JPS60192468A - Picture quality adjusting device - Google Patents

Abstract

PURPOSE:To attain automatically optimum picture quality adjustment to various video signals different in horizontal scanning frequency by detecting a horizontal scanning frequency of a video signal and using the detecting signal to control the frequency characteristic of the video signal. CONSTITUTION:A video signal (a) is inputted to an input terminal 1 and a signal (b) delayed by tau is obtained at a delay circuit 4 having a delay time tau of a picture quality adjusting circuit 14. Further, a signal (c) delayed by 2tau to the input video signal (a) is obtained by a delay circuit 5. The signal (c) and the video signal (a) are added by an adder circuit 6 so as to halve the gain and a signal (d) is outputted. It is subtracted from the signal (b) at a subtraction circuit 7 and a profile signal (e) is outputted and added to the signal (b) at an adder circui 9 via a gain control circuit 8 and a video signal (f) subject to picture quality adjustment is outputted from an output terminal 3. Further, a horizontal synchronizing signal from an input terminal 10 is detected for frequency at a frequency detection circuit 11. This detection signal is fed to a control circuit 12 to control the delay time of the delay circuits 4, 5. Thus, the frequency band emhasized for the video signal in response to the horizontal scanning frequency is controlled.

Description

[Detailed Description of the Invention] Industrial Field of Application Conventional configuration and its problems 2/ In a conventional television receiver, since the electron beam has a finite size in the picture tube, the light output on the screen is limited. The high frequency components of the signal are reduced. It is necessary to compensate for this deterioration of high frequency components. Further, by adding appropriate preshoot and overshoot to the step response waveform of the signal, the sharpness of the image can be substantially improved. To achieve this, the characteristics are designed to emphasize the high-frequency components, but depending on the noise during weak electric field signal reception or the viewer's preference, the overall frequency characteristics may be designed to be variable as shown in Figure 3. many.

FIG. 1 shows an example of an image quality adjustment circuit, and FIG. 2 shows its waveforms. The video signal shown in FIG. 2a is input to the input terminal 1 in FIG. A second derivative waveform is obtained. Therefore, at the position of terminal 4, the sliding terminal of variable resistor VR with an intermediate terminal has a step response waveform with preshoot and overshoot as shown in FIG. At the terminal 5 position, a response waveform with no distortion occurs, that is, the normal state shown in Figure 3, and at the terminal 6 position, due to the effect of the capacitor C2, a response with a gradual rise, that is, the response waveform shown in Figure 3. A video signal in a soft state is output to the output terminal 3.

As shown in the overall frequency characteristic in FIG. 3, the sharpness of the image can be improved by variably adjusting the amount of preshoot and overshoot applied to the video signal in the image quality adjustment circuit.

However, in the conventional image quality adjustment circuit, the frequency characteristic varies depending on the image quality adjustment, as shown in FIG. 3, at a specific frequency f. The frequency band emphasized by image quality adjustment is f. For example, when a wideband video signal is input, appropriate image quality adjustment can be performed for the narrowband video signal, but the wideband video signal is emphasized by the image quality adjustment. Since the frequency band of the video signal is too low compared to the band of the video signal, the image quality adjustment may not be appropriate.

In other words, in an image quality adjustment circuit that improves image quality by emphasizing a predetermined frequency band of a video signal, in order to obtain appropriate image quality, the frequency band to be emphasized must be changed according to the band of each video signal. However, in conventional image quality adjustment circuits, the frequency band to be emphasized is fixed and only the gain is adjustable, so it is difficult to always obtain appropriate image quality depending on the frequency band of the video signal. was there.

OBJECTS OF THE INVENTION An object of the present invention is to provide a configuration of the invention in the conventional image quality adjustment circuit. This is an image quality adjustment circuit equipped with an image quality adjustment means for controlling characteristics, and the frequency 5, - is emphasized according to the horizontal scanning frequency of the video signal.

It is capable of automatically controlling several bands.

DESCRIPTION OF EMBODIMENTS The present invention will be described in detail below with reference to the drawings showing one embodiment thereof. FIG. 4 is a block diagram showing the configuration of an image quality adjustment circuit according to an embodiment of the present invention, and FIG. 6 is a waveform diagram for explaining its operation. 5th to input terminal 1
The video signal shown in FIG.
A delayed signal is obtained from the delay circuit 4 as shown in the figure. The output from the delay circuit 4 is also supplied to the delay circuit 5, and as shown in FIG. 6C, a signal delayed by 2τ with respect to the input video signal shown in FIG. 5a is obtained from the delay circuit 5. An adder circuit 6 adds the video signal from the input terminal 1 shown in FIG. 6a and the signal delayed by 2τ from the delay circuit 5 shown in FIG. 5C.
, the gain is halved, and the signal shown in FIG. 6d is output. The signal delayed by τ from the delay circuit 4 shown in FIG. 5S and the addition output from the adder circuit 6 shown in FIG. .

A contour signal is output, which means that the second-order differentiation is performed isometrically. The contour signal from the subtraction circuit 7 shown in FIG. The gain-controlled contour signal from the gain control circuit 8 is added to the two-delayed signal from the delay circuit 4 shown in FIG. The video signal obtained is output from the output terminal 3.

A horizontal synchronizing signal is still supplied to the input terminal 10, and the frequency is detected by the frequency detection circuit 11. This detection signal is supplied to the control circuit 12, and a control signal for controlling the delay time of the delay circuits 4 and 5 is output. Therefore, the frequency band to be emphasized in the video signal can be controlled according to the horizontal scanning frequency.

In order to explain in detail, the resolution characteristic diagram shown in FIG. 6 will be used.

The contour signal can be created by using two delay circuits 4.6 each having a delay time τ, but in order to know the resolution characteristics in the horizontal 7 page direction, the number of resolution lines in the horizontal direction is set within the horizontal effective scanning section. Now, when the input signal EiN is EiN = Sin2πm (t + τ), the output F1 from the delay circuit 4 is E1 = 5in2πmτ, and the output E2 from the delay circuit 5 is E2 = 5in2πm (t - r ).

m is the number of repetitions of the sine wave within the horizontal effective scanning section.

At this time, the contour signal E)I is = (1-cos2πmτ)Sin2πmr -----(
1), and it can be seen that the response of (1-cos2πmτ) has a comb-shaped frequency characteristic as shown in FIG.

From the above, for example, in the case of a standard television signal, if the frequency band to be emphasized is 3 MHz, the delay time of the delay circuits 4 and 5 will be 1 as (ns:).

In addition, the number of scanning lines is approximately twice that of the standard method, and the band width is approximately 6
In the case of a double high definition television signal, if the frequency band to be emphasized is 20 MHz, the delay time of the delay circuits 4 and 5 will be 26 (ns).

Next, in order to explain the operation in detail, Figs.
Use the waveform diagram and frequency characteristic diagram shown in the figure.

In order to create a contour signal, a delay means is required, but for this purpose charge transfer elements and memory elements are extremely difficult to control because the delay time can be controlled arbitrarily by controlling the frequency of the clock signal. It's convenient.

When the standard television signal shown in FIG. 7a is supplied to the input terminal 1 of FIG. 4, the horizontal synchronization signal shown in FIG. 7C is also supplied to the input terminal 1o.

This horizontal synchronizing signal is supplied to a frequency detection circuit 11, and a detection signal 9B, which has been subjected to frequency/voltage conversion, is output, for example.

The frequency-voltage converted detection signal from the frequency detection circuit 11 is supplied to the control circuit 12.

The control circuit 12 is composed of a voltage controlled oscillator, and generates a clock signal in response to the detection signal, and the clock signal is supplied to the delay circuits 4 and 5 (charge transfer elements). 5 delay time is controlled.

Therefore, when the standard format television signal is supplied, image quality adjustment suitable for the standard format signal is performed as shown in FIG. 7, and the image quality is emphasized as shown in FIG. 8. The frequency band is set to f3 (for example, 3 MHz). Similarly, when a high-definition television signal is supplied to the input terminal 1 as shown in FIG. 11, frequency-voltage conversion is performed, and this detection signal
The delay time is controlled by controlling the clock signal of the voltage controlled oscillator of the control circuit 12.

Therefore, the high-definition television 10 page
7 When the signal is supplied, image quality adjustment suitable for the high-definition signal is performed as shown in Fig. 7C, and as shown in Fig. 8, the emphasis frequency band is f, (for example, 20 MHz).
) is set.

FIG. 2 is a block diagram of an image quality adjustment circuit showing a second embodiment of the present invention, and FIGS. 10 and 11 are frequency characteristic diagrams for explaining its operation.

Components that operate in the same way as in FIG. 4 are designated by the same numerals and explanations will be omitted. The difference from FIG. 4 is that an extraction circuit 15 is provided to extract the video signal component of the frequency band to be emphasized, and the signal level from the extraction circuit 15 is supplied to the input terminal 13 for controlling the gain for image quality adjustment. It is a point.

Therefore, it is emphasized as shown in Figure 10a.

When the frequency band is f and many video signal components (diagonal lines) exist, the level of the signal from the extraction circuit 15 becomes large, for example. This signal is supplied to the input terminal 13 which controls the gain of the image quality adjustment □11.

Further, as shown in FIG. 10, when there is no video signal component in the emphasized frequency band fS, the level of the signal from the extraction circuit 15 is low.

By supplying this signal to the input terminal 13 that controls the gain for image quality adjustment, the gain of the frequency band f5 to be emphasized becomes smaller, as shown by the solid line in FIG.

Therefore, the gain for image quality adjustment can be automatically controlled according to the video signal.

In this embodiment, the case where a specific frequency band is emphasized has been described above, but the frequency band may be controlled.

Incidentally, in this embodiment, a case has been described in which a charge transfer element is used as the delay means, but a variable delay line such as a tap delay line or the like may be used for stepwise switching.

In addition, we have explained the delay line method as a means of creating a contour signal, but the contour signal can be divided by taking the difference between the original signal and a low-pass filter (active filter), or it can be second-order differentiated using a passive element such as C. The method may be switched in stages.

What has been described above is a means for performing second-order differentiation and creating a contour signal, but the above-mentioned means performs first-order differentiation, and the velocity of the deflected electron beam is velocity-modulated (V, M) to adjust the image quality. may be done.

Effects of the Invention The image quality adjustment circuit of the present invention is provided with a frequency detection means for detecting the horizontal scanning frequency of a video signal, and an image quality adjustment means for controlling the frequency characteristics of the video signal using a signal from the frequency detection means. Since optimal image quality adjustment can be automatically performed for various video signals with different horizontal scanning frequencies, high-quality images can be obtained. ! 13, . . . further, the image quality adjustment means is provided with an extraction circuit for extracting a video signal component in a frequency band for controlling frequency characteristics, and the gain of image quality adjustment is controlled by the signal level from this extraction circuit.
7

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional image quality adjustment circuit, Fig. 2 is a waveform diagram for explaining its operation, Fig. 3 is a frequency characteristic diagram for explaining its operation, and Fig. 4 is a diagram of a conventional image quality adjustment circuit. FIG. 5 is a waveform diagram to explain its operation; FIG. 6 is a resolution characteristic diagram to explain its operation; and FIG. 7 is a more detailed diagram of its operation. FIG. 8 is a frequency characteristic diagram to explain its operation. FIG. 9 is a block diagram showing the second embodiment of the present invention. FIGS. 1o and 11 are its operation. FIG. 2 is a frequency characteristic diagram for explaining. 4.5...Delay circuit, 6,9...Addition circuit, End...Subtraction circuit, 8...Gain control circuit, 15... ...Extraction circuit, 12...
Control circuit, 14... Image quality adjustment circuit, 10...
...Frequency detection circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure fII I Fumi Min+-Kun

Claims (2)

[Claims] (1) An image quality adjustment device comprising: a frequency detection means for detecting the horizontal scanning frequency of a video signal; and an image quality adjustment means for controlling the frequency characteristics of the video signal using a signal from the frequency detection means. . (2) The image quality adjustment means includes an extraction circuit that extracts a video signal component in a frequency band in which the frequency characteristics of the video signal are controlled, and a gain control circuit that controls the gain of the image quality adjustment based on the signal level from the extraction circuit. The image quality adjustment device according to claim 1 is used.