JP2004157559A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device that causes no deterioration in picture quality even when an image signal level is low and has lower power consumption. <P>SOLUTION: The liquid crystal display device is equipped with an amplitude value detecting means 14 of detecting the amplitude value of a supplied image signal, a liquid crystal display 10 which displays an image on a main surface according to the image signal, a back light 8 which emits light whose illumination is freely varied and set from the back surface side of the liquid crystal display 10 to the main surface side, and an illumination setting means 9 of varying and setting the illumination of the back light 8 according to the amplitude value detected by the amplitude value detecting means 14. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device provided with a liquid crystal display whose illuminance is adjusted using a backlight.

  For example, as shown in FIG. 4, the liquid crystal display device 30 includes a timing signal generation circuit 31 that receives a horizontal / vertical synchronization signal to generate a timing signal, and a liquid crystal in which transparent electrodes are arranged in a matrix to form each pixel. A display 32, a column driver 33 to which an image signal is supplied and driving an electrode of each pixel in each horizontal line of the liquid crystal display 32 at an image signal level of each pixel, and a line driver to drive each pixel in each horizontal line And a backlight 35 for irradiating light from the back side to the main surface side of the liquid crystal display 32.

  In the liquid crystal display device 30, while the liquid crystal display 32 is irradiated with light from the backlight 35, the column driver 33 and the line driver 34 are synchronized by the timing signal and sequentially driven by the line driver 34. An image signal level is supplied to each pixel of each horizontal line by the column driver 33 by the column driver 33, and an image is output from the liquid crystal display 32 according to the image signal of each pixel.

  By the way, in the liquid crystal display device 30, when the image signal level is low, the image signal level is amplified by amplifying the image signal level according to the image signal level or by increasing the zero level of the image signal level. The image is output from the liquid crystal display 32 at a high level.

  However, when the image signal level is amplified when the image signal level is extremely low, the amplification rate becomes extremely large, causing distortion in the image signal and deteriorating the image quality of the image, or displaying the image when switching the amplification rate. The problem that an image changes unnaturally arises. In addition, when the zero level is increased, there is a problem that the number of displayable gradations is small and image quality such as a false contour is deteriorated.

  Further, in the liquid crystal display device 30, when the image signal level of the image signal changes transiently such as at the time of tuning or when the power supply voltage is turned ON / OFF, the image signal level is fixed to a black level or the like. Thus, the image quality of the output screen of the liquid crystal display 32 is improved.

  However, since the column driver 33 and the line driver 34 of the liquid crystal display 32 are driven at the black signal level and the like, and the backlight 35 is turned on, there is a problem that power consumption is large.

  In view of the above problems, an object of the present invention is to provide a liquid crystal display device which does not deteriorate image quality even when the image signal level is low and consumes low power.

  A liquid crystal display device according to a first aspect of the present invention includes an amplitude value detecting unit that detects an amplitude value of a supplied image signal, a liquid crystal display that displays an image based on the supplied image signal, and a back surface of the liquid crystal display. A backlight that irradiates light whose illuminance can be set variably from the side to the main surface side; an illuminance setting unit that variably sets the illuminance of the backlight based on the amplitude value detected by the amplitude value detecting unit; Determining means for determining whether an amplitude value of the image signal detected by the value detecting means is equal to or less than a predetermined level; and determining, by the determining means, an amplitude value equal to or less than a predetermined level in the amplitude value of the image signal And control means for controlling the illuminance setting means to variably set the illuminance of the backlight according to the level of the amplitude value of the image signal. Characterized in that it comprises Te.

  Further, in the liquid crystal display device according to the second invention, in the liquid crystal display device according to the first invention, when the determination unit determines that the amplitude value of the image signal has an amplitude value equal to or less than a predetermined level, The control means controls the illuminance setting means to reduce the illuminance of the backlight according to the level of the amplitude value of the image signal.

  The liquid crystal display device according to a third aspect of the present invention is the liquid crystal display device according to the first aspect, wherein an amplifier for amplifying the image signal whose amplification factor is variably settable, and an amplitude detected by the amplitude value detecting means. Further comprising an amplification factor setting means for variably setting the amplification factor of the amplifier based on the value, wherein the determination means determines that the amplitude value of the image signal has an amplitude value equal to or less than a predetermined level. The control means controls the illuminance setting means to reduce the illuminance of the backlight according to the level of the amplitude value of the image signal.

  Further, the liquid crystal display device according to a fourth aspect of the present invention is the liquid crystal display device according to the first aspect of the present invention, further comprising time counting means for counting the duration of the non-signal level of the supplied image signal, and the illuminance setting means is provided. The illuminance of the backlight is variably set based on the duration counted by the time counting means.

  Further, the liquid crystal display device according to a fifth aspect of the present invention is the liquid crystal display device according to the first aspect, further comprising: a transient signal detecting unit configured to detect a transient state of the supplied image signal. The illuminance of the backlight is variably set when a transient state is detected by the transient signal detecting means.

  According to the liquid crystal display device of the present invention, when it is determined that the amplitude value of the image signal has an amplitude value equal to or less than the predetermined level, the illuminance of the backlight is determined according to the level of the amplitude value of the image signal. By controlling the illuminance setting means by the control means so as to variably set the gradation, it is possible to suppress a decrease in the displayable gradation of the liquid crystal display. For this reason, it is possible to output a high-quality image while maintaining an optimal display state.

  For example, when the determination unit determines that the amplitude value of the image signal has an amplitude value equal to or less than a predetermined level, the control unit sets the illuminance setting unit according to the level of the amplitude value of the image signal. By controlling the illuminance of the backlight to be reduced, it is possible to suppress a decrease in the displayable gradation of the liquid crystal display.

  Further, when a predetermined time is counted by the time counting means, the illuminance setting means lowers or stops the illuminance of the backlight, thereby outputting an image such as a black level from the liquid crystal display. For this reason, it is possible to stably output an image such as a black level while reducing power consumption without requiring drive power for a liquid crystal display and power applied to a backlight.

  Further, when a transient state of the image signal is detected by the transient signal detecting unit, the illuminance of the backlight is reduced or stopped by the illuminance setting unit to output an image such as a black level from the liquid crystal display. For this reason, it is possible to stably output an image such as a black level while reducing power consumption without requiring drive power for a liquid crystal display and power applied to a backlight.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  The liquid crystal display device according to the present invention is a liquid crystal display device that displays a suitable image signal on a liquid crystal display for use in, for example, a wall-mounted television receiver or a thin-type television receiver for multimedia.

  As shown in FIG. 1, the liquid crystal display device includes an NTSC demodulation double-speed conversion circuit 1 to which an image signal is supplied, and a color difference signal processing circuit 2 for converting the image signal supplied from the NTSC demodulation double-speed conversion circuit 1 into RGB signals. An A / D converter 3 for A / D converting the RGB signals supplied from the color difference signal processing circuit 2, an FRC circuit 4 for converting the frame rate of the RGB signals supplied from the A / D converter 3, A liquid crystal driver 5 that drives the plasma addressed liquid crystal display (hereinafter referred to as PALC) 10 to supply an image signal level to each pixel of each horizontal line based on the RGB signals supplied from the FRC circuit 4. An LCD controller 6 for generating a timing signal in synchronization with an image signal supplied from the NTSC demodulation double speed conversion circuit 1; A plasma driver 7 for driving each pixel of each horizontal line of the PALC 10 based on the backlight signal, a backlight 8 for irradiating the PALC 10 with light, illuminance setting means 9 for adjusting the illuminance of the backlight 8, and the liquid crystal driver And a PALC 10 driven by the plasma driver 7 and output by adjusting the illuminance of the backlight 8 by the illuminance setting means 9.

  The NTSC demodulation double-speed conversion circuit 1 is provided with an NTSC for UHF broadcasting from a UV tuner, VHF broadcasting from a UV tuner, or BS broadcasting from a BS tuner by switching an operation unit provided outside the liquid crystal display device. A composite image signal is provided.

  The NTSC demodulation double-speed conversion circuit 1 includes a demodulation unit that demodulates an NTSC composite image signal into a luminance signal and a color difference signal based on the luminance signal, a frame memory that stores the color difference signal for each frame, and a frame memory that stores the color difference signal. A motion detection unit that detects a motion of an image from the color difference signal, and an interpolation processing unit that performs interpolation processing of the color difference signal based on the motion detection unit. In the detected still image area, the image data is read twice continuously from the frame memory at double speed, and in the moving image area in which the motion detecting section detects that there is a motion, the image signal level of the horizontal lines above and below each horizontal line is obtained. Interpolated and read out at double speed, converted to a 525H / 60 Hz non-interlace signal, supplied to the color difference signal processing circuit 2, and provided with a luminance signal and a demodulated signal demodulated by the demodulation unit. The supplying non-interlace signal to the LCD controller 6.

