Liquid crystal display and backlight adjusting method
First Claim
1. A liquid crystal display apparatus having a liquid crystal interposed between two substrates and a backlight as a light source for the liquid crystal, comprising:
- a luminance sensor formed on one of the substrates (this substrate is referred to as the first substrate), the luminance sensor and thin film devices as pixels being formed on the first substrate in the same process, the luminance sensor that detects the luminance of the backlight; and
a control circuit that generates a drive signal that keeps the luminance of the backlight almost constant on the basis of a detection signal detected by the luminance sensor.
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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.
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Citations
10 Claims
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1. A liquid crystal display apparatus having a liquid crystal interposed between two substrates and a backlight as a light source for the liquid crystal, comprising:
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a luminance sensor formed on one of the substrates (this substrate is referred to as the first substrate), the luminance sensor and thin film devices as pixels being formed on the first substrate in the same process, the luminance sensor that detects the luminance of the backlight; and
a control circuit that generates a drive signal that keeps the luminance of the backlight almost constant on the basis of a detection signal detected by the luminance sensor. - View Dependent Claims (2, 3, 4, 5, 8)
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6. The liquid crystal display apparatus,
wherein the second substrate opposite to the first substrate on which the thin film devices are formed is disposed on the backlight side when viewed from the liquid crystal, wherein the luminance sensor detects an output voltage into which an off current due to light excitation corresponding to luminance of light emitted from the backlight is converted in the state that a thin film device that composes the luminance sensor is sufficiently turned off, and wherein the liquid crystal display apparatus further comprises: -
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 and that the user does not recognize as flickering, the input signal generation portion that supplies the input signal to the thin film device that compose the luminance sensor;
a sample hold portion that sample-holds a detection signal of the luminance sensor; and
a control circuit that generates a drive signal that keeps the luminance of the backlight almost constant on the basis of a signal sample-held by the sample hold portion. - View Dependent Claims (7)
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9. 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, thin film devices being formed as a screen on the liquid crystal display panel, a luminance sensor being disposed on the liquid crystal display panel, comprising the steps of:
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detecting luminance of the backlight;
generating a drive signal on the basis of the detected result at the first step; and
driving at least three-color light emitting devices with the drive signal generated at the second step and keeping the luminance of the backlight almost constant. - View Dependent Claims (10)
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Specification