JP2006030352A - Liquid crystal display - Google Patents

Abstract

An image quality of a liquid crystal display device is improved with a low-cost circuit.
An interlace-progressive conversion circuit that converts an interlace video signal into a progressive video signal from a frame memory, a video signal delayed by one field or one frame by the frame memory, and a current video;
An overdrive circuit for determining and outputting gradation data corresponding to a voltage actually applied to the liquid crystal based on the gradation of the input video signal and the gradation of the video signal delayed by one frame by the frame memory;
The frame memory is exclusively used for either an interlace-progressive conversion circuit or an overdrive circuit.
[Selection] Figure 1

Description

  The present invention relates to a liquid crystal display device such as a liquid crystal television receiver using a liquid crystal display panel.

  In recent years, liquid crystal display devices have been recognized for the benefits of improved image quality and thinness, and have been drastically reduced in price and used in a wide variety of applications such as PC monitors and home TVs, as well as product information display terminals in stores. It has come to be.

  In some cases, a high-resolution signal is displayed like a monitor for a PC, but generally it corresponds to an interlaced composite video signal and is often displayed. In general, high-quality machines have improved vertical resolution and reduced screen flicker by introducing motion-adaptive interlace-progressive conversion (hereinafter referred to as IP conversion) in order to improve image quality.

  Various circuit configurations such as (Patent Document 1) have been proposed as IP conversion technologies, but motion detection and video between lines of an input video signal using a video signal delayed by one field or one frame are proposed. Interpolating the signal.

In addition, liquid crystal display panels have been improved in response speed in recent years. However, when compared with cathode ray tubes (CRTs), video display performance is not sufficient, so video signal processing improves the blurring of moving images. So-called overdrive circuits have also been introduced. For example, FIG. 6 shows a conventional liquid crystal display device for improving image quality.
JP 2001-320678 A Japanese Patent No. 2708746

  However, in a low-priced liquid crystal display device, it is inevitably difficult to mount both an IP conversion circuit that requires a frame memory that has a large impact on cost and an overdrive circuit.

In addition, a general IP conversion circuit that determines a still image and a moving image for each pixel basically improves the image quality of the still image, and has almost no image quality improvement effect on the moving image.
On the other hand, since the overdrive circuit has no effect of improving the image quality for still images, even if any of them is introduced, the image quality may not be improved depending on the actually displayed image.

  In order to solve this problem, a first invention converts a frame memory, a video signal delayed by one field or one frame by the frame memory, and an interlace video signal from a current video to a progressive video signal. The interlace-progressive conversion circuit, the gradation of the input video signal, and the gradation of the video signal delayed by one frame by the frame memory determine gradation data corresponding to the voltage actually applied to the liquid crystal. An overdrive circuit for outputting, and the frame memory relates to a liquid crystal display device configured to be used exclusively for either the interlace-progressive conversion circuit or the overdrive circuit. One frame memory with IP conversion or LCD Either a bar drive drive can be realized, and by selecting one of the appropriate circuits, the effect of improving the resolution and flickering of still images or improving the response speed of liquid crystals to moving images can be enjoyed with a low-cost display device. It is possible.

  According to a second aspect of the present invention, in the first aspect of the invention, a luminance information detection circuit that detects all or any of the maximum value, minimum value, average value, and histogram of the luminance of the video signal is provided. Correspondingly, it is a liquid crystal display device characterized by selecting and operating either an interlace-progressive conversion circuit or an overdrive circuit, and it is easy to determine whether a video signal is a moving image or a still image with a simple circuit configuration. Therefore, among the IP conversion circuit and the overdrive circuit, a circuit having a higher image quality improvement effect can be operated.

  According to the present invention, since it is possible to improve image quality for both moving images and still images in a low-cost circuit, it is possible to provide a low-priced and high-quality liquid crystal display device.

  According to the first and second aspects of the present invention, the interlace video signal is converted from the frame memory, the video signal delayed by one field or one frame by the frame memory, and the current video to the progressive video. An interlace-progressive conversion circuit for converting into a signal, gradation data corresponding to a voltage actually applied to the liquid crystal based on the gradation of the input video signal and the gradation of the video signal delayed by one frame by the frame memory; An overdrive circuit that determines and outputs the liquid crystal display device, wherein the frame memory is exclusively used for either the interlace-progressive conversion circuit or the overdrive circuit; Maximum, minimum, and average brightness of video signal during the period All histograms, or provided with a brightness characteristic detection circuit for detecting either, so as to correspond to the output of the detection circuit, the interlace - and to perform switching of the progressive conversion circuit and the overdrive circuit.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1, 2, 3, 4, and 5.

  In FIG. 1, reference numeral 11 denotes an IP conversion circuit that performs interlace-progressive conversion of a video signal using a video signal delayed by one field or one frame by the frame memory 12 and the current video signal input.

