JPS6113676B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a color television signal compounding method for synthesizing three primary color signals such as those output from a television camera to form a composite color television signal in which a carrier color signal is superimposed on a luminance signal. It is related to.

This is the current standard color television system.
In the NTSC system, the upper limit of the signal frequency band is set to 4.2 for the luminance signal component, taking advantage of the fact that there is a difference in visual spatial frequency characteristics between luminance, which represents the brightness and darkness of an image, and chromaticity, which represents the hue of the image. M
Hz, 1.5MHz for the wideband color difference signal E _I , and 0.5MHz for the narrowband color difference signal E _Q , but the basis for selecting each signal component frequency band is based on the color chart of Middleton et al. Based on data based on psychological experiments.

However, subsequent research on vision revealed that the broadband and narrowband axes of chromaticity were
The wideband color difference axis I and the narrowband color difference axis Q in the NTSC system are different from each other, and as shown in Figure 1, on the chromaticity diagram, the I axis moves towards red, and the Q axis moves towards blue. Furthermore, it is revealed that each of the opposite colors rotates in the opposite direction.

Furthermore, research on color vision has shown that chromaticity is not determined by spatial frequency characteristics alone, but that the distribution of three types of cones in the retina of the eye is one of the factors that causes frequency band limitations in spatial frequency characteristics. It has been clarified that this affects the spatial frequency characteristics of

The NTSC system, which was established before this new recognition of vision and color vision, simply used narrowband color difference signals, which did not necessarily match visual characteristics and allowed direct viewing of patterns exhibiting minute color changes. However, when viewing the same pattern of a color image reproduced from a composite color television signal via the transmission system, the above-mentioned minute color changes become invisible. It was hot.

It is an object of the present invention to provide a color television signal that eliminates such conventional drawbacks in the NTSC composite color television signal and allows minute color changes to be viewed in reproduced color images in the same way as in the original image. The objective is to provide a composite method.

That is, the present invention aims at combining the color television signal by making the composition of the composite color television signal, which is a color image information transmission signal, more suitable for the characteristics of the eye related to vision and color vision. Yes, the compounding method of the present invention is
In synthesizing the three primary color signals representing a color image to form a composite color television signal in the form of a combination of a luminance signal and a color signal, the upper limit of the frequency band of the blue signal among the three primary color signals is approximately
The feature is that the signal is limited to 0.6MHz and then combined with other primary color signals.

FIG. 2 shows a model of a visual color information transmission system corresponding to the conventional NTSC composite color television signal transmission system for transmitting visual color information.

In the color information transmission system shown in the second figure, optical stimulation by color images is red (R), green (G), and blue (B).
If we omit the non-linear characteristics of light-to-electrical signal conversion, the three primary color components decomposed by three types of cones on the retina of the eye are The transmission to the visual center of the cerebrum is
It is thought that this is done by the bright and dark components Br and the mutually opposite color components of red-green (r-g) and yellow-blue (y-b), and if we focus on the spatial frequency characteristics, we can see that the transmission path The spatial filters shown in the figure are respectively inserted, and the frequency bands of each component are narrowed in the order of Br, (rg), and (yb) as per the upper limit described above.

As mentioned above, the NTSC system started from the visual model as described above with reference to FIG. 2, and established a transmission system with the configuration shown in FIG. 3. In this NTSC color image information transmission system, wide and narrow color difference component signals I and Q are used instead of the opposite color components (r-g) and (y-b) in Fig. 2, but the basic The transmission system shown in Figure 2 and the transmission system shown in Figure 3 are shown in Figure 2.
This is equivalent to the NTSC transmission system.

On the other hand, according to recent research, the visual model is based on the lack of cones corresponding to blue (B) in the center of the eye's retina, where photoreceptor cells are densely packed. As mentioned above, in terms of the linear part, the configuration is as shown in Figure 4, in which a low-pass filter for spatial frequencies is inserted in the blue (B) line of the transmission system shown in Figure 2. It's summery.

When adapted to the recent visual model shown in FIG. 4, the configuration of the color signal transmission system for transmitting color image information will also change, as shown in FIG. ) should insert a low-pass filter into the transmission channel.

In the transmission system shown in Figure 5, the cutoff frequency of the low-pass filter inserted in the blue (B) channel is f
_b , the cut-off frequencies of the low-pass filters inserted in each channel of (r-g) and (y-b) are f ₂ and f ₁ , respectively, and the luminance signals are E _Y , (r
-g) The signal is E _r - _g and the (y-b) signal is E _y - _b. Furthermore, when the change in luminance signal ΔE _Y = 0, the frequency f of the (y-b) signal is set as f>f Set to ₁ .

Therefore, the narrowest band color component y−b mentioned above
The pattern shown in Fig. 6, which consists of stripes of yellow y and blue b, and whose brightness is constant, is transmitted through a visual system that has a blue transmission system that lacks high frequencies, as shown in Fig. 4. When viewed visually, the pattern itself shown in Figure 6 is a stripe of yellow y and blue b, so when the brightness is constant, the three primary color RGB components are respectively a, b, and 7 in Figure 7.
However, when input to the matrix through the low-pass filter inserted only in the blue B system, the high frequency component B' of the blue B system changes as shown in Figure 7 c'. As shown, there is no change due to the deletion of the high range.