  The color difference signal processing circuit 2 adjusts the color difference signal supplied from the NTSC demodulation double speed conversion circuit 1 into color hue and performs an inverse matrix conversion process to generate RGB signals.

  The A / D converter 3 A / D converts the image signal levels of the RGB signals supplied from the color difference signal processing circuit 2 with 8-bit quantization accuracy.

  In the FRC circuit 4, the least significant bit of the RGB signal digitized with 8-bit quantization precision supplied from the A / D converter 3 is rounded to be converted into a 7-bit quantized RGB signal. .

  The liquid crystal driver 5 forms the image signal level of each of the RGB image signals having a 7-bit resolution supplied from the FRC circuit 4 in 128 gradations, and applies the image signal level to the transparent electrode of each pixel of each horizontal line of the PALC 10. Supply and drive.

  The LCD controller 6 generates a timing signal based on the luminance signal supplied from the NTSC demodulation double-speed conversion circuit 1 for each pixel of the PALC 10 and generates a double-speed H clock signal based on a non-interlace signal. The signal is supplied to the liquid crystal driver 5 and the plasma driver 7, and the double-speed H clock signal is supplied to the plasma driver 7.

  The LCD controller 6 receives a horizontal / vertical synchronization signal from the NTSC demodulation double-speed conversion circuit 1 and generates a timing signal for synchronizing the liquid crystal driver 5 and the plasma driver 7 to operate, as shown in FIG. A circuit 11, an amplifier 12 for variably setting and amplifying an amplification factor of the image signal supplied from the NTSC demodulation double-speed conversion circuit 1, and a time for counting a time during which the image signal level of the image signal continues below a predetermined level. The image processing apparatus includes a counting means, an amplitude value detecting means for detecting an amplitude value of an image signal level of the image signal, and a transient signal detecting means for detecting a transient state of the image signal.

  The time counting means 13 resets the count value when the image signal level is equal to or higher than the no-signal level, counts the time when the image signal level is equal to the no-signal level, and the count time exceeds a predetermined time. At this time, the illuminance of the backlight 8 is reduced by the illuminance setting means 9.

  The amplitude value detection means 14 detects the amplitude value of the image signal level, and when the amplitude value is equal to or less than a predetermined level, increases the amplification factor of the amplifier 12 according to the image signal level, and sets the illuminance. The illuminance of the backlight 8 is reduced by the means 9. When the amplitude value is equal to or higher than a predetermined level, the amplification factor of the amplifier 12 is set to 1.

  The transient signal detecting means 15 detects a transient state of the image signal at the time of music selection or ON / OFF of the power supply voltage. When the transient state is detected, the illuminance of the backlight 8 is changed by the illuminance setting means 9. Lower.

  In the LCD controller 6 having the above configuration, when no image signal is supplied, the illuminance of the backlight 8 is reduced by the illuminance setting means 9 based on the count result of the time counting means 13. When the image signal level is low, the image signal level is amplified by the amplifier 12 based on the detection result of the amplitude value detecting means 14 and the illuminance of the backlight 8 is reduced by the illuminance setting means 9. When the image signal is in a transient state, the illuminance of the backlight 8 is reduced by the illuminance setting means 9.

  The plasma driver 7 sequentially synchronizes the cathode and anode electrodes of each plasma chamber of the PALC 10 in the horizontal direction while the liquid crystal driver 5 drives the transparent electrodes for each horizontal line of the PALC 10 in synchronization with the liquid crystal driver 5. And the plasma chamber is sequentially driven to perform scanning and plasma discharge is sequentially performed.

  The backlight 8 is provided so as to irradiate light from the back side of the PALC 10 to the main surface side so that the illuminance can be variably set.

  The illuminance setting unit 9 reduces the illuminance by lowering the power supplied to the backlight 8 or stops the supply of the power when the time detecting unit 13 detects a no-signal level for a predetermined time or more. This stabilizes the screen of the PALC 10 and suppresses the power consumption of the backlight 8. Also, based on the detection result of the amplitude value detecting means 14, the power supplied to the backlight 8 is reduced in accordance with the reduction of the image signal level to reduce the illuminance, thereby suppressing a decrease in the gray scale that can be displayed by the PALC 10.

