Touch Sensing Using Shadow and Reflective Modes

• US 20120075256A1
• Filed: 12/07/2011
• Published: 03/29/2012
• Est. Priority Date: 11/27/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Izadi, Shahram, Hodges, Stephen, Butler, David Alexander, Rrustemi, Alban
• Granted Patent: US 8,368,663 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 arbitrary 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:

scanning at least a portion of the touch panel to measure a level of ambient infrared radiation using at least one infrared sensor;

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

switching to a reflective mode of operation if the level of ambient infrared radiation does not exceed both the first threshold and a second threshold, wherein the switching between the shadow mode and the reflective mode changes an angle of illumination of an object adjacent to the touch panel; and

determining the three-dimensional shape and thickness of the object based in part on the changes in the angle of illumination.

2. The method of claim 1, further comprising:

determining that a battery level is below a predetermined limit while the level of ambient infrared radiation exceeds the second threshold and not the first threshold; and

switching to the shadow mode of operation after the battery level drops below the predetermined limit.

3. The method of claim 2, further comprising switching to the reflective mode of operation after the battery level rises above the predetermined limit.

4. The method according to claim 1, wherein scanning at least a portion of the touch panel further comprises:

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

5. The method according to claim 2, wherein the first threshold is higher than the second threshold.

6. The method according to claim 2, 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.

7. The method according to claim 2, 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.

8. The method according to claim 1, further comprising, periodically recalibrating the touch panel system based on the scanning at least the portion of the touch panel.

9. The method according to claim 1, further comprising, periodically recalibrating the touch panel system based on the scanning the touch panel.

10. 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;

scan at least a portion of the touch panel to measure a level of ambient infrared radiation;

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

switch to a reflective mode of operation if the level of ambient infrared radiation does not exceed both the first threshold and a second threshold, wherein the switching between the shadow mode and the reflective mode changes an angle of illumination of an object adjacent to the touch panel; and

determining the three-dimensional shape and thickness of the object based in part on the changes in the angle of illumination.

11. The touch panel system according to claim 10, 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.

12. The touch panel system according to claim 10, wherein control element is further arranged to:

determine that a battery level is below a predetermined limit while the level of ambient infrared radiation exceeds the second threshold and not the first threshold;

switch to the shadow mode of operation after the battery level drops below the predetermined limit; and

switch to the reflective mode of operation after the battery level rises above the predetermined limit.

13. The touch panel system according to claim 11, further comprising an array of infrared sources, wherein the memory is further arranged to stored executable instructions arranged to cause the processor, in the 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.

14. The touch panel system according to claim 11, further comprising:

a red light emitting diode (LED) placed behind the infrared sensor;

a green LED placed behind the infrared sensor;

a blue LED placed behind the infrared sensor; and

an infrared LED placed behind the infrared sensor.

15. The touch panel system according to claim 14, further comprising:

a red color filter placed above the infrared sensor; and

a blue color filter placed above the infrared sensor;

16. The touch panel system according to claim 15, further comprising a plurality of pixel electrodes placed adjacent to the infrared sensor.

17. The touch panel system according to claim 16, further comprising an Infrared-transmitting polymer black matrix polymer filter located above the infrared sensor.

18. The touch panel system according to claim 17, further comprising a common electrode located below the red color filter and the blue color filter and above the infrared sensor.

19. The touch panel system according to claim 18, wherein the infrared sensor and the plurality of pixel electrodes reside on a surface of a piece of glass.

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;

switching to the shadow mode of operation after the level of ambient infrared radiation surpasses a threshold; and

switching to the reflective mode of operation after the level of ambient infrared radiation drops below the threshold, wherein the switching between the first mode and the second mode changes an angle of illumination of an object adjacent to the touch panel; and

determining the three-dimensional shape and thickness of the object based in part on the changes in the angle of illumination.