Position detection system

• US 7,295,329 B2
• Filed: 09/08/2005
• Issued: 11/13/2007
• Est. Priority Date: 09/08/2005
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Gruhlke, Russell W., Helbing, Rene P.
• Primary Examiner(s): Nguyen; Sang H
• Application Number:
  US11/222,258
• Publication Number:
  US 20070052692A1
• Time in Patent Office: 796 Days
• Field of Search: 356601-625, 356631-636, 356/638, 250/559.12, 250/559.13, 250/559.24, 250/559.19, 250/222.2, 340555-557
• US Class Current: 356/614
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A position detection system. In representative embodiments, the position detection system comprises a support structure having a cavity, a first light source configured to emit light into at least part of the cavity, a second light source configured to emit light into at least part of the cavity, a first image sensor configured to capture at least part of the light emitted into the cavity by the first and second light sources, an article moveable relative to the support structure, a protuberance attached to the article, and a computation circuit configured to receive a signal from the first image sensor. Movement of the support structure moves the protuberance within the cavity. The computation circuit is configured to compute the location of the protuberance from shadows cast by the protuberance onto the first image sensor.

Claims

1. A position detection system, comprising:

a support structure having a cavity;

a first light source configured to emit light into at least part of the cavity;

a second light source configured to emit light into at least part of the cavity;

a first image sensor configured to capture at least part of the light emitted into the cavity by the first and the second light sources;

an article moveable relative to the support structure;

a protuberance attached to the article, wherein movement of the article moves the protuberance within the cavity; and

a computation circuit configured to receive a signal from the first image sensor, wherein the computation circuit is configured to compute the location of the protuberance when light from the first light source casts a first shadow of the protuberance onto the first image sensor and when light from the second light source casts a second shadow of the protuberance onto the first image sensor.

2. The position detection system as recited in claim 1, wherein the protuberance has a cylindrical shape.

3. The position detection system as recited in claim 1, wherein the computation circuit is configured to compute the location of the protuberance using triangulation techniques.

4. The position detection system as recited in claim 1, further comprising:

a base attached to the support structure.

5. The position detection system as recited in claim 1, further comprising:

multiple first filters configured to pass light of a first color and to block light of a second color; and

multiple second filters configured to pass light of a second color and to block light of a first color, wherein the first image sensor comprises multiple first photosensitive elements and multiple second photosensitive elements, wherein each of the multiple first filters pass light of a first color onto one of the first photosensitive elements and block light of a second color from that first photosensitive element, and wherein each of the multiple second filters pass light of a second color onto one of the second photosensitive elements and block light of a second color from that second photosensitive element.

6. The position detection system as recited in claim 1, further comprising:

a timing circuit, wherein the first image sensor comprises multiple first photosensitive elements and multiple second photosensitive elements, wherein the timing circuit is configured to turn-on the multiple first photosensitive elements during a first time period and to turn off the multiple second photosensitive elements during the first time period, and wherein the timing circuit is configured to turn-on the multiple second photosensitive elements during a second time period and to turn off the multiple first photosensitive elements during the second time period; and

a collection circuit configured to collect signals from the multiple first photosensitive elements and to separately detect signals from the multiple second photosensitive elements, wherein the computation circuit is further configured to perform the computation of the location of the protuberance using the signal from the multiple first photosensitive elements and using the separated signal from the multiple second photosensitive elements.

7. The position detection system as recited in claim 1, further comprising:

a second image sensor configured to capture at least part of the light emitted into the cavity by the first and the second light sources, wherein the computation circuit is further configured to compute the location of the protuberance when light from the first light source casts first shadow of the protuberance onto the first image sensor and when light from the second light source casts second shadow of the protuberance onto the second image sensor and wherein the computation circuit is further configured to compute the location of the protuberance when light from the first light source casts first shadow of the protuberance onto the second image sensor and when light from the second light source casts second shadow of the protuberance onto the second image sensor.

8. The position detection system as recited in claim 7, wherein the protuberance has a cylindrical shape.

9. The position detection system as recited in claim 7, wherein the computation circuit is configured to compute the location of the protuberance using triangulation techniques.

10. The position detection system as recited in claim 7, further comprising:

a base attached to the support structure.

11. The position detection system as recited in claim 7, further comprising:

multiple first filters configured to pass light of a first color and to block light of a second color; and

multiple second filters configured to pass light of a second color and to block light of a first color, wherein the first image sensor and the second image sensor each comprise multiple first photosensitive elements and multiple second photosensitive elements, wherein each of the multiple first filters pass light of a first color onto one of the first photosensitive elements and block light of a second color from that first photosensitive element, and wherein each of the multiple second filters pass light of a second color onto one of the second photosensitive elements and block light of a second color from that second photosensitive element.

12. The position detection system as recited in claim 7, further comprising:

a timing circuit, wherein the first image sensor and the second image sensor each comprise multiple first photosensitive elements and multiple second photosensitive elements, wherein the timing circuit is configured to turn-on the multiple first photosensitive elements during a first time period and to turn off the multiple second photosensitive elements during the first time period, and wherein the timing circuit is configured to turn-on the multiple second photosensitive elements during a second time period and to turn off the multiple first photosensitive elements during the second time period; and

a collection circuit configured to collect signals from the multiple first photosensitive elements and to separately detect signals from the multiple second photosensitive elements, wherein the computation circuit is further configured to perform the computation of the location of the protuberance using the signal from the multiple first photosensitive elements and using the separated signal from the multiple second photosensitive elements.

