JPS588194B2 - Color television signal processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention addresses the high frequency modulation degree of high chroma images, which is one of the drawbacks of narrow band transmission of NTSC color television signals.
That is, the present invention relates to a color television signal processing device that compensates for a decrease in contrast.

Traditionally, color television signals have been transmitted using the NTSO system in Japan and the United States, the PAL system in Europe, and the SEC system.
Like the iAM system, the luminance signal was transmitted over a wide band, and the color difference signal was transmitted over a narrow band, but in both systems,
When transmitting a high-chroma image, due to the nonlinear characteristics of the color picture tube, the modulation degree decreases in the high-frequency component region that cannot be transmitted using narrow-band color difference signals, resulting in a low-resolution image. For example, if a red or blue illumination light source was used, the image would be blurred, which would limit the use of the system.

To explain the above using an NTSC color television signal as an example, the input signals of the NTSC color coder are E'R, E'G, E'B, and the transmission signals are E'Y, E'■, E'. If 'Q', E'E signal is 4.2
MHz, E'I signal is 1.5MHz, E'Q signal is 0.
It has a frequency band of 5MHz.

To simplify the explanation, the frequency f of the high frequency component is set as f>1
．． If the frequency is 5 MHz, such high-frequency components will be transmitted only by the luminance signal.

For example, assume that the high-frequency component of the imaging output signal of a color television camera using red illumination light is E'R=e(1+cosωt) E'G=E'B=0.

That is, assuming 100% modulation for red and 0% modulation for green and blue, the transmission signal is expressed by the following equation.

E'Y=0.3e(1+cosωt) E'I=0.60E'R-0.28. E'G-0.32
E'R=0.6e(1+cosωt) E'Q=0.21E'RO. 52E'G+0.31E'
B=0.21e(1+cosωt) Furthermore, due to the band limitation of the color difference signal, E'I=0.6e E'Q=0.21e, so the three primary color signals of the receiver are expressed as follows.

E'R=E'Y+0.96E'l+0.62E'Q=e
(1+0.3cosωt) E'G=E'y-0.27E'■-0.65E'Q=e
゜0.3cosωt E'B=E'Y-1.11E'I+1.70E'Q=e
・Q. 3cosωt Therefore, if the conversion characteristic of the electrical signal input to the optical output of a color picture tube is linear, at least for the luminance component, 1
00% modulation can be reproduced, but in reality, since the conversion characteristic of the color picture tube is a high gamma characteristic, that is, γ = 2.2 to 3.0, the color difference signal E'G
, E'B becomes negligible, and only E'R is modulated, so the degree of modulation of the high frequency components decreases to about 30%.

Similarly, the degree of modulation of the high frequency component in the imaging output signal of the color television camera due to blue illumination light decreases to 11%.

The above is always true for high-frequency components in the horizontal direction of the screen, and in actual NTSO color receivers, E'I and E'Q are not distinguished for color difference signals, and both are 0. Since the simple type with a frequency of .5 MHz is the mainstream, the degree of modulation of high-chroma images decreases in the frequency range of f>0.5 MHz.

In addition, in the PAL color television signal, similar development is performed in the frequency range of f > 1 MHz, that is,
A decrease in the degree of modulation of high-chroma images occurs.

An object of the present invention is to slightly change the configuration of the transmission signal when transmitting a color television signal, or to correct the signal components in advance before configuring the transmission signal, so that the resolution of high-chroma images can be reduced. The goal is to prevent it from happening.

That is, the color television signal processing device of the present invention has the following features:
When transmitting a color television signal through a narrowband transmission path, a color difference signal and a narrowband color difference signal are formed for each primary color from the three primary color signals, and the amplitude of the color difference signals is Only if positive,
The present invention is characterized in that the high-frequency characteristics of the color difference signal are compensated for by adding it to the luminance signal.

The present invention will be explained in detail below with reference to the drawings.

First, FIG. 1 shows the basic configuration of a processing device of the present invention that forms a transmission signal when transmitting an NTSO color television signal.

In the basic configuration example shown in Figure 1, input terminals 1 to 3 are supplied with three primary color signals E'R, E
'G, E'B, and supply these three primary color signals to the matrix circuit 4 to convert them into transmission signals E'Y, E'■, E'Q, but the three primary color signals E'R, E'GE'B The following relationship exists between and the transmission signals E'Y, E'■, and E'Q.

Among those transmission signals, signal E' has a frequency band of 1.5
MHz low-pass filter 6 also filters the signal E'
Q is band-limited by a low-pass filter 8 with a frequency band of 0.5 MHz.

On the other hand, a delay line 5 with a delay time τL inserted in the path of the signal E'Y and a delay time τ inserted in the path of the signal E/1
The L delay line 7 is for equalizing the delays of the transmission signals E'Y, E'I, and E'Q.

