JP2699582B2 - Contour corrector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a next-generation television system, EDTV (Extruded D).
The present invention relates to a contour corrector for improving sharpness of an image suitable for an efinition television (extended definition television) system.

2. Description of the Related Art As a conventional contour corrector, for example, there is a configuration as shown in FIG. In FIG. 5, 1 is an input terminal to which a luminance signal is input, 2 is a contour signal forming circuit for producing horizontal and vertical contour signals, and 3 is a level detector for adjusting the amplitude of the contour signal according to the level of the input luminance signal. A pendant circuit, 4 is a noise slice circuit, 5 is an adder for adding a luminance signal and a contour signal, 6 and 7 are delay lines for timing adjustment, and 8 is an output terminal.

The operation of the contour corrector configured as described above will be described with reference to FIGS.

FIG. 6 is a block diagram showing the internal configuration of the contour signal forming circuit 2 of FIG. 5, wherein 15 is a 1H (one horizontal scanning time) delay circuit, 16 is a t time delay circuit, and 17 is a multiple of the number in the circle. amplifier,
18 is an adder. The operation of each section will be described. In the vertical contour signal section, assuming that the luminance signal shown in FIG. 7 (a) is input during the 1V (field) period, the output of each 1H delay circuit 15 is shown in FIG. , (C), and the output signal of each amplifier 17 is added by each adder 18 to obtain a vertical contour signal shown in FIG. 7 (d). Similarly, in the horizontal contour signal section, assuming that the luminance signal shown in FIG. 7 (e) is input during the 1H period, the output of each t-time delay circuit 16 is shown in FIGS. 7 (f) and 7 (g). Signal
The output signal of each amplifier 17 is added by each adder 18 to obtain a horizontal contour signal shown in FIG. 7 (h). The two-dimensional contour signal is obtained by adding the horizontal contour signal and the vertical contour signal thus obtained by the adder 18. The frequency characteristics of the horizontal and vertical contour signal portions are as shown in FIGS. 8 (a) and 8 (b), respectively.

The contour signal generated by the contour signal forming circuit 2 as described above passes through the level dependent circuit 3 and the noise slicing circuit 4 and passes through the 1H delay luminance signal time-adjusted by the adder 5 and the delay lines 6 and 7. And output terminal 8
A luminance signal with more contour correction can be obtained.

The level dependent circuit 3 is, for example, shown in FIGS.
As shown in FIG. 9C, when the input luminance signal is a staircase wave shown in FIG. 9A, an outline signal as shown in FIG. 9B is obtained from the outline signal forming circuit 2. The signal is gain-controlled as shown in FIG. 9 (c). This is because the contour signal forming circuit 2 also amplifies high-frequency noise with a so-called high-pass filter, so that the gain of the contour signal is controlled in accordance with the level of the luminance signal in order to reduce noise in dark areas.

In addition, the noise slice circuit 4 is shown in FIG.
As shown in (b), by emphasizing the contour, high-frequency noise in a flat portion of the signal (with little change in brightness) is sliced and removed.

As described above, in the level dependent circuit 3 and the noise slice circuit 4, the S / N ratio is prevented from deteriorating by emphasizing the contour. Then, a good luminance signal having a good S / N ratio is obtained from the output terminal 8.

In the above, the contour signal is formed from the luminance signal. Alternatively, the contour signal is formed only from the green signal, and this signal is defined as R signal.
(Red), G (Green), B (Blue) Mix in each process amplifier, so-called OUT OF GREE
N) method (for example, "Contour Compensator for Plumbicon Color Camera" by Hiroshi Marubayashi et al., 44.6.26, No. 14
Television system circuit research committee material). 『OUT OF G
The “REEN” method is widely used in cameras using an image pickup tube due to registration, circuit scale, and the like.

On the other hand, in recent years, BTA (Broadcasting Technology
Association: The next-generation television system (EDTV system), which is being studied and promoted by the Broadcasting Technology Association, is one of the items to improve the picture quality problem of the current television system due to the high brightness of the picture tube. There is an improvement (S1) of the deterioration phenomenon of the luminance detail (sharpness) in the dark part of the image due to the increase of the gamma value and the leakage light.

As an implementation technique of S1, there is a so-called adaptive emphasis in which a high-frequency component of a luminance signal is also compensated on a transmission side so that a detail component (high-frequency component) increases in a dark part by a compensation circuit.

FIG. 11 is a block diagram of a configuration example of an adaptive emphasis circuit.

In FIG. 11, 19 is an input terminal to which a luminance signal is input, 20 is an emphasis circuit that creates a compensation signal from the input luminance signal, 21 is a low-pass filter, 22 is an inverting amplifier, 23 is a fixed attenuator, and 24 is a multiplication. , 25 is an adder, and 26 is an output terminal.

FIG. 12 shows a frequency characteristic diagram (emphasis curve) of the emphasis circuit 20.

The operation of the S1 compensation circuit configured as described above
This will be described with reference to FIGS.

If the luminance signal is, for example, an input as shown in FIG. 13 (a), the output of the low-pass filter 21 becomes as shown in FIG. 13 (b), and the output of the inverting amplifier 22 becomes as shown in FIG. 13 (c). Become like This output is attenuated at a fixed rate by the fixed attenuator 23 and multiplied by the compensation signal of the emphasis circuit 20 and the multiplier 24, and as shown in FIG.
The compensation amount is controlled according to the level amounts of ▼ and ▲ ▼. In other words, the adaptive emphasis circuit converts the amplitude of the emphasis signal into a low-pass filter
The signal monotonically increases and decreases in the opposite direction to the direction of the change in accordance with the signal (signal information indicating the brightness of the image) obtained by 21.

The compensation amount is based on an emphasis curve obtained using a time constant of 100 nsec.When the amplitude of the low frequency component of the luminance signal is 0%, the maximum is 3 dB minimum 1 dB at 4 MHz, the maximum 2 dB minimum 1 dB at 2 MHz, When the amplitude of the low frequency component is 100%, it is recommended to set it to 0 dB.

The adaptive emphasis circuit as described above compensates for the deterioration of the detail in the dark part of the image, and provides a sharper image in the dark part as compared with the related art.

However, in the configuration of the adaptive emphasis circuit as described above, sharpness in a dark portion of an image is obtained, and
Even if the S / N ratio in the transmission system can be improved by performing de-emphasis of the luminance signal on the receiver side, the conventional contour correction is required to emphasize the high frequency components in the dark part of the image. In order to suppress the S / N ratio degradation in the dark part of the image with the device, the contour signal, that is, the gain of the high frequency component is controlled according to the level of the luminance signal, and the darker the part, the smaller the gain is. This is inconsistent, and there is a problem in the camera output signal that the S / N ratio in the dark part is deteriorated. For example, the first
The compensation as shown in FIG. 14 (b) is performed on the luminance signal of FIG. 4 (a).

In view of the foregoing, an object of the present invention is to provide a contour corrector that suppresses an increase in circuit scale and does not cause deterioration of the S / N ratio even when an adaptive emphasis operation for a next-generation TV system is incorporated. .

Means for Solving the Problems In order to achieve the above object, the present invention provides a first and second contour signal formation for forming desired first and second contour signals from a luminance signal or a signal similar to the luminance signal. A low-pass filter to which the luminance signal or a signal similar to the luminance signal is input and that limits a band to a predetermined frequency; an inverting amplifier circuit that inverts and amplifies an output signal of the low-pass filter; A gain control circuit to which a contour signal is input and for controlling a gain of the second contour signal by an output signal of the inverting amplifier circuit; and a coring circuit for clipping a noise level of an output signal of the gain control circuit at a coring level. An addition circuit for adding an output signal of the coring circuit and the first contour signal; and an output signal of the low-pass filter or A data conversion circuit that converts an output signal of the inverting amplifier circuit and outputs the output signal as coring level data to the coring circuit, and the output signal of the low-pass filter or the output signal of the inverting amplifier circuit. This is a contour corrector that controls the coring level.

Effect of the Invention With the above-described configuration, the present invention provides the same signal as the signal for controlling the adaptive emphasis effect (inverted signal of a low-pass filtered luminance signal) or its inverted signal (low-pass filter of the luminance signal). Control the coring level. In addition, a noise component emphasized by the adaptive emphasis is clipped by setting a coring level to a darker portion of the luminance signal by using a data conversion circuit to set the coring level higher.

First Embodiment FIG. 1 is a block diagram showing a configuration of a contour corrector according to a first embodiment of the present invention.

In FIG. 1, 1 is an input terminal to which a luminance signal is input, 2 is a first contour signal forming circuit for generating a first contour signal which is a horizontal and vertical contour signal, 3 is a level dependent circuit, Is a noise slice circuit, 5 is an adder, 8 is an output terminal, and 9 is a contour signal for adaptive emphasis.
A contour control circuit for controlling the gain of the second contour signal; 11, a coring circuit for clipping noise of the second contour signal; and 12, a low-pass signal. A filter, 13 is an inverting amplifier, and 14 is a data conversion circuit that creates coring level data from the output of the inverting amplifier 13.

