LIQUID CRYSTAL DISPLAY APPARATUS AND BACKLIGHT ADJUSTMENT METHOD

• US 20100079368A1
• Filed: 12/04/2009
• Published: 04/01/2010
• Est. Priority Date: 12/08/2003
• Status: Active Grant

• Current Assignee: Saturn Licensing LLC (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Ichikawa, Hiroaki
• Granted Patent: US 8,305,338 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A liquid crystal display apparatus and backlight adjustment method are provided.

Backlight luminance sensors 111A to 111D are disposed in the vicinity of four outer corners of an effective screen of an LCD panel 121. Each of the backlight luminance sensors 111A to 111D detects the luminance of each of three primary colors. A backlight unit is composed of a three-primary LED array and a light diffusion unit. Transistors of the backlight luminance sensors and transistors of a pixel portion are formed on the same substrate in the same process. When a transistor is irradiated with backlight in its sufficient off region, an off current occurs due to light excitation. Since the value of the off current corresponds to the luminance of the rays of backlight that irradiates the transistor, the luminance of the backlight is detected with an output voltage into which the off current is converted. As a result, the luminance of the backlight is kept constant.

Claims

1. A liquid crystal display apparatus comprising:

a liquid crystal interposed between a first substrate and a second substrate;

a backlight as a white color light source for the liquid crystal;

a luminance sensor and a thin film device as pixels being formed on the first substrate in a same process, wherein the luminance sensor detects a luminance of the backlight;

a control circuit that generates a drive signal to maintain the luminance of the backlight at an almost constant level with respect to time based on a detection signal detected by the luminance sensor;

an input signal generation portion that generates an input signal having a repetitive period that is shorter than a period for which the liquid crystal transmits light without recognition of flickering, the input signal generation portion supplying the input signal to the thin film device; and

a sample hold portion that holds a detection signal of the luminance sensor,

wherein the control circuit that generates the drive signal to maintain the luminance of the backlight at the almost constant level with respect to time is based on the detection signal held by the sample hold portion, and the second substrate opposite to the first substrate on which the thin film device is formed is disposed on the backlight side when viewed from the liquid crystal.

2. The liquid crystal display apparatus as set forth in claim 1, wherein the sample hold portion is formed on the first substrate on which the thin film devices is formed.

3. The liquid crystal display apparatus as set forth in claim 1, wherein the backlight includes a light emitting device array configured to generate mixed white light.

4. The liquid crystal display apparatus as set forth in claim 3, wherein the mixed white light includes at least a component of blue light emitted from a blue light emitting diode.

5. The liquid crystal display apparatus as set forth in claim 3,

wherein color filters corresponding to at least three different colors components of the mixed white light are disposed on one of the two substrates,

wherein the luminance sensors are disposed corresponding to the light emitting devices and detect the luminance of each of the at least three different color components of the mixed white light, and

wherein the control circuit generates drive signals for the light emitting devices corresponding to the luminance of each of the color components.

6. The liquid crystal display apparatus as set forth in claim 1,

wherein the backlight includes a light emitting device array and a diffusion portion, wherein the diffusion portion diffuses mixed white color light rays emitted from the light emitting device.

7. The liquid crystal display apparatus as set forth in claim 1,

wherein the substrate on which the thin film device is formed when viewed from the liquid crystal side is disposed on the backlight side, wherein at least one luminance sensor is disposed in a screen on which the pixels are formed, and wherein a light shield portion is disposed on the second substrate so that the light shield portion is opposite to the luminance sensor.

8. The liquid crystal display apparatus as set forth in claim 1,

wherein at least one luminance sensor is disposed outside a screen on which the pixels of the thin film devices are formed, and wherein the liquid crystal display apparatus further comprises a housing that houses the first substrate, the second substrate, the backlight, and the control circuit and that covers the luminance sensor.

9. The liquid crystal display apparatus as set forth in claim 1,

wherein the sample hold portion is formed on the first substrate on which the thin film devices is formed.

10. A method for adjusting a luminance of a mixed white light backlight as a light source, wherein the mixed white light backlight includes a plurality of light emitting devices and one or more thin film devices are formed as a screen on the liquid crystal display panel, and wherein a luminance sensor is disposed on the liquid crystal display panel, the method comprising:

detecting luminance of the backlight;

generating a drive signal based on detection of luminance of the backlight; and

driving the light emitting devices with the drive signal generated to maintain the luminance level of the backlight at an almost constant level with respect to time;

generating an input signal having a repetitive period that is shorter than a period for which the liquid crystal transmits light without recognition of flickering and supplying the input signal to the thin film device that composes the luminance sensor;

sample-holding the detected signal of the luminance sensor based on the input signal;

generating a drive signal based on the signal detected during sample holding; and

driving the light emitting devices with the drive signal generated to maintain the luminance of the backlight at an almost constant level.

11. The method for adjusting a luminance of a mixed white light backlight as set forth in claim 10, wherein the mixed white light includes at least a component of blue light emitted from a blue light emitting diode.