Then, normally in a color coder, the signals E',
.
is added to the luminance signal E'Y to complete the NTSC color television transmission signal.

In the processing device of the present invention, the output signals E1' and EQ' from the matrix circuit 4 are further processed by the matrix circuit 12.
In addition to the color difference signals ER'-EY', EG'-EY', E
At the same time, the output signals E■' and EQ' from the matrix circuit 4 are applied to low-pass filters 6 and 8, respectively, and the extracted low-frequency signals are guided to the matrix circuit 13 for low-frequency signals. A color difference signal is formed.

The following relational expression holds between the two types of color difference signals obtained by these matrix circuits 12 and 13.

That is, the signal E that has passed through the low-pass filters 6 and 8
I' and EQ' are connected to the above (2) via the matrix circuit 13.
Low-frequency color difference signals ER'-EY' and EG'-EY according to the formula
'． EB'-EY', but in order to form respective difference signals between the color difference signals containing only low frequency components and the color difference signals including high frequency components from the matrix circuit 12, color difference signals from the matrix circuit 13. The signals are led to differential amplifiers 17, 18, and 19 through delay lines 14, 15, and 16, respectively, each having a delay time τL that equalizes the delay time with the signal, and the difference between the low-frequency color difference signal and the low-frequency color difference signal from the matrix circuit 13 is determined.

Furthermore, among those color difference signals, taking ER'-EY' as an example, ER' where the amplitude of the color difference signal is negative
If the signal component with −EY′<0 is not removed, a phenomenon will occur in which the high-frequency component generated in the Ike color difference signal is canceled out, so for example, the delayed output of the delay line 14 is applied to the amplitude limiting amplifier 20.
The amplification characteristics of this amplitude limiting amplifier 20 are such that, as shown in FIG. The amplitude-limited amplified output signal is applied to the multiplier circuit 23 and multiplied by the color difference signal of the high frequency component from the differential amplifier 17, and ER'-EY'≧ in the high frequency color difference signal is applied. Extract only the 0 part.

For other color difference signals EG'-EY' and EB'-EY', EG'-EY'≧0, EB'-EY
'≧0, only high-frequency color difference signals having positive amplitudes are taken out, these positive high-frequency color difference signals are guided to a coupling circuit 26 to be synthesized, and the synthesized output signal is guided to an adder 27 to generate a luminance signal EY. ', and the added output is led to the adder 11, where it is added to the carrier color signal described above.

Although the coupling circuit 26 may be approximately a simple addition circuit, it is preferable to configure it so that an output e0 of three inputs can be obtained, as shown in FIG.

As mentioned above, to explain the effects of the processing device of the present invention using the case where the screen is red as an example, ER'=e(1+c
os(z)t) (w: high angular frequency) From this equation (4), ER'-EY'≧0, Eo'-EY'≧0, EB'-
If the positive high-frequency color difference signal with EY'≧0 is the combined output ECH of the coupling circuit 26, then EOH=0.7 ecosωt (5), and if the luminance signal from the adder 27 to which this signal EOH is added is EY'', then , EY"=EY'+EcH=e(0.3+cosωt)
(6), and the three primary color signals obtained in the color receiver are as follows.

However, due to the nonlinear characteristics of the color picture tube, the signal EG
Since the changes in ' and EB' can be ignored, the modulation degree of the signal ER' can be maintained at 100%.

As mentioned above, the reason why the combining circuit 26 forms a composite output with the following relationship is to take into consideration the case where a high-chroma color image is composed not only of three primary colors but also of complementary colors of these three primary colors. .

That is, if a simple addition circuit is used as the coupling circuit 26, the amount of compensation for a color image consisting of complementary colors will be twice the required amount of compensation, resulting in overcompensation.

However, since the degree of modulation of a color picture tube in the high frequency range generally tends to decrease, there is no practical problem even if a simple adder circuit as described above is used as the coupling circuit 26.

Next, in a color receiver, 0. Considering that a narrow color difference signal bandwidth of 5 MHz is used,
Even if the processing apparatus of the present invention is configured in a simplified manner as shown in FIG. 4, the same effects as described above for the configuration shown in FIG. 1 can be obtained.

In the configuration example shown in FIG. 4, the matrix circuit 12 uses the color difference signals ER/-EY'. Eo'-EY', EB'
The color difference signals are applied to the rectifier circuits 28, 29, 30 and rectified, so that ER'-EY'≧0, Eo'-EY'≧0,
Only color difference components having positive amplitudes such as EB'-EY'≧0 are extracted.

These positive color difference signal components are each 0. 5 Mf{
Low-pass filter 31.32.3 with a bandwidth of z
3 to narrow the band, and then connect the differential amplifier 3 to
In addition to 7.38.39, delay lines 34 , 35 . The above-mentioned positive color difference signal components via differential amplifiers 37 and 36 are also
. Similarly, it is added to the luminance signal EY'.