Each circuit of this embodiment is constituted by a digital circuit, and the components 1 to 5 and 8 are the same as those of the conventional example shown in FIG.

In the present embodiment, there are two contour signal forming circuits of the second contour signal forming circuit 9 of the first contour signal forming circuit 2 because the first contour signal for increasing the sharpness of a normal image is generated. The emphasis frequency of the first contour signal forming circuit 2 is different depending on the user's preference, but the emphasis frequency of the second contour signal forming circuit 9 for producing the second contour signal for adaptive emphasis is S / S. For example, as described in the conventional example, a maximum of 4 MHz is recommended in relation to the N ratio, appearance, and the like, in order to show that the emphasis frequencies of the two contour signal forming circuits are different. However, in the following description, for convenience of explanation, it is assumed that the emphasis frequencies of the two contour signals are substantially the same, and a similar contour signal can be generated for the same luminance signal level change.

The operation of the contour corrector of the present embodiment configured as described above will be described with reference to FIGS. 2 (a) to 2 (i).

2 (a) to 2 (h) show the respective parts (a) to 1 in FIG.
It is a signal waveform diagram of (h). FIG. 2 (i) is an input / output characteristic diagram of the data conversion circuit 14. Incidentally, adaptive emphasis is assumed to act on the time t ₁ following the luminance signal level.

In FIG. 1, assuming that a luminance signal having a horizontal change as shown in FIG.
In the same manner as in the conventional example shown in the drawing, the first contour signal generated by the first contour signal forming circuit 2 is compressed by the level dependent circuit 3 in amplitude corresponding to the low-level portion of the luminance signal. Then, noise components in the low-level portion, that is, the dark portion are also suppressed. Further, the noise slice circuit 4
As a result, a noise component superimposed on a flat portion of the signal (a portion with little change in brightness) is sliced, and a contour signal shown in FIG. 2B is obtained.

The second contour signal forming circuit 9, the gain control circuit 10, the low-pass filter 12, and the inverting amplifier 13 constitute a circuit having the same function as the adaptive emphasis circuit of FIG. ing. That is, the luminance signal is converted into a luminance signal as shown in FIG. 2C by the low-pass filter 12, and this signal becomes a control signal shown in FIG. 2D by the inverting amplifier 13. On the other hand, in the second contour signal forming circuit 9, a second contour signal which is a compensation signal of a desired emphasis characteristic is generated. The gain of the second contour signal is adaptively controlled by the gain control circuit 10 in accordance with the output signal (d) of the inverting amplifier 13, whereby a contour signal as shown in FIG. 2 (e) is obtained. If this contour signal is added to the luminance signal, the sharpness in the dark part is increased and the purpose of adaptive emphasis is achieved, but as shown in FIG. 2 (e), noise is also emphasized and the S / N ratio is degraded. I do.

Here, in this embodiment, the input / output characteristics of the data conversion circuit 14 are as shown in FIG. 2 (i). That is, the output signal level of the inverting amplifier 13 when the input level is time t1 is
M1 and below (corresponding to the luminance level without adaptive emphasis) is 0, and from M1 to MAX (corresponding to the luminance signal level with adaptive emphasis) monotonically increases,
Convert to data up to CL1 level. Therefore, when the signal shown in FIG. 2D is input to the data conversion circuit 14 having the input / output characteristics, coring level data as shown in FIG. 2F is obtained. This coring level data is used in the coring circuit 11.

The coring circuit has exactly the same operation and function as the conventional noise slice circuit except for the name, and clips the ± (plus or minus) signal level set by the coring level. Circuit. Accordingly, the contour signal shown in FIG. 2 (e) input to the coring circuit 11 has a coring level (equivalently as shown by a dotted line in FIG. 2 (e)) having the characteristic shown in FIG. 2 (f). 2), a contour signal from which noise components have been removed is obtained as shown in FIG. 2 (g). In other words, just as adaptive emphasis increases the contour signal monotonically, contrary to the change in brightness, the coring level also increases monotonically, contrary to the change in brightness.
Noise components that increase due to adaptive emphasis are removed.

The contour signal for adaptive emphasis (FIG. 2 (g)) from which the noise component has been removed and the conventional contour signal (FIG. 2 (b)) are added by the adder 5, and FIG. 2 (h). Are obtained from the output terminal 8.

As described above, with the contour corrector of the present embodiment, it is possible to obtain a contour signal that has an adaptive emphasis effect and does not deteriorate the S / N ratio.

FIG. 3 is a block diagram showing a configuration of a contour corrector according to a second embodiment of the present invention. Each circuit is constituted by a digital circuit as in the first embodiment.

In FIG. 3, 1 is an input terminal to which a luminance signal is input, 2 is a first contour signal forming circuit for producing a first contour signal which is a horizontal and vertical contour signal, 3 is a level dependent circuit, 5 Is an adder, 8 is an output terminal, 9 is a second contour signal forming circuit for producing a second contour signal which is a contour signal for adaptive emphasis, and 10 is a gain control circuit for controlling the gain of the second contour signal. Reference numeral 11 denotes a coring circuit for clipping noise of the contour signal, 12 denotes a low-pass filter, 13 denotes an inverting amplifier, and 14 denotes a data conversion circuit that creates coring level data from the output of the inverting amplifier.

The difference from the first embodiment is that the coring circuit 11 is disposed after the adder 5 in FIG. 1 so that the noise slice circuit 4 is not required. The emphasis frequency of the contour signal is almost the same as in the first embodiment.

The operation of the contour corrector of the second embodiment configured as described above will be described with reference to FIGS. 2 (a), 2 (d) and 2 (e) and FIGS. 4 (a) to 4 (e). .

4 (a) to 4 (d) show the respective parts (a) to
It is a signal waveform diagram of (d). FIG. 4 (e) is an input / output characteristic diagram of the data conversion circuit 14.

The input terminal 1 is connected to the input terminal 1 in the same manner as in the embodiment of FIG.
When the luminance signal of the horizontal change shown in FIG. 4 is input, the first contour signal is formed by the first contour signal forming circuit 2, and the contour signal shown in FIG. can get. In this case, since the contour signal corresponding to the low-level part (dark part) of the luminance signal is compressed,
The superimposed noise component is suppressed as compared to the noise component superimposed on the contour signal corresponding to the high-level portion (bright portion) of the luminance signal.

On the other hand, the contour signal for adaptive emphasis shown in FIG. 2E is obtained from the gain control circuit 10 as described in the first embodiment. This contour signal and the contour signal shown in FIG. 4A are added by the adder 5, and the contour signal shown in FIG. 4B is obtained. The magnitude of the noise to be superimposed on the contour signal after the addition differs between the contour signals corresponding to the bright part and the dark part of the luminance signal due to the gain setting of the gain control circuit 10. In the case of this example, the noise component superimposed on the contour signal corresponding to the dark part of the luminance signal is larger than the noise component superimposed on the contour signal corresponding to the bright part.

Here, the input / output characteristics of the data conversion circuit 14 are as shown in FIG. The difference from the input / output characteristics of the data conversion circuit 14 in the case of the first embodiment (FIG. 2 (i)) is that the input level is a constant level of CL3 when the input level is less than M1, and monotonically increases from M1 to MAX. , The characteristic is that the data is converted into data up to L2. In other words, CL3 is constant at the luminance signal level where adaptive emphasis does not work,
At the luminance signal level at which the adaptive emphasis operates, the characteristic monotonically increases as the emphasis operation increases.

When the signal shown in FIG. 2 (d) is input to the data conversion circuit 14 having the input / output characteristics, the coring level data which becomes larger as the dark portion of the luminance signal as shown in FIG. The characteristics of the obtained coring level data are changed according to the ratio of the level of the noise superimposed on the contour signal corresponding to the bright portion and the dark portion of the luminance signal.

Therefore, in the coring circuit 11, the contour signal shown in FIG. 4B is changed to the coring level (maximum ± CL) shown in FIG.
(Equivalent to the characteristic shown by the dotted line in FIG. 4 (b) in FIG. 4)
As in the first embodiment, the noise due to the adaptive emphasis function can be removed, and the noise due to the normal contour signal without the adaptive emphasis function can also be removed, as shown in FIG. 4 (d). Such a contour signal is obtained from the output terminal 8.

As described above, in the second embodiment, the noise slicing circuit can be eliminated, an adaptive emphasis effect can be obtained, and a contour signal without deterioration in the S / N ratio can be obtained.

In the first and second embodiments described above, the case of a luminance signal having only a change in the horizontal direction has been described. However, it is needless to say that the same description can be given in consideration of a change in the vertical direction.

It should be noted that processes such as contour signal formation, data conversion, clipping, and the like are specialty of digital circuits, and it goes without saying that the first and second embodiments are easily configured.

In the first and second embodiments, even if the input of the data conversion circuit 14 uses the output of the low-pass filter 12 instead of the output of the inverting amplifier 13, the same effect can be obtained by changing the conversion characteristics. It goes without saying that it can be obtained.

