JPH0686100A - Picture quality controller - Google Patents

Abstract

PURPOSE:To effectively control the picture quality with respect to the input signals of different bands of a video equipment. CONSTITUTION:A band detector 12 detects the band of an input video signal and identifies a TV signal of an NTSC, an DETV signal and an HDTV signal respectively. A control circuit 24 outputs a control signal to a contour emphasizing circuit 25 based on the type of the video signal. The circuit 25 selects the delay time based on the type of the video signal and generates a luminance signal having its amplitude which changes much at the signal rise and fall parts through each delay circuit and the subtraction and addition circuits. Thus the luminance signal having its contour emphasized is obtained through an output terminal 26 according to the type of each video signal. Then the picture quality of images can be effectively controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image quality adjusting device for adjusting the image quality of an image in video equipment.

[0002]

2. Description of the Related Art In some video equipment such as a television receiver, the outline of an image is emphasized in order to improve the sharpness of the image. As one of such contour emphasis methods, there is a brightness modulation method in which a secondary differential signal is created from a brightness signal of a video signal, and this signal is superimposed on the original brightness signal to emphasize the edge portion. Another edge enhancement method is a velocity modulation method in which the amount of electron beam in the cathode ray tube is kept constant and the horizontal scanning speed is changed at the portion where the luminance signal of the video signal changes. Both types are currently used in television receivers.

An example of a conventional image quality adjusting device in the brightness modulation system will be described. FIG. 7 is a block diagram showing a configuration example of a conventional image quality adjusting device, and FIG. 8 is a signal waveform diagram showing its operation. In FIG. 7, an input terminal 1 is a terminal to which the luminance component of the video signal is input, and is connected to the first delay circuit 2 and the first subtractor 3. The output of the delay circuit 2 is given to the second delay circuit 4, the second subtractor 5, and the first adder 6, respectively. The delay circuits 2 and 4 are circuits that delay the video signal for a predetermined time. The subtractor 3 receives the video signal b output from the delay circuit 2 from the video signal a input to the input terminal 1.
Is a circuit for subtracting. The subtractor 5 is a circuit that subtracts the video signal output from the delay circuit 4 from the video signal b from the delay circuit 2.

The second adder 7 is a circuit for adding the signals c and d output from the subtracters 3 and 5, respectively. Adder 6
Is a circuit for adding the video signal b of the delay circuit 2 and the output signal e of the adder 7, and outputs the addition output f to a display unit (not shown).

The operation of the image quality adjusting device having such a configuration will be described with reference to FIG. When a pulsed luminance signal as shown in FIG. 8A is input to the input terminal 1, the delay circuit 2 outputs the luminance signal b delayed by the time τ ₁ as shown in FIG. 8B. The subtractor 3 subtracts the signal a from the signal b to generate a signal c as shown in FIG. The delay circuit 4 also delays the signal b by the time τ ₁ . The subtractor 5 subtracts the signal output from the delay circuit 4 from the signal b.
Therefore, the subtractor 5 outputs an edge pulse delayed by a time τ ₁ from the rising and falling times of the input video signal a as shown in FIG. 8 (d).

Next, the adder 7 adds the signal c and the signal d,
A bipolar pulse signal e as shown in FIG. 8E is generated. The adder 6 adds the signal e and the signal b to generate a signal f as shown in FIG. The signal f becomes a luminance signal in which the amplitudes at the rising edge and the falling edge are increased as compared with the input signal a and the level difference between black and white is emphasized at the change point.
In this way, the overshoot and undershoot are added to the changing points at the rise and fall of the luminance signal, so that the contour of the image on the cathode ray tube is emphasized. (References
NHK Television Technical Textbook (1st) Japan Broadcasting Corporation

[0007]

However, in such an image quality adjusting device, as shown in FIG. 9 (a), the circuit constants are determined in correspondence with the television signal whose luminance signal band is NTSC. As shown in FIG. 9B, the image quality adjusting device is effective for the luminance signals of different bands such as a clear vision signal (hereinafter referred to as EDTV signal) and a high-definition television signal (hereinafter referred to as HDTV signal). The outline cannot be emphasized. Further, if the circuit constant of the image quality adjusting device is fixed for a signal having a wide signal band as shown in FIGS. 9B and 9C, there is a problem that the effect of image quality adjustment is deteriorated in the current TV signal having a narrow signal band. It was

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to detect the band of an input video signal and perform optimum image contour enhancement on a luminance signal having a different band. An object is to provide an image quality adjustment device.

