Optical pointing device with variable focus

• US 20050264531A1
• Filed: 05/25/2004
• Published: 12/01/2005
• Est. Priority Date: 05/25/2004
• Status: Active Grant

• Current Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Tai, Li Chong, Koay, Ban-Kuan, Quek, Theng Theng
• Granted Patent: US 7,339,575 B2
• Time in Patent Office: Days
• US Class Current: 345/163
• CPC Class Codes: G06F 3/0317 in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface
• CPC Class Codes: G06F 3/03543 Mice or pucks G06F3/03541 takes precedence

Abstract

A method and apparatus for focusing an image of a work surface on an optical sensor array in an optical pointing device. Light from a region of the work surface is captured by an imaging system incorporating an optical coupling system and the optical sensor array. The focus of the imaging system is adjusted in accordance with the distance between the optical pointing device and the work surface. The distance may be sensed, or inferred by adjusting the imaging system to maximize the focus of the image.

Claims

1. An optical pointing device comprising:

a support structure operable to move across a work surface;

an illumination source, coupled to the support structure, operable to illuminate a region of the work surface;

an imaging system coupled to the support structure comprising;

an optical sensor array; and

an optical coupling system operable to receive light from the illuminated region of the work surface and transmit the received light to the optical sensor array; and

an auto-focus circuit operable to focus an image of the illuminated region of the work surface on the optical sensor array.

2. An optical pointing device in accordance with claim 1, further comprising a motion detection circuit coupled to the optical sensor array and operable to detect motion of the optical pointing device.

3. An optical pointing device in accordance with claim 1, wherein the optical coupling system comprises a variable focus lens and the auto-focus circuit is operable to adjust the focal length of the variable focus lens.

4. An optical pointing device in accordance with claim 1, wherein the auto-focus circuit is operable to maximize a measure of spatial variations in the image of the illuminated work surface.

5. An optical pointing device in accordance with claim 1, wherein the auto-focus circuit is operable to maximize the surface quality of the image of the illuminated work surface.

6. An optical pointing device in accordance with claim 1, wherein the auto-focus circuit is operable to sense a distance to illuminated work surface and to determine a desired focus of the imaging system therefrom.

7. An optical pointing device in accordance with claim 6, wherein the auto-focus circuit provides, as an output, a focus control signal that is supplied to the imaging system and wherein the motion detection circuit is disabled when the focus control signal is outside of a predetermined range.

8. An optical pointing device in accordance with claim 1, wherein the optical coupling system comprises a variable focus liquid lens in which electro-wetting is used to alter the focal length of the lens.

9. An optical pointing device in accordance with claim 1, wherein the optical coupling system comprises a variable focus liquid lens having a deformable membrane covering a volume of liquid, wherein a force is applied to the liquid by an actuator, thereby causing the membrane to deform and alter the focal length of the lens.

10. An optical pointing device in accordance with claim 1, wherein the optical coupling system comprises a variable focus lens and one or more fixed optical elements.

11. An optical pointing device in accordance with claim 1, wherein the position of the illumination source is adjustable to align the position of the illuminated region of the work surface with the optical coupling system.

12. An optical pointing device in accordance with claim 1, wherein the optical coupling system comprises a lens moveable by action of an actuator, and wherein the auto-focus circuit is operable to control the actuator to adjust the position of the lens and thereby adjust the focus of the imaging system.

13. An optical pointing device in accordance with claim 1, wherein the actuator is a piezoelectric actuator.

14. An optical pointing device in accordance with claim 1, wherein the optical sensor array is moveable by action of an actuator, and wherein the auto-focus circuit is operable to control the actuator to adjust the position of the optical sensor array and thereby adjust the focus of the imaging system.

15. A method for focusing an image of a work surface on an optical sensor array in an imaging system of an optical pointing device, the method comprising:

coupling light from a region of the work surface through an optical coupling system in the imaging system to the optical sensor array; and

adjusting the focus the imaging system in accordance with the distance between the optical pointing device and work surface, such that an image of a work surface is focused on the optical sensor array.

16. A method in accordance with claim 15, wherein adjusting the focus of the imaging system comprises:

measuring the distance from a reference point in the optical pointing device to the work surface;

determining, from the measured distance, a control signal to be applied to the imaging system; and

applying the control signal to the imaging system.

17. A method in accordance with claim 16, wherein determining the control signal to be applied to the imaging system comprises retrieving one or more parameters of the control signal from a predetermined look-up table indexed by the measured distance.

18. A method in accordance with claim 15, wherein adjusting the focus of the imaging system comprises:

determining the focus of a previous image from spatial variations of the image;

adjusting the focus of the imaging system in a first direction; and

repeatedly performing;

determining the focus of a current image from spatial variations of the image;

adjusting the focus of the imaging system in the first direction if the focus has increased; and

adjusting the focus of the imaging system in a direction opposite to the first direction if the focus has decreased.

19. A method in accordance with claim 18, further comprising determining motion of the optical pointing device from successive images of a work surface on an optical sensor array only if successive adjustments to the focus of the imaging system indicate that sufficient focusing has been achieved.

20. A method in accordance with claim 18, wherein adjusting the focus of the imaging system comprises supplying a control signal to the imaging system, and further comprising determining the distance between the optical pointing device and work surface from control signal.

21. A method in accordance with claim 20, further comprising determining motion of the optical pointing device from successive images of a work surface on the optical sensor array if the distance between the optical pointing device and work surface is within a predetermined range.

22. A method in accordance with claim 15, wherein adjusting the focus of the imaging system comprises energizing an actuator to adjust the position of the optical sensor array relative to the work surface.

23. A method in accordance with claim 15, further comprising:

illuminating a region of the work surface by passing light from an illumination source though illumination optics; and

adjusting at least one of the illumination source and the illumination optics to align the illuminated region of the work space with the imaging system.

24. A method in accordance with claim 23, further comprising:

determining the intensity of the image formed on the optical sensor array; and

adjusting the position of at least one of the illumination source and the illumination optics to maximize the intensity of the image.

25. An apparatus for sensing motion of a structure across an illuminated work surface, the apparatus comprising:

an imaging means coupled to the structure, the imaging means comprising;

an optical sensing means for producing an image of the illuminated work surface; and

an optical coupler for receiving light from the illuminated work surface and transmitting the received light to the optical sensing means;

a focus means for adjusting the imaging means such that an image of the illuminated work surface is focused on the optical sensing means; and

a motion detection means for determining motion of the structure from successive images of the illuminated work surface.

26. An apparatus in accordance with claim 25, further comprising an illumination means for illuminating the work surface, the illumination means being coupled to the structure.

27. An apparatus in accordance with claim 25, wherein the focus means comprises a control means for adjusting the imaging means automatically, such that an image of the illuminated work surface is focused on the optical sensing means

28. An apparatus in accordance with claim 27, wherein the focus means further comprises a means for sensing the distance from the structure to the illuminated work surface and wherein the control means is responsive to the sensed distance.

29. An apparatus in accordance with claim 27, wherein the focus means further comprises a means for determining a measure of the focus of the image on the optical sensing means and wherein the control means is responsive to the measure of the focus.

30. An apparatus in accordance with claim 25, wherein the optical coupler comprises a variable focus lens and the focus means is operable to adjust the focal length of the variable focus lens.

31. An apparatus in accordance with claim 25, wherein the focus means is operable to adjust the position of the optical sensing means.