JPH11203467A - Display and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display and its method capable of reducing blur in an interpolated image due to interpolating processing applied to a signal having steep edges such as a character or a graph at the time of generating a display signal by applying pixel number converting to an original signal. SOLUTION: When a selector 14 selects an interpolation signal in a cubic interpolating processing circuit 11 in the case of generating a display signal by applying enlarging or reducing signal processing, i.e., pixel number converting, to an original signal, interpolating processing using a cubic interpolating method is applied to the original signal, but when a waveform discriminating circuit 13 discriminates the original signal as a step-like waveform, the selector 14 selects an interpolation signal in a nearest interpolation processing circuit 12 based on the discriminated result, so that the interpolating method for the original signal is switched from the cubic interpolating method to a nearest interpolating method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device and a display method, and more particularly to a display device for generating a display signal by performing enlargement or reduction signal processing (pixel number conversion processing) on an original signal and a display method thereof. About.

[0002]

2. Description of the Related Art In a display device for a personal computer, the resolution of a video signal output from the personal computer is different from the resolution of a video signal displayed on the display device, or an image in a specific area on the personal computer is displayed. , It is necessary to perform enlargement or reduction signal processing, that is, pixel number conversion processing, on the original signal output from the personal computer.

In such a pixel number conversion process, a display signal to be displayed on a display device is generated by interpolating an original signal. As the interpolation method for interpolating the original signal, a nearest neighbor interpolation method in which the value of the interpolated pixel is replaced by a pixel at the closest position on the original image, or a method in which a sampling function is approximated by a cubic expression from 16 neighboring points is used. Cu to interpolate
Various techniques such as a bic interpolation method are known.

[0004]

Incidentally, in these interpolation methods, when the interpolation processing is performed using the Cubic interpolation method, the interpolation processing is generally performed more easily than when the interpolation processing is performed using the nearest neighbor interpolation method. High sharpness and natural image quality. On the other hand, the image quality obtained by performing the Cubic interpolation is more blurred than the image quality obtained by performing the nearest neighbor interpolation.

[0005] In particular, as signals handled by a personal computer, there are many signals having sharp edges such as characters and figures. Therefore, when interpolation processing is performed using the Cubic interpolation method, the edge is blurred. there were. Also, this blurring feeling is noticeable when the screen is enlarged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to generate a display signal by performing a pixel number conversion process on an original signal. It is an object of the present invention to provide a display device and a display method capable of reducing a blur of an interpolated image accompanying an interpolation process for a signal having a sharp edge.

[0007]

A display device according to the present invention comprises a first interpolation circuit for performing an interpolation process on an original signal by using a nearest neighbor interpolation method, and a method other than the nearest neighbor interpolation method for an original signal. A second interpolation processing circuit that performs an interpolation process using the interpolation method, a waveform identification circuit that identifies whether or not the original signal is a staircase waveform, and when the waveform identification circuit identifies the original signal as a staircase waveform, A selector is provided for selecting an interpolation signal interpolated by the first interpolation processing circuit instead of the interpolation signal interpolated by the second interpolation processing circuit and outputting the selected signal as a display signal.

In the display device having the above configuration, usually, the selector selects an interpolation signal that has been subjected to the interpolation processing by the second interpolation processing circuit, so that an interpolation method other than the nearest neighbor interpolation method is used for the interpolation pixel. Perform interpolation processing. In this normal interpolation processing, if the waveform identification circuit identifies the original signal as a staircase waveform, based on the identification result, the selector replaces the interpolation signal interpolated by the second interpolation processing circuit with the first interpolation processing. The interpolation signal that has been subjected to the interpolation processing by the circuit is selected. That is, interpolation processing is performed on the original signal of the staircase waveform, that is, the steep edge of the image, using the nearest neighbor interpolation method.

A display method according to the present invention identifies whether or not an original signal has a staircase waveform when performing an interpolation process on the original signal using an interpolation method other than the nearest neighbor interpolation method. When a staircase waveform is identified, the interpolation method for the original signal is switched from an interpolation method other than the nearest neighbor interpolation method to the nearest neighbor interpolation method.

In the above display method, usually, an interpolation process is performed on the original signal using an interpolation method other than the nearest neighbor interpolation method. In this normal interpolation processing, when the original signal is identified as a staircase waveform, the interpolation method for the original signal is switched to the nearest interpolation method based on the identification result. That is, interpolation processing is performed on the original signal of the staircase waveform, that is, the steep edge of the image, using the nearest neighbor interpolation method.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a system block diagram showing an embodiment of the present invention. For example, a case where the present invention is applied to an LCD (Liquid Crystal Display) for a personal computer will be described.

