LCD touchscreen panel with external optical path

• US 20080079687A1
• Filed: 09/28/2006
• Published: 04/03/2008
• Est. Priority Date: 09/28/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Cernasov, Andrei
• Granted Patent: US 7,679,610 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G02F 1/13312 Circuits comprising photodetectors for purposes other than feedback
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A liquid crystal display (LCD) device (5) having an integrated touchscreen includes a probe light source (80) behind the liquid crystal (LC) layer (20) for transmitting a probe signal. The device further includes a probe light sensor (90) behind the LC layer for sensing the probe signal. An external optical path is provided whereby the probe signal traverses from the probe light source, across the touchscreen surface (1), and toward the probe light sensor. By sensing interruptions in the probe signal traversing the external optical path, using the probe light sensor, the LCD device is capable of detecting user contact with the touchscreen surface.

Claims

1. A liquid crystal display (LCD) device, comprising:

an external optical path for a probe signal to traverse across a touchscreen surface, and

a device for detecting user contact with the touchscreen surface by sensing interruptions in the probe signal traversing the external optical path.

2. The LCD device of claim 1, further comprising:

a casing configured to hold the touchscreen surface in place, such that the casing and touchscreen surface are configured to provide an enclosure for;

a liquid crystal (LC) layer disposed behind the touchscreen surface,

a probe light source disposed behind the LC layer, the probe light source being configured to transmit a probe light through the touchscreen surface, and

a probe light sensing device disposed behind the LC layer, the probe light sensing device being configured to sense the probe light,

wherein

the probe light traverses from the probe light source, across an external face of the touchscreen surface, to the probe light sensing device via the optical path, and

the user contact is detected in response to the probe light sensing device sensing an interruption of the probe light traversing the optical path.

3. The LCD device of claim 2, the optical path comprising:

first and second reflective elements, external to the enclosure, disposed at the periphery of the touchscreen surface along opposite edges,

wherein

the probe light source is configured to transmit the probe light to the first reflective element,

the first reflective element is configured to reflect the probe light from the probe light source across the touchscreen surface to the second reflective element, and

the second reflective element is configured to reflect the probe light from the first reflective element to the probe light sensing device.

4. The LCD device of claim 3, wherein the first and second reflective elements are mirrors tilted substantially at 45 degrees with respect to the touchscreen surface.

5. The LCD device of claim 3, the optical path further comprising:

a translucent opening in a first peripheral portion of the LC layer through which the probe light is transmitted from the probe light source to the first reflective element; and

a translucent opening in a second peripheral portion of the LC layer through which the probe light is reflected by the second reflective element to the probe light sensing device

6. The LCD device of claim 5, wherein the LC layer is configured to:

set the first and second peripheral portions to a state of opacity; and

scan the translucent openings simultaneously through the first and second peripheral portions, respectively, such that a location coordinate of the user contact is determinable based on the scan locations of the translucent openings when the interruption is sensed by the probe light sensing device.

7. The LCD device of claim 2, further comprising:

first and second probe light sources disposed behind the LC layer in the enclosure, which are configured to transmit the probe light through the touchscreen surface;

first and second probe light sensing devices disposed behind the LC layer in the enclosure, which are configured to sense the probe light,

wherein

a first optical path is provided for the probe light from the first probe light source to traverse across the external face of the touchscreen surface to the first probe light sensing device, and

a second optical path is provided for the probe light from the second probe light source to traverse across the external face of the touchscreen surface to the second probe light sensing device.

8. The LCD device of claim 7, wherein

the first probe light sensing device is operable to detect a horizontal location of the user contact, with respect to the touchscreen surface, by sensing an interruption of the probe light traversing the first optical path, and

the second probe light sensing device is operable to detect a vertical location of the user contact, with respect to the touchscreen surface, by sensing an interruption of the probe light traversing the second optical path.

9. The LCD device of claim 7, wherein

the first optical path comprises reflective elements, external to the enclosure, disposed at the periphery of the touchscreen surface along the top and bottom edges, respectively, and

the second optical path comprises reflective elements, external to the enclosure, disposed at the periphery of the touchscreen surface along the left- and right-side edges, respectively.

10. The LCD device of claim 9, wherein

the first optical path further comprises a pair of translucent openings in the LC layer corresponding to top and bottom edges, respectively, and

the second optical path further comprises a pair of translucent openings in the LC layer corresponding to the left- and right-side edges, respectively.

11. The LCD device of claim 10, wherein

the LC layer is configured to:

simultaneously scan the translucent openings of the first optical path in a horizontal direction along opaque portions of the top and bottom edges, respectively, and

simultaneously scan the translucent openings of the second optical path in a vertical direction along opaque portions of the left- and right-side edges, respectively.

12. The LCD device of claim 11, further comprising:

a contact locating unit configured to;

receive intensity measurements from the first and second probe light sensing devices,

detect user contact with the touchscreen surface based on the received intensity measurements,

determine a horizontal coordinate based on the scan locations of the translucent openings of the first optical path when the user contact is detected, and

determine a vertical coordinate based on the scan locations of the translucent openings of the second optical path when the user contact is detected.

13. The LCD device of claim 2, wherein the probe light source is a light-emitting diode (LED).

14. The LCD device of claim 2, wherein the probe light source is configured to operate in the infrared range.

15. The LCD device of claim 2, wherein the probe light source and the probe light sensing device are partitioned off from a backlight source in the enclosure.