[0009]

According to a first aspect of the present invention, a band detector for detecting a type of an input video signal, a control circuit for outputting a switching control signal based on an output signal of the band detector, Sharpness characteristic varying means for correcting the sharpness characteristic of the input video signal in response to the switching control signal of the control circuit.

According to a second aspect of the present invention, a band detector for detecting the type of the input video signal, a control circuit for outputting a switching control signal based on the output signal of the band detector, and a control circuit for the input video signal. And a sharpness characteristic varying means for correcting the sharpness characteristic of the video signal output from the LPF circuit according to the switching control signal of the control circuit. To do.

According to a third aspect of the present invention, a signal switching circuit for switching a plurality of input video signals of different types, a band detector for detecting the type of a video signal output from the signal switching circuit, and a band detector. And a sharpness characteristic varying means for correcting the sharpness characteristic of the video signal output by the signal switching circuit according to the switching control signal of the control circuit. To do.

[0012]

According to the invention of claim 1 of the present application having such a feature, when the video signal is input, the band detector detects the type thereof. The control circuit outputs a switching control signal to the sharpness characteristic changing means based on the output signal of the band detector. The sharpness characteristic changing means corrects the sharpness characteristic of the input video signal by the switching control signal of the control circuit. In this way, the image signal whose image quality has been adjusted is output.

According to the invention of claim 2 of the present application, when the video signal is input, the band detector detects the type. The control circuit outputs a switching control signal to the LPF circuit and the sharpness characteristic varying means based on the output signal of the band detector.
The LPF circuit cuts off the input video signal at a cut-off frequency or higher indicated by the control signal from the control circuit. The sharpness characteristic varying means corrects the sharpness characteristic by using the video signal output from the LPF circuit according to the switching control signal of the control circuit. In this way, the image signal whose image quality has been adjusted is output.

Further, according to the invention of claim 3 of the present application, the signal switching circuit switches a plurality of input video signals of different types, respectively. The type of the switched video signal is detected by the band detector. The control circuit outputs a switching control signal to the signal switching circuit and the sharpness characteristic varying means based on the output signal of the band detector. The sharpness characteristic varying means corrects the sharpness characteristic by using the video signal output from the switching circuit according to the switching control signal from the control circuit. In this way, the image signal whose image quality has been adjusted is output.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image quality adjusting apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the overall configuration of the image quality adjusting apparatus of the first embodiment. In the figure, an input terminal 11 is a terminal to which a luminance component of a video signal is input. The band detector 12 has an input terminal 11
2 is a circuit for detecting the type of the luminance signal input to, and its detailed block diagram is shown in FIG.

In FIG. 2, a signal extractor 13 is a circuit for extracting a blanking synchronizing signal from an input video signal. The amplifier 14 is a circuit that amplifies the signal from the signal extractor 13, and the outputs thereof are given to the first to third band pass filters (BPF) 15, 16 and 17, respectively. BPF
Reference numerals 15 to 17 are filters each having a bandwidth of about 1 MHz, and their center frequencies are, for example, 2 MHz, 6 MHz, 15 MHz.
Is set to. That is, the BPFs 15, 16 and 17 are
The signal components included in the NTSC signal, the EDTV signal, and the HDTV signal are extracted, respectively.

