LCD circuit and a method for triggering at least one pixel of a liquid crystal display

• US 8,749,474 B2
• Filed: 05/04/2007
• Issued: 06/10/2014
• Est. Priority Date: 05/05/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Jarczyk, Alexander
• Primary Examiner(s): HARRIS, DOROTHY H
• Application Number:
  US12/299,678
• Publication Number:
  US 20100013814A1
• Time in Patent Office: 2,594 Days
• Field of Search: 345/208, 345/156, 345/173, 345/104, 345/174
• US Class Current: 345/104
• 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: H04M 1/0214 Foldable telephones, i.e. with body parts pivoting to an open position around an axis parallel to the plane they define in closed position combined with translation movement H04M1/0235
• CPC Class Codes: H04M 2250/22 including a touch pad, a touch sensor or a touch detector

Abstract

The invention relates to an LCD circuit and a method for triggering at least one pixel (3) of a liquid crystal display (LCD) in order to optionally apply a voltage (V) between a first and a second electrode (1, 2), between which a layer (4) of liquid crystals is arranged. The pixel (3) switches into a non-transparent state when a voltage (V) is applied whose value is greater than or equal to the value of a threshold voltage (VD, VD⁻) between the electrodes (1, 2), a sensor voltage (VS) which changes across a sensor period (T) being applied to at least one of the electrodes (1; 1, 2) as said voltage (V) or part of said voltage (V) in order to generate a sensor signal for detecting an object (5) approaching the pixel (3). Also disclosed are an advantageous liquid crystal display encompassing such a circuit as well as an advantageous communication device (7) comprising a first housing part (8) that is provided with a display device (9), a second housing part (10), and an adjusting mechanism (11) for moving the housing parts into a position in which the display device is located at a distance from the second housing part and moving the housing parts into a position in which the display device adjoins a bottom area (12) of the second housing part, said bottom area (12) being embodied by means of such a liquid crystal display.

Claims

1. A mobile computing device comprising:

a display device including a plurality of pixels, the plurality of pixels including a first pixel that comprises (i) first and second electrodes, and (ii) a layer of liquid crystals positioned between the first and second electrodes;

a voltage source; and

a processor to;

detect an object approaching the first pixel in each of a transparent mode and a non-transparent mode of the first pixel;

when operating the first pixel in the transparent mode, detect the object approaching the first pixel by measuring an amount of time needed for a voltage provided across the first and second electrodes to increase to a sensor threshold voltage level associated with the transparent mode; and

when operating the first pixel in the non-transparent mode;

detect the object approaching the first pixel by causing a variable voltage provided across the first and second electrodes of the first pixel using the voltage source, the variable voltage having a voltage amount composed of (i) a first voltage amount corresponding to a non-transparency threshold voltage level in which the first pixel is non-transparent, wherein the non-transparency threshold voltage level is greater than the sensor threshold voltage level associated with the transparent mode, and (ii) a second voltage amount that periodically increases at a predetermined rate starting at a first time until the variable voltage reaches a sensor threshold voltage level associated with the non-transparent mode at a second time; and

measure an elapsed duration of time between the first time and the second time; and

determine that the elapsed duration of time is greater than a predetermined period of time.

2. The mobile computing device as claimed in claim 1, wherein the first electrode is part of a first layer of a first plurality of electrodes, and the second electrode is part of a second layer of a second plurality of electrodes.

3. The mobile computing device as claimed in claim 1, further comprising a switching device for short-circuiting the first and second electrodes.

4. The mobile computing device as claimed in claim 1, wherein the second voltage amount corresponds to a sensor voltage, and wherein in response to the variable voltage reaching the sensor threshold voltage level associated with the non-transparent mode, the processor causes the variable voltage to be set to 0.

5. The mobile computing device as claimed in claim 1, wherein the processor further determines a distance of an approaching object based on the elapsed duration of time.

6. The mobile computing device as claimed in claim 5, wherein the processor is configured to:

measure a first capacity of the first electrode against a base voltage,

measure a second capacity of the second electrode against base voltage, and

determine that the variable voltage has reached the non-transparency threshold voltage based on the first and second capacities.

7. The mobile computing device as claimed in claim 1, wherein the processor causes the second voltage amount to periodically increase at a predetermined rate by following a nonlinear voltage curve.

