Optical touchpad system and waveguide for use therein

• US 20080007541A1
• Filed: 07/06/2006
• Published: 01/10/2008
• Est. Priority Date: 07/06/2006
• Status: Abandoned Application

• Current Assignee: Taktio APS
• Original Assignee: O-Pen A/S
• Inventors: Stubbe Ostergaard, Jens Wagenblast, Larsen, Niels Agersnap, Bastue, Jens, Eliasson, Jonas Ove Philip
• Application Number:
  US11/480,892
• Publication Number:
  US 20080007541A1
• Time in Patent Office: Days
• US Class Current: 345/176
• 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
• CPC Class Codes: H03K 17/9638 using a light guide

Abstract

An optical touchpad system that includes a waveguide having a plurality of waveguide layers. For example, the waveguide may include an intervening layer, a signal layer, and/or other layers. The intervening layer may be defined by a first surface, a second surface and a substantially transparent material having a first index of refraction disposed between the first and the second surface of the interface layer. The signal layer may be defined by a first surface, a second surface and a substantially transparent material having a second index of refraction that is greater than the first index of refraction.

Claims

1. An optical touchpad system comprising:

one or more emitters configured to emit electromagnetic radiation;

one or more sensors configured to receive electromagnetic radiation and output one or more output signals that correspond to one or more properties of the received electromagnetic radiation; and

a waveguide that guides a portion of the electromagnetic radiation emitted by the emitters to the sensors, the waveguide comprising;

an interface surface that is generally planar and forms a touchpad surface;

an intervening layer having a first index of refraction and being disposed within the waveguide;

a signal layer having a second index of refraction that is greater than the first index of refraction and being disposed within the waveguide abutting the intervening layer on a side of the intervening layer opposite from the outer surface,

wherein the abutment between the signal layer and the intervening layer forms a generally planar boundary therebetween, and

wherein the signal layer is optically coupled to (i) the one or more emitters to receive electromagnetic radiation emitted therefrom, and (ii) the one or more sensors such that the sensors receive electromagnetic radiation from the signal layer;

a total internal reflection mirror having a predetermined critical angle, the total internal reflection mirror being formed at the boundary between the signal layer and the intervening layer such that electromagnetic radiation that is incident on the total internal reflection mirror from within the signal layer is deflected back into the signal layer if the electromagnetic radiation becomes incident on the total internal reflection mirror at an angle of incidence greater than the critical angle;

a reflective surface formed on a side of the signal layer opposite from the boundary between the signal layer and the intervening layer, wherein the reflective surface reflects electromagnetic radiation that is incident on the reflective surface from within the signal layer back into the signal layer; and

a plurality of microstructures disposed within the waveguide, wherein the microstructures are formed (i) to receive electromagnetic radiation from the signal layer that is traveling with an angle of incidence to the plane of the boundary between the signal layer and the intervening layer that is greater than the critical angle of the total internal reflection mirror, and (ii) to leak at least a portion of the received electromagnetic radiation from the signal layer into the intervening layer.

2. The optical touchpad system of claim 1, wherein the microstructures are further formed (iii) to receive electromagnetic radiation that has been leaked from the signal layer by the microstructures and scattered and/or reflected by an object to travel back toward the boundary between the signal layer and the intervening layer at an angle of incidence to the plane of the boundary between the signal layer and the intervening layer that is less than the critical angle of the total internal reflection mirror, and (iv) to bend the path of at least a portion of the received electromagnetic radiation such that the at least a portion of the received electromagnetic radiation enters the signal layer with an angle of refraction to the plane of the boundary between the signal layer and the intervening layer that is greater than the critical angle of the total internal reflection mirror so that the electromagnetic radiation with the angle of refraction to the plane of the boundary between the signal layer and the intervening layer that is greater than the critical angle of the total internal reflection mirror is guided to the one or more sensors by the reflective surface and the total internal reflection mirror.

3. The optical touchpad system of claim 2, further comprising one or more processors that are operatively coupled with the one or more sensors to receive the output signals output by the/one or more sensors, the one or more processors being configured to determine information about the position of the object with respect to the outer surface based on the received output signals that correspond to one or more of the properties of electromagnetic radiation that is scattered and/or reflected by the object and guided to the one or more sensors by the total internal reflection mirror and/or the reflective surface.

4. The optical touchpad system of claim 1, wherein the reflective surface comprises a second total internal reflection mirror.

5. The optical touchpad system of claim 2, wherein the signal layer comprises a first sub-layer that is optically coupled to the one or more emitters and a second sub-layer that is optically coupled to the one or more detectors.

6. The optical touchpad system of claim 1, wherein the plurality of microstructures include one or more microstructures that intrude from the boundary between the intervening layer and the signal layer into the intervening layer.

7. The optical touchpad system of claim 1, wherein the plurality of microstructures include one or more microstructures that intrude from the boundary between the intervening layer and the signal layer into the signal layer.

8. The optical touchpad system of claim 1, wherein the plurality of microstructures include one or more microstructures that are embedded within the signal layer.

9. The optical touchpad system of claim 1, wherein the plurality of microstructures include one or more microstructures that extend from the boundary between the intervening layer and the signal layer to the reflective surface.