  The IP conversion circuit 11 has a built-in motion detection circuit, performs interpolation between lines from a video signal in the same field as the input video signal for the motion region, and uses a field delay signal for the static region. The video signal is interpolated.

  This improves the vertical resolution of the still area and reduces line flicker.

  The IP-converted video signal is subjected to image quality correction such as edge enhancement in the image quality correction / resolution conversion circuit 13 and converted into a resolution corresponding to the liquid crystal display panel, and is input to the overdrive circuit 14.

  The overdrive circuit 14 outputs a video signal for driving the liquid crystal display panel 15 from the input video signal of the current frame and the video signal obtained by delaying the output of the image quality correction / resolution conversion circuit 13 by one frame in the frame memory 12. Accordingly, it is possible to provide a high-quality display device that can speed up the response of the liquid crystal to the gradation change and has less blurring feeling with respect to the moving image.

  Here, the IP conversion circuit 11 and the overdrive circuit 14 are connected to the same frame memory 12, and either one is configured to use the frame memory 12 exclusively, and at the same time, the original operation is not performed.

  For example, when the IP conversion circuit 11 uses the frame memory 12, the overdrive circuit 14 outputs the input signal as it is. Conversely, when the overdrive circuit 14 uses the frame memory 12, the IP conversion circuit 11 doubles the number of lines by interpolation from the video signal in the same field as the input video signal.

  The luminance information detection circuit 16 is provided to select which of the IP conversion circuit 11 and the overdrive circuit 14 uses the frame memory 12.

  FIG. 2 shows a block diagram of the luminance information detection circuit 16. In FIG. 2, an LPF circuit 21 is a pre-filter for removing the noise component of the video signal and thinning and sampling the luminance in order to reduce the circuit scale.

  FIG. 3 schematically shows thinning sampling of a video signal for one screen.

  As shown in FIG. 4, the maximum luminance detection circuit 22, the minimum luminance detection circuit 23, and the average luminance 24 are, for example, the maximum value, minimum value, and average value of luminance data sampled in one field period (or one frame period). Then, the comparison circuit 26 compares the data of one field before held in the comparison circuit 26 to determine whether or not the video signal has changed. The histogram detection circuit 25 obtains the frequency for each divided luminance level range as shown in FIG. 5, and is similarly used by the comparison circuit 26 to determine whether there is a change in the image. When the difference between the detection value of each detection circuit and the detection value in the previous field is larger than a predetermined value, it is determined that there is a change in the image. That is, when it is determined that the image is a moving image, the overdrive circuit 14 is selected, and when there is no image change, that is, when it is determined that the image is a still image, the IP conversion circuit 11 is selected, and a predetermined operation using the frame memory 12 is performed. Let

  With the above configuration, it is possible to apply IP conversion to still images and to switch and use a circuit with a higher image quality improvement effect than an overdrive circuit for moving images. A display device can be provided.

The liquid crystal display device of the present invention is
A low-cost but high-quality liquid crystal display device can be provided, which contributes to the further spread of liquid crystal display devices.

The block diagram which shows Example 1 of this invention 1 is a block diagram showing a luminance information detection circuit in Embodiment 1 of the present invention. The figure which shows the sampling of the brightness data in the brightness information detection circuit The figure which shows the luminance distribution of the luminance information detection circuit The figure for demonstrating operation | movement of the histogram detection circuit of a luminance information detection circuit A diagram showing a conventional liquid crystal display device with improved image quality

Explanation of symbols

11 IP conversion circuit 12 Frame memory 13 Image quality correction / resolution conversion circuit 14 Overdrive circuit 15 Liquid crystal display panel 16 Luminance information detection circuit 21 LPF circuit 22 Maximum luminance detection circuit 23 Minimum luminance detection circuit 24 Average luminance detection circuit 25 Histogram detection circuit 26 Comparison circuit 61 Frame memory

Claims (2)

A frame memory, an interlace-progressive conversion circuit for converting an interlaced video signal into a progressive video signal from a video signal delayed by one field or one frame by the frame memory and a current video, and an input video signal And an overdrive circuit that determines and outputs gradation data corresponding to the voltage actually applied to the liquid crystal based on the gradation of the video signal and the gradation of the video signal delayed by one frame by the frame memory. A liquid crystal display device used exclusively for an interlace-progressive conversion circuit or the overdrive circuit. A luminance information detection circuit that detects all or any of the maximum value, minimum value, average value, and histogram of the luminance of the video signal in a specific period, and an interlace-progressive conversion circuit corresponding to the output of the detection circuit; 2. The liquid crystal display device according to claim 1, wherein any one of the overdrive circuits is selected and operated.

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