8. The mobile computing device as claimed in claim 1, wherein the processor reduces the variable voltage to a negative voltage after the first duration of time.

9. The mobile computing device as claimed in claim 1, wherein the processor is configured to output, depending on a maximum value of the variable voltage, a corresponding sensor signal within the first duration of time.

10. The mobile computing device as claimed in claim 1, wherein the predetermined period of time is calculated by determining, for a default voltage provided across the first and second electrodes of the first pixel, the default voltage having a default voltage amount composed of (i) a first default voltage amount corresponding to the non-transparency threshold voltage level in which the first pixel is non-transparent and (ii) a second default voltage amount that periodically increases at the predetermined rate starting at a beginning time until the default voltage reaches the sensor threshold voltage level associated with the non-transparent mode at an end time, the amount of time elapsed between the beginning time and end time in an absence of an object approaching the first pixel.

11. The mobile computing device as claimed in claim 1, wherein the variable voltage is a saw tooth-like voltage.

12. A liquid crystal display comprising:

a plurality of pixels, the plurality of pixels including a first pixel comprising a first electrode layer, a second electrode layer, and a layer of liquid crystals positioned between the first and second electrode layers;

wherein the liquid crystal display is coupled to a processor for;

detecting an object approaching the first pixel in each of a transparent mode and a non-transparent mode of the first pixel;

when operating the first pixel in the transparent mode, detecting the object approaching the first pixel by measuring an amount of time needed for a voltage provided across the first and second electrodes to increase to a sensor threshold voltage level associated with the transparent mode; and

when operating the first pixel in the non-transparent mode;

detecting the object approaching the first pixel by causing a variable voltage provided across the first and second electrode layers of the first pixel using a voltage source, the variable voltage having a voltage amount composed of (i) a first voltage amount corresponding to a non-transparency threshold voltage level in which the first pixel is non-transparent, wherein the non-transparency threshold voltage level is greater than the sensor threshold voltage level associated with the transparent mode, and (ii) a second voltage amount that periodically increases at a predetermined rate from a first time until the variable voltage reaches a sensor threshold voltage level associated with the non-transparent mode at a second time;

measure an elapsed duration of time between the first time and the second time; and

determine that the elapsed duration of time is greater than a predetermined period of time.

13. The liquid crystal display as claimed in claim 12, wherein the first and second electrode layers each have a plurality of first or second electrodes for forming sensor elements to be activated from both sides.

14. A method performed by one or more processors for detecting an object approaching a first pixel of a display device, comprising:

detecting an object approaching the first pixel in each of a transparent mode and a non-transparent mode of the first pixel, wherein the pixel comprises (i) first and second electrodes, and (ii) a layer of liquid crystals positioned between the first and second electrodes;

when operating the first pixel in the transparent mode, detecting the object approaching the first pixel by measuring an amount of time needed for a voltage provided across the first and second electrodes to increase to a sensor threshold voltage level associated with the transparent mode; and

when operating the first pixel in the non-transparent mode;

detecting the object approaching the first pixel by causing a variable voltage provided across the first and second electrodes of the pixel using a voltage source, the variable voltage having a voltage amount composed of (i) a first voltage amount corresponding to a non-transparency threshold voltage level in which the first pixel is non-transparent, wherein the non-transparency threshold voltage level is greater than the sensor threshold voltage level associated with the transparent mode, and (ii) a second voltage amount that periodically increases at a predetermined rate from a first time until the variable voltage reaches a sensor threshold voltage level associated with the non-transparent mode at a second time;

measuring an elapsed duration of time between the first time and the second time; and

determing that the elapsed duration of time is greater than a predetermined period of time.

15. The method as claimed in claim 14, wherein the first electrode is part of a first layer of a first multiplicity of electrodes and the second electrode is part of a second layer of a second multiplicity of electrodes.

16. The method as claimed in claim 15, wherein the second electrode is connected to the first electrode to short-circuit into the transparent mode.

17. The method as claimed in claim 14, wherein the second voltage amount corresponds to a sensor voltage, and further comprising, in response to the variable voltage reaching the sensor threshold voltage level associated with the non-transparent mode, causing the variable voltage to be set to 0.

18. The method as claimed in claim 14, further comprising determining a distance of an approaching object based on the elapse duration of time.