JPS6116078B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color difference signal synthesis device for a color encoder in a color television system, and is intended to improve coloring in a color changing portion of a colored image.
Furthermore, the main purpose of the present invention is to improve the image quality of detailed colored image parts of text and graphic images that are logically synthesized by a computer, etc.
In view of the effects of the invention described later, the present invention also includes a configuration for the purpose of improving the image quality of general television images. The present invention will be explained in detail below.

A color encoder used on the image transmission side of a color television system converts primary color signals of red, green, and blue into a composite color video signal. FIG. 1 is a block diagram showing the configuration of the main parts of a conventional color encoder. In the figure, primary color signals R, G, and B sent from a color camera, signal generator, etc. are sent to a luminance signal generator 20.
The luminance signal Y is produced by addition and mixing. The same primary color signals R, G, and B are also supplied to the color difference signal generation device 1, where color difference signals of R-Y and B-Y are generated by linear calculation. (Usually, the above Y signal is often used to generate color difference signals, but here, the color difference signal generating device 1 is illustrated separately to clarify the correspondence with the later explanation.) .) The R-Y and B-Y signals undergo amplitude phase modulation of the color carrier wave in the chroma modulator 21,
A carrier color signal C is produced. The carrier color signal C is added to the luminance signal Y and is transmitted as a composite color video signal F.

FIG. 2 is a block diagram showing the main points of normal signal processing on the image receiving side. In the figure, a composite color video signal F is separated into a luminance signal Y and a carrier color signal C by a luminance signal separator 22 and a band filter 23, respectively. The carrier color signal C is sent to the chroma demodulator 2
4, where the color difference signals R-Y, G-
Y, B-Y are demodulated. Adder 25, 26, 2
At step 7, the luminance signal Y is added to the color difference signal to reproduce primary color signals R, G, and B. A color image is reproduced by applying these primary color signals to the cathode of the picture tube 28.

As described above, in the color television transmitting/receiving system shown in FIGS. 1 and 2, it seems that the color difference signal on the sending side is completely reproduced on the receiving side, but in reality, the following problem occurs. That is, since the band of the carrier color signal is narrow, the signal band of the color difference signal obtained on the receiving side is at most 500 KHz, which is considerably narrower than the luminance signal band of at least 3 MHz. Since the color difference signal is a signal that carries color information of an image, the fact that the band of this signal is narrow causes a phenomenon in which detailed image parts are poorly colored.

FIG. 3 is a signal waveform diagram for explaining this phenomenon. A in the figure depicts color difference signal waveforms on the sending side (indicated by solid line a) and the receiving side (indicated by dotted line b) when a thin difference color image exists on an achromatic screen. As can be seen from this figure, due to the insufficient bandwidth of the color difference signal transmission path, a sufficient color difference signal peak value cannot be obtained in the colored image area, resulting in poor coloring.
FIG. 3B depicts the color difference signal waveforms in the same way as in A in the case where a thin complementary color image exists in a specific colored background. As shown in this figure, in pixels with complementary colors, even the polarity of the color difference signal may not change. This means that a predetermined color is not applied to a predetermined portion, and the image deteriorates significantly.

The present invention aims to solve the image quality deterioration problem that occurs in color television systems as described above by using a new color difference signal synthesis method to improve the coloring of fine image parts. The most basic requirement of the present invention is to observe the signal corresponding to the temporal change of the color difference signal on the sending side, and to effectively detect the signal in the vicinity of the time position where the color difference signal does not respond sufficiently on the receiving side. The first step is to reset the color difference signal to zero.

FIG. 4 is a signal waveform diagram showing one example.
A in the same figure is a waveform that is exactly the same as the solid line in FIG. 3B, and is a color difference signal waveform on the sending side when thin pixels of a complementary color exist in the colored background, and C is a corresponding waveform on the receiving side. B shows the waveform effect according to one embodiment of the invention. In this example, the color difference signal is reset to zero before and after a thin colored pixel, but as a result, the color difference signal waveform on the receiving side becomes like D, and the polarity of the color difference signal is reversed at a predetermined pixel. Coloring is improved. Note that FIG. 4 is merely a waveform example for explaining the present invention, and the present invention is not limited to this diagram in any way.

