Optical coupling of light into touch-sensing systems

• US 9,857,917 B2
• Filed: 11/24/2014
• Issued: 01/02/2018
• Est. Priority Date: 12/17/2012
• Status: Active Grant

• Current Assignee: FlatFrog Laboratories AB
• Original Assignee: FlatFrog Laboratories AB
• Inventors: Wassvik, Ola, Bergstrom, Hakan, Craven-Bartle, Thomas, Fahraeus, Christer
• Primary Examiner(s): Leiby, Christopher E
• Application Number:
  US14/551,248
• Publication Number:
  US 20160026337A1
• Time in Patent Office: 1,135 Days
• CPC Class Codes: G02B 6/0023 provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• 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 3/042 by opto-electronic means
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A touch-sensitive apparatus operates by light frustration (FTIR) and comprises a light transmissive panel (1) with a front surface and a rear surface. Light emitters (2) and light detectors (3) optically face the rear surface along a perimeter of a touch-sensitive region (4) on the panel (1). At least one diffusively reflecting element (40) is arranged on the front surface (5) along the perimeter of the touch-sensitive region (4). The light emitters (2) are arranged to emit a respective beam of light onto the diffusively reflecting element (40), so as to generate propagating light that propagates by total internal reflection inside the panel (1) across the touch-sensitive region (4), and the light detectors (3) are arranged to receive detection light generated as the propagating light impinges on the diffusively reflecting element (40), so as to define a grid of propagation paths (D) across the touch-sensitive region (4) between pairs of light emitters (2) and light detectors (3).

Claims

1. A touch-sensitive apparatus, comprising:

a light transmissive panel that defines a front surface and an opposite, rear surface;

a plurality of light emitters and a plurality of light detectors arranged to optically face the rear surface along a perimeter of a touch-sensitive region on the light transmissive panel; and

at least one diffusively reflecting element arranged on the front surface along the perimeter of the touch-sensitive region;

wherein the plurality of light emitters are configured to emit respective beams of light onto said at least one diffusively reflecting element, said at least one diffusively reflecting element configured to generate propagating light that propagates by total internal reflection inside the light transmissive panel across the touch-sensitive region; and

wherein the plurality of light detectors are configured to receive detection light generated as the propagating light impinges on said at least one diffusively reflecting element, to define a grid of propagation paths across the touch-sensitive region between pairs of light emitters and light detectors.

2. The touch-sensitive apparatus of claim 1, wherein said at least one diffusively reflecting element comprises:

at least one elongate strip of diffusively reflecting material.

3. The touch-sensitive apparatus of claim 1, wherein said at least one diffusively reflecting element is further configured to define a coherent frame that surrounds the touch-sensitive region.

4. The touch-sensitive apparatus of claim 1, wherein said at least one diffusively reflecting element has a shape of a sequence of partially overlapping dots, the partially overlapping dots having at least one of an elliptical shape and a circular shape.

5. The touch-sensitive apparatus of claim 1, wherein said at least one diffusively reflecting element comprises:

a plurality of spatially separated dots arranged along the perimeter of the touch-sensitive region.

6. The touch-sensitive claim 1, wherein said at least one diffusively reflecting element is configured to exhibit at least 50% diffuse reflection.

7. The touch-sensitive apparatus of claim 1, wherein said at least one diffusively reflecting element is a Lambertian diffuser.

8. The touch-sensitive apparatus of claim 1, wherein said at least one diffusively reflecting element is further configured to promote emission of diffusively reflected light at angles that sustain light propagation by said total internal reflection inside the light transmissive panel.

9. The touch-sensitive apparatus of claim 1, wherein said at least one diffusively reflecting element comprises:

at least one of white paint, white paper, Spectralon, a light transmissive diffusing material covered by a reflective material, an engineered diffuser, or a reflective semi-random micro-structure.

10. The touch-sensitive apparatus of claim 1, further comprising:

a shielding layer applied to said at least one diffusively reflecting element, the shielding layer configured to define an opaque frame around the perimeter of the touch-sensitive region.

11. The touch-sensitive apparatus of claim 10, wherein the shielding layer comprises diamond-like carbon.

12. The touch-sensitive apparatus of claim 1, further comprising:

a light reflective edge element arranged on an edge portion that connects the front surface and the rear surface of the light transmissive panel adjacent to at least one of (i) each of the plurality of light emitters or (ii) each of the plurality of light detectors.

13. The touch-sensitive apparatus of claim 1, further comprising:

a plurality of light reflective rear elements arranged on the rear surface, wherein

each of the plurality of light reflective rear elements define a light transmissive opening, which is aligned with a respective light emitter among the plurality of light emitters.

14. The touch-sensitive apparatus of claim 1, further comprising:

a light absorptive edge element arranged on an edge portion that connects the front surface and the rear surface of the light transmissive panel adjacent to each of the plurality of light detectors.

15. The touch-sensitive apparatus of claim 1, further comprising:

a plurality of light absorptive rear elements arranged on the rear surface, wherein

each of the plurality of light absorptive rear elements defines a light transmissive opening, which is aligned with a respective light detector among the plurality of light detectors.

16. The touch-sensitive apparatus of claim 1, wherein the plurality of light emitters and the plurality of light detectors are arranged with an air gap between the rear surface and the plurality of light emitters, and between the rear surface and the plurality of light detectors.

17. The touch-sensitive apparatus of claim 1, further comprising:

a filter arranged between the rear surface and each of the plurality of light detectors, the filter including at least one of (i) a wavelength filter configured to selectively transmit light at wavelengths included in the light emitted by the plurality of light emitters, and (ii) an angular filter configured to selectively transmit the detection light from said at least one diffusively reflecting element directly above a light detector among the plurality of light detectors.

18. The touch-sensitive apparatus of claim 1, wherein the plurality of light emitters and the plurality of light detectors are arranged relative to said at least one diffusively reflecting element such that adjacent propagation paths partially overlap along their extent across the touch-sensitive region.

19. The touch-sensitive claim 6, wherein said at least one diffusively reflecting element is further configured to exhibit at least 90% diffuse reflection.

20. A touch-sensitive apparatus, comprising:

a light transmissive panel that defines a front surface and an opposite, rear surface;

a plurality of light emitters arranged to optically face the rear surface along a perimeter of a touch-sensitive region on the light transmissive panel;

a plurality of light detectors optically connected to the light transmissive panel; and

at least one diffusively reflecting element arranged on the front surface along the perimeter of the touch-sensitive region;

wherein the plurality of light emitters are configured to emit respective beams of light onto said at least one diffusively reflecting element, said at least one diffusively reflecting element configured to generate propagating light that propagates by total internal reflection inside the light transmissive panel across the touch-sensitive region; and

wherein the plurality of light detectors are configured to define a grid of propagation paths across the touch-sensitive region between pairs of light emitters and light detectors.

21. A touch-sensitive apparatus, comprising:

a light transmissive panel that defines a front surface and an opposite, rear surface;

a plurality of light emitters optically connected to the light transmissive panel to generate propagating light that propagates by total internal reflection inside the light transmissive panel across a touch-sensitive region on the light transmissive panel;

a plurality of light detectors arranged to optically face the rear surface along a perimeter of the touch-sensitive region on the light transmissive panel; and

at least one diffusively reflecting element arranged on the front surface along the perimeter of the touch-sensitive region;

wherein the plurality of light detectors are configured to receive detection light generated, by diffusive reflection of the propagating light by said at least one diffusively reflecting element, to define a grid of propagation paths across the touch-sensitive region between pairs of light emitters and light detectors.