  The PALC 10 is a liquid crystal display of a type in which each pixel is driven by using discharge plasma. A large-sized liquid crystal display is manufactured at a high yield at a low cost, and realizes high resolution and high contrast. This is a plasma address liquid crystal device disclosed in Japanese Patent Application Laid-Open No. 217396/1992 and Japanese Patent Application Laid-Open No. 4-265931.

  In the PALC 10, as shown in FIG. 3, a plasma chamber 21 provided on a glass substrate 20 and a liquid crystal layer 26, which is an electro-optical material, are arranged to face each other via a thin dielectric sheet 25 made of glass or the like. The plasma chamber 21 is formed by forming a plurality of grooves parallel to each other on the upper surface of the glass substrate 20. For example, 450 grooves are formed, and each of the grooves is formed of helium, neon, argon, or these. A gas that can be ionized, such as a mixed gas of The groove is provided with a pair of mutually parallel anode electrode 22 and cathode electrode 23 for ionizing the gas in the plasma chamber 21 to generate discharge plasma. On the other hand, the liquid crystal layer 26 is disposed on the upper surface of the glass substrate 20 and is sandwiched between the dielectric sheet 25 and the color filters 27 provided with red, green, and blue polarization filters of three colors. 27 is provided on lines parallel to each other and orthogonal to the plasma chamber 21 constituted by the grooves. For example, 765 transparent electrodes 28 are provided for each horizontal line. The intersection of 21 functions as 450 × 768 pixels. The backlight 8 is provided so as to irradiate the entire display surface of the PALC 10 with light so as to face the transparent electrode 28 side from the glass substrate 20 via the color filter 27.

  In the PALC 10, while the liquid crystal driver 5 drives the image signal level of each pixel at, for example, a full scale of 60 V to the transparent electrode 28 of each pixel of each horizontal line, it synchronizes with the drive of the liquid crystal driver 5. Then, the plasma driver 21 drives the plasma chambers 21 of the PALC 10 sequentially so that the anode electrode 22 is set to the ground potential and, for example, the cathode electrode is set to −300 V so that horizontal lines are sequentially switched and scanned. Plasma discharge is sequentially performed to sequentially maintain the image signal level in each pixel disposed on the horizontal line. Similarly, an image is output by sequentially holding the image signal level in each pixel of each horizontal line and updating the image signal for each frame.

  In the above embodiment, the case where the plasma address liquid crystal device is used as the liquid crystal display has been described. However, the present invention is not limited to such a liquid crystal display. An active element such as a transistor is provided on a transparent electrode of a pixel, and the present invention can be applied to an active matrix type liquid crystal display that drives the active element.

It is a block diagram of the liquid crystal display concerning the present invention. It is a block diagram of the principal part of the above-mentioned liquid crystal display. FIG. 3 is a configuration diagram of a liquid crystal display of the liquid crystal display device. FIG. 9 is a block diagram of a conventional liquid crystal display device.

Explanation of reference numerals

  Reference Signs List 8 backlight, 9 illuminance setting means, 10 plasma-addressed liquid crystal display, 13 time counting means, 14 amplitude value detecting means, 15 transient signal detecting means

Claims (4)

Amplitude value detection means for detecting the amplitude value of the supplied image signal,
A liquid crystal display that displays an image based on the supplied image signal,
A backlight that irradiates illuminance variably settable light from the back side of the liquid crystal display to the main surface side,
Illuminance setting means for variably setting the illuminance of the backlight based on the amplitude value detected by the amplitude value detection means,
Determining means for determining whether there is an amplitude value equal to or less than a predetermined level in the amplitude value of the image signal detected by the amplitude value detecting means,
When the determining means determines that there is an amplitude value equal to or less than a predetermined level in the amplitude value of the image signal, the illuminance is variably set according to the level of the amplitude value of the image signal. A liquid crystal display device comprising: control means for controlling setting means.   When the determining means determines that the amplitude value of the image signal has an amplitude value equal to or less than a predetermined level, the control means sets the illuminance setting means in accordance with the level of the amplitude value of the image signal. 2. The liquid crystal display device according to claim 1, wherein the illuminance is controlled to decrease. Further provided is a time counting means for counting the duration of the no-signal level of the supplied image signal,
2. The liquid crystal display device according to claim 1, wherein the illuminance setting means variably sets the illuminance of the backlight based on the duration counted by the time counting means. And a transient signal detecting means for detecting a transient state of the supplied image signal.
2. The liquid crystal display device according to claim 1, wherein the illuminance setting means variably sets the illuminance of the backlight when a transient state is detected by the transient signal detecting means.

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