Liquid crystal display and backlight adjusting method
First Claim
1. A liquid crystal display apparatus comprising:
- a liquid crystal interposed between a first substrate and a second substrate;
a backlight as a 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; and
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;
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,wherein 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.
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Accused Products
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.
22 Citations
8 Claims
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1. A liquid crystal display apparatus comprising:
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a liquid crystal interposed between a first substrate and a second substrate; a backlight as a 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; and 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; 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, wherein 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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A luminance adjustment method for backlight as a light source of white light that is a mixture of rays emitted from an arrangement of repetition of at least three-color light emitting devices disposed on a liquid crystal display panel, wherein 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:
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detecting luminance of the backlight; generating a drive signal based on detection of luminance of the backlight; and driving at least three-color 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 at least three-color light emitting devices with the drive signal generated to maintain the luminance of the backlight almost constant.
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Specification