FIG. 5 is a block diagram showing a basic configuration example of the present invention. In the same figure, the color designation signal is a signal that represents the type of color of the image portion to be displayed, and may be substantially the same as the primary color signal, and the color can be determined using a logic code using a plurality of binary signals. It may be a signal expressed as . Part or all of the color designation signal is supplied to the color change determination device 3. The color change discrimination device 3 observes the temporal change in the color specified by the color designation signal, and when the series matches a predetermined series, generates a reset signal and transmits it to the color difference signal conversion device 2. . The color designation signal is also supplied to the color difference signal conversion device 2, which generates a color difference signal corresponding to the color designated by the color designation signal, but when it receives the reset signal, it exceptionally changes to zero level. Output. With the above functions, the response waveform of the color difference signal on the receiving side can be effectively improved.

The color difference signal conversion device 2, as shown in FIG.
Primary color signal synthesis device 4 and color difference signal matrix circuit 5
The configuration may also include. The primary color signal synthesis device 4 generates a primary color signal corresponding to the color designated by the color designation signal, but when a reset signal is transmitted from the color change discrimination device 3, it exceptionally generates a primary color signal corresponding to an achromatic color. Output. The color difference signal matrix circuit 5 is supplied with the primary color signals, synthesizes color difference signals corresponding to the primary color signals, and outputs the synthesized color difference signals. This color difference signal matrix circuit 5 may be substantially the same as the color difference signal generating device 1 shown in FIG.

FIG. 6 shows an example of the configuration of the primary color signal synthesis device 4 shown in FIG. In the figure, a color designation signal and a reset signal are supplied to a reset circuit 6. When the reset circuit 6 receives the reset signal, it converts the color designation signal into a code designating an achromatic color and outputs the code. These codes are supplied to a primary color signal conversion circuit 7, where they are converted into primary color signals corresponding to each code and output. This embodiment has the advantage that the configuration is easy when the color designation signal is composed of a combination of binary signals.
It is not limited to this.

Next, in order to show a more detailed embodiment, a specific example of a system that logically generates an image will be shown as an image generation system, and an embodiment of the present invention related to this system will be described in detail. It goes without saying that the present invention is not limited to the illustrated image generation system, and can be widely applied to other systems that logically generate images using a computer or the like, or even general image display systems such as those that take pictures with a camera.

[System example]

(1) The color designation signal representing the image content is composed of binary primary color signal pulses Rp, Gp, Bp and a binary signal Zp for distinguishing the background color from the designated color.

(2) When Zp is logic level 1, it represents the specified color,
In this case, the primary color signals R, G, B are Rp, Gp, Bp
1.0 or 1.0, respectively, corresponding to the logical level of
It is controlled to take a value of 0.0.

(3) When Zp is logic level 0, it represents the background color,
In this case, the primary color signals R, G, B are Rp, Gp, Bp
0.5 or 0.5, respectively, corresponding to the logical level of
It is controlled to take a value of 0.0.

(4) Rp, Gp, Bp, and Zp are temporally discrete, and therefore R, G, and B are also temporally discrete.

(5) The temporal discrete unit is 175nS. That is, the clock signal of the image generator that generates Rp, Gp, Bp, and Zp is 5.73MHz.

In the above system, in the case of the specified color (Zp = 1), a signal corresponding to each color of the normal color bar is generated, and in the case of the background color (Zp = 0), a signal with half the level is generated. will be done.

FIG. 7 shows an example of the present invention adapted to the above system. Color specification signal Rp,
Gp, Bp, and Zp are delay elements (8-1) to (8-n), (9-1) to (9-n) connected in series, respectively.
n), (10-1) ~ (10-n), (11-1) ~
(11-n). The output signal of each delay element is a signal obtained by delaying the corresponding color designation signal by an integral multiple of 175 nS. The logic discrimination circuit 12 is supplied with all or part of the output signal of the modified delay element,
These signals are subjected to logical operation processing, a reset signal is generated at an appropriate position, and the reset signal is supplied to the reset circuit 6. The reset circuit 6 is supplied with signals Rpk, Cpk, and Bpk having delay times matching the timing of the reset signal among the outputs of the delay elements, and the logical product of these signals and the reset signal is ANDed. taken by circuits 13, 14 and 15. Therefore, the output of the reset circuit is reset to a logic zero level when the reset signal is received. These signals are fed to a variable gain amplifier 16. variable gain amplifier 16
When the binary signal Zpk that distinguishes between the background color and the specified color is at logic level 1, the input signal is transmitted to the output terminal at a specific gain, and when the logic level is 0, the input signal is transmitted at a gain that is half of the above specific gain. Transmit with.
As a result, desired primary color signals R, G, and B whose levels are controlled by Zpk are produced, and these are supplied to the color difference signal matrix circuit 5. The color difference signal matrix circuit 5 converts the primary color signals into color difference signals RY and BY using a well-known method.

