JPS60192467A - Picture quality adjusting device - Google Patents

Abstract

PURPOSE:To attain automatically optimum picture quality adjustment well balanced in vertical and horizontal directions to various video signals different in the number of scanning lines by detecting the number of scanning lines of a video signal, and using the detected 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 at a delay circuit 4 of a picture quality adjusting circuit 16 is obtaind. Further, a signal (c) delayed by 2 is obtained by a delay circuit 5. The signal (c) and the video signal (a) are added at an adder circuit 6 to halve the gain and a signal (d) is outputted. Then it is subtracted with the signal (b) at a subtraction circuit 7 and a signal (e) is outputted, it is added to the signal (b) at an adder circuit 9 via a gain control circuit 8 and a video signal (f) subject to picture quality adjustment is outputted. Moreover, a horizontal synchronizing signal is fed to an input terminal 10 and a vertical synchronizing signal is fed to an input terminal 14 and the number of scanning lines is detected by a scanning line number detection circuit 11. This detection signal is fed to a control signal generating circuit 12 via an operation circuit 15 to control the delay time of the delay circuits 4, 5 and th frequency band where the horizontal direction is emphasized through the operation in response to the number of scanning lines is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION 2--A Field of Industrial Application The present invention relates to a horizontal image quality adjustment device suitable for a television receiver.

Conventional Structure and Problems In a conventional television receiver, since the electron beam in the picture tube has a finite size, the high-frequency components of the optical output signal on the screen are reduced. It is necessary to compensate for this deterioration of high frequency components. Furthermore, by adding appropriate printout and overshoot to the step response waveform of the signal, the sharpness of the image can be substantially improved.

To achieve this, the characteristics emphasize high-frequency components, but due to noise when receiving weak electric field signals or the viewer's preference,
As shown in FIG. 3, the design is often such that the overall frequency characteristics can be varied.

FIG. 1 shows an example of an image quality adjustment circuit, and FIG. 2 shows its waveforms. A video signal indicated by a second Na is input to the input terminal 1 in FIG. 1, and the capacitor C1 and inductance L1 connected to the collector of the transistor 2 cause
As shown in Figure 2, a second-order differential waveform of the video signal '3 Vane signal 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 pre-sheet and over-sheet as shown in Fig. 2C, that is, a sharp state shown in Fig. 3, and the terminal At position 5, there is a response waveform with no waveform distortion, that is, the normal state shown in Figure 3, and at position 6, there is a response with a gradual rise due to the effect of capacitor C2.
In other words, the video signal in the soft state shown in FIG. 3 is output to the output terminal 3.

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

In the conventional image quality adjustment circuit, the frequency characteristics of the conventional image quality adjustment circuit are changed only in a portion centered around a specific frequency fo as shown in Fig. 3, so that the frequency band emphasized by image quality adjustment is fa. 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, it is necessary to change the frequency band to be emphasized depending on 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 It is an object of the present invention to eliminate the drawbacks of the conventional image quality adjustment circuits and to provide an inventive configuration that can be applied to various types of video signals. The image quality adjustment circuit includes a number detection means and an image quality adjustment means for controlling the frequency characteristics of the video signal according to the signal from the scanning line number detection means, and the frequency characteristics of the video signal are emphasized according to the number of scanning lines of the video signal. The frequency band can be automatically controlled.

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. 5 is a waveform diagram for explaining its operation.

A video signal shown in No. 5 Na is input to the input terminal 1, and the signal is supplied to the delay circuit 4 having a delay time τ of the image quality adjustment circuit 16, and the signal delayed by τ is sent to the delay circuit as shown in FIG. Obtained from 4.

The output from the delay circuit 4 is also supplied to the delay circuit 5, and as shown in FIG. 5C, a signal delayed by 2τ with respect to the input video signal shown in FIG. 5A is obtained from the delay circuit 6. The video signal from the input terminal 1 shown in FIG. 5A and the 2τ delayed 6-time signal from the delay circuit 5 shown in FIG.
The signal shown in FIG. 5d is output.

A subtraction circuit 7 subtracts the signal delayed by τ from the delay circuit 4 shown in FIG. 5S and the addition output from the addition circuit 6 shown in FIG.
After subtraction, a contour signal as shown in Figure 5e is output,
So how many songs have we performed quadratic differentiation on?

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 signal delayed by τ from the delay circuit 4 shown in FIG. 5 in an adder 9, and the image quality is adjusted as shown in FIG. The video signal obtained is output from the output terminal 3.

Further, a horizontal synchronizing signal is supplied to the input terminal 1o, and a vertical synchronizing signal is supplied to the input terminal 14, and the number of scanning lines is detected by a scanning line number detection circuit 11. This detection signal of the number of scanning lines is transmitted to a control circuit 1 composed of an arithmetic circuit 15 and a control signal generation circuit 12.
6. The arithmetic circuit 16 performs arithmetic operations to create a seven-page contour signal in the horizontal direction according to the number of scanning lines.

The calculation output from the calculation circuit 15 is transmitted to the control signal generation circuit 12.
A control signal for controlling the delay time of the delay circuits 4 and 5 is output. Therefore, it is possible to control the frequency band in which the horizontal direction is emphasized, which is calculated according to the number of scanning lines.

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

The contour signal can be created by using two delay circuits 4.5 having a delay time τ, but in order to know the horizontal resolution characteristics, the number of horizontal resolution lines is determined by repeating the sine wave within the horizontal effective scanning period. Considering this, when the input signal Eln is Eln = 5in2πm(t-)τ), the output E1 from the delay circuit 4 is E+ = sin2yrmt, and the output E2 from the delay circuit 5 is E2 = 5in2πm (t-7). Become.

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

At this time, the contour signal FH is EH=-sin2πmr--;[sin2yrm(t+
τ)-1-sin2πm(t-r)]m=1-cos
2yr+nr) sin 2πmτ−−−−−−−−−
-(1), and it can be seen that the response of (1-cos 2πmτ) has a comb-shaped layer wavenumber characteristic as shown in FIG.

Next, the arithmetic circuit 15 that calculates the frequency characteristic to be emphasized in the horizontal direction from the number of stroke lines will be described.

To simplify the explanation, we will discuss the case of a standard television signal.

The vertical contour signal has the same configuration as the horizontal contour signal described above, but was created using two 1H delay circuits, but in order to know the vertical resolution characteristics, the number of vertical resolution lines was changed by repeating a sine wave. Considering that, f(t-h)=sin2πnt
・・・・・・・・・・・・・・・・・・・・・(2)f
(t) = sln 2πn (t+h)...
・・・・・・・・・・・・・・・・・・(3) f(t-2h
)=sin2πn(t-h)--------・-be4)
becomes.

Here, n is the number of repetitions of the nine sinusoidal vanes in the vertical effective scanning section. Since h corresponds to 1H, if the effective scanning section in the vertical direction is 1, then the number of scanning lines is 525, and if the effective scanning section is 93.5%, then h=v245.

The vertical contour signal Ev is Ev=5i from equations (2) to (4).
n2 yrn t-2[:5in2πn(t+h)+5
in2 πn(t-4)]=(1-cos2yrnh)
sin2πnt-・-=beat... (5) From equation (5), the response with n in the amplitude term (1-cos2πnh) as a parameter indicates the resolution characteristic, and when h = 1-,
Solution 45 of (1-cos2πnh) The image power characteristics are shown in FIG. As shown in FIG. 7, the maximum response is obtained at n=122.5.

Since this is the number of repetitions of the sine wave within the vertical effective scanning section, it corresponds to 245 lines in terms of television resolution.

Therefore, if the maximum response n=1225 in the vertical direction is converted into the horizontal direction, it becomes m=ding n-ding X 122.5=163 from the aspect ratio of 4:3.

In equation (1), the condition that the amplitude term (1-cos2πmτ) reaches a maximum of 1obe-2 is when the second term Cog2πmτ becomes -1,
In this case, by setting m=163 and subtracting τ, the horizontal and vertical resolution characteristics can be made equal.

00327r! If we set ll7 = -1 and m = 163, then 26. If the horizontal scanning period is 63.6 μs and the effective scanning rate is 83, then τ = 1"62[4S'126] Therefore, horizontal direction By using a 162 .mu.s delay circuit as a delay circuit for contour signal creation, horizontal image quality adjustment having a peak at a resolution of 245 televisions is obtained, which is equal to the peak in the vertical case.

Similarly, the arithmetic circuit 16 performs calculations in the case of a high-definition television signal of 20 MH2, in which the number of scanning lines is 1126, which is about twice that of the standard system, and the band is about five times as large. In this case 1M = 29, 63μs (fH = 33.rtsM
tlz), effective scanning rate of 95% vertically and 83.13% horizontally
Then, the vertical resolution will be about 760 lines, which is 117 lines.
, :, If the act ratio is 4:3, a bandwidth of about 20M [IZ] is required. Also, the vertical peak, that is, the number of TV resolutions, is approximately 534 from the number of scanning lines, and if the horizontal peak is chosen to be the same as the vertical, it is approximately 14.5 MI
Tz is therefore τ-36 μs.

However, in reality, sharpness and naturalness can be obtained by setting the horizontal position higher than the vertical setting.

Therefore, in the case of a standard television signal, the horizontal is about 1.3 times higher than the vertical, and τ=125 μS peak frequency 4Mt frequency 4tIz is calculated.

Further, in the case of a high-definition television signal, calculations are similarly made to raise the horizontal by about 1.3 times as much as the vertical to achieve a peak frequency of τ-25 μs of 2oMFIz.

Next, in order to explain the operation in detail, the waveform diagrams and frequency characteristic diagrams shown in FIGS. 8 and 9 will be used. A delay means is required to create a horizontal contour signal, and charge transfer devices are very convenient for this purpose because the delay time can be arbitrarily controlled by controlling the frequency of the flock signal.

When the standard television signal shown in FIG. 8a is supplied to input terminal 1 of FIG. 4, the horizontal and vertical synchronization signals shown in FIG. 8C5d are also supplied to input terminal 10.14. . Horizontal and vertical synchronization signals from input terminals 10 and 14 are supplied to a scanning line number detection circuit 11, which detects how many horizontal synchronizations exist in a vertical period, that is, the number of scanning lines. A detection signal that detects the number of scanning lines from the scanning line number detection circuit 11 is supplied to a control circuit 16 composed of an arithmetic circuit 15 and a control signal generation circuit 12. As described above, the arithmetic circuit 15 calculates the frequency band to be emphasized in the horizontal direction from the number of scanning lines. The calculation output from the calculation circuit 16 is supplied to the control circuit 12, and the control signal generation circuit 12 is composed of, for example, a voltage control oscillator, and generates a clock signal according to the calculation output. , are supplied to the delay circuits 4 and 6 (charge transfer elements), and control the delay times of the delay circuits 4 and 6.

Therefore, when the television signals of the various standard formats shown in FIG. Then, as shown in FIG. 9, the frequency band to be emphasized is set to fs (for example, 4 M tlz). Also, television signals of various high-definition systems as shown in FIG. 8e are supplied to input terminal 1. Similarly, when
As shown in Figure 9, image quality adjustment suitable for high-definition signals is performed, and as shown in Figure 9, the frequency bands to be emphasized are 14 (
For example, it is set to 20MHz).

In the above-mentioned embodiments, in order to provide an easy-to-understand explanation, a case has been described in which an arithmetic circuit is used that can calculate the frequency band for automatically controlling the frequency characteristics of image quality adjustment based on the number of scanning lines. You may omit it and perform initial settings.

FIG. 10 is a block diagram of an image quality adjustment circuit showing a second embodiment of the present invention, and FIGS. 11 and 12 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. It should be noted that FIG. 10 shows a block diagram for performing initial settings, with the arithmetic circuit described above omitted. The difference from Fig. 4 is that frequency 14 is emphasized.

An extraction circuit 17 for extracting video signal components in several bands is provided,
The point is that the signal level from the extraction circuit 17 is supplied to the input terminal 13 for controlling the gain of image quality adjustment.

Therefore, as shown in FIG. 11a, when the frequency band to be emphasized is fs and many video signal components (shaded) are present, the level of the signal from the extraction circuit 17 will be high, for example. 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 increases as shown by the broken line in FIG.

Moreover, as shown in FIG. 11, the frequency band f5 to be emphasized is
On the other hand, when no video signal component exists, the level of the signal from the extraction circuit 17 is low. By supplying this signal to the input terminal 13 that controls the gain for image quality adjustment, the frequency band f5 is emphasized as shown by the solid line in FIG.
gain becomes smaller.

Therefore, it is possible to automatically control the gain (image quality tone) according to the video signal.

15. In this embodiment, a case has been described in which a specific frequency band is emphasized, but the frequency band may also 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, as a means of creating a contour signal, we have explained the delay line method, but using a low-pass filter method that takes the difference between the original signal and a low-pass filter, such as an active filter, to create a contour signal, it is possible to create a contour signal continuously or stepwise. You may switch to

Alternatively, the method of second-order differentiation using a passive element such as C may be switched in stages.

What has been described above is a means for performing second-order differentiation and creating a contour signal. However, the means described above performs -order differentiation, modulates the velocity of the deflected electron beam, and adjusts the image quality. Good too.

Effects of the Invention The image quality adjustment circuit of the present invention includes a scanning line number detection means for detecting the number of scanning lines of a video signal, and an image quality adjustment means for controlling the frequency characteristics of the video signal using a signal from the scanning line number detection means. By providing this, it is possible to automatically perform optimum image quality adjustment with a balance in the vertical and horizontal directions for various video signals having different numbers of scanning lines, so that high-quality images can be obtained.

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 by controlling the gain of image quality adjustment using the signal level from this extraction circuit, a good S/N ratio can be achieved. High quality images can be obtained.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional image quality adjustment device, 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 for explaining its operation. 1st
5 is a waveform diagram for explaining its operation, FIGS. 6 and 7 are resolution characteristic diagrams for explaining its operation, and FIG. 8 is its operation. FIG. 9 is a frequency characteristic diagram for explaining its operation, FIG. 10 is a block diagram of the image quality adjustment device in the second embodiment of the present invention, and FIG. 12 are frequency characteristic diagrams for explaining the operation. 16... Image quality adjustment circuit, 4, 5... Delay circuit, 6.9... Addition circuit, 7...
Subtraction circuit, 8...Gain control circuit, 16...
... Arithmetic circuit, 12 ... Control signal generation circuit, 1
1...Scanning line number detection circuit. Name of agent Patent attorney Toshio Nakao and 1 other person Figure 1 Figure 2 Figure 3 151 ■Thoughts

Claims (3)

[Claims] (1) An image quality adjustment device comprising a scanning line number detection means for detecting the number of scanning lines of a video signal, and an image quality adjustment means for controlling the frequency characteristics of the video signal using a signal from the scanning line number detection means. (2) The image quality adjustment according to claim 1, wherein the image quality adjustment means uses an arithmetic circuit that calculates the frequency band in which the frequency characteristics of the video signal are controlled based on the signal from the scanning line number detection means. Device. (3) 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 this extraction circuit. The image quality adjustment device according to claim 1 is used.