JP4483255B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device and method, and more particularly, to a liquid crystal display device and method for converting image resolution, and preferably used for resolution conversion related to image display in a matrix display device such as a liquid crystal display. It is.

  In a matrix display type display device such as a liquid crystal display, the resolution and aspect ratio of a display image are physically determined for each display device. On the other hand, the resolution and aspect ratio of video signals to be displayed on these display devices are various. For example, a signal generally called VGA has a resolution of 640 × 480 dots. In the field of television broadcasting, the horizontal resolution is not strictly defined, but the vertical direction is generally an interlace signal of 480 lines. When these signals are displayed on a liquid crystal panel having a resolution different from the resolution of the input signal, such as 1024 × 768 dots called XGA, for example, a kind of resolution conversion called resolution conversion is used to convert the resolution of the input video signal to the resolution of the display device. Interpolation operation is required.

  In order to convert the resolution of the input video signal into the resolution of the display device for display, a liquid crystal display device for converting the horizontal resolution and the vertical resolution of the video signal input to the liquid crystal panel is required. As such a liquid crystal display device, one described in Japanese Patent Application Laid-Open No. 2001-331145 is known. The conventional liquid crystal display device will be described below.

FIG. 9 is a block diagram showing the configuration of this conventional liquid crystal display device. As shown in FIG. 9, input pixel data is sequentially input, and the four input pixel data supplied to each tap is multiplied by a predetermined tap coefficient and then added to output the output pixel data. The tap coefficient setting unit includes a versatile filter and a tap coefficient setting unit that sets a tap coefficient. The tap coefficient set by the tap coefficient setting unit is an input pixel corresponding to four input pixel data supplied to each tap of the transversal filter. And a predetermined quartic function equation according to the distance x between the pixel and the output pixel (see, for example, Patent Document 1).
JP 2001-331145 A

  In this liquid crystal display device, when an upper and lower letterbox signal is input as an input signal, depending on the quaternary function equation for setting the tap coefficient, an overshoot is generated near the upper and lower boundary lines of the letterbox of the output pixel, and the quality of image quality is improved. There was a problem of being damaged.

  It is an object of the present invention to provide a high-quality liquid crystal display device that does not cause overshoot near the upper and lower boundary lines of the letterbox of the output pixel even when resolution conversion is performed when the upper and lower letterbox signals are included in the input signal. Objective.

  In order to solve this problem, the present invention uses a 2-tap interpolation filter that does not overshoot in areas other than the effective video area and in the vicinity of the upper and lower boundary lines of the effective video area, and uses a higher-order interpolation filter in other areas. It is composed.

  As a result, a high-quality liquid crystal display device that does not emphasize the upper and lower boundary lines of the letterbox even if resolution conversion is performed when the upper and lower letterbox signals are included in the input signal can be obtained.

  According to the present invention, there is provided an advantageous effect of providing a high-quality liquid crystal display device that does not emphasize the upper and lower boundary lines of the letterbox even if resolution conversion is performed when the upper and lower letterbox signals are included in the input signal. Is obtained.

  A first invention of the present application is a liquid crystal display device for converting the resolution of an image input signal to a predetermined resolution, and means for detecting position information of an effective area of an image, and an interpolation processing method at the time of resolution conversion using the position information The liquid crystal display device is characterized by preventing overshoot from being applied to the upper and lower boundary lines of the letterbox by providing an interpolation means for changing the upper and lower letterbox signals. In this case, even if resolution conversion is performed, the upper and lower boundary lines of the letterbox are not emphasized.

  The second invention of the present application is a horizontal resolution conversion means for converting a horizontal resolution of an input video signal to a predetermined resolution, and a time axis conversion means for performing a horizontal time axis conversion of a digital video signal output from the horizontal resolution conversion means. Timing control means for determining the timing of the time axis conversion means according to the conversion rate of the input resolution with respect to the output resolution, and timing control means for determining the position of the output pixel data with respect to the input pixel data; A high-order interpolation filter that multiplies a plurality of supplied input pixel data by a predetermined tap coefficient and adds them to output output pixel data; and high-order filter coefficient generation means for generating coefficients of the high-order interpolation filter; , Pixel data is sequentially input from the time axis conversion means, and two input pixel data supplied to each tap A 2-tap interpolation filter that multiplies and then adds output coefficients and outputs output pixel data, 2-tap coefficient generation means for generating coefficients of the 2-tap interpolation filter, and digital video from the time axis conversion means An effective image area detecting means for detecting that the luminance level of the signal is equal to or higher than a predetermined threshold and determining a vertical start position end position of the image signal; and a result of the determination by the effective image area detecting means; A liquid crystal display device comprising a selector for switching output pixel data and output pixel data of the 2-tap interpolation filter and outputting the data to a liquid crystal panel, wherein upper and lower letterbox signals are included in the input signal. In this case, the upper and lower border lines of the letterbox are not emphasized even if resolution conversion is performed.