The level detectors 18, 19, 20 are respectively B
This is a circuit that detects the levels of the filtered components output from the PFs 15, 16 and 17 and holds the values for a certain period of time. Next, the level comparators 21, 22, and 23 respectively include the level detector 18,
The outputs of 19 and 20 are compared with the reference level and the large and small signals are output. The outputs of the level comparators 21 to 23 are output to the control circuit 24 shown in FIG. 1, respectively. The control circuit 24 includes a microcomputer, and the level comparator 2
Based on the outputs of 1 to 23, the type of the video signal input to the input terminal 11 is identified, and the switching control signal for selecting the delay time of the video signal is output.

The contour emphasizing circuit 25 shown in FIG. 1 has the same configuration as that shown in FIG. As shown in FIG. 7, the contour enhancement circuit 25
1 is provided with a first delay circuit 2a and a second delay circuit 4a. Unlike the conventional example, the delay circuits 2a and 4a are provided.
Includes a plurality of delay elements.

FIG. 3 shows the delay circuit 2a of the contour enhancement circuit 25,
It is a block diagram which shows the internal structure of 4a. In FIG. 3, the video luminance signal input from the input terminal 30 of the contour enhancement circuit 25 is input to the delay elements 31 to 33. The delay elements 31 to 33 are circuits that have delay times τ _{1 to} τ ₃ and delay the input NTSC signals, EDTV signals, and HDTV signals by different times. The outputs of the delay elements 31 to 33 are given to the switching circuit 34, respectively. The switching circuit 34 is switched by a control signal output from the control circuit 24. The video signal switched by the contour emphasizing circuit 25 of FIG. 1 is output from the output terminal 26 thereof. Here, the contour emphasis circuit 25
The sharpness characteristic changing means for correcting the sharpness characteristic of the video signal based on the switching control signal of the control circuit 24 is configured.

The operation of the image quality adjusting apparatus of the first embodiment having the above configuration will be described. In FIG. 1, when the luminance component of the video signal is applied to the input terminal 11, the band detector 12 extracts the blanking signal from the video signal by the signal extractor 13 of FIG. 2 and amplifies the blanking signal by the amplifier 14.
The amplified video signal is output to the BPFs 15-17.
If the input video signal is, for example, an NTSC TV signal, the BPF 15 outputs a signal having a center frequency of 2 MHz and a width of 1 MHz. On the other hand, the BPFs 16 to 17 do not output signals because their pass bands are 6 MHz and 15 MHz, respectively.

Next, the level detector 18 holds the signal level output from the BPF 15 and supplies the value to the level comparator 21. The level comparator 21 compares with a built-in reference voltage,
If it is higher than the reference value, an H level signal is output. When the control circuit 24 of FIG. 1 receives the H-level signal from the level comparator 21, the signal at the input terminal 11 changes to NTSC.
And the switching signal is output to the switching circuit 34 shown in FIG.

On the other hand, the video signal inputted to the input terminal 11 is inputted to the same contour emphasizing circuit 25 as shown in FIG. 7, and the first delay circuit 2a, the second delay circuit 4a, the first and second delay circuits 2a and 4a.
Through the subtractors 3 and 5 and the first and second adders 6 and 7,
Edge-enhanced luminance signals are generated respectively. In the delay circuits 2a and 4a, the delay elements 31 to 33 having delay times τ _{1 to} τ ₃ respectively perform delay processing, and three types of edge-enhanced luminance signals are input to the switching circuit 34. Here, the control circuit 24 switches the switching circuit 34 to select the output signal of the delay element 31. Therefore, as shown in FIG. 8F, the output terminal 26 outputs a luminance signal whose contour is emphasized at time τ ₁ .

Next, when, for example, an EDTV signal is input to the input terminal 11, the level comparator 22 in the band detector 12 outputs an H level signal to the control circuit 24. In this case, the control circuit 24 switches the switching circuit 34 to select the luminance signal delayed by the delay element 32. In this case, the contour emphasis circuit 2
Similarly to FIG. 8 (f), 5 produces a luminance signal whose contour is emphasized at time τ ₂ . In this way, the band detector 12 detects the signal band, the control circuit 24 determines the type of the video signal, and switches the signals output from the delay elements 31 to 33. Therefore, the delay circuits 2a and 4a perform the delay processing adapted to the type of each signal.

Next, an image quality adjusting apparatus according to a second embodiment of the present invention will be described with reference to FIGS. Figure 2 is the second
1 is a block diagram showing the overall configuration of an image quality adjusting device of an embodiment, which is a band detector 12, a control circuit 24, and an edge enhancement circuit 25.
Is provided as in the first embodiment. First
Unlike the embodiment, the LPF circuit 40 is provided between the input terminal 11 and the contour emphasis circuit 25. FIG. 5 is a block diagram showing the internal configuration of the LPF circuit 40. As shown in FIG. 5, the LPF circuit 40 includes three low-pass filters (LP
F) 41, 42, 43 and its switching circuit 44. The cutoff frequencies of the LPFs 41, 42 and 43 are set to 5 MHz, 10 MHz and 32 MHz, respectively. That is, the LPFs 41 to 43 are filters that pass the NTSC TV signal, the EDTV signal, and the HDTV signal, respectively, and the respective outputs are given to the switching circuit 44. L in FIG.
The switching circuit 44 of the PF circuit 40 is switched by the switching signal output from the control circuit 24, similarly to the contour emphasizing circuit 25.

With regard to the image quality adjusting apparatus of the second embodiment having such a configuration, only the operation of the part different from that of the first embodiment will be described. When the luminance component of the video signal is given to the input terminal 11, the band detector 12 detects the signal band and gives the output signal to the control circuit 24. Control circuit 2
4 outputs a switching signal to the LPF circuit 40. For example, if the input signal is an NTSC TV signal, the switching circuit 44 is switched to select the LPF 41 signal.

The edge enhancement circuit 25 processes the band-limited luminance signal in the same manner as in the first embodiment to generate an edge enhanced signal. Even when an EDTV signal or an HDTV signal is input to the input terminal 11, the control circuit 24 switches the switching circuit 44 and selects the signal of the LPF 42 or 43, respectively. As described above, in this embodiment, the band of the input signal is detected, the band is limited according to each video signal, and unnecessary components of the signal are removed. Therefore, the image quality can be adjusted more effectively according to the type of video signal.

Next, an image quality adjusting apparatus according to the third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing the overall configuration of the image quality adjusting apparatus of the third embodiment. In this figure, the band detector 12, the control circuit 24, and the contour emphasis circuit 25 are provided, which is the same as in the first embodiment.
Different from the conventional example, three types of input terminals 11a, 11b, 11
c is provided. Input terminals 11a, 11b, 11c
Is an input terminal for inputting NTSC TV signals, EDTV signals, and HDTV signals without specifying them. Each input terminal 11
The outputs of a to 11c are given to the signal switching circuit 50. The signal switching circuit 50 selects a signal from the input terminals 11a to 11c according to a switching signal output from the control circuit 24 and supplies the signal to the band detector 12 and the contour emphasizing circuit 25.

In such a configuration, N as an input video signal
This is effective when TSC TV signals, EDTV signals, and HDTV signals are input to the unspecified input terminals 11a to 11c, respectively. The signals switched by the signal switching circuit 50 are detected by the band detector 12 as video signal types. Confirmed, first and second
Processed as in the example.

In the first to third embodiments, the band detector 1
Although 2 is composed of a BPF, a level detector, and a level comparator as shown in FIG. 2, other structures may be used as long as they can discriminate the kind of signal. Although the first delay circuit 2a and the second delay circuit 4a are each configured as shown in FIG. 3, other configurations may be used as long as the delay time can be changed according to the switching signal. Further, the LPF circuit 40 of the second embodiment has a configuration as shown in FIG. 5, but it is not limited to this configuration as long as the cutoff frequency of the LPF can be changed.

[0030]

As described in detail above, according to the invention of claim 1 of the present application, by providing the band detector, the control circuit, and the sharpness characteristic varying means, the type of the input video signal is detected, Optimal image quality adjustment can be effectively performed for different types of video signals.

Further, according to the invention of claim 2 of the present application, by providing the band detector, the LPF circuit, the control circuit, and the sharpness characteristic varying means, the type of the input signal is detected, and different video signals are detected. Unnecessary band components can be removed in advance. Therefore, the optimum image quality adjustment can be performed more effectively for different types of video signals.

Further, according to the invention of claim 3 of the present application, the type of the video signal inputted to each input terminal is detected by providing the signal switching circuit, the band detector, the control circuit and the sharpness characteristic varying means. be able to. Therefore, even if different kinds of video signals are given to the respective input terminals, the optimum image quality adjustment can be performed more effectively.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an image quality adjusting device in a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a band detector included in the image quality adjusting apparatus of the first embodiment.

FIG. 3 is a block diagram showing a configuration of a contour emphasis circuit included in the image quality adjustment apparatus of the first embodiment.

FIG. 4 is a block diagram showing the overall configuration of an image quality adjustment device according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an LPF circuit included in the image quality adjusting apparatus according to the second embodiment of the present invention.

FIG. 6 is a block diagram showing an overall configuration of an image quality adjusting device according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration example of a conventional image quality adjustment device.

FIG. 8 is a signal waveform diagram showing an operation of the image quality adjusting apparatus of the present embodiment and the conventional example.

FIG. 9 is an explanatory diagram showing bands of respective video signals input to the image quality adjustment device.

[Explanation of symbols]

 2a 1st delay circuit 3 1st subtractor 4a 2nd delay circuit 5 2nd subtractor 6 1st adder 7 2nd subtractor 11 input terminal 12 band detector 13 signal extractor 14 amplifier 15 -17 BPF 18-20 Level detector 21-23 Level comparator 24 Control circuit 25 Edge enhancement circuit 31-33 Delay element 34,44 Switching circuit 40 LPF circuit 41-43 LPF 50 Signal switching circuit

Claims (5)

[Claims] 1. A band detector that detects a type of an input video signal, a control circuit that outputs a switching control signal based on an output signal of the band detector, and a sharpness of the input video signal by the switching control signal of the control circuit. An image quality adjusting apparatus comprising: a sharpness characteristic changing unit that corrects characteristics. 2. A band detector that detects the type of an input video signal, a control circuit that outputs a switching control signal based on the output signal of the band detector, and an input video signal that indicates the control signal of the control circuit. An image quality adjusting apparatus comprising: an LPF circuit that cuts off at a cut-off frequency or higher; and a sharpness characteristic changing unit that corrects the sharpness characteristic of a video signal output from the LPF circuit according to a switching control signal of the control circuit. . 3. A signal switching circuit for switching a plurality of input video signals of different types, a band detector for detecting the type of a video signal output by the signal switching circuit, and switching based on an output signal of the band detector. An image quality adjusting apparatus comprising: a control circuit that outputs a control signal; and a sharpness characteristic changing unit that corrects the sharpness characteristic of a video signal output by the signal switching circuit according to the switching control signal of the control circuit. 4. The sharpness characteristic varying means is a contour enhancement circuit for enhancing the contour of an input video signal in accordance with a switching control signal of the control circuit.
The image quality adjustment device according to item 2 or item 3. 5. The contour emphasis circuit delays an input video signal by a delay time determined based on a control signal of the control circuit, and an input video signal from an output of the first delay circuit. A second subtractor for delaying the output of the first delay circuit by the same delay time as that of the first delay circuit; and a second subtractor for delaying the first delay circuit from the second delay circuit. Second subtractor for subtracting the output of the delay circuit, a first adder for adding the signals of the first and second subtractors, an output of the first delay circuit and the first addition An image quality adjusting apparatus according to claim 4, further comprising a second adder for adding outputs of the adders.