Although the present invention does not limit the logic of the logic discrimination circuit 12 shown in FIG. 7, in order to more effectively implement the present invention, it is effective to generate a reset signal according to the following conditions. .

(Condition 1) When Z changes from 0 level to 1 level,
A reset signal is generated in the time zone of Z=0 immediately before Z=1. This relationship is shown in FIG. 8A.

(Condition 2) When Z changes from 1 level to 0 level, Z
A reset signal is generated in the time period Z=0 immediately after Z=1. This relationship is shown in FIG. 8B.

(Condition 3) When Z changes from 0 level to 1 level and returns to 0 again at the next clock time, a reset signal is generated in the time zone of Z=0 immediately before and immediately after Z=1. This relationship is shown in FIG. 8C.

The above three conditions improve the coloring of pixels in color changing areas by generating a reset signal based on only the change in the designated color and background color among the color information specified by the color designation signal. Therefore, the basic effects of the present invention can be obtained.

In order to carry out the present invention more effectively, the above three
Some or all of the following conditions may be added to any of the following conditions.

(Condition 4) At the time corresponding to the part of Z=1, R=1
Alternatively, generation of a reset signal is enabled only when G=1 holds true. In other words, if the specified color is red,
It is possible to generate a reset signal before and after magenta, green, cyan, yellow, and other colors only. This condition has the effect of preventing unnecessary darkening on both sides when the specified color is blue or black.

(Condition 5) At the time corresponding to the part where Z=0, R=0
It is possible to generate a reset signal only when That is, the reset signal can be generated only when the background color is blue, green, or cyan. This condition has the effect of preventing an increase in dot interference (image quality deterioration caused by leakage of the carrier color signal to the luminance signal channel) when the background color is red or magenta.

It goes without saying that the above-described conditions to be satisfied by the logic discrimination circuit 12 are merely examples, and other appropriate conditions should be selected depending on the image generation system to which the present invention is applied.

Furthermore, the color change discriminating device 3 itself is not limited to a binary logical discriminating device; it can perform discrimination using an analog circuit and generate a reset signal having an analog quantity, thereby completely resetting the color difference signal. It goes without saying that you may choose not to do so, and that it is included in this disclosure.

As explained in detail above, regarding the "color defective phenomenon of fine pixels in colored images," which was previously considered to be an unavoidable phenomenon due to a defect in color television systems such as insufficient bandwidth in the color signal transmission system, The present invention is effective in greatly improving the coloring of the corresponding pixels by an extremely simple means of resetting the dye signal to zero near the portion where the color changes.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts of a normal encoder, Fig. 2 is a block diagram of the main parts of a normal color television receiver, and Figs. 3A and B explain the distortion of the color difference signal due to the narrowband nature of the color difference signal. FIGS. 4A, B, C, and D are waveform diagrams showing the effects of the present invention. FIGS. 5, 6, and 7 are main circuit configurations showing embodiments of the present invention. Figure, Figure 8 A, B,
C is a diagram showing an example of a partial signal waveform in the present invention. DESCRIPTION OF SYMBOLS 1... Color difference signal generation device, 2... Color difference signal conversion device, 3... Color change discrimination device, 4... Primary color signal synthesis device, 5... Color difference signal matrix circuit, 6...
Reset circuit, 7...Primary color signal conversion circuit, (8-
1) ~ (8-n), (9-1) ~ (9-n), (10
-1) ~ (10-n), (11-1) ~ (11-
n)...Delay element, 12...Logic discriminator circuit, 1
3, 14, 15...AND circuit, 16...variable gain amplifier.

