JP2007110327A - Image display apparatus and image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method which realizes a velocity modulation effect of a CRT television receiver for displaying an analog image by freely controlling a black width at edges of digital image of a television receiver and a camera. <P>SOLUTION: The apparatus for freely controlling the black width at the edges of a received digital image to realize the velocity modulation effect and displaying the analog image includes two kinds of filters, a band pass filter and a low pass filter, and extracts the edges of the image depending on the combination of the filters to carry out the velocity modulation processing. The velocity modulation processing is carried out in both horizontal and vertical directions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and apparatus for realizing a speed modulation effect of a CRT television or the like that displays an analog image by freely controlling the black width at the edge of the image with respect to a digital image such as a television or a camera.

  In an analog CRT television, there is a method for improving the image edge characteristics by controlling the scanning speed. By increasing the scanning speed to the black side in the edge area, the black width of the edge can be increased. For example, for an edge that changes from black to white as shown in FIG. 9, a point A is scanned at a constant speed, a point A and a point B are scanned at a speed faster than the constant speed, and the point B is passed. By returning to the constant speed again, the black width of the edge can be increased. A curve i0 is an image edge without velocity modulation, and a curve i1 is an image edge obtained by performing velocity modulation. This method is proposed in Patent Document 1 and Patent Document 2.

  Moreover, the proposal method of patent document 1 and patent document 2 can acquire the effect shown in FIG. However, it can be clearly seen that Overshot and Undershot are attached. A curve i0 in FIG. 10 is an image edge without speed modulation. A curve i2 is an effect obtained by performing the same speed modulation as that of the curve i1 in FIG. 9, but the point A is not completely black. At this time, since the electron gun did not give enough electrons to the CRT at a high scanning speed, the right side of the point A became darker than the point A, and an undershot occurred.

The curve i3 in FIG. 10 can be realized by changing the scan speed between the points A and B. Point C is between point A and point B. Scanning is performed between point A and point C at a scanning speed faster than the constant speed and between point C and point B at a slow scanning speed. In the obtained curve i3, undershoot is generated between the points A and C in the same manner as the curve i2. Further, since the scanning speed is low between the points C and B on the curve i3, the number of electrons emitted from the electron gun increases. As a result, the brightness increases between the points C and B, and Overshoot is generated.
U.S. Pat. No. 3,980,819 US Pat. No. 5,587,745

  In matrix panel televisions such as liquid crystals, images are displayed in pixel units. In such a matrix panel, it is necessary to improve the edge of the image. For example, a function is required that can freely control the black width of the edge in both the horizontal and vertical directions. However, there is no scanning electron gun on the matrix panel, and the image data is mapped as it is on the panel as it is on one screen. At this time, the image edge characteristics cannot be improved by the conventional scanning speed control (speed modulation).

  Also, overshoot and undershot that cannot be controlled occur around the edge of the image processed by the conventional velocity modulation. This can adversely affect the image as ringing.

  Moreover, when extracting edge information with one digital filter, a filter with a long tap number is required. Line filtering is required to perform filtering in the vertical manner. A long tap number filter is expensive.

  The present invention provides an apparatus and method capable of realizing a speed modulation effect of a CRT television or the like that displays an analog image by freely controlling the black width at the edge of the image with respect to a digital image such as a television or a camera. The purpose is to do.

  The present invention is an apparatus that displays an analog image by freely controlling a black width at an edge of an image for an input digital image, and displays an analog image. This is an image display device that has two types of filters, that extracts image edges by a combination of the filters, and performs speed modulation processing.

  The present invention is also an image display device that performs speed modulation processing in both horizontal and vertical directions.

  The present invention is an image display device that performs speed modulation processing with overshoot control.

  Furthermore, the present invention is an image display device that performs noise prevention by performing speed modulation processing having coring processing.

  In addition, the present invention is an image display device in which the gain can be set to positive or negative.

  Then, the present invention is a method of displaying an analog image by freely controlling the black width at the edge of the image for an input digital image, and displaying an analog image, which includes a band-pass filter and a low-pass filter. This is an image display method in which image edge extraction is performed by a combination of two types of filters, and velocity modulation processing is performed.

  According to the present invention, it is possible to realize the speed modulation effect of a CRT television or the like that displays an analog image by freely controlling the black width at the edge of the image with respect to a digital image such as a television or a camera.

The best mode for carrying out the present invention will be described.
The outline of the image display apparatus and the image display method of the present invention will be described.

  The present invention realizes the effect obtained by scanning speed control in both horizontal and vertical directions by digital image processing. First, image edge extraction is realized by combining two filters instead of one filter. The image edge is composed of high frequency components other than direct current. FIG. 5 shows the frequency characteristics of the digital FIR filter, where the horizontal axis is the normalized frequency and the vertical axis is the amplitude. A curve f0 is a frequency characteristic of the band pass filter. The characteristic like the curve f0 can be realized by a filter having a short tap number. However, the curve f0 includes a very high frequency component up to the normalized frequency 1.0, which is mainly a noise component. In order to remove this noise component, another low-pass filter is used. The frequency characteristic of this low-pass filter is a curve f1. A low-pass filter like the curve f1 can also be realized with a short number of taps. When the curve f0 and the curve f1 are added together, a curve f2 is obtained. If the frequency characteristic of the curve f2 is used, edge information from which noise has been removed can be detected. It should be noted that a long tap number is necessary to directly realize the characteristic of the curve f2 with one filter.

  The ordinate in FIG. 5 is a log scale, and the unit is dB (sibel). A curve f2 is a result of adding the curve f0 and the curve f1. When the log of the scale is removed, the curve f2 becomes the product of the curve f0 and the curve f1.

  FIG. 6 shows the output of the filter, the horizontal axis is the pixel position, and the vertical axis is the luminance gradation. A curve c0 indicates the luminance data value of the original image. A curve d0 is a filtering result of the bandpass filter, and a curve d1 is an output result of the lowpass filter. A curve d2 is a multiplication result (d2 = d0 × d1) of the curve d0 and the curve d1. A curve d2 is information of the detected edge, and is also a correction signal for realizing a speed modulation effect.

FIG. 7 shows a method for realizing the velocity modulation effect using the correction signal d2 of FIG. A curve c0 is the luminance data value of the original image, and a curve c + and a curve c− are the effect of speed modulation realized.
c = c0 + k × d2
Here, a curve c− is obtained when k <0. When calculating with k> 0, a curve c + is obtained. A curve c− is a case where the edge black width is thick, and a curve c + is a case where the edge black width is narrow.

  Also, Overshoot and Undershot are eliminated by the method shown in FIG. FIG. 4 shows Overshot clipping processing. A curve c0 is the luminance data value of the original image, and a broken line c1 is an effect of the obtained velocity modulation. max / min is the maximum value and the minimum value of the luminance signal obtained from the vicinity of the current pixel. If the broken line c1 is clipped with this max / min, the Overshoot and Undershot of the image data disappear. As a result of clipping, the Undershot part of the broken line c1 becomes a horizontal straight line corresponding to min, and the Overshot part becomes a horizontal straight line corresponding to max.

  In the case of only the vertical direction or the horizontal direction, max / min is obtained from n pixels (including itself) above and below or right and left of the current pixel. n is an odd number. In the two-dimensional case of the vertical direction and the horizontal direction, it is obtained from the pixels on the left and right and upper and lower crosses including itself.

  In order to match the input pixel position and the output pixel position, the digital filter is an odd tap here. For example, a 5-tap or 15-tap FIR filter.

  There are luminance Y and color difference (Cr / Cb) in television image data. Here, only the luminance data Y is subjected to filtering processing. The Cb / Cr data is bypassed as it is. The speed modulation processing block of FIG. 1 executes.

  Using the above-described processing technique, the velocity modulation effect can be obtained in both the horizontal and vertical directions by the velocity modulation processing circuit shown in FIG. Since the result of the band pass filter processing is negative for the falling edge (white to black), it is necessary to add absolute value processing. The speed modulation processing circuit has horizontal LPF processing, horizontal BPF processing, vertical BPF processing, vertical LPF processing, absolute value processing, horizontal coring, vertical coring, horizontal gain, vertical gain, and OVERSHOT control.

As an example, coefficients of a digital filter (5 taps) are shown below.
Bandpass filter BPF: {0.07, -0.99, 0.00, -0.99, 0.07}.
Low pass filter LPF: {0.03, 0.31, 0.32, 0.31, 0.03}.

  The coring process is for preventing noise, and the principle is shown in FIG. When the input value is smaller than the threshold t, the output is set to zero. When the input value is larger than the threshold value t, the input is output as it is. The horizontal gain / vertical gain controls the intensity of the velocity modulation effect. The gain can be set to both positive and negative values. When negative, the black width of the edge increases. When positive, the black width of the edge is narrowed.

  The horizontal and vertical correction signals are added to the luminance Y and sent to the Overshot control block. The Overshoot control block obtains max / min from the luminance signal Y, clips the corrected luminance signal, and outputs it.

  Using a digital image processing technique on a matrix panel television such as a liquid crystal, the speed modulation effect of an analog television was realized at a low cost by combining two bandpass and lowpass filters with a small number of taps. It is possible to freely control the black width of the image edge and to prevent Overshoot / Undershot. An image actually processed by this method is shown in FIG. 8A is an original image, FIG. 8B is an image in which the gain in FIG. 2 is negative and the black width of the edge is black, and FIG. 8C is a graph in which the gain in FIG. This is an image with a narrow black width.

The speed modulation processing block diagram. Speed modulation processing circuit diagram. Explanatory drawing of a coring process. Explanatory drawing of clipping processing of Overshoot. Explanatory drawing of the frequency characteristic of a speed modulation filter. Explanatory drawing of the output of a filter. Explanatory drawing of the correction result of edge. Explanatory drawing of a speed modulation process result. Explanatory drawing of a velocity modulation principle. Explanatory drawing of a velocity modulation principle.

Claims (6)

A device that displays an analog image for an input digital image by realizing a speed modulation effect by freely controlling the black width at the edge of the image,
An image display device having two types of filters, a band-pass filter and a low-pass filter with a small number of taps, extracting image edges by a combination of the filters, and performing speed modulation processing. The image display device according to claim 1,
An image display device that performs velocity modulation processing in both horizontal and vertical directions. The image display device according to claim 1,
An image display device that performs velocity modulation processing with overshoot control. The image display device according to claim 1,
An image display apparatus characterized by performing a speed modulation process having a coring process to prevent noise. The image display device according to claim 1,
An image display device characterized in that the gain can be set to positive or negative. For an input digital image, a method of displaying an analog image by realizing a speed modulation effect by freely controlling the black width at the edge of the image,
An image display method characterized in that an image edge is extracted by a combination of two types of filters, a band-pass filter and a low-pass filter, and velocity modulation processing is performed.