JPS5824989B2 - tv jiyeonji yuzouki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION As a method for improving the sharpness of television images, 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.

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.

or. 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+τ) 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 sharpest sharpness.

Actually, τ is about 0.1 μsec.

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

However, when using a primary color drive, as shown in Figure 1,
Needless to say, this first signal E(t) is supplied to the matrix circuit M to which the color difference signals (R-y) and (B-y) are supplied.

Then, the original signal E(t+τ) and the second signal E(t
-τ) to the subtractor 3, the terminal 9 receives a signal E■(t) (EV(t)=
E(t+τ)-E(-τ)], but this signal Ey(t) is the beam scanning velocity modulