Touch Sensing Using Shadow and Reflective Modes

• US 20080122803A1
• Filed: 03/29/2007
• Published: 05/29/2008
• Est. Priority Date: 11/27/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Rrustemi, Alban, Izadi, Shahram, Butler, David Alexander, Hodges, Stephen
• Granted Patent: US 8,094,129 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• CPC Class Codes: G06F 2203/04109 FTIR in optical digitiser, i.e. touch detection by frustrating the total internal reflection within an optical waveguide due to changes of optical properties or deformation at the touch location
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A touch panel is described which uses at least one infrared source and an array of infrared sensors to detect objects which are in contact with, or close to, the touchable surface of the panel. The panel may be operated in both reflective and shadow modes, in arbirary per-pixel combinations which change over time. For example, if the level of ambient infrared is detected and if that level exceeds a threshold, shadow mode is used for detection of touch events over some or all of the display. If the threshold is not exceeded, reflective mode is used to detect touch events. The touch panel includes an infrared source and an array of infrared sensors.

Claims

1. A method of operating a touch panel system for detecting one or more objects in proximity with a touchable surface of a touch panel, the method comprising:

monitoring signals from infrared sensors that are distributed throughout the touch panel parallel to the touchable surface; and

switching between a reflective mode of operation and a shadow mode of operation for at least a portion of the touch panel based on the monitored signals, wherein in reflective mode, at least one of the infrared sensors is able to detect infrared radiation reflected from one of the objects and in shadow mode, at least one of the infrared sensors are able to detect ambient infrared radiation.

2. A method according to claim 1, wherein switching between a reflective mode of operation and a shadow mode of operation for at least a portion of the touch panel based on the monitored signals comprises:

if criteria for a low power mode are satisfied, switching to shadow mode of operation; and

if criteria for a low power mode are not satisfied, switching to reflective mode of operation.

3. A method according to claim 1, wherein monitoring signals from infrared sensors that are distributed throughout the touch panel parallel to the touchable surface comprises:

scanning at least a portion of the touch panel to measure a level of ambient infrared radiation.

4. A method according to claim 3, wherein monitoring signals from infrared sensors that are distributed throughout the touch panel parallel to the touchable surface further comprises:

scanning different portions of the touch panel dependent upon time and upon signals from infrared sensors.

5. A method according to claim 3, wherein switching between a reflective mode of operation and a shadow mode of operation for at least a portion of the touch panel based on the monitored signals comprises:

if the level of ambient infrared radiation exceeds a first threshold, switching to shadow mode of operation; and

if the level of ambient infrared radiation does not exceed the first threshold, switching to reflective mode of operation.

6. A method according to claim 3, wherein switching between a reflective mode of operation and a shadow mode of operation for at least a portion of the touch panel based on the monitored signals comprises:

if the level of ambient infrared radiation exceeds a first threshold, switching to shadow mode of operation;

if the level of ambient infrared radiation does not exceed both a first and a second threshold, switching to reflective mode of operation; and

if the level of ambient infrared radiation exceeds the second threshold and not the first threshold, determining if criteria for a low power mode are satisfied; and

if the criteria for low power mode are satisfied, switching to shadow mode of operation; and

if the criteria for low power mode are not satisfied, switching to reflective mode of operation.

7. A method according to claim 6, wherein the first threshold is higher than the second threshold.

8. A method according to claim 1, wherein the touch panel system further comprises a plurality of infrared sources configured to illuminate the objects with infrared radiation through the touchable surface, the method further comprising, in reflective mode of operation:

scanning the touch panel; and

on detection of a touch event at an infrared sensor;

illuminating those infrared sources in proximity to said infrared sensor.

9. A method according to claim 1, further comprising, in reflective mode of operation:

illuminating the touchable surface with infrared radiation of a first wavelength;

detecting infrared radiation reflected from an object at said first wavelength; and

repeating the illuminating and detecting steps at a second wavelength.

10. A method according to claim 1, further comprising, periodically recalibrating the touch panel system based on the monitored signals from infrared sensors.

