JPS5834992B2 - tv jiyeonji yuzouki - Google Patents

Description

[Detailed Description of the Invention] As a method for improving the sharpness of a television picture, video signals (
A method is known in which the scanning speed of the electron beam of a picture tube is modulated using a contour signal obtained from a luminance signal.

As shown in FIG. 1, this has a scanning speed modulation signal forming circuit 5 composed of delay lines 1 and 2 having the same delay amount τ and a subtraction circuit 3, and an amplifier 6 is installed here. A luminance signal is supplied through the radiance.

Now, for convenience, if the signal E supplied to the terminal 7 is expressed as E(t+τ) using the delay amount τ (see FIG. 2A, the same applies hereinafter), this luminance signal E(t+τ) The first luminance signal E(t) delayed by τ by passing through the terminal 8
will be obtained.

Furthermore, by supplying this signal E(t) to the delay line 2 in the subsequent stage, a second luminance signal E(t) delayed by 2τ is obtained.
−τ) is obtained.

Here, the signal E(t+te) changes from the black level to the white level (
(or vice versa) The delay time τ is selected so that the rise time (or fall time) of the signal E(t+τ) is 2τ when the signal E(t+τ) changes the most and therefore requires the highest sharpness.

Actually, τ is about 0.1 μsec.

By the way, the fourth signal E(t) is supplied to the picture tube as a luminance signal, and the electron beam is density-modulated.

However, in the case of primary color drive, as shown in FIG. 1, it goes without saying that this first signal E(t) is supplied to the matrix circuit M to which the color difference signals (R-Y) (B-Y) are supplied. .

Then, by supplying the original signal E (t+τ) and the second signal E (-τ) to the subtracter 3, the terminal 9 receives a signal Ev (t) ( Ey (
t)=E (t+τ)E(t-τ)] is obtained, but
This signal EV(t) is a beam scanning velocity modulation signal (contour signal), and as shown in FIG. is supplied to the deflection means 13 for use.

As shown in the figure, the deflection means 13 is composed of a pair of electrostatic deflection plates 13a and 13b that face each other in the horizontal direction.

Since various signal supply directions are possible, their explanation will be omitted.

When such a signal Ev(t) is supplied to the deflection means 13, the scanning speed of the electron beam on the screen is modulated by this signal Ev(t). The amount of light emitted at positions on the screen corresponding to the rising and falling edges of ) changes rapidly, thereby improving the sharpness of the image.

By the way, let's consider the effect of such a speed modulation method, that is, the problem of the sharpness of a television image, as a response of a step function.

Now, a step signal that can pass through the video signal transmission band (0 to 4.5 MHz) and has the fastest rise is applied to the picture tube, and the brightness distribution of the step image on the screen at that time is measured. , the sharpness of the stepped image is considered by observing the rise time, overshoot, etc. of the height.

Note that the rise time of the step signal used in this example is 0.12 μsec.

FIG. 4 shows the step response of the step signal, in which the horizontal axis is the distance (time) in the horizontal direction of the screen, and the vertical axis is the relative brightness on the screen.

A curve 20 is a step response when the beam spot diameter of the electron beam is set to zero.

Therefore, this curve 20 is the most ideal.

In contrast to this ideal curve 20, an observation result as shown by a curve 21 was obtained in the conventional example in which speed modulation was not performed.

When speed modulation is performed as described above, the curve becomes as shown by curve 22, and it can be seen that the rise is faster and much closer to the ideal curve than in the conventional case.

In other words, it can be confirmed that it is useful for improving sharpness.

By the way, it is known that the sharpness of a television image is also related to the amount of overshoot of this step signal.

That is, as the amount of overshoot increases, sufficient sharpness can be obtained.

In order to achieve this purpose using the speed modulation method, it is sufficient to increase the supply amount of this speed modulation signal Ev(t), and as the amount of supply increases, the amount of overshoot increases, for example, as shown in curve 23.
A step response with an overshoot of more than 10% can be obtained as shown in FIG.

However, in this method, as shown in the figure, a time delay (positional shift) with respect to the ideal curve 20 becomes noticeable, so that the rising and falling positions of the image appear to have moved.

This phenomenon is not limited to step signals, and it goes without saying that it also occurs when normal video signals are displayed. When reproduced, white images appear thinner, while black images tend to appear too thick.

The present invention eliminates these drawbacks with a simple structure,
This is intended to further improve sharpness and to effectively correct image positional deviations.

A television receiver according to the present invention will be explained below with reference to the drawings.

However, the same reference numerals are given to the parts corresponding to those in the previous figure, and the explanation thereof will be omitted.

In the present invention, as shown in FIG. 5, a pair of delay lines 1 and 2 and a subtraction circuit 3 are provided, and from these, the electron beam velocity modulation signal EV(t) is obtained in the same way as shown in FIG. At the same time, the electron beam is density-modulated using a sum signal obtained by adding the first luminance signal E(t) to a signal obtained by squaring this velocity modulation signal Ev(t).

10 is a signal source of signal E(t+τ).

That is, if the signal for density modulation is Ep(t), this signal Ep(t) is given by the following equation.

Ep(t)=E(t)+βEV(t)2 ・
・・・・・・・・・(1) Here, β is the signal E p (t
) is a constant greater than or equal to zero that determines the amount of overshoot.

In order to obtain the signal Ep(t) of equation (1), for example, as shown in the figure, a square circuit 30 made up of, for example, a transistor is provided, and a scanning speed modulation signal EV(t) is supplied to this. In order to increase the sharpness improvement effect in the part where the black level changes to the white level or vice versa, the signal
After obtaining the square characteristic of , the signal βEV(t)2 is multiplied by β (β is a constant determined in consideration of the characteristics of the picture tube, etc., and is greater than or equal to zero) by supplying it to the level control circuit 31. obtain.

By supplying this signal βEv(t)2 to the adder 32 together with the first luminance signal E(t), the desired density modulation signal Ep(t) can be obtained from the terminal 33.

A waveform diagram of this signal Ep(t) is shown in FIG.

In this way, the scanning velocity modulation signal Ev(t
) as well as a signal E having an overshoot as shown in FIG.
When p(t) is supplied, the response of the step signal becomes as shown by a curve 41 in FIG.

As is clear from this characteristic curve diagram, not only can a sufficient overshoot be provided in the large current region of the electron beam, but the curve approaches the ideal curve 20.

However, although the rise is shifted to the left side of the curve 20, the peak point of overshoot, which is particularly related to positional deviation, is located on the right side, and this peak point is not closer to the peak point of the ideal curve 20 than in the past. Therefore, the positional deviation with respect to the original image can be effectively corrected.

Furthermore, since the overshoot is 20% or more, the sharpness is further increased.

Note that as the overshoot increases, the smear also tends to increase, but according to the present invention, even though this overshoot can be made sufficiently large, the smear decreases, so that the sharpness improvement effect appears even more strongly.

To explain the smear relationship using FIG. 7, the curve 23 is the characteristic curve explained in FIG. 4.

Further, a curve 42 shows a step response when an aperture-corrected signal EA(t) is used as the density modulation signal Ep(t) of the present invention in place of the scanning speed modulation signal.

The signal EA(t) determined by the following equation was used.

Here, τ represents the amount of delay of the delay line provided in the circuit for obtaining the aperture correction signal, and is selected as τ > τ.

In the illustrated example, τ, -〇, 295μ seconds, τ=0.12μ
Seconds.

As is clear from a comparison between curves 23 and 42 and curve 41 according to the present invention, the present invention provides sufficient overshoot and small smear, and the peak point of the overshoot is close to that of ideal curve 20.

As described above, in the present invention, the electron beam is velocity modulated and the density modulation signal Ep(t) is formed based on the signal EV(t) used for this velocity modulation, so that sufficient overshoot can be obtained. It has the feature that not only can sharpness be further improved, but also image positional deviation can be almost completely corrected.

Moreover, in the present invention, although sufficient overshoot is obtained, smear can be reduced, so that the sharpness improvement effect appears even more strongly.

As described above, the squaring circuit 30 may use the static characteristics of a diode in addition to using a transistor.

In other words, since the static characteristics of the diode exhibit characteristics close to square-law characteristics at low levels, the signal E as shown in FIG.
After V(t) is once supplied to the level control circuit 45 to adjust the level, it is led to a square circuit or rectifier circuit 46 consisting of a diode, and the square characteristic portion of the diode is used to adjust the signal EV(t) by 2. Imparts a multiplicative property.

Thereafter, the signal is supplied to an amplification circuit 47, amplified to a predetermined level, and added to an adder 32.

Even with this configuration, the same effects as described above can be achieved.

The television receiver of the present invention may be either black and white or color.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an example of speed modulating an electron beam, FIG. 2 is a diagram for explaining its operation, FIG. 3 is a diagram showing an example of a picture tube suitable for applying the present invention, and FIG. FIG. 4 is a characteristic diagram showing the response of the step signal, and FIG. 5 is a configuration diagram showing an example of the essential parts of the television receiver according to the present invention.
FIGS. 6 and 7 are diagrams for explaining the present invention, and FIG.
This figure is a configuration diagram similar to FIG. 5 showing another example of the present invention. 5 is a speed modulation and density modulation signal forming circuit, 1.2 is a delay line, 3 is a subtracter, 30.46 is a square circuit, Ev(t
) is the velocity modulation signal, Ep(t) is the density modulation signal, τ, τ
, is the amount of delay.

Claims (1)

[Claims] A luminance signal is supplied to the delay means to obtain a first luminance signal delayed by a certain period of time, and a second luminance signal delayed by approximately twice the time, and the above-mentioned original luminance signal is obtained. A difference signal between the luminance signal and the second luminance signal is supplied to a deflection means for beam scanning velocity modulation provided in the picture tube to modulate the scanning velocity of the electron beam, and a signal obtained by substantially squaring the difference signal is supplied. A television receiver characterized in that the sum signal of the first luminance signal is supplied to the receiver tube to perform density modulation of the electron beam.