Claims (1)

[Scope of Claims] 1. Part or all of a plurality of color designation signals representing the types of colors of an image portion to be displayed are supplied, and a series of temporal changes in colors designated by the color designation signals is a color change discrimination device that generates a reset signal when matching a predetermined series; and a color change discriminator that is supplied with the plurality of color designation signals and the reset signal, and corresponds to the color designated by the plurality of color designation signals. A color difference signal synthesizing device for a color television system, comprising a color difference signal conversion device that generates a color difference signal and resets the color difference signal to substantially zero level when receiving the reset signal. . 2. In the description of claim 1, the color difference signal conversion device generates a primary color signal corresponding to the color specified by the color designation signal, and when receiving the reset signal, substantially converts the primary color signal. a color difference signal matrix circuit which is supplied with the primary color signal and generates a color difference signal corresponding to the primary color signal; Color difference signal synthesis device for television systems. 3. In the description of claim 2, the primary color signal synthesis device is supplied with the color designation signal and the reset signal, and upon receiving the reset signal, converts the color designation signal to substantially designate an achromatic color. 1. A color difference signal synthesis device for a color television system, comprising: a reset circuit for converting a signal into a corresponding primary color signal; and a primary color signal conversion circuit for converting an output signal of the reset circuit into a corresponding primary color signal. 4. In the statement of claim 1, the color designation signal includes three types of signals corresponding to red, green, and blue.
A color difference signal synthesis device for a color television system, characterized in that the signal is a value level signal. 5. In claim 2, the color designation signal includes three types of signals corresponding to red, green, and blue.
Distinguishing between value level signals and specified color and background color 2
When the signal for distinguishing between the designated color and the background color is at a level indicating the designated color, the primary color signal synthesis device first outputs the signals corresponding to red, green, and blue. When the signal is at a level indicating the background color, the signals corresponding to red, green, and blue are transmitted at a second gain that is smaller than the first gain, and when the reset signal is received, the signal is forced to be reset. 1. A color difference signal synthesis device for a color television system, characterized in that the device is configured to output primary color signals of red, green, and blue at the same level. 6. In the description of claim 1, the color change discriminating device is configured to change the color specified by the color designation signal from the first color to the second color again.
color difference in a color television system, characterized in that, when the second color is returned to the first color and the second color is specified for a short duration, a reset signal is generated before and after the second color. Signal synthesizer. 7. In the description of claim 1, the color change discriminating device is configured to change the color specified by the color designation signal from the first color to the second color again.
When the duration of specifying the second color is short, and the second color is one of red, magenta, green, cyan, yellow, or white. , a color difference signal synthesis device for a color television system, characterized in that it is configured to generate a reset signal before and after a second color. 8. In the description of claim 1, the color change discriminating device is configured to detect the first color again after the color specified by the color designation signal changes from the first color to the second color.
When the duration of specifying the second color is short and the first color is one of blue, green, or cyan, the second color 1. A color difference signal synthesis device for a color television system, characterized in that the device is configured to generate a reset signal before and after each color. 9. In the description of claim 1, the color change discrimination device is configured to change the color specified by the color designation signal from the first color to the second color again.
The duration of the second color is short, and the first color is one of blue, green, or cyan, and the second color is A color difference in a color television system, characterized in that the color television system is configured to generate a reset signal before and after a second color when the second color is one of red, magenta, green, cyan, yellow, and white. Signal synthesizer. 10 In claim 1, the color change discrimination device is configured to generate a reset signal at the time of the substantial change when the color specified by the color designation signal changes. A color difference signal synthesis device for a color television system, characterized in that: 11. In the description of claim 1, the color change determination device is configured to determine whether the color designated by the color designation signal changes from a first color to a second color, or from a second color to a first color. , and the second color is red, magenta,
When the color is green, cyan, yellow, or white,
1. A color difference signal synthesis device for a color television system, characterized in that the device is configured to generate a reset signal immediately before or after a second color. 12. In the description of claim 1, the color change determination device is configured to determine whether the color designated by the color designation signal changes from a first color to a second color, or from a second color to a first color. , and when the first color is one of blue, green, and cyan, a reset signal is generated immediately before or after the second color. A color difference signal synthesis device in a color television system, characterized in that: 13. In the description of claim 1, the color change determination device is configured to determine whether the color designated by the color designation signal changes from a first color to a second color, or from a second color to a first color. The first color is one of blue, green, or cyan, and the second color is one of red, magenta, green, cyan, yellow, or white. 1. A color difference signal synthesis device for a color television system, characterized in that the device is configured to generate a reset signal immediately before or after a second color when the second color is present.