JP3014102B2 - Contour correction circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction circuit for correcting a contour portion of a video signal to enhance sharpness of the video.

[Conventional technology]

2. Description of the Related Art Conventionally, in order to clearly display a video signal such as a television signal, a television receiver or the like has performed contour correction for enhancing a contour portion of the video signal. As a circuit for performing contour correction, for example, Japanese Patent Application Laid-Open No. Sho 64-5168
And various forms as described in JP-A-63-311875 and JP-A-63-310279.

[Problems to be solved by the invention]

The prior art described above does not consider noise and the like, and has problems such as a reduction in S / N with contour correction. In addition, no consideration has been given to the visual characteristics of characteristics such as the characteristics of the contour correction, and there has been a problem that the natural feeling is lost by this correction.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a contour correction circuit that does not cause a reduction in S / N due to the influence of noise or the like and that improves sharpness suitable for visual characteristics without impairing natural feeling.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a function of extracting a contour region of an image, and performs a contour correction operation on a contour portion of a video signal and a region in the vicinity thereof.

In the contour correction, a function of adding an edge signal subjected to non-linear processing is provided, so that a so-called black fringe image is displayed.

[Action]

According to the present invention, the function of extracting a contour region of an image performs a contour correction operation only in the vicinity of the contour region. Since the contour correction operates so as to emphasize the high-frequency component of the video signal, the sharpness of the contour portion is improved by edge emphasis. On the other hand, since the contour correction operation is not performed on the flat portion of the image, the noise component included in the video signal remains at the original level in this region without being emphasized. That is, since edge enhancement is performed only in the vicinity of the contour region, noise in a flat portion of an image that is visually conspicuous does not increase, and a problem such as a reduction in S / N can be solved.

As an edge signal added in the contour correction, for example, a signal obtained by performing a nonlinear process of extending an amplitude value several times with respect to a negative level signal of a high frequency component of a video signal is used. With this, the contour-corrected video signal becomes a signal in which the undershoot portion is further emphasized, and an image is displayed with a so-called black border, so that characteristics matching the visual characteristics can be realized without impairing the natural feeling.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. This is an overall configuration diagram of the present invention.

Input signal S is input to the HPF circuit 1 extracts the high frequency components as the signal S _H. The contour extraction circuit 2 uses the _SH signal to determine the contour of the image and its neighboring areas as contour information.
Detected as EDT. The nonlinear processing circuit 3 calculates the contour information E
Follow the DT connexion, row Natsuta signal a predetermined non-linear processing to the signal S _H
Generates S _H ′. The S _H ′ signal is added to the signal _SD delayed by the delay circuit 4 in the addition circuit 5.
The signal S _ENH subjected to the contour correction is obtained.

Hereinafter, the configuration and operation of each unit will be described in detail based on embodiments.

2 and 3 show one embodiment of the HPF circuit 1. FIG. FIG. 2 shows an example of a horizontal one-dimensional high-pass filter, in which a signal sequence delayed by one pixel by a one-pixel delay circuit 6 is added to a signal weighting circuit 7 to obtain a signal sequence of −1/4, 1/2, −1/4. those weighted coefficients, extracts a high-frequency component S _H by adding by the adding circuit 8.

On the other hand, FIG. 3 shows an example of a horizontal and vertical two-dimensional high-pass filter, which includes a one-pixel delay circuit 6, a coefficient weighting circuit 7,
And a vertical LPF circuit composed of a 1H delay circuit 9, a coefficient weighting circuit 7, and an addition circuit 8 are cascaded, and a subtraction circuit is used to subtract a signal from the signal whose delay is adjusted by the delay circuit 10. The high frequency component _SH is extracted by subtracting in step 11.

Next, one embodiment of the contour extraction circuit 2 is shown in FIG.
Signal S _H to the previously extracted by HPF circuit in absolute value quantization circuit 12, generates an absolute value quantized signal D _H. 5 and 6 show examples of the characteristics of this quantization circuit. In the example of Figure 5 is binary quantized amplitude value of the input signal S _H is -Δ _H ~Δ
D _H = 0 during _H , and D _H = 1 in other regions, such as D _H = 1.
Value. Also, FIG. 6 is an example of a multi-level quantization, S between the amplitude values - [delta _H ～Deruta _H of _H is D _H = 0, in other areas,
Quantize to D _H1 , D _H2 ,... D _Hm according to the amplitude value.

The operation of the contour extraction circuit is the same for both the binary quantization and the multi-level quantization, and hence the operation will be described hereinafter for the case of binary quantization.

The smoothing circuit 13 removes a noise component from the _DH signal and smoothes the contour area. Specifically, smoothing processing is performed by removing isolated points, supplementing discontinuous points, and the like.
An example of this operation is shown in FIGS. 7 (a) and (b).

The signal sequence _DH includes a noise component in addition to the original contour component, as shown in FIG. Of these, the noise component is generated due to random noise, and thus appears as an isolated point in the _DH signal sequence. Therefore, as shown in FIG. 1B, noise components are removed by removing such isolated points. On the other hand, an area where 1s are continuous corresponds to a contour area. Therefore, when a discontinuous point occurs in these areas (corresponding to 0), 1 is supplemented as shown in FIG. The discontinuous points are removed and smoothing is performed. As a result, the output signal D _AV of the smoothing circuit 13 is obtained as a signal sequence as shown in FIG.

Further, the contour discriminating circuit 14 generates contour information EDT in which a region before and after the contour component is enlarged as shown in FIG. 7C based on the _DAV signal.