The configuration shown in the second figure explained above is such that when most of the color receivers are of a simple narrow band color difference signal system as in Japan, the color coder itself is also configured as a simple type and the signal is Color difference signal ER instead of E■', EQ'
,'-EY/. Even greater effects can be obtained when Eo'-EY', EB'-EA is used.

In the above explanation, we have described the case where compensation is performed in a color coder, but in order to perform high frequency compensation by applying the present invention without making any changes to a ready-made color coder. As shown in FIG. 6, a compensation circuit similar to that described above in FIG. 1 and FIG. ', and from these signals, the three primary color signals ER', EG', and EB' are regenerated through a multiplex circuit which performs the function shown by the following equation, and the reproduced three primary color signals are produced as ready-made signals. color coder.

That is, in color television signals of the PAL system and the SEOAM system, the frequency band of the color difference signal is unified to IMHz, so even if the present invention is applied with the configuration shown in the second figure, the same result as described above will be achieved. , a nearly satisfactory high-frequency compensation effect can be obtained.

As is clear from the above description, according to the present invention, the high-frequency component of the color difference signal in the color television signal is added to the luminance signal in proportion to the saturation, thereby preventing the resolution of high-saturation images from deteriorating. The effects of this can be mentioned.

In the configuration example shown in the first diagram of the processing apparatus of the present invention, the NTS
The signal E I', like the O system color television signal,
E Q' (7) High-frequency compensation is performed for signal systems with different bands, and this circuit configuration sufficiently transmits the high-frequency components of the color difference signal to prevent low resolution. .

In addition, the configuration example shown in FIG. 4 shows an example in which a color television signal is received or processed using a simple color television receiver or a simple color coder, and the positive amplitude of the color difference signal is By adding the high-frequency component to the luminance signal, it is effective in preventing the resolution of high-chroma images from becoming low.

In addition, in television broadcasting stations, etc., in addition to applying the high frequency compensation according to the present invention to all color television cameras, the high frequency compensation according to the present invention is applied only to image transmission systems that transmit particularly high chroma images. It is also possible to do so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of the processing device of the present invention;
FIG. 2 is a waveform diagram showing a mode of signal processing in a part of the same, FIG. 3 is a block diagram showing an example of the configuration of a coupling circuit, which is also a part of the same, and FIG. FIG. 5 is a waveform diagram showing a part of the signal processing mode, and FIG. 6 is a block diagram showing an embodiment of the present invention. 1 to 3... Input terminal, 4... Matrix circuit, 5, 7... Delay line, 6, 8...
・Low pass filter, 9, 10...Modulator,
11... Addition circuit, 12, 13... Matrix circuit, 14, 16... Delay line, 17,
19...Differential amplifier, 20-22...
Amplitude limiting amplifier, 23 to 25...Multiplication circuit, 2
6... Combining circuit, 27... Adding circuit,
28-30... Rectifier circuit, 31-33...
...Low pass filter, 34-36...Delay line, 37-39...Differential amplifier, 40...
...Addition circuit.

Claims (1)

[Claims] 1. When transmitting a color television signal through a narrowband transmission path, a color difference signal and a narrowband color difference signal are formed for each primary color from the three primary color signals, and a difference signal between the color difference signals is generated. , a high frequency television signal processing apparatus characterized in that the high frequency characteristics of the color difference signals are compensated for by adding them to the luminance signal only when the amplitudes of the color difference signals are positive. 2. Adding the three primary color signals to the first matrix circuit and adding the formed engineering signal and Q signal to the second matrix circuit to form a color difference signal for each of the primary colors, and lowering the ■ signal and the Q signal, respectively. 2. The color television signal processing device according to claim 1, further comprising a narrow band color difference signal for each of the primary colors in addition to the third matrix circuit via a pass filter. 3 Add the three primary color signals to the first matrix circuit to form a 1 signal and the Q signal to the second matrix circuit to form a color difference signal for each of the primary colors, and lower the color difference signals for each of the primary colors, respectively. 2. The color television signal processing apparatus according to claim 1, further comprising a band-pass F wave filter and a narrow band color difference signal for each of said primary colors. 4. When adding the difference signal for each primary color to the luminance signal, a signal e0 having the relationship e0=e12+e22+e32/e1+e2+e3 is added to the luminance signal, where the difference signals for each primary color are e1, e2, and e3. A color television signal processing device according to claim 1, characterized in that: 5. A signal formed by adding the difference signal for each primary color to a luminance signal only when the amplitude of the color difference signal is positive, together with a ■ signal and a Q signal formed by adding the three primary color signals to the first matrix circuit. , in addition to the fourth matrix circuit, a new three primary color signal is formed, and the new three primary color signal is applied to a color coder. .