10. A waveguide configured to receive electromagnetic radiation from one or more emitters and guides a portion of the received electromagnetic radiation to one or more sensors, the waveguide comprising:

an outer surface that is generally planar and forms a touchpad surface;

an intervening layer having a first index of refraction and being disposed within the waveguide;

a signal layer having a second index of refraction that is greater than the first index of refraction and being disposed within the waveguide abutting the intervening layer on a side of the intervening layer opposite from the outer surface,

wherein the abutment between the signal layer and the intervening layer forms a generally planar boundary therebetween, and

wherein the signal layer is optically coupled to (i) the one or more emitters to receive electromagnetic radiation emitted therefrom, and (ii) the one or more sensors such that the sensors receive electromagnetic radiation from the signal layer;

a total internal reflection mirror having a predetermined critical angle, the total internal reflection mirror being formed at the boundary between the signal layer and the intervening layer such that electromagnetic radiation that is incident on the total internal reflection mirror from within the signal layer is deflected back into the signal layer if the electromagnetic radiation becomes incident on the total internal reflection mirror at an angle of incidence greater than the critical angle;

a reflective surface formed on a side of the signal layer opposite from the boundary between the signal layer and the intervening layer, wherein the reflective surface reflects electromagnetic radiation that is incident on the reflective surface from within the signal layer back into the signal layer; and

a plurality of microstructures disposed within the waveguide,

wherein microstructures are formed to receive electromagnetic radiation from the signal layer that is traveling with an angle of incidence to the plane of the boundary between the signal layer and the intervening layer greater than the critical angle of the total internal reflection mirror, and to leak at least a portion of the received electromagnetic radiation from the signal layer into the intervening layer.

11. The waveguide of claim 10, wherein the microstructures are further formed (iii) to receive electromagnetic radiation that has been leaked from the signal layer by the microstructures and scattered and/or reflected by an object to travel back toward the boundary between the signal layer and the intervening layer at an angle of incidence to the plane of the boundary between the signal layer and the intervening layer that is less than the critical angle of the total internal reflection mirror, and (iv) to bend the path of at least a portion of the received electromagnetic radiation such that the at least a portion of the received electromagnetic radiation enters the signal layer with an angle of refraction to the plane of the boundary between the signal layer and the intervening layer that is greater than the critical angle of the total internal reflection mirror so that the electromagnetic radiation with the angle of refraction to the plane of the boundary between the signal layer and the intervening layer that is greater than the critical angle of the total internal reflection mirror is guided to the one or more sensors by the reflective surface and the total internal reflection mirror.

12. The waveguide of claim 10, wherein the reflective surface comprises a second total internal reflection mirror.

13. The waveguide of claim 11, wherein the signal layer comprises a first sub-layer that is optically coupled to the one or more emitters and a second sub-layer that is optically coupled to the one or more detectors.

14. The waveguide of claim 10, wherein the plurality of microstructures include one or more microstructures that intrude from the boundary between the intervening layer and the signal layer into the intervening layer.

15. The waveguide of claim 10, wherein the plurality of microstructures include one or more microstructures that intrude from the boundary between the intervening layer and the signal layer into the signal layer.

16. The waveguide of claim 10, wherein the plurality of microstructures include one or more microstructures that are embedded within the signal layer.

17. The optical touchpad system of claim 10, wherein the plurality of microstructures include one or more microstructures that extend from the boundary between the intervening layer and the signal layer to the reflective surface.

20. The optical touchpad system of claim 16, wherein the plurality of microstructures are formed such that the ratio of the total area of the microstructures in the plane of the interface surface to the total area of the interface surface is less than 1/20.

18. An optical touchpad system comprising:

one or more emitters configured to emit electromagnetic radiation;

one or more sensors configured to receive electromagnetic radiation and output one or more output signals that correspond to one or more properties of the received electromagnetic radiation; and

a waveguide that guides a portion of the electromagnetic radiation emitted by the emitters to the sensors, the waveguide comprising;

an interface surface that is generally planar and forms a touchpad surface;

a signal layer that is optically coupled to (i) the one or more emitters to receive electromagnetic radiation emitted therefrom, and (ii) the one or more sensors such that the sensors receive electromagnetic radiation from the signal layer, the signal layer being formed to direct electromagnetic radiation that has been emitted by the one or more emitters to the one or more detectors at least in part by total internal reflecion; and

a plurality of microstructures disposed within the waveguide, wherein the microstructures are formed (i) to receive electromagnetic radiation emitted by the one or more emitters that is being directed toward the one or more detectors, (ii) to leak at least a portion of the received electromagnetic radiation from the signal layer out of the signal layer and toward the interface surface, (iii) to receive electromagnetic radiation that has been leaked from the signal layer by the microstructures and scattered and/or reflected by an object to travel back toward the signal layer, and (iv) to bend the path of at least a portion of the received electromagnetic radiation such that the at least a portion of the received electromagnetic radiation is directed by the signal layer to the one or more detectors.

19. The optical touchpad system of claim 18, wherein the plurality of microstructures are disposed within the waveguide such that the electromagnetic radiation the is received by the microstructures from the signal layer is leaked to the interface surface only at one or more predetermined interface areas on the interface surface.