The absolute value quantization circuit 12, the smoothing circuit 13, and the contour identification circuit 14 can be easily realized by using a ROM or the like.

Next, an embodiment of the nonlinear processing circuit 3 is shown in FIG. 8, and examples of input / output characteristics thereof are shown in FIGS. 9 and 10. These non-linear processes can be realized by using the input signal S _H and the contour information EDT as an address signal sequence of the ROM circuit 15 and the corresponding characteristics as the output signal S _H ′.

Now, the outline information EDT = 1, i.e., for the region corresponding to the contour of the image, when the high frequency components S _H is negative level, as shown in FIG. 10, the gain than the positive level Is set to be several times higher, and a signal at a negative level generates a signal S _H ′ obtained by subjecting a signal at a positive level to amplitude expansion by several times. This S _H 'signal is added to the original signal as an edge signal.

On the other hand, EDT = 0, i.e., for the region corresponding to the flat portion of the image, as shown in FIG. 9, - [delta _N, the suppression of the output signal S _H 'is for example zero within the ～Deruta _N I do. In addition,
The value of delta _N is preferably than the noise level that normally occurs is set to large. In the but connexion, flat portion of the EDT = 0, usually because S _H 'signal becomes zero, due to the operation of the contour correction connexion, is no problem when was the noise is increased in this region.

As described above, according to the present invention, it is possible to realize contour correction suitable for visual characteristics without deteriorating S / N and spoiling natural feeling.

Next, another embodiment of the present invention is shown in FIG. In this embodiment, the input signal S
Of determining the amplitude level S _A, in accordance connexion non-linear processing circuit 17 to the S _A, for example, performs non-linear processing characteristic as shown in FIG. 12, to generate an edge signal S _H 'to be added.

According to this embodiment, finer contour correction can be realized.

Now, in the embodiments so far, based on the high frequency components S _H signal extracted by HPF circuit 1 performs signal processing of the configuration of detecting the contour of the image, and Zutsu simplification of the circuit. On the other hand, the characteristics of the contour extraction are defined to some extent by the characteristics of the HPF circuit 1.

For this reason, a configuration in which a contour area is directly detected from the input signal S is also conceivable. This embodiment is shown in FIG. 13 and FIG. For the contour extraction, it is also possible to use a technique performed in pattern recognition or the like. Since the operation and the like are almost the same as those in the previous case, the description thereof is omitted.

Furthermore, it is also possible to combine the contour correction circuit according to the present invention with a non-linear circuit to improve the characteristic of the intermediate luminance level of the video signal and to reproduce a soft image. This embodiment is shown in FIG. 15, and one characteristic of the nonlinear circuit 20 is shown in FIG.

In the embodiment described above, the input signal S can be of various types such as a luminance signal, three primary color signals of red, green, and blue, or a color difference signal.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, since it becomes possible to aim at sharpness improvement without a problem, such as a fall of S / N, and spoiling a natural feeling, improvement in image quality, such as a television image,
It has a great effect on high quality.

The present invention can be applied to any video signal of the current interlaced scanning system, a video signal converted to a progressive scanning system by signal processing such as scanning line interpolation, or a video signal of the progressive scanning system. That is clear.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a circuit according to an embodiment of the present invention, FIGS. 2 and 3 are block diagrams showing an example of the configuration of an HPF circuit, and FIG. 4 is an example of a configuration of a contour extraction circuit. 5 to 7 are characteristic diagrams of the circuit shown in FIG. 4, FIG. 8 is a block diagram showing an example of the configuration of a nonlinear processing circuit, and FIGS. 9 and 10 are circuit diagrams of FIG. Characteristic chart of Fig. 11, Fig. 13
FIG. 14 is a block diagram showing the overall configuration of a circuit according to another embodiment of the present invention, FIG. 12 is a characteristic diagram of the nonlinear processing circuit of FIG. 11, and FIG. 15 is a non-linear circuit in the circuit of the present invention. And FIG. 16 is a characteristic diagram of a non-linear circuit. 1 ... HPF circuit, 2 ... Contour extraction circuit, 3 ... Non-linear processing circuit, 4 ... Delay circuit, 5 ... Addition circuit, 6 ... 1 pixel delay circuit, 7 ... Coefficient weighting circuit, 8 ... Adder circuit, 9
... 1H delay circuit, 10 ... delay circuit, 11 ... subtraction circuit, 12
…… Absolute value quantization circuit, 13 …… Smoothing circuit, 14 …… Contour identification circuit, 15… ROM circuit, 16 …… Amplitude level judgment circuit, 17 …… Non-linear processing circuit, 18 …… Contour extraction circuit, 19 ...
... A contour correction circuit according to the present invention, 20 ... A non-linear circuit.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-32278 (JP, A) JP-A-65-1168 (JP, A) JP-A-63-311875 (JP, A) 111259 (JP, U) Shokai Sho 63-7860 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/14-5/217

Claims (2)

(57) [Claims] A means for extracting a high frequency component of an image signal;
Means for detecting a contour region and a flat region of the image signal, wherein an edge signal in which the low amplitude level of the high frequency component is suppressed is added to the image signal in the flat region, and a negative level of the high frequency component is amplitude-converted in the contour region. A contour correction circuit for adding an expanded edge signal to the image signal and outputting the added image signal. 2. The contour correction circuit according to claim 1, wherein said detecting means detects a contour area and a flat area from said high frequency component.