13. The position detection system as recited in claim 1, further comprising:

a second image sensor configured to capture at least part of the light emitted into the cavity by the first and the second light sources; and

a third image sensor configured to capture at least part of the light emitted into the cavity by the first and the second light sources, wherein the computation circuit is further configured to compute the location of the protuberance when light from the first light source casts first shadow of the protuberance onto the first image sensor and when light from the second light source casts second shadow of the protuberance onto the second image sensor, wherein the computation circuit is further configured to compute the location of the protuberance when light from the first light source casts first shadow of the protuberance onto the third image sensor and when light from the second light source casts second shadow of the protuberance onto the first image sensor, wherein the computation circuit is further configured to compute the location of the protuberance when light from the first light source casts first shadow of the protuberance onto the second image sensor and when light from the second light source casts second shadow of the protuberance onto the second image sensor, wherein the computation circuit is further configured to compute the location of the protuberance when light from the first light source casts first shadow of the protuberance onto the third image sensor and when light from the second light source casts second shadow of the protuberance onto the third image sensor, and wherein the computation circuit is further configured to compute the location of the protuberance when light from the first light source casts first shadow of the protuberance onto the second image sensor and when light from the second light source casts second shadow of the protuberance onto the third image sensor.

14. The position detection system as recited in claim 13, wherein the protuberance has a cylindrical shape.

15. The position detection system as recited in claim 13, wherein the computation circuit is configured to compute the location of the protuberance using triangulation techniques.

16. The position detection system as recited in claim 13, further comprising:

a base attached to the support structure.

17. The position detection system as recited in claim 13, further comprising:

multiple first filters configured to pass light of a first color and to block light of a second color; and

multiple second filters configured to pass light of a second color and to block light of a first color, wherein the first image sensor, the second image sensor, and the third image sensor each comprise multiple first photosensitive elements and multiple second photosensitive elements, wherein each of the multiple first filters pass light of a first color onto one of the first photosensitive elements and block light of a second color from that first photosensitive element, and wherein each of the multiple second filters pass light of a second color onto one of the second photosensitive elements and block light of a second color from that second photosensitive element.

18. The position detection system as recited in claim 13, further comprising:

a timing circuit, wherein the first image sensor, the second image sensor, and the third image sensor each comprise multiple first photosensitive elements and multiple second photosensitive elements, wherein the timing circuit is configured to turn-on the multiple first photosensitive elements during a first time period and to turn off the multiple second photosensitive elements during the first time period, and wherein the timing circuit is configured to turn-on the multiple second photosensitive elements during a second time period and to turn off the multiple first photosensitive elements during the second time period; and

a collection circuit configured to collect signals from the multiple first photosensitive elements and to separately detect signals from the multiple second photosensitive elements, wherein the computation circuit is further configured to perform the computation of the location of the protuberance using the signal from the multiple first photosensitive elements and using the separated signal from the multiple second photosensitive elements.

19. The position detection system as recited in claim 13, wherein the angle between the first image sensor and the second image sensor is ninety degrees and wherein the angle between the first image sensor and the third image sensor is ninety degrees.

20. A position detection system, comprising:

a support structure having a cavity;

a first light source configured to emit light into at least part of the cavity;

a second light source configured to emit light into at least part of the cavity;

a first image sensor configured to capture at least part of the light emitted into the cavity by the first and the second light sources;

a second image sensor configured to capture at least part of the light emitted into the cavity by the first and the second light sources;

an article moveable relative to the support structure;

a protuberance attached to the article, wherein movement of the article support structure moves the protuberance within the cavity and wherein the protuberance comprises multiple retro-reflectors;

a first lens configured to focus light from the first light source reflected back from at least one of the retro-reflectors onto the first image sensor;

a second lens configured to focus light from the second light source reflected back from at least one of the retro-reflectors onto the second image sensor; and

a computation circuit configured to receive a signal from the first image sensor, wherein the computation circuit is configured to compute the location of the protuberance when light from the first light source casts a first hotspot as reflected from the protuberance onto the first image sensor and when light from the second light source casts a second hotspot as reflected from the protuberance onto the first image sensor.

21. A position detection system, comprising:

a support structure having a cavity;

a light source configured to emit light into at least part of the cavity;

a first image sensor configured to capture at least part of the light emitted into the cavity by the light source;

a second image sensor configured to capture at least part of the light emitted into the cavity by the light source;

a first lens configured to focus light from the light source onto the first image sensor;

a second lens configured to focus light from the light source onto the second image sensor;

an article moveable relative to the support structure;

a protuberance attached to the article, wherein movement of the article moves the protuberance within the cavity and wherein the light source is located on the protuberance; and

a computation circuit configured to receive a signal from the first image sensor, wherein the computation circuit is configured to compute the location of the protuberance when light from the light source is focused by the first lens onto the first image sensor and when light from the light source is focused onto the second image sensor.