The inputs of such states are matrixed, and each band is sequentially limited as described above.
Regarding each component of Br, (r-g) and (y-b), as shown in Figure 7 d, e and f, in the low range, the (r-g) component follows the pattern shown in Figure 6. Since that component does not exist, the change will be zero, but the (y-b) component will be as shown in the figure,
The brightness component Br changes as shown in the figure in response to changes in only the (y-b) component, but as mentioned above, only the blue B system lacks the high range, so in the high range The color component of (y-b) is also (r
-g) Together with the component, their changes become zero as shown in Figure 7 h and i, respectively, and there is no change in color, but the light and dark component Br remains even in the high range as shown in Figure 7 g, Therefore, in the pattern shown in FIG. 6, at high frequencies, that is, when the stripes become fine, the change in color becomes invisible, but it appears as bright and dark stripes.

To put the above in other words, Fig. 7 a, b,
Each waveform of c is each component of the chromaticity pattern shown in Figure 6, which corresponds to the spectral characteristics of the three primary colors R, G, and B.
In the fovea of the retina of the eye, the cones that sense blue B are missing, so there is no high-frequency blue B component, and cos2
Since the frequency component πfx of the pattern shown in FIG. 6 cannot be transmitted, the high frequency band of blue B is added to the conversion matrix to the opposite color signal without any change as shown in FIG. 7 c'. The opposite color signal which is the matrix output is Br, (r-g), (y-b).
The components become as shown in Fig. 7 d, e, and f. In other words, since there is no (r-g) component in the pattern shown in Figure 6, the (r-g) component of the matrix output is 0.
becomes. When the B component in the matrix input is c in Fig. 7, the brightness of the pattern shown in Fig. 6 is constant, so the brightness component Br of the matrix output is flat, that is, the change is 0, but when the B component is in the high range, as shown in Fig. 7.
c′, so as shown in Figure 7d, the brightness component Br
The balance of the three primary colors will be disrupted and variations will occur. The (y-b) component is the 7th component in the low range.
As shown in Figure f, a change in cos2πfx occurs, but
In the high range where f > f ₁ , the change in the (y-b) component is not transmitted to the cerebral center, and the bright and dark components become as shown in Figure 7 g, h, and i.
Only Br transmits the change in cos2πfx, and the pattern shown in Figure 6 is seen as a change in brightness and darkness.

On the other hand, in the conventional NTSC color signal transmission system shown in FIG. 3, signal processing as shown in FIG. 8 is performed.

The three primary color signals E _R , E _G , and E _B of the camera output that captured the chromaticity pattern shown in Figure 6 are shown in Figure 8 a, b, and c.
The matrix output of the color coder that supplied these three primary color signals is E Y , _E instead of the visual system information Br, (r-g), (y-b) shown in Figure 7.
_I , E _Q , and the narrowband color information (y
-b) corresponds to the Q-axis color signal, and their matrix output signal waveforms are shown in FIG. 8d, e, and f. Therefore, for the chromaticity pattern shown in Figure 6, E
Each of _{the Y} and E _I signals becomes 0, and there is a change only in the E _Q signal. However, since the band of the Q signal channel is the narrowest among each matrix output, the high frequency component of the E _Q signal is deleted by the narrowest low-pass filter of the Q channel, and the reproduction end The signal transmitted to E _Q
The change in the signal also disappears, and as shown in Figure 8g,
As shown in h, i, each matrix output E _Y , E
There is no change in both _I and E _Q , and there is no spatial high-frequency change information on the playback screen.In other words, when the stripes in the pattern shown in Figure 6 become fine, the conventional NTSC color signal transmission shown in Figure 3 disappears. Nothing will appear on the playback screen for the system.

Therefore, even if the chromaticity pattern shown in Figure 6 shows a fine striped pattern when viewed directly, the same fine striped pattern will appear on the playback screen when passed through the conventional NTSC color signal transmission system. One of the drawbacks of the conventional NTSC system is that the pattern cannot be seen.

On the other hand, in the color signal transmission system shown in FIG. 5 based on the composite system of the present invention, the change in the color information signal having a waveform almost the same as that of the visual system color information shown in FIG. 4 is as shown in FIG. transmitted to.

