JP2006227646A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device with low electric power consumption that shows no degradation in the picture quality even when an image signal level is low. <P>SOLUTION: The device includes an amplitude detecting means 14 to detect the amplitude value of a supplied image signal, a backlight 8 capable of setting illuminance, and a liquid crystal display 10 to display an image based on the supplied image signal under the set illuminance, wherein the illuminance of the backlight 8 is set to decrease according to the amplitude level detected by the amplitude detecting means 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display device such as 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 generates a timing signal when supplied with a horizontal / vertical synchronization 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 that is supplied with an image signal and drives an electrode of each pixel of each horizontal line of the liquid crystal display 32 at an image signal level of each pixel; and a line driver that drives each pixel for each horizontal line 34 and a backlight 35 that irradiates light from the back side to the main surface side of the liquid crystal display 32.

  In the liquid crystal display device 30, the column driver 33 and the line driver 34 are synchronized with the timing signal and sequentially driven by the line driver 34 in a state where the liquid crystal display 32 is irradiated with light from the backlight 35. Further, the image is output from the liquid crystal display 32 by the image signal for each pixel supplied with the image signal level by the column driver 33 to each pixel for each horizontal line.

Japanese Patent Laid-Open No. 06-160811 Japanese Patent Laid-Open No. 06-102484 Japanese Patent Laid-Open No. 03-009320 Japanese Utility Model Publication No. 05-071888

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

  However, if the image signal level is amplified when the image signal level is extremely small, the amplification factor becomes extremely large, causing distortion in the image signal, degrading the image quality of the image, or switching the amplification factor. The problem is that the image changes unnaturally. In addition, when the zero level is increased, there is a problem in that there are few displayable gradations and image quality degradation such as pseudo contours occurs.

  Further, in the liquid crystal display device 30, when the image signal level of the image signal changes transiently, such as when selecting a channel or turning on / off the power supply voltage, 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 with the black signal level or 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 display device that does not deteriorate image quality even when the image signal level is small and that has low power consumption.

  The display device according to the present invention displays an amplitude value detecting means for detecting an amplitude value of a supplied image signal, a backlight capable of setting illuminance, and displays an image based on the supplied image signal with set illuminance. Display means, and the illuminance of the backlight is set so as to decrease according to the level of the amplitude value detected by the amplitude value detection means.

  In the display device according to the present invention, the amplitude value of the supplied image signal is detected by the amplitude value detecting means, and the illuminance of the backlight whose illuminance can be set depends on the level of the amplitude value detected by the amplitude value detecting means. Therefore, the display means for displaying the image based on the supplied image signal at the set illuminance suppresses a decrease in displayable gradation and maintains an optimal display state to provide a high-quality image. You can display.

  The display device according to the present invention further includes time counting means for counting a time during which the non-signal level of the supplied image signal continues, so that the duration time counted by the time counting means is a predetermined time or more. At this time, by setting the illuminance of the backlight to be lowered, it is possible to stably output a black level or the like while reducing the power consumption without requiring the drive power of the display means and the applied power of the backlight.

  Further, the display device according to the present invention further includes a transient signal detecting means for detecting a transient state of the image signal supplied at the time of channel selection or power-on, whereby the transient state is detected by the transient signal detecting means. By setting so that the illuminance of the backlight is lowered at this time, it is possible to stably output a black level or the like while reducing the power consumption without requiring the drive power of the display means and the applied power of the backlight.

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

  The present invention is applied to, for example, a liquid crystal display device that displays an image signal suitable for use on a liquid crystal display, for example, for a wall-mounted television receiver or a thin 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 that converts the image signal supplied from the NTSC demodulation double speed conversion circuit 1 into an RGB signal. An A / D converter 3 for A / D converting the RGB signal supplied from the color difference signal processing circuit 2; an FRC circuit 4 for converting a frame rate of the RGB signal supplied from the A / D converter 3; A liquid crystal driver 5 is driven to supply an image signal level to each pixel of each horizontal line of a plasma addressed liquid crystal display (hereinafter referred to as PALC) 10 based on the RGB signal supplied from the FRC circuit 4. An LCD controller 6 that generates a timing signal in synchronization with the 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 switching signal, a backlight 8 for irradiating the PALC 10 with light, an illuminance setting means 9 for adjusting the illuminance of the backlight 8, and the liquid crystal driver 5 and a PALC 10 which is driven by the plasma driver 7 and outputs an image by adjusting the illuminance of the backlight 8 by the illuminance setting means 9.

  The NTSC demodulating double speed conversion circuit 1 is used 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 supplied.

  The NTSC demodulation double speed conversion circuit 1 includes a demodulator that demodulates an NTSC composite image signal into a color difference signal based on the luminance signal, a frame memory that stores the color difference signal for each frame, and a memory stored in the frame memory. A motion detection unit that detects the motion of the image from the color difference signal that has been performed, and an interpolation processing unit that performs an interpolation process of the color difference signal based on the motion detection unit, and if there is no motion in the motion detection unit In the detected still image area, the frame memory is continuously read twice as fast as the frame memory, and in the moving image area detected by the motion detection unit, the image signal level of the horizontal line above and below each horizontal line is used. Interpolated and read out at double speed, converted to a non-interlace signal of 525H / 60 Hz, supplied to the color difference signal processing circuit 2, and the luminance signal demodulated by the demodulator and The supplying non-interlace signal to the LCD controller 6.

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

  The A / D converter 3 performs A / D conversion on the image signal level of the RGB signal supplied from the color difference signal processing circuit 2 with an 8-bit quantization accuracy.

  In the FRC circuit 4, the least significant bit of the RGB signal digitized with 8-bit quantization accuracy supplied from the A / D converter 3 is rounded and converted to an RGB signal quantized with 7 bits. .

