Speckle navigation system

• US 7,737,948 B2
• Filed: 12/20/2005
• Issued: 06/15/2010
• Est. Priority Date: 12/20/2005
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Sanders, Steven, Spurlock, Brett A., Carlisle, Clinton B., Trisnadi, Jahja I.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Sheng, Tom V
• Application Number:
  US11/313,133
• Publication Number:
  US 20070139381A1
• Time in Patent Office: 1,638 Days
• Field of Search: 345/156, 345/157, 345/163, 345/166
• US Class Current: 345/166
• 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

Abstract

One embodiment relates to a laser positioning device for sensing relative movement between a data input device and a surface by determining displacement of image features in a succession of images of the surface. The device forms a single integrated package, which includes a planar substrate and a transparent encapsulant that also embodies a collimating lens. Both a coherent light source and a sensor array and associated circuitry are configured on the planar substrate. Another embodiment relates to a method of sensing relative movement between a data input device and a surface. Coherent light is emitted from a laser and collimated so as to form a collimated illumination beam with a predetermined diameter, D, and a substantially uniform phase front. A speckle pattern is generated by impingement of the collimated illumination beam on the surface and detected by a sensor array. Other embodiments are also disclosed.

Claims

1. A method of sensing relative movement between a data input device and a surface by determining displacement of optical features in a succession of images of the surface, the method comprising:

emitting coherent light from a laser;

collimating the coherent light so as to form a collimated illumination beam with a predetermined diameter, D, and is transmitted to the surface at a normal angle thereto;

generating a speckle pattern by impingement of the coherent light from the collimated illumination beam on the surface; and

detecting the images of the surface using a sensor array comprising a comb array,

wherein the laser and the sensor array are both configured on a same planar substrate that is configured to lie parallel to the surface, and the predetermined diameter, D, of the collimated illumination beam satisfies an equation D=(h λ

)/(ξ

Λ

cos²θ

), wherein h is a height from the planar substrate to the surface, λ

is a wavelength of the coherent light, ξ

is a fraction between 0.25 and 0.5, Λ

is a period of the comb array, and θ

is an angle subtended by the beam from a point on the sensor.

2. The method according to claim 1, further comprising use of an opaque edge for lift detection.

3. The method according to claim 1, wherein, due to a substantially uniform phase front of the collimated beam, a small lateral displacement between the planar substrate and the surface results in a shift of a speckle pattern.

4. The method according to claim 1, wherein, due to the predetermined diameter of the collimated beam, a speckle size at the surface matches a period of the comb array.

5. A laser positioning device for sensing relative movement between a data input device and a surface by determining displacement of optical speckle in a succession of images of the surface, the device comprising:

a planar substrate;

a coherent light source configured on the planar substrate to shine a collimated illumination beam on the surface; and

a comb array and associated circuitry configured on the planar substrate,

wherein a predetermined diameter, D, of the collimated illumination beam satisfies an equation D=(h λ

)/(ξ

Λ

cos²θ

), wherein h is a height from the planar substrate to the surface, λ

is a wavelength of the coherent light, ξ

is a fraction between 0.25 and 0.5, Λ

is a period of the comb array, and θ

is an angle subtended by the beam from a point on the sensor.

6. The laser positioning device of claim 5, wherein the comb array receives light forming an image of the surface without use of a collection lens.

7. The laser positioning device of claim 5, wherein the collimating lens is embodied as one of the following:

a) part of a transparent encapsulant which covers the planar substrate;

b) part of a molded transparent plastic which covers the planar substrate;

or c) a small lens that is plugged into a package covering the planar substrate.

8. The laser positioning device of claim 5, further comprising an opaque edge for lift detection.

9. The laser positioning device of claim 8, wherein the edge is placed so as to block an illuminated portion of the surface from a field of view of the sensor array if the device is lifted by more than a predetermined height above the planar substrate.

10. The laser positioning device according to claim 5, wherein the collimating lens is configured to receive coherent light from the coherent light source and to provide a collimated illumination beam which is transmitted to the surface at or near a normal angle to the surface.

11. The laser positioning device according to claim 10, wherein, due to uniformity of a phase front of the collimated beam, a small lateral displacement between the planar substrate and the surface results in a shift of a speckle pattern with minimal boiling.

12. The laser positioning device according to claim 5, wherein, due to the predetermined diameter of the collimated beam, a speckle size at the surface matches a period of the comb array.

13. The laser positioning device according to claim 5, wherein a transparent encapsulant covers the coherent light source and sensor array.

14. The laser positioning device according to claim 13, wherein the transparent encapsulant is part of a package in which the laser positioning device is packaged.

15. A laser positioning device comprising:

a substrate with a light source configured thereon;

a collimating lens between the light source and a surface over which the device is positioned to illuminate the surface with an illumination beam;

a sensor array configured on the substrate, the sensor array having a field of view of the illuminated surface; and

a lift detection mechanism that causes the device to stop tracking if the device is lifted from a nominal height distance (h) above the surface by more than a predetermined distance (Δ

h) above the surface, the lift detection mechanism comprises an opaque edge located a horizontal distance (x) from a center of the sensor array, parallel to a plane of the sensor array, given by the equation;

$x=\frac{4<br><br>\mathrm{hs}+\mathrm{\Delta <br><br>}<br><br><br><br>h<br><br>\left(2<br><br>s+w-D<br><br>\left(h,s\right)\right)}{4<br><br>\mathrm{hw}-4<br><br>\mathrm{hD}<br><br>\left(h,s\right)+2<br><br>\mathrm{\Delta <br><br>}<br><br><br><br>h<br><br>\left(2<br><br>s+w-D<br><br>\left(h,s\right)\right)}·<br><br>w$

where w is a width of the sensor array, s is a center-to center separation between the sensor array and the light source, and D(h,s) is a diameter of the illumination beam.

16. The laser positioning device according to claim 15, wherein the opaque edge is located a vertical distance (y) from the plane of the sensor array, given by the equation:

$y=\frac{2<br><br>x+w}{2<br><br>s+w-D<br><br>\left(h,s\right)}·<br><br>h.$

17. The laser positioning device according to claim 15, wherein Δ

h is a predetermined distance between one to five millimeters.