That is, Fig. 9 a, b, and c correspond to Fig. 8 a,
Similar to b and c, these are the three primary color signals E _R , E _G , and E _B of the camera imaging output for the chromaticity pattern shown in Figure 6, and for the high frequency range, the high frequency blue component is generated by the newly inserted low pass filter. The high frequency blue signal E _B ' disappears and becomes 0 as shown in FIG. 9c'. Each matrix output signal E _Y , E _r - _g , E _y - _b obtained in the same way as in the visual system for an unbalanced input due to the omission of the high-frequency blue signal E _B ' is the ninth
As shown in Figures d, e, and f, the signal E _r - _g of the (r-g) component that does not exist in the chromaticity pattern shown in Figure 6 becomes 0, and only the E _Y and E _y - _b signals have a change. appears. However, in the matrix output, the band of E _Y signal is 4.2MHz due to the low pass filter inserted in each channel, E _r - _g , E _y - _b
Each signal band of is limited to f ₂ and f ₁ , respectively,
If the color signal bands f ₂ and f ₁ are adjusted to the conventional NTSC transmission system, f ₂ = 1.5 MHz, f ₁ = 0.5 MHz, and in the output of each filter, the high frequency band is the visual system transmission shown in Figure 8. Similar to the waveform, the high-frequency components of the E _y - _b signal also disappear, as shown in Figure 9 g, h, and i, and both the color information signal components E _r - _g and E _y - _b show high-frequency changes. becomes 0, but even when there is a change in the luminance signal component _E Although the change disappears, the pattern shown in Figure 6 can be recognized as a change in brightness and darkness.

In summary, the feature of the color television signal combination system of the present invention is that in order to perform the combination of color information transmission signals that are more similar to the visual system in the color signal transmission system, the color The point is to add a band limit to the signal E _B.

In the above explanation, in accordance with the conventional NTSC system, all filters were assumed to limit the band in one dimension, that is, only in the horizontal direction of spatial information, but when reproduced as an image, it becomes two-dimensional. Similar E _B signal band limitation can be applied to the case of performing two-dimensional filter processing. In that case, E _B , E _Y , E
It is desirable to insert two-dimensional low-pass filters into all of the _r - _g and _Ey - _b signals.

Such a two-dimensional filter can be used to blur the optical image in the imaging system for the E _B signal, for example by installing a diffuser plate in front of the imaging tube, or in the case of a telecine system, by changing the focus of the optical system. The diameter of the scanning beam can be increased by intentionally shifting it or by shifting the focus of the scanning beam of the image pickup tube.

In addition, as a two-dimensional filter for the E _r - _g and E _y - _b color signals, there are two methods: a method in which a group of delay lines in units of one line is used in the vertical direction and the delayed outputs are added together with an appropriate amplitude ratio; , it is possible to take a method such as once forming a reproduced image on the picture tube using the signals E _r - _{g and} E _y - _b , and then re-imaging the reproduced image on the picture tube in the same manner as described above. It is possible, and in that case,
A method similar to that used for the E _B signal described above can be used.

As is clear from the above description, according to the present invention, color television signals can be composited by performing signal processing that is more suited to visual characteristics than the conventional NTSC method. It is possible to reproduce a color image that looks exactly the same as when viewing it directly, and the effect is that it is possible to recognize finer patterns of changes only due to chromaticity changes in the reproduced color image. can get.

In the above-mentioned embodiment, as shown in FIG. 5, only horizontal band limitation was applied as in the conventional NTSC system, but the present invention improves spatial fineness in the horizontal direction. By taking advantage of the system's effects, it is possible to achieve such effects by limiting the band of the video signal and narrowing the band of the blue channel camera.

Furthermore, when applying the method of the present invention by extending it to two-dimensional spatial information, E _B , E _r - _g ,
By using a two-dimensional filter as the band-limiting filter for each E _y - _b signal, it is possible to save the vertical band.Furthermore, blue channel cameras do not require a thick scanning beam from the image pickup tube. Become.

In all of the above, even though the blue channel is band-limited, if only the chromaticity of the subject exhibits a yellow-blue (y-b) change, it can be directly detected by visual perception. Just like what we saw in
Even if the change in color is unknown, the color television signal can be composited so that a reproduced image in exactly the same state as the subject is obtained as a change in brightness and darkness, and the composite color television signal can be transmitted. In the above explanation, an example of a 525/60 scanning standard NTSC signal was described.
Of course, the present invention can be similarly applied to color image signals of other standard formats such as PAL format signals and SECAM format signals.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the broadband axis and narrowband axis on the chromaticity diagram for the NTSC system and the visual system, Figure 2 is a block diagram showing the conventional visual system model, and Figure 3 is the diagram of the conventional NTSC system. A block diagram showing the configuration of a system color television signal transmission system, FIG. 4 is a block diagram showing a visual system model corresponding to the system of the present invention,
Fig. 5 is a block diagram showing a configuration example of a color television signal transmission system according to the method of the present invention, Fig. 6 is a diagram showing an example of a chromaticity pattern, and Fig. 7 a to i correspond to the method of the present invention. Waveform diagrams showing signal waveforms of each part in the visual system, FIGS. 8 a to i are waveform diagrams showing signal waveforms of each part in the conventional transmission system shown in FIG. 3, and FIGS. 9 a to i show the waveforms of the present invention shown in FIG. 5. FIG. 3 is a waveform diagram showing signal waveforms of various parts in a transmission system according to the method. A, A ^-1 ... Matrix, F ₁ , F ₂ , F ₃ , F _B ...
...low-pass filter, CRT...picture tube.

Claims (1)

[Claims] 1. When synthesizing the three primary color signals representing a color image to form a composite color television signal in the form of a combination of a luminance signal and a color signal, the upper limit of the frequency band of the blue signal among the three primary color signals is approximately
A color television signal compounding method characterized by limiting the signal to 0.6MHz and combining it with other primary color signals.