  In the liquid crystal driver 5, the image signal level of each RGB image signal having 7-bit resolution supplied from the FRC circuit 4 is formed in 128 gradations, and is applied to the transparent electrode of each pixel for 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 the non-interlaced 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.

  As shown in FIG. 2, the LCD controller 6 is supplied with a horizontal / vertical synchronizing signal from the NTSC demodulating double speed conversion circuit 1 and generates a timing signal for generating a timing signal for operating the liquid crystal driver 5 and the plasma driver 7 in synchronization. A circuit 11; an amplifier 12 for variably amplifying the amplification factor of the image signal supplied from the NTSC demodulation double speed conversion circuit 1; and a time for counting the time during which the image signal level of the image signal is kept below a predetermined level. It has a counting means 13, an amplitude value detecting means 14 for detecting the amplitude value of the image signal level of the image signal, and a transient signal detecting means 15 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 reaches a predetermined time or more. At this time, the illuminance setting means 9 reduces the illuminance of the backlight 8.

  The amplitude value detecting means 14 detects the amplitude value of the image signal level, and when the amplitude value is equal to or lower than the predetermined level, the amplification factor of the amplifier 12 is increased in accordance with the image signal level, and the illuminance setting is performed. 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 the transient state of the image signal at the time of channel selection or ON / OFF of the power supply voltage, and the illuminance setting means 9 determines the illuminance of the backlight 8 when the transient state is detected. Reduce.

  In the LCD controller 6 having the above configuration, when the image signal is not supplied, the illuminance setting unit 9 reduces the illuminance of the backlight 8 based on the count result of the time counting unit 13. Further, when the image signal level is small, the amplifier 12 amplifies the image signal level based on the detection result of the amplitude value detection unit 14, and the illuminance setting unit 9 reduces the illuminance of the backlight 8. In addition, when the image signal is in a transient state, the illuminance setting means 9 reduces the illuminance of the backlight 8.

  The plasma driver 7 synchronizes with the liquid crystal driver 5 while the liquid crystal driver 5 is driving the transparent electrode for each horizontal line of the PALC 10, and sequentially applies the cathode and anode electrodes of each plasma chamber of the PALC 10 in the horizontal direction. The plasma chamber is sequentially plasma-discharged by driving to scan.

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

  The illuminance setting means 9 reduces the illuminance by reducing the power supplied to the backlight 8 or stops the supply of power when the time detection means 13 detects a no-signal level for a predetermined time or longer. This stabilizes the screen of the PALC 10 and suppresses the power consumption of the backlight 8. Further, the decrease in gradation that can be displayed on the PALC 10 is suppressed by reducing the illuminance by reducing the power supplied to the backlight 8 in accordance with the reduction in the image signal level based on the detection result of the amplitude value detection means 14.

  The PALC 10 is a liquid crystal display using a discharge plasma to drive each pixel. A large-screen liquid crystal display is manufactured at a low yield with a high yield, and achieves high resolution and high contrast. This is a plasma addressing / liquid crystal device disclosed in Japanese Patent Application Laid-Open No. 217396 or Japanese Patent Application Laid-Open No. 4-265931.

  In this 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-optic material, are arranged to face each other through 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 these grooves has helium, neon, argon, or these. An ionizable gas such as a mixed gas is sealed. The groove is provided with a pair of an anode electrode 22 and a cathode electrode 23 which are parallel to each other 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 a color filter 27 provided with three color red, green and blue polarizing filters. 27 is arranged on a line orthogonal to and parallel to the plasma chamber 21 constituted by the groove, and for example, 765 transparent electrodes 28 are provided for each horizontal line. 21 intersections function as 450 × 768 pixels. Further, the backlight 8 is provided so as to irradiate the entire display surface of the PALC 10 so as to face the transparent electrode 28 side through the color filter 27 from the glass substrate 20.

  In the PALC 10, the liquid crystal driver 5 synchronizes with the drive of the liquid crystal driver 5 while the image signal level of each pixel is driven to the transparent electrode 28 of each pixel for each horizontal line at a full scale of 60V, for example. Then, each plasma chamber 21 of the PALC 10 is sequentially driven by the plasma driver 7 so that the anode electrode 22 is set to the ground potential, for example, the cathode electrode is set to −300 V, and the horizontal chamber is sequentially switched to scan the plasma chamber 21. Plasma discharge is sequentially performed, and the image signal level is sequentially retained in each pixel arranged on the horizontal line. Similarly, the image signal level is sequentially held in each pixel for each horizontal line, and an image is output by updating the image signal for each frame.

  In the above embodiment, the case where a 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. The present invention can also be applied to an active matrix type liquid crystal display in which an active element such as a transistor is provided on a transparent electrode of a pixel and the active element is driven.

1 is a block diagram of a liquid crystal display device according to the present invention. It is a block diagram of the principal part of the said liquid crystal display device. It is a block diagram of the liquid crystal display of the said liquid crystal display device. It is a block diagram of the conventional liquid crystal display device.

Explanation of symbols

  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 (3)

Amplitude value detecting means for detecting the amplitude value of the supplied image signal;
A backlight with illuminance setting,
Display means for displaying an image based on the supplied image signal at a set illuminance,
An illuminance of the backlight is set so as to decrease in accordance with the level of the amplitude value detected by the amplitude value detecting means. A time counting means for counting a time during which the no-signal level of the supplied image signal continues,
2. The display device according to claim 1, wherein the illuminance of the backlight is set so as to decrease when the duration counted by the time counting unit is equal to or longer than a predetermined time. A transient signal detecting means for detecting a transient state of the image signal supplied at the time of channel selection or power-on,
The display device according to claim 1, wherein the illuminance of the backlight is set so as to decrease when a transient state is detected by the transient signal detection unit.

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