  According to a third aspect of the present invention, there is provided the liquid crystal display device according to the second aspect, wherein a portion where an overshoot occurs is detected and the letter is obtained by changing a mixing ratio of the 4-tap interpolation filter and the 2-tap interpolation filter according to the detection result. The liquid crystal display device is characterized in that it reduces overshoot on the upper and lower boundary lines of the box and prevents sudden changes in image quality due to filter switching. It has the effect of preventing sudden changes in image quality due to switching.

  A fourth invention of the present application is the liquid crystal display device according to claim 3, wherein higher-order interpolation is performed based on the interpolation timing information output from the timing control means and the effective video area information output from the effective video area detection means. An interpolation filter mixture ratio determining means for detecting a location of an overshoot generated by applying a filter and determining a mixing ratio of a high-order interpolation filter and a 2-tap interpolation filter according to the location, and an output from the interpolation filter mixture ratio determining means A liquid crystal display device comprising an interpolation filter result mixing means for mixing the output of the high-order interpolation filter and the output of the 2-tap interpolation filter in accordance with the mixing ratio and outputting the output pixel to the liquid crystal panel. There is an effect of preventing an abrupt change in image quality due to switching between a high-order interpolation filter and a 2-tap interpolation filter.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment 1)
FIG. 1 shows an example of a liquid crystal display device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a horizontal resolution for thinning out or interpolating horizontal pixels of an input video signal to convert the horizontal resolution to a predetermined resolution. Conversion means 2 is a time axis conversion means for obtaining a predetermined number of lines by changing the horizontal time axis, and 3 is a timing control of the time axis conversion means and a position of the output pixel relative to the input pixel according to the conversion rate of the input resolution with respect to the output resolution 4 is a high-order interpolation filter that performs interpolation calculation processing using a high-order filter for resolution conversion of the input signal, and 5 is a coefficient output from the timing control means for each tap of the high-order interpolation filter. High-order filter coefficient generating means for determining based on position information of the output pixel with respect to the input pixel, 6 is a 2-tap filter for converting the resolution of the input signal A 2-tap interpolation filter that performs interpolation calculation processing, and 7 is a 2-tap coefficient generation unit that determines a coefficient applied to two taps of the 2-tap interpolation filter based on position information of the output pixel with respect to the input pixel output from the timing control unit , 8 detects the luminance level of the input video signal and detects the vertical start / end position of the effective video region from the comparison result of the magnitude relationship with a predetermined threshold, and 9 indicates the output of the 2-tap interpolation filter. And a selector 10 for switching and outputting the result of the high-order filter based on the detection result of the effective image area position detecting means, and 10 is composed of a liquid crystal panel for displaying an output signal.

  Next, an operation example of the liquid crystal display device of the present invention will be described. When the input video signal is an interlace signal of 480 lines in the vertical direction called NTSC, for example, and the resolution of the liquid crystal panel of the display device is 640 × 480 of VGA, for example, the horizontal resolution conversion means 1 first converts the horizontal resolution to 640 dots. Resolution conversion is performed by simply sampling to a predetermined resolution, or sampling once to a predetermined horizontal resolution of 640 dots or more, for example, 1280 dots by double sampling and then thinning to 640 dots.

  After the horizontal resolution conversion, the timing control means 3 generates a horizontal synchronizing signal having a frequency that is twice the input horizontal frequency so that the vertical resolution becomes a predetermined 480 dots. The horizontal time axis is converted from the generated horizontal synchronization signal by a time axis conversion means, for example, a memory such as a FIFO, so that the number of vertical dots becomes a predetermined number. The video signal subjected to time axis conversion is subjected to interpolation processing by a high-order interpolation filter and a 2-tap interpolation filter based on the position of the output pixel with respect to the input pixel. For example, a transversal filter as shown in FIG. 2 is used as the high-order filter.

  In FIG. 2, input pixel data are sequentially input and four input pixel data supplied to each tap are multiplied by respective predetermined tap coefficients and then added to output output pixel data. The tap coefficient is determined by a distance x between the input pixel and the output pixel using a high-order function as shown in Equation 1. When interpolation processing using such a high-order filter is performed, overshoot also occurs at the upper and lower boundary lines of the letterbox in the output pixel as shown in FIG.

  Furthermore, overshooting is emphasized when image creation processing such as vertical peaking for television broadcasting is added. As the 2-tap filter, for example, a linear filter as shown in FIG. 3 is used. In FIG. 3, input pixels are sequentially input, and two input pixel data supplied to two taps are respectively multiplied by a predetermined tap coefficient and then added to output output pixel data. The tap coefficient is determined by the distance x between the input pixel and the output pixel using a linear function as shown in Formula 2. When such a 2-tap filter interpolation process is performed, no overshoot occurs in the output pixel as shown in FIG.

  However, although an overshoot occurs, the higher-order interpolation filter can obtain a high-quality image after interpolation processing in a natural image than the 2-tap interpolation filter. In order to make the best use of the advantages of the high-order interpolation filter and the 2-tap interpolation filter, the output of each interpolation filter is selected by the selector 11 according to the effective image area position detected by the effective image area position detecting means 8 and is supplied to the liquid crystal panel 12. Is output. As shown in FIG. 5, the effective image area position detecting means 8 compares the input pixel with a predetermined threshold and determines the start / end position of the vertical effective image area based on the magnitude relationship.