11. A touch panel system for detecting one or more objects in proximity with a touchable surface of the touch panel system, the touch panel system comprising:

a touch panel having integrated therein infrared sensors distributed throughout the touch panel parallel to the touchable surface;

at least one infrared source configured to illuminate objects through the touchable surface; and

a control element arranged to;

monitor signals from the infrared sensors; and

switch between a reflective mode of operation and a shadow mode of operation for at least a portion of the touch panel based on the monitored signals, wherein in reflective mode, at least one of the infrared sensors is able to detect infrared radiation reflected from one of the objects and in shadow mode, at least one of the infrared sensors are able to detect ambient infrared radiation.

12. A touch panel system according to claim 11, wherein the control element comprises:

a processor; and

a memory arranged to store executable instructions arranged to cause the processor to monitor signals from the infrared sensors; and

switch between the reflective mode of operation and the shadow mode of operation for at least a portion of the touch panel based on the monitored signals.

13. A touch panel system according to claim 11, wherein switching between a reflective mode of operation and a shadow mode of operation for at least a portion of the touch panel based on the monitored signals comprises:

if criteria for a low power mode are satisfied, switching to shadow mode of operation; and

if criteria for a low power mode are not satisfied, switching to reflective mode of operation.

14. A touch panel system according to claim 11, wherein monitoring signals from infrared sensors that are distributed throughout the touch panel parallel to the touchable surface comprises:

scanning at least a portion of the touch panel to measure a level of ambient infrared radiation.

15. A touch panel system according to claim 14, wherein switching between a reflective mode of operation and a shadow mode of operation for at least a portion of the touch panel based on the monitored signals comprises:

if the level of ambient infrared radiation exceeds a first threshold, switching to shadow mode of operation; and

if the level of ambient infrared radiation does not exceed the first threshold, switching to reflective mode of operation.

16. A touch panel system according to claim 14, wherein switching between a reflective mode of operation and a shadow mode of operation for at least a portion of the touch panel based on the monitored signals comprises:

if a level of ambient infrared radiation exceeds a first threshold, switching to shadow mode of operation;

if the level of ambient infrared radiation does not exceed both a first and a second threshold, switching to reflective mode of operation; and

if the level of ambient infrared radiation exceeds the second threshold and not the first threshold, determining if criteria for a low power mode are satisfied; and

if the criteria for low power mode are satisfied, switching to shadow mode of operation; and

if the criteria for low power mode are not satisfied, switching to reflective mode of operation.

17. A touch panel system according to claim 12, further comprising an array of infrared sources wherein the memory is further arranged to stored executable instructions arranged to cause the processor, in reflective mode of operation, to:

scan the touch panel; and

on detection of a touch event at an infrared sensor;

to illuminate those infrared sources in proximity to said infrared sensor.

18. A touch panel system according to claim 12, wherein the at least one infrared source is configured to illuminate objects at one of a plurality of infrared wavelengths, the infrared sensors are configured to detect infrared radiation of the plurality of infrared wavelengths and wherein the memory is further arranged to stored executable instructions arranged to cause the processor, in reflective mode of operation, to:

illuminate the touchable surface with infrared radiation of a first wavelength;

detect infrared radiation reflected from an object at said first wavelength; and

repeat the illuminating and detecting steps at a second wavelength.

19. A touch panel system according to claim 18, wherein the at least one infrared source comprises:

at least one infrared source configured to illuminate objects at the first wavelength; and

at least one infrared source configured to illuminate objects at the second wavelength.

20. A method of operating a touch panel system for detecting an object in proximity with a touchable surface of the touch panel system, the method comprising:

detecting a level of ambient infrared light over a portion of the touchable surface;

selecting between a first mode of operation and a second mode of operation for a region of the touch panel system according to said level,

wherein said first mode comprises detecting said object by detecting infrared radiation reflected from said object; and

wherein said second mode comprises detecting said object by detecting ambient infrared radiation.