LCD panel with integral touchscreen

• US 20080055261A1
• Filed: 09/05/2006
• Published: 03/06/2008
• Est. Priority Date: 09/05/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Cernasov, Andrei
• Granted Patent: US 8,203,540 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• 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 (100) having an integrated touchscreen includes a built-in probe signal source behind the liquid crystal (LC) layer (20). The probe signal source may include a pair of light sources (82 and 84) modulated at first and second frequencies (f1 and f2), respectively. A pair of probe light sensing devices (92 and 94) may also be implemented behind the LC layer, each configured to measure the intensities of the first and second frequencies, respectively. The probe light sensing devices are designed to detect user contact with the touchscreen surface by sensing a reflection of the probe light signals from the touchscreen surface. Using the multiple intensity measurements from each probe light sensing device, the location of the point of contact on the touchscreen surface is determined.

Claims

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

a casing configured to hold a transparent touchscreen surface in place;

a liquid crystal (LC) layer disposed within the casing behind the touchscreen surface;

a probe signal source disposed within the casing behind the LC layer, the probe signal source being configured to transmit a probe signal through the touchscreen surface;

a probe signal sensing device disposed within the casing behind the LC layer; and

a contact locating device configured to locate a point of contact on the touchscreen surface based on a reflection of the probe signal from the touchscreen surface.

2. The LCD device of claim 1, wherein the probe signal sensing device is configured to measure an intensity of the probe light, and the reflection of the probe light is detected based on an increase in the measured intensity.

3. The LCD device of claim 1, wherein the LCD device includes a backlight source configured to transmit backlight through the touchscreen surface to convey information to a user.

4. The LCD device of claim 3, wherein the backlight source comprises a plurality of light-emitting diodes (LEDs) including the probe light source.

5. The LCD device of claim 1, wherein

the probe signal source includes first and second probe light sources configured to emit light at a first and second frequency, respectively, and

the probe signal sensing device includes first and second probe light sensing devices, each probe light sensing device including a pair of light sensors for measuring light intensities at the first and second frequencies, respectively.

6. The LCD device of claim 5, wherein the first and second probe light sources are light-emitting diodes (LEDs).

7. The LCD device of claim 5, wherein the first and second frequencies are above 50 Hz.

8. The LCD device of claim 5, wherein the first and second probe light sources are operating in the infrared range.

9. The LCD device of claim 5, wherein the contact locating device includes a digital signal processor (DSP) configured to:

receive the measured light intensities of the first and second frequencies from each of the first and second probe light sensing devices, and

determine location coordinates of the point of contact with respect to the planar dimensions of the touchscreen surface based on the received measured intensities.

10. The LCD device of claim 9, further comprising a lookup table (LUT) with location information, the lookup table being accessible to the contact locating device,

wherein the DSP is configured to determine the location coordinates of the point of contact by performing a lookup of the LUT based on the received measured intensities.

11. The LCD device of claim 10, wherein the location data in the LUTs are calibrated according to internal conditions of the LCD device.

12. The LCD device of claim 10, further comprising an ambient light detector for detecting an ambient light level, wherein DSP is configured to adjust the received measured intensities based on an ambient light level

13. The LCD device of claim 9, wherein the DSP configured to:

calculate an angle (α

1) associated with a path from the point of contact to the first probe light sensing device;

calculate an angle (α

2) associated with a path from the point of contact to the second probe light sensing device; and

calculate the location coordinates based on α

1 and α

2.

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

a casing configured to hold a transparent touchscreen surface in place;

a liquid crystal (LC) layer disposed within the casing behind the touchscreen surface;

first and second light-emitting diodes (LEDs) disposed within the casing behind the LC layer, the first and second LEDs being configured to transmit first and second probe lights, respectively, through the touchscreen surface;

first and second light sensing devices disposed within the casing behind the LC layer, each configured to measure intensities of both the first and second probe lights; and

a processing device configured to detect a point of contact on the touchscreen surface by calculating location coordinates from which the first and second probe signals are reflected back to the first and second light sensing devices based on the measured intensities.