(Embodiment 2)
Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 6, reference numeral 14 denotes the result of the high-order interpolation filter 4 and the 2-tap interpolation filter 6 based on the distance x between the input pixel and the output pixel output from the timing control unit 3 and the detection result of the effective image area position detection unit 8. Interpolation filter result mixture ratio determining means 15 for determining the mixture ratio is added after the mixture ratios determined by the interpolation filter result mixture ratio determining means 15 are multiplied by the results of the high-order interpolation filter 4 and the 2-tap interpolation filter 6, respectively. It comprises interpolation filter result mixing means. In addition, about the same structure as embodiment mentioned above, the same symbol is used and description is abbreviate | omitted.

  As shown in FIG. 7, the interpolation filter result mixture ratio determining means 14 is based on the detection result of the effective image area position detecting means 8 and the distance x between the input pixel and the output pixel output from the timing control means 3. The ratio of the result of the high-order interpolation filter 4 is larger on the inner side, and the ratio of the 2-tap interpolation filter is larger on the outer side of the effective video area, and the ratio is continuously changed. As shown in FIG. 8, this mixture ratio is multiplied by the results of the high-order interpolation filter 4 and the 2-tap interpolation filter 6 and then added and output to the liquid crystal panel, thereby reducing the overshoot of the upper and lower boundary lines of the letterbox. In addition, a sudden change in image quality due to switching of the interpolation filter is prevented.

  In the above description, an example of a vertical letterbox has been described. However, an aspect ratio of an input signal having an aspect ratio of 4: 3 is maintained on a horizontal side cut (a liquid crystal panel having an aspect ratio of 16: 9). This is also possible in the case of displaying as it is and adding blanking to the left and right).

  The liquid crystal display device according to the present invention provides a high-quality liquid crystal display device that does not emphasize the upper and lower borders of the letterbox even if resolution conversion is performed when the upper and lower letterbox signals are included in the input signal. It is useful for resolution conversion related to image display in a matrix display device such as a liquid crystal display.

The figure which shows the structure of one embodiment of this invention The figure which shows the structure of an example of a high-order interpolation filter The figure which shows the structure of an example of a 2-tap interpolation filter The figure which shows the output signal with respect to the input signal by an interpolation filter The figure which shows an effective image area position detection means The figure which shows the structure of another one Embodiment of this invention. The figure which shows the interpolation filter result mixture ratio determination means Diagram showing interpolation filter result mixing means The figure which shows the structure of the conventional liquid crystal display device

Explanation of symbols

1 horizontal resolution conversion means 2 time axis conversion means (memory)
3 Timing control means 4 High-order interpolation filter 5 High-order filter coefficient generation means 6 2-tap interpolation filter 7 2-tap coefficient generation means 8 Effective video area position detection means 9 Selector 10 Liquid crystal panel 11 Unit delay element 12 Multiplier 13 Adder 14 Interpolation filter result mixing ratio determining means 15 Interpolation filter result mixing means

Claims (3)

Horizontal resolution conversion means for converting the horizontal resolution of the input video signal to a predetermined resolution, time axis conversion means for performing horizontal time axis conversion of the digital video signal output from the horizontal resolution conversion means, and input resolution for the output resolution Timing control means for determining the timing of the time axis conversion means based on the conversion rate and timing control means for determining the position of the output pixel data relative to the input pixel data, and a plurality of input pixels in which pixel data is sequentially input from the time axis conversion means and supplied to each tap A high-order interpolation filter that multiplies data by a predetermined tap coefficient and then adds them to output output pixel data; a high-order filter coefficient generation means that generates coefficients of the high-order interpolation filter; and a time axis conversion means. Pixel data is sequentially input and a predetermined tap coefficient is applied to each of the two input pixel data supplied to each tap. The luminance level of the digital video signal output from the 2-tap interpolation filter for multiplying and adding and outputting output pixel data, 2-tap coefficient generating means for generating the coefficients of the 2-tap interpolation filter, and the time axis converting means Effective video area detecting means for detecting a vertical start position end position of the video signal by detecting that it is equal to or greater than a predetermined threshold; output pixel data of the high-order interpolation filter based on a determination result of the effective video area detecting means; and A liquid crystal display device comprising: a selector that switches output pixel data of a 2-tap interpolation filter and outputs the same to a liquid crystal panel. 2. The liquid crystal display device according to claim 1, wherein a portion where overshoot occurs is detected, and a mixing ratio of the 4-tap interpolation filter and the 2-tap interpolation filter is changed according to the detection result. 3. The liquid crystal display device according to claim 2 , wherein an overshoot occurs when a high-order interpolation filter is applied by interpolation timing information output from the timing control means and effective video area information output from the effective video area detection means. Interpolation filter mixture ratio determining means for detecting the location of the chute and determining the mixture ratio of the high-order interpolation filter and the 2-tap interpolation filter according to the location, and high-order interpolation according to the mixture ratio output from the interpolation filter mixture ratio determining means A liquid crystal display device comprising: an interpolation filter result mixing means for mixing an output of a filter and an output of a 2-tap interpolation filter and outputting an output pixel to a liquid crystal panel.

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