JPS6158079B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a luminance/chromaticity signal separation device that separates a luminance signal component and a chromaticity signal component of a color image signal, and in particular, the present invention relates to a luminance/chromaticity signal separation device that separates a luminance signal component and a chromaticity signal component of a color image signal. Responding appropriately to the presence or absence of movement,
This allows separation of both luminance and chromaticity signal components without constant image quality deterioration.

For example, a conventional luminance/chromaticity signal separation device of this type that separates luminance signal components and chromaticity signal components in an NTSC color image signal originally had the following two types.
They were broadly classified into different types, but each had its own drawbacks.

(1) In the case of frequency-separating the luminance signal component and chromaticity signal component using a normal filter, as shown in Figure 1a, a low-pass filter 1 with a cutoff frequency near 2MHz is used. to extract the luminance signal component, and extract the carrier chromaticity signal component by a bandpass filter 2 with a center frequency of 3.58 MHz, or, as shown in FIG. The extracted carrier chromaticity signal component is subtracted from the color image signal passed through a phase adjuster 4 for adjusting the phase of the high frequency component to extract the luminance signal component. However, in the separation of luminance and chromaticity signals using such a conventional filter, the high-frequency components of the luminance signal components are lost, resulting in a drawback that the horizontal resolution of the color image is significantly degraded.

(2) One or two one-line delay lines 3 are combined via an adder/subtractor and a multiplier, as shown in FIG. is extracted through the bandpass filter 2, and
In the case where the luminance signal component is extracted by subtracting the carrier chromaticity signal component from the color image signal whose high-frequency components have been phase-matched by the phase adjuster 4, the image signal between two lines arranged vertically on the screen is Since the luminance signal component and the chromaticity signal component are separated by arithmetic processing such as averaging, there is a drawback that the resolution in the vertical direction and diagonal direction is significantly degraded.

In order to eliminate the above-mentioned drawbacks of the originally developed device of this type, a luminance/chromaticity signal separation device constructed as follows has been developed in the past.

That is, for example, the color subcarrier frequency in a color image signal of the NTSC system is in an interleaved relationship with the line frequency, and is also in an interleaved relationship with the frame frequency.
Unlike the original device shown in Figure 1b, which utilized the former interleaving relationship with the line frequency, the previously developed luminance/chromaticity signal separation device utilized the latter interleaving relationship with the frame frequency, and The comb filter circuit configured using delay elements eliminates the above-mentioned drawbacks of the original device, and the comb filter circuit configured using delay elements eliminates the above-mentioned drawbacks of the original device. The deterioration in image quality caused to the resulting moving image is removed by switching between the filter circuit and another filter circuit constructed without using a one-frame delay element.

However, in conventionally developed devices of this type,
Since image movement is detected based on the presence or absence of changes in signal components for the same pixel point between image signals spaced apart by one frame period, if noise is superimposed on the image signal to an extent that cannot be ignored. Even if the target image signal is a still image,
The noise component is detected as a difference between frames, and the image is incorrectly determined to be a moving image.

It is an object of the present invention to eliminate all of the above-mentioned conventional drawbacks, to appropriately respond to the presence or absence of image movement due to color image signals without being caught by the presence of noise, and to constantly produce color images without deterioration in image quality. An object of the present invention is to provide a luminance/chromaticity signal separation device capable of separating a luminance signal component and a chromaticity signal component of an image signal.

That is, the luminance/chromaticity signal separation device of the present invention has the following features:
a first comb filter circuit that includes at least one frame delay element and separates a luminance signal component and a chroma signal component of a color image signal by combining input and output image signals of the frame delay element; A second circuit which includes a delay line and separates the luminance signal component and chromaticity signal component of the color image signal by combining the input and output image signals of the line delay line.
a comb filter circuit, a motion detection section that detects motion of an image signal based on a difference between the input and output image signals of the frame delay element, and a switching means that responds to the motion detection output of the motion detection section. and when the motion detection output of the motion detection section does not exceed a predetermined threshold value, the luminance signal component and the chromaticity signal component separated by the first comb filter circuit are extracted through the switching means, and the motion detection output is In the luminance/chromaticity signal separation device, which extracts the luminance signal component and chromaticity signal component separated by the second comb filter circuit via the switching means when The switching means operates so as to extract the luminance signal component and chromaticity signal component separated by the first comb filter circuit when the motion detection output no longer reaches the first threshold value. The switching means is characterized in that the switching means operates so as to extract the luminance signal component and the chromaticity signal component separated by the second comb filter circuit when the threshold value of 2 is exceeded.

The invention will be explained in detail below by way of example embodiments with reference to the drawings.

The luminance/chromaticity signal separation device of the present invention uses a 1-frame delay element, for example, a 1-frame delay element that uses a delay of an image signal due to a time difference between writing and reading an image signal to a 1-frame memory, to separate a 1-frame period. By performing comb filter separation between the luminance signal spectrum and the chromaticity signal spectrum by utilizing the interleaving relationship between the color subcarrier frequency and the frame frequency between the color image signals, a similar method can be achieved using a one-line delay line. In addition to eliminating the resolution degradation in the vertical and diagonal directions that occurs when comb filter separation is performed, the image quality degradation that cannot be ignored due to the afterimage effect caused by the signal delay of the frame period can be eliminated. For moving images where resolution deterioration does not significantly affect the visual sense, we not only prevent it by switching to comb filter separation using a 1-line delay line, but also eliminate noise by using a delay circuit to distinguish between still and moving images. This configuration example of the device of the present invention is shown in the third example.
As shown in the figure.

In the configuration example shown in FIG. 3, two one-frame delay elements 5 are connected in cascade, and a color image signal having a two-frame period difference obtained from both ends of the cascade connection is transmitted through an adder and a 1/2 multiplier. supplying the averaged and one frame delayed color image signal obtained from the midpoint of the above-mentioned cascade to a subtractor;
The carrier color signal component spectrum is extracted based on the comb filtering effect of the combination of color image signals at one frame period interval, and is passed through the phase adjuster 4 as a chromaticity signal component C _V corresponding to the still color image signal. Take it out.

On the other hand, in exactly the same manner as described above, two one-line delay lines 3 are connected in cascade, and a color image signal having a two-line period difference obtained from both ends of the cascade connection is transmitted through an adder and a 1/2 multiplier. The averaged value and the one-line delayed color image signal obtained from the intermediate point of the above-mentioned cascade are fed to a subtracter, and based on the comb filtering effect by the combination of the color image signals with one line period interval. The carrier color signal component spectrum is extracted and taken out as the chromaticity signal component C _H corresponding to the motion color image signal.

The above-mentioned chromaticity signal component C _V for a still image and chromaticity signal component C _H for a moving image have their mutual phases matched by the phase adjuster 4, so that the chromaticity signal component C V for a still image and the chromaticity signal component C H for a moving image have their mutual phases matched by the phase adjuster 4. Both chromaticity signal components C _V and _CH If the color image signal is appropriately switched and extracted, the movement of the image can be detected based on the presence or absence or magnitude of a change in the color image signal for the same pixel point of the color image. For example, "SMPTE Journal" magazine, No. 87
Vol. 3, No. 3, pp. 129-130, the chromaticity signal components of the still image and the moving image are consecutively determined according to the determination result of whether the image is a still image or a moving image by the well-known motion detection unit 6. It can be taken out. The chromaticity signal component is extracted through a bandpass filter 2 having a center frequency of 3.58 MHz, and the original color image signal obtained from the midpoint of the cascaded connection of the one-line delay line 3 is sent to a phase modulator 4. In addition, by subtracting the filtered output chromaticity signal component of the bandpass filter 2 from the phase-matched high-frequency component, the luminance signal component can be extracted.

The chromaticity signal component C _V of a still image obtained as described above is obtained by separating and extracting the chrominance signal component spectrum using a comb filter with a frame period configured using the 1-frame delay element 5. It does not cause any resolution deterioration for still images; on the other hand, the chromaticity signal component C _H for moving images is generated by a line-period comb filter, so this disadvantage does not occur for moving images. The reduction in resolution in the vertical and diagonal directions can be ignored thanks to the visual characteristics for moving images, and therefore does not cause any deterioration in image quality.

Therefore, regarding image motion detection by the motion detection unit 6, if a difference signal exceeding an appropriately set threshold level is detected, that is, a positional shift due to image movement or the same pixel point due to image movement is detected. It is detected as a moving image only when there is rapid movement such that the change in the signal component increases significantly beyond the threshold level, and even if a difference that does not reach the above threshold level is detected, the movement is extremely small. As it can be considered as a substantially still image, it is necessary to ignore it together with the detected noise. That is, when the noise detection reaches the threshold level, the changeover switch 7 is controlled by the noise detection, which may cause flickering in the image, so it is necessary to prevent malfunctions due to the noise detection. There is.

In order to prevent such malfunctions, (1) noise in the image signal supplied to the motion detection section 6 can be reduced in advance, for example, simply by placing the low-pass filter 1 in front of the motion detection section 6. .

(2) Luminance and chromaticity separated signal components of the frame period formed by a frame delay comb filter,
At least one of the types shown in FIGS.
The luminance/chromaticity separated signal components formed by a filter that does not use a frame delay element are linearly combined using, for example, a resistance matrix circuit, and the weighting coefficients to be multiplied by each signal component are detected as output from the motion detection unit 6. change according to the signal,
Make sure to perform a smooth switching operation.

However, in the apparatus of the present invention, the ambiguity associated with such preventive measures is eliminated, and the following slow switching between still images and moving images is performed.

In other words, when the difference signal of the detection output exceeds the threshold level for still image/moving image discrimination by a considerable amount, that is, the threshold level for conventional still/moving image discrimination exceeds, for example, normal noise detection. The upper and lower auxiliary threshold levels are respectively set at level positions that are appropriately vertically distanced from each other, and when the difference signal of the detection output increases and exceeds the upper auxiliary threshold level, The motion detecting section includes a slow-acting circuit 9 exhibiting a slow-acting hysteresis characteristic such that the changeover switch 7 switches between a still image and a moving image only when the signal decreases and no longer reaches the lower auxiliary threshold level. 6 and the changeover switch 7.

Therefore, the above-mentioned two types of chromaticity signal components and the two types of luminance signal components obtained by subtracting these two types of chromaticity signal components from the original color image signal can be used to distinguish between still images and moving images due to the presence of noise. It is possible to selectively switch and extract the signals according to the results of appropriate discrimination without causing any errors due to capture, and it is possible to obtain luminance/chromaticity separated signals with almost no deterioration in image quality.

Next, FIG. 4 shows another configuration example of the luminance/chromaticity separation device of the present invention, which is a simplified version of the configuration shown in FIG.
In the configuration example shown in FIG. 4, the one-frame delayed color image signal obtained from the intermediate point in the cascade connection of the one-frame delay elements 5 in the configuration example shown in FIG. By supplying the signal to the bandpass filter 2, the chromaticity signal component C _H for a moving image is obtained in the same manner as in the conventional device shown in FIG. The delayed color image signal is supplied to the phase adjuster 4, and the high-frequency component is phase-matched, and the luminance signal component is extracted by subtracting it.
_V is taken out in exactly the same manner as in the configuration example shown in FIG.

In the simplified configuration example shown in FIG. 4, since the line-period comb filter is omitted, the resolution in the horizontal direction for a moving image is degraded, but the visual perception for a moving image similar to that described above is degraded. Thanks to its characteristics, there is almost no deterioration in image quality.

Next, FIG. 5 shows a configuration example in which the above-described configuration examples of the luminance/chromaticity separation device of the present invention are further simplified to include only one one-frame delay element 5.

Therefore, as shown in FIG. 6a, the frequency characteristic of the response in the frame-period comb filter constructed by cascading two one-frame delay elements 5 is as shown in FIG. Since the spread is large and exhibits a frequency characteristic that is almost symmetrical to the spread near the maximum response, the component spectra are sufficiently separated and the phase characteristics are also flat. On the other hand, the frequency characteristic of the response in a frame-period comb filter constructed using a single one-frame delay element 5 as described later with reference to FIG. 5 is as shown in FIG. 6b. Compared to a configuration in which two one-frame delay elements 5 are connected in series, the spread near the zero response is considerably narrower and is asymmetrical to the spread near the maximum response, making it difficult to separate the component spectra. This is not achieved satisfactorily, and the phase characteristics are also not flat. However, for a still image, the spectrum of the chromaticity signal is equal to the frame frequency f _F
However, it is concentrated at frequency positions that are odd multiples of 1/2, and does not exist at frequency positions that are even multiples of that. Therefore, even with the above-mentioned one-frame delay comb filter, the component spectrum can be sufficiently separated and extracted for the chromaticity signal component, so when the phase characteristics are not a problem,
Desired effects can also be obtained with such a one-frame delay comb filter.

In the configuration example of the luminance/chromaticity signal separation device of the present invention constructed using a one-frame delay comb filter shown in FIG. They are commonly supplied to form sum and difference signal components, respectively, and the sum signal component obtained from the adder is used as the luminance signal component Y _V ' for a still image, and the difference signal component obtained from the subtracter is Let be the chromaticity signal component C _V ' at the time of a still image.

On the other hand, the conventional luminance/chromaticity signal separation circuit 8 configured without using at least one frame delay element as shown in FIGS. 1a, b and 2,
The color image signal with a one-frame delay from the one-frame delay element 5 is separated into luminance and chromaticity signals without causing a deviation of the signal components due to image movement, and the luminance signal components Y M and Y _M of the moving image are separated. A switch 7a separates and extracts the chromaticity signal components C _M for a moving image, and switches between the luminance signal components Y _V ′ and Y _M and the chromaticity signal components C _V ′ and _CM for the still image and the moving image. and 7b, and are respectively extracted as continuous luminance signal components and chromaticity signal components.

Therefore, the above-mentioned changeover switches 7a and 7b
Regarding the detection of moving images for controlling the switching operation, since the phases of the carrier chromaticity signal components are the same between color image signals separated by two frame periods, the color images delayed by two frames are By taking the difference between signals, it is possible to detect a moving image by extracting only the difference based on the movement of the image, but between color image signals that are separated by one frame period, the phase of the carrier chromaticity signal are inverted with respect to each other, therefore, simply finding the difference between them will result in a mixed detection of a difference based on the movement of the image and a difference based on the phase difference of the carrier chromaticity signal. Therefore, in the configuration example shown in FIG. 5, the difference signal obtained from the subtracter is supplied to the low-pass filter 1 as a preprocessing for motion image detection in the motion detection unit 6, and the carrier chromaticity signal component is removed. Only the luminance signal difference component of the filtered output is supplied to the motion detection unit 6 to detect a moving image only with respect to the difference signal component based on the motion of the image, and the delay circuit 9 prevents malfunctions due to noise. prevent.

As is clear from the above description, according to the present invention, when separating and extracting the luminance signal component and the chromaticity signal component of a color image signal, a comb structure using a frame delay element is applied to a still image. A filter separates and extracts component spectra, and for moving images, at least a conventional filter configured without using a frame delay element separates and extracts component spectra or frequency. Based on the process of separating signal components, it is possible to significantly reduce the degradation in image quality caused by resolution degradation that conventionally occurs.Furthermore, since it performs slow switching between still and moving images, it prevents malfunctions due to noise, etc. can do.

In particular, if a line-period comb filter constructed using a one-line delay line is used as a filter for moving images, there will be little loss of resolution even for moving images, and it will be possible to simply band-pass filter the color image signal. If the chromaticity signal components of a moving image can be extracted by simply supplying the chromaticity signal components to a device, a luminance/chromaticity signal separation device with excellent performance can be obtained with a relatively simple configuration.

[Brief explanation of the drawing]

1A and 1B are block diagrams showing the configuration of a conventional luminance/chromaticity signal separation device, FIG. 2 is a block diagram showing another configuration, and FIG.
The figure is a block diagram showing a configuration example of the luminance/chromaticity signal separation device of the present invention, FIG. 4 is a block diagram showing another configuration example, and FIG. 5 is a block diagram showing still another configuration example. 6A and 6B are characteristic curve diagrams showing examples of frequency characteristics of a comb filter with a two-frame delay and a one-frame delay, respectively. 1...Low pass filter, 2...Band pass filter, 3...1 line delay line, 4...Phase modulator, 5...
...1 frame delay element, 6...Motion detection section, 7,
7a, 7b...changeover switch, 8...conventional circuit shown in FIG. 1 or FIG. 2, 9...delayed circuit.

Claims (1)

[Claims] 1. A first comb filter circuit that includes at least one frame delay element and separates a luminance signal component and a chromaticity signal component of a color image signal by combining input and output image signals of the frame delay element;
a second comb filter circuit that includes at least a line delay line and separates a luminance signal component and a chromaticity signal component of a color image signal by a combination of input and output image signals of the line delay line; It has a motion detection section that detects the movement of the image signal based on the difference between the input and output image signals, and a switching means that responds to the motion detection output of the motion detection section, and the motion detection output of the motion detection section is When the predetermined threshold value is not exceeded, the luminance signal component and the chromaticity signal component separated by the first comb filter circuit are extracted via the switching means, and when the motion detection output exceeds the predetermined threshold value, the switching means In the luminance/chromaticity signal separation device that extracts the luminance signal component and chromaticity signal component separated by the second comb filter circuit through The switching means operates so as to extract the luminance signal component and the chromaticity signal component separated by the first comb filter circuit when the motion detection output exceeds the second threshold value. A luminance/chromaticity signal separation device, characterized in that the switching means operates to take out the luminance signal component and the chromaticity signal component separated by the second comb filter circuit.