In FIG. 1, a video signal (hereinafter, referred to as an original signal) output from a personal computer (not shown) is supplied to a Cubic interpolation processing circuit 11 and a nearest neighbor interpolation processing circuit 12, and a waveform identification circuit is provided. Circuit 1
3 is supplied. The Cubic interpolation processing circuit 11 performs an interpolation process on the original signal using the Cubic interpolation method.
On the other hand, the nearest neighbor interpolation processing circuit 12 performs an interpolation process on the original signal using the nearest neighbor interpolation method.

Here, the Cubic interpolation method is used to calculate the neighborhood 16
This is an interpolation method for interpolating using a sampling function approximated by a cubic expression from a point. In other words, an interpolation signal is obtained by performing arithmetic processing from original signals of two pixels (a total of four pixels) before and after the interpolation point (pixel). Therefore, as for the oblique lines as shown in FIG. 2A, smooth oblique lines can be obtained as shown in FIG. However, in the case of a staircase waveform signal as shown in FIG. 3A, since the interpolation signal has a gray signal level, the edge of the interpolation signal is blurred as shown in FIG. 3C.

On the other hand, the nearest neighbor interpolation method is an interpolation method in which the value of an interpolated pixel is replaced with a pixel at the closest position on the original image. That is, the original signal closest to the interpolation point (pixel) is the interpolation signal. Therefore, as shown in FIG. 2 (b), the oblique lines as shown in FIG. 2 (a) make a specific portion thicker, giving a sense of incongruity in image quality. However, in the case of a signal having a staircase waveform as shown in FIG. 3A, the level of the interpolation signal is not different from the level of the original signal, so that the edge of the interpolation signal is blurred as shown in FIG. Never.

The waveform discriminating circuit 13 is a circuit for discriminating whether or not the original signal has a staircase waveform. Here, the staircase waveform means that the signal levels of a plurality of pixels before and after the interpolation point (pixel) are constant and the signal level changes between pixels adjacent to the interpolation point, as shown in FIG. Waveform. Therefore, the waveform identification circuit 13
Then, the signal level of a plurality of pixels before the interpolation point, the signal level of a plurality of pixels after the interpolation point, and the signal level of two pixels before and after the interpolation point are compared to determine whether the waveform is a staircase waveform.

The identification result of the waveform identification circuit 13 is supplied to a selector 14 as an adaptive condition for nearest neighbor interpolation. The selector 14 has two inputs, an interpolation signal interpolated by the Cubic interpolation processing circuit 11 and an interpolation signal interpolated by the nearest neighbor interpolation processing circuit 12, and usually receives the interpolation signal from the Cubic interpolation processing circuit 11. And supplies it as a display signal to an LCD panel (not shown).
3 identifies the original signal as a staircase waveform, selects an interpolation signal from the nearest neighbor interpolation processing circuit 12 based on the identification result, and supplies it to the LCD display unit as a display signal.

FIG. 4 is a block diagram showing an example of a specific configuration of FIG. 1. In FIG. 4, the same parts as those of FIG. 1 are denoted by the same reference numerals.

In FIG. 4, the original signal is sequentially delayed by, for example, four cascaded delay circuits (D) 21 to 24. The delay circuits 21 to 24 have a delay amount corresponding to one pixel (dot). Each delay output of the delay circuits 21 and 22 becomes two inputs of the coincidence detection circuit 25. Delay circuit 23,
Each of the 24 delayed outputs becomes two inputs of the coincidence detecting circuit 26. Further, each delay output of the delay circuits 22 and 23 becomes two inputs of the mismatch detection circuit 27.

The coincidence detection circuit 25 includes delay circuits 21 and 22
When the logic of each of the delay outputs coincides, an "H" level coincidence detection signal is output. In addition, the coincidence detection circuit 26
When the logic of each delay output of the delay circuits 23 and 24 matches, an "H" level match detection signal is output. On the other hand, when the logics of the delay outputs of the delay circuits 22 and 23 do not match, the mismatch detection circuit 27 outputs a "H" level mismatch detection signal. Each detection signal of the coincidence detection circuits 25 and 26 and the non-coincidence detection circuit 27 becomes three inputs of an AND circuit 28.

The AND circuit 28 includes the coincidence detecting circuits 25 and 2
6 and the respective detection signals of the mismatch detection circuit 27 are both "H".
At the time of the level, the output of the "H" level is generated. The match detecting circuits 25 and 26, the mismatch detecting circuits 27 and A
The ND circuit 28 constitutes a waveform identification circuit 13 for identifying whether or not the original signal is a staircase waveform. Therefore, the output signal of the “H” level of the AND circuit 28 becomes the selector 14 as an identification result indicating that the original signal has a staircase waveform.
Will be supplied.

Of the delay circuits 21 to 24 connected in cascade in four stages, for example, the delay output of the delay circuit 23 in the third stage becomes one input of the selector 14 as an interpolation signal by nearest neighbor interpolation. Each of the delay outputs of the delay circuits 21 to 24 is multiplied by an interpolation coefficient K in multipliers 31 to 34 and then added to an adder 3.
5 is added to the other input of the selector 14. The multipliers 31 to 34 and the adder 35 perform an interpolation process on the original signal using the Cubic interpolation method.
The c interpolation processing circuit 11 is configured.

Next, the circuit operation in the above-described circuit configuration will be described with reference to the timing charts of FIGS. FIG. 5A shows the delay circuits 21 to 24 on the d line (signal level display line) in FIG.
3 shows a timing chart of each delay output (a) to (d). FIG. 5B is a timing chart of the delay outputs (a) to (d) of the delay circuits 21 to 24 on the d line in FIG. 3A.

First, focusing on the period T in the timing chart of FIG. 5A, the delay outputs (a) and (b) of the delay circuits 21 and 22 are both "FF" (logic "1"), The delay output (c) of the circuit 23 is "00"
(Logic “0”), the delay output (d) of the delay circuit 24 is “F
F ".

That is, although the two inputs of the coincidence detecting circuit 25 are coincident and the two inputs of the non-coincidence detecting circuit 27 are not coincident, the two inputs of the coincidence detecting circuit 26 are not coincident. Not satisfied, AND circuit 28
Is at "L" level. Therefore, selector 1
Reference numeral 4 selects an interpolation signal based on Cubic interpolation, and supplies this to the LCD panel as a display signal.

In the timing chart of FIG. 5B, focusing on the period T, each of the delay outputs (a) and (b) of the delay circuits 21 and 22 is “00”, and
Each of the delay outputs (c) and (d) of 3, 24 becomes "FF".

That is, each of the coincidence detecting circuits 25 and 26
Since both inputs match and two inputs of the mismatch detection circuit 27 do not match, the adaptive condition of the nearest neighbor interpolation is satisfied, and A
The output of ND circuit 28 attains "H" level. Therefore, the selector 14 selects the interpolation signal based on the nearest neighbor interpolation instead of the interpolation signal based on the Cubic interpolation, and supplies this to the LCD panel as a display signal.

As described above, when a display signal is generated by performing enlargement or reduction signal processing on the original signal, that is, conversion processing of the number of pixels, a Cubic signal is usually applied to the original signal.
When the interpolation process is performed using the interpolation method, and the original signal is identified as a staircase waveform, the interpolation method for the original signal is changed to Cubi.
By switching from the c-interpolation method to the nearest-neighbor interpolation method, it becomes possible to display images optimally suited to the respective images to be interpolated.

In other words, for the oblique lines shown in FIG. 2A, a sharp image can be obtained with a high sharpness by applying the Cubic interpolation method. A smooth diagonal line can be obtained. FIG.
For a signal having a staircase waveform as in (a), that is, a signal having a sharp edge such as a character or a figure, the level of the interpolation signal is changed from the level of the original signal by applying the nearest neighbor interpolation method. Therefore, it is possible to obtain an interpolation signal as shown in FIG.

In the above embodiment, a case has been described in which the signal level between two pixels is compared to determine the adaptive condition of the nearest neighbor interpolation, that is, whether the original signal has a staircase waveform. However, the present invention is not limited to this.

That is, in general, the blurring of a signal due to Cubic interpolation differs depending on the display environment such as the size of the display screen and the enlargement ratio. Therefore, as a condition for performing nearest neighbor interpolation, the signal levels before and after the interpolation point are compared. The number of pixels to be set is arbitrary depending on the display environment, and by setting conditions according to the environment (the size of the display screen, the enlargement ratio, and the like), it is possible to obtain a more natural image quality.

In the above embodiment, the case where the Cubic interpolation method is applied as a normal interpolation method has been described. However, the present invention is not limited to this, and an interpolation signal is obtained by calculation from an original signal near an interpolation point. The same operation and effect can be obtained by performing the same processing in an interpolation method other than the nearest neighbor interpolation method such as a linear interpolation method.

Here, the linear interpolation method is a method in which interpolation is performed by linearly interpolating one pixel on each side of a position (pixel) to be interpolated, and has a feature that a smooth image can be created. . When the linear interpolation method is applied instead of the Cubic interpolation method, it can be handled by omitting the multipliers 31 and 34 in the block diagram of FIG.

Further, in the above embodiment, the LCD
(Liquid crystal display device), but the present invention is not limited to LCDs.
The present invention can be applied to all display devices having a fixed number of pixels, such as a (plasma display).

[0034]

As described above, according to the present invention,
When a display signal is generated by performing a pixel number conversion process on an original signal, usually, the original signal is interpolated using an interpolation method other than the nearest neighbor interpolation method, while the original signal is processed in a staircase waveform. When it is identified that the interpolation method for the original signal is switched to the nearest interpolation method, it is possible to display images optimally adapted to the image to be interpolated. This makes it possible to reduce the blurring of the interpolated image accompanying the interpolation processing for a signal having a sharp edge.

[Brief description of the drawings]

FIG. 1 is a system block diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a Cubic interpolation method and a nearest neighbor interpolation method for oblique lines.

FIG. 3 is an explanatory diagram of a Cubic interpolation method and a nearest neighbor interpolation method for a staircase waveform.

FIG. 4 is a block diagram showing a specific configuration of FIG. 1;

5A is a timing chart for explaining the operation of the circuit in FIG. 4; FIG. 5A is a timing chart when Cubic interpolation is selected; FIG.
Indicates a time when the nearest neighbor interpolation is selected.

[Explanation of symbols]

11: Cubic interpolation processing circuit, 12: nearest neighbor interpolation processing circuit, 13: waveform identification circuit, 14: selector, 21-2
4 ... Delay circuit, 25, 26 ... Match detection circuit, 27 ... Match detection circuit, 28 ... AND circuit, 31-34 ... Multiplier,
35 ... Adder

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G09G 3/20 660 G09G 3/20 660C 3/36 3/36 5/00 520 5/00 520V 5/36 520 5/36 520C H04N 1/409 H04N 1/40 101D

Claims (8)

[Claims] 1. A first interpolation processing circuit for performing an interpolation process on an original signal using a nearest neighbor interpolation method, and a first interpolation processing circuit for performing an interpolation process on the original signal using an interpolation method other than the nearest neighbor interpolation method. 2, an interpolation processing circuit, a waveform identification circuit for identifying whether or not the original signal is a staircase waveform, and when the waveform identification circuit identifies the original signal as a staircase waveform,
A selector for selecting an interpolation signal interpolated by the first interpolation processing circuit instead of the interpolation signal interpolated by the second interpolation processing circuit and outputting the selected signal as a display signal. Display device. 2. An interpolation method other than the nearest neighbor interpolation method is Cub.
The display device according to claim 1, wherein the display device is an ic interpolation method. 3. The waveform discriminating circuit discriminates a staircase waveform when a signal level of a plurality of pixels before and after an interpolation pixel is constant and a signal level changes between pixels adjacent to the interpolation pixel. The display device according to claim 1, wherein: 4. The display device according to claim 3, wherein the waveform identification circuit changes the number of pixels having a constant signal level serving as an identification condition depending on a display environment. 5. The display device according to claim 4, wherein the display environment is a size of a display screen. 6. When performing an interpolation process on an original signal by using an interpolation method other than the nearest neighbor interpolation method, it is determined whether or not the original signal has a staircase waveform. A display method characterized by switching an interpolation method for an original signal from an interpolation method other than the nearest neighbor interpolation method to a nearest neighbor interpolation method when identified. 7. An interpolation method other than the nearest neighbor interpolation method is Cub.
7. The display method according to claim 6, wherein the display method is an ic interpolation method. 8. When the signal level of a plurality of pixels before and after the interpolation point is constant and the signal level changes between pixels adjacent to the interpolation point, the original signal is identified as a staircase waveform. 7. The display method according to claim 6, wherein: