The apparatus of claim 3 in which the lateral position measurement detector comprises a CCD linear array.

8. The apparatus of claim 4 in which the lateral position measurement detector comprises a CCD 2D array.

9. The apparatus of claim 4 in which the lateral position measurement detector comprises a position sensing detector (PSD).

10. The apparatus of claim 1 in which the light comprises infrared light.

11. The apparatus of claim 1 in which the optical system comprises a lens.

12. The apparatus of claim 11 in which the lens comprises a single spherical lens.

13. The apparatus of claim 11 in which the lens has a cross-section that is constant along a length of the lens.

14. The apparatus of claim 13 in which the lens comprises a single cylindrical lens.

15. The apparatus of claim 11 in which the lens comprises a single aspheric lens.

16. The apparatus of claim 1 in which the optical system is configured to concentrate the light into an elongated shape on the array.

17. The apparatus of claim 16 in which the shape is a line.

18. The apparatus of claim 1 in which concentrating comprises focusing the light onto the array.

19. The apparatus of claim 1 in which the optical system comprises an opening in an optically opaque material.

20. The apparatus of claim 1 in which the optical system comprises a combination of a transparent refractive lens and an opening in an optically opaque material.

21. The apparatus of claim 1 in which the optical system comprises a series of two or more lenses.

22. The apparatus of claim 1 in which the optical system comprises a pinhole aperture.

23. The apparatus of claim 1 in which the optical system comprises a slit aperture.

24. The apparatus of claim 1 in which the optical system comprises a single Fresnel lens.

25. The apparatus of claim 1 in which the optical system comprises a series of two or more Fresnel lenses.

26. The apparatus of claim 1 in which the optical system comprises a single binary lens.

27. The apparatus of claim 1 in which the optical system comprises a series of two or more binary lenses.

28. The apparatus of claim 1 in which the optical system comprises a reflective surface positioned to reflect light from the light source onto a lens.

29. The apparatus of claim 1 in which the optical system comprises a material to transmit infrared light and not transmit other light.

30. The apparatus of claim 1 in which the computed position of the light source is a vertical projection of a position of the light source onto a plane defined by the writing surface.

31. The apparatus of claim 1 also comprising

a second array of sensitive pixel elements configured to generate signals representative of the sensed light, and

a second lens to concentrate light from the light source across a section of the second array of sensitive pixel elements,

the signals from the first and second arrays being useful to compute a subpixel measurement in two dimensions of the position of the light source.

32. The apparatus of claim 31 in which the computed position of the light source is a vertical projection of a position of the light source onto a plane defined by the writing surface.

33. The apparatus of claim 31 in which the first and second lens each comprise an opening in an optically opaque material.

34. The apparatus of claim 31 in which the first and second lens each comprise a combination of a transparent refractive lens and an opening in an optically opaque material.

35. The apparatus of claim 31 in which the first array and first lens together comprise a first sensor, and the second array and second lens together comprise a second sensor,

in which the first and second sensors are each rotated such that the first and second arrays are not in a common plane.

36. The apparatus of claim 35 in which the first and second sensors are positioned such that the sensors can detect the light source as it is moved over a writing surface.

37. The apparatus of claim 36 in which the writing surface comprises an area corresponding to a standard size of paper.

38. The apparatus of claim 36 in which the writing surface comprises a whiteboard.

39. The apparatus of claim 36 in which the writing surface comprises a drawing pad.

40. The apparatus of claim 35 in which the first and second sensors are located about 120 mm apart and are each rotated about twelve degrees towards each other, as measured from parallel lines through the two sensors.

41. The apparatus of claim 35 in which the first and second sensors are located at adjacent corners of a writing surface, and each rotated forty-five degrees relative to an adjacent edge of the writing surface.

42. The apparatus of claim 35 also comprising a third and forth sensor, in which the sensors are located at four corners of a writing surface and are each rotated forty-five degrees relative to an adjacent edge of the writing surface.

43. The apparatus of claim 35 also comprising a third and forth sensor, in which the sensors are located along four sides of a writing surface.

44. The apparatus of claim 31 also comprising a structure configured to hold the arrays and lenses in positions where they can detect the position of the light source as it is moved over a writing surface.

45. The apparatus of claim 44 in which the structure comprises a pen holder.

46. The apparatus of claim 44 in which the structure comprises a pen cap.

47. The apparatus of claim 45 in which the light source is associated with a writing instrument, and the pen holder is configured to accommodate the writing instrument.

48. The apparatus of claim 45 in which the pen holder is configured to be attached to an edge of the writing surface.

49. The apparatus of claim 44 in which the structure comprises a body of a computer, and the writing surface comprises a screen of the computer.

50. An apparatus comprising

an array of sensitive pixel elements configured to generate signals representative of sensed light that is associated with writing being done by a user, the array being characterized by a plane defined by the sensitive pixel elements, an axis through the sensitive pixel elements, and a center point between equal sets of the sensitive pixel elements, and

a lens to concentrate light from a light source onto the array of sensitive pixel elements, the lens being characterized by an axis through its center and positioned with its axis offset from the center point of the array,

the signals being useful to compute a subpixel measurement of a position of the light source.

51. The apparatus of claim 50 in which the lens is also characterized by a curved surface and a flat surface, and also positioned such that the flat surface is not parallel to the plane of the array.

52. An apparatus comprising

an array of sensitive pixel elements configured to generate signals representative of sensed light that is associated with writing being done by a user, the array being characterized by a plane defined by the sensitive pixel elements, an axis through the sensitive pixel elements, and a center point between equal sets of the sensitive pixel elements, and

a lens to concentrate light from a light source onto the array of sensitive pixel elements, the lens having a curved surface and a flat surface, and positioned such that the flat surface is not parallel to the plane of the array,

the signals being useful to compute a subpixel measurement of a position of the light source.

53. The apparatus of claim 52 in which the lens is cylindrical.

54. The apparatus of claim 53 in which an axis through the cylindrical shape of the lens is in a plane perpendicular to the axis of the sensitive pixel elements.

55. The apparatus of claim 52 in also comprising an opening in an optically opaque material to control an amount of light reaching the lens.

56. The apparatus of claim 52 also comprising

a second array of sensitive pixel elements configured to generate signals representative of the sensed light, the second array being characterized by a plane defined by the sensitive pixel elements, an axis through the sensitive pixel elements, and a center point between equal sets of the sensitive pixel elements, and

a second lens to concentrate light from the light source onto the second array of sensitive pixel elements, the second lens having a curved surface and a flat surface, and positioned such that the flat surface is not parallel to the plane of the second array,

the signals from the first and second arrays being useful to compute a subpixel measurement in two dimensions of the position of the light source.

57. An apparatus comprising

a writing surface,

an array of sensitive pixel elements configured to generate signals representative of sensed light that is associated with writing being done by a user

a lens to concentrate light from a light source in a shape other than a spot onto the array of sensitive pixel elements, and

a reflective surface positioned to reflect light from the light source onto the lens, when the light source is near the writing surface,

the signals being useful to compute a subpixel measurement of a position of the light source.

58. The apparatus of claim 57 also comprising an optically opaque barrier positioned between the writing surface and the reflective surface, a portion of the barrier defining an opening positioned to admit light from the light source when the light source is near the writing surface.

59. A method comprising

using two optical sensors separated by a lateral distance to generate a set of signals representing subpixel values and usable to reconstruct a position of a light source that is associated with a writing instrument being used by a user, and

using the signals to compute a measurement of a position in two dimensions of the light source near a writing surface,

in which using the optical sensors includes using an optical system to concentrate light from the light source in a shape other than a spot onto an array of sensitive pixel elements.

60. The method of claim 59 in which computing the measurement comprises using a quasi-triangulation algorithm.

61. The method of claim 59 in which computing the measurement comprises using calibrated parameters.

62. The method of claim 59 in which computing the measurement comprises using a lookup table.

63. The method of claim 59 in which computing the measurement comprises using a polynomial approximation.

64. The method of claim 59 also comprising

using the two optical sensors to generate a second set of signals representing subpixel values and usable to reconstruct a position of a second light source that is associated with a second position along a length of the writing instrument, and

using the first and second sets of signals to compute a measurement of an angle between the writing instrument and the writing surface.

65. The method of claim 64 also comprising

using the first and second sets of signals to compute a position in two dimensions of a tip of the writing instrument on the writing surface.

66. An apparatus comprising

a device to hold paper in a location, and

at least two sensor assemblies located near the location, to generate signals representative of sensed light that is associated with writing being done on the paper,

the sensor assemblies each comprising

an array of sensitive pixel elements, and

a lens to concentrate light from a light source in a shape other than a spot onto the array of sensitive pixel elements.

67. An apparatus comprising

a housing for a computer display, and

at least two sensor assemblies to generate signals representative of sensed light that is associated with writing being done on the display,

the sensor assemblies each comprising

an aperture in the housing,

an array of sensitive pixel elements,

a lens to concentrate light from a light source in a shape other than a spot onto the array of sensitive pixel elements, and

a reflective surface to direct light entering through the aperture onto the lens.

68. The apparatus of claim 67 in which the computer display is a monitor of a tablet computer.

69. The apparatus of claim 67 in which the computer display is a monitor of a laptop computer.

70. The apparatus of claim 67 in which the computer display is a screen of a portable communications device.