Further, the first contour signal forming circuit 2 and the second contour signal forming circuit 9 may be formed of the same contour signal forming circuit, and may output two systems of contour signals having a desired emphasis frequency. Needless to say.

Further, a second contour signal forming circuit 9 for forming a second contour signal for adaptive emphasis, and a low-pass filter
The twelve frequency characteristics may be appropriate characteristics other than those recommended by the BTA, and it goes without saying that there is no effect on achieving the object of the present invention.

Effect of the Invention As described above, according to the present invention, it is possible to obtain an adaptive emphasis effect, and to adaptively control the coring level of the coring circuit inversely with the increase or decrease of the luminance signal level. Noise that increases due to dynamic emphasis can be removed, and contour correction with a good S / N ratio suitable for the next-generation TV system can be performed, and the practical effect is large.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a contour corrector according to a first embodiment of the present invention, and FIGS. 2 (a) to 2 (h) show signals of respective parts (a) to (h) of the first embodiment. Waveform diagram, FIG. 2 (i)
Is an input / output characteristic diagram of the data conversion circuit 14 in the first embodiment,
FIG. 3 is a block diagram showing a configuration of a contour corrector according to a second embodiment of the present invention, and FIGS. 4 (a) to 4 (d) show signals of respective parts (a) to (d) of the second embodiment. Waveform diagram, FIG. 4 (e)
Is an input / output characteristic diagram of the data conversion circuit 14 in the second embodiment,
FIG. 5 is a block diagram showing the configuration of a conventional contour corrector, FIG. 6 is a block diagram showing the internal configuration of a contour signal contour signal forming circuit in the conventional contour corrector, and FIGS.
(H) is a waveform diagram for explaining the operation of the contour signal forming circuit, FIGS. 8 (a) and (b) are frequency characteristic diagrams of the horizontal and vertical contour signal portions, and FIGS. 9 (a) to (c). Is a waveform diagram for explaining the operation of the level dependent circuit, FIGS. 10 (a) and (b) are waveform diagrams for explaining the operation of the noise slice circuit, and FIG. 11 is a configuration of the adaptive emphasis circuit. FIG. 12 is a block diagram showing an example, FIG. 12 is a frequency characteristic diagram of the emphasis circuit, FIGS. 13 (a) to 13 (d) are waveform diagrams for explaining the operation of the adaptive emphasis circuit, FIGS.
(B) is a waveform diagram showing an example of adaptive emphasis. 1 ... input terminal, 2 ... contour signal forming circuit a, 3 ... level dependent circuit, 4 ... noise slice circuit, 5
... adder, 8 ... output terminal, 9 ... contour signal forming circuit b, 10 ... gain control circuit, 11 ... coring circuit, 12 ... low-pass filter, 13 ... inverting amplifier, 14 ... ... Data conversion circuit.

Claims (2)

(57) [Claims] 1. A first and a second signal for forming desired first and second contour signals from a luminance signal or a signal similar to the luminance signal.
A contour signal forming circuit, a low-pass filter to which the luminance signal or a signal similar to the luminance signal is input, and that limits a band to a predetermined frequency; and an inverting amplifier circuit that inverts and amplifies an output signal of the low-pass filter. A gain control circuit to which the second contour signal is input, the gain control circuit controlling a gain of the second contour signal by an output signal of the inverting amplifier circuit; and a noise level of an output signal of the gain control circuit at a coring level. A coring circuit for clipping, an adding circuit for adding an output signal of the coring circuit and the first contour signal, and converting an output signal of the low-pass filter or an output signal of the inverting amplifier circuit, A data conversion circuit that outputs coring level data to a coring circuit; A contour corrector for controlling the coring level according to an output signal or an output signal of the inverting amplifier circuit. 2. A method according to claim 1, wherein said first and second contour signals are formed from a luminance signal or a signal similar to said luminance signal.
A contour signal forming circuit, a low-pass filter to which the luminance signal or a signal similar to the luminance signal is input, and that limits a band to a predetermined frequency; and an inverting amplifier circuit that inverts and amplifies an output signal of the low-pass filter. A gain control circuit to which the second contour signal is input, the gain control circuit controlling a gain of the second contour signal by an output signal of the inverting amplifier circuit; and an output signal of the gain control circuit and the first contour signal. And a coring circuit that clips a noise level of an output signal of the adding circuit at a coring level, and converts an output signal of the low-pass filter or an output signal of the inverting amplifier circuit, and A data conversion circuit that outputs the data as coring level data to a ring circuit, wherein an output signal of the low-pass filter is provided. A contour corrector for controlling the coring level in accordance with a signal or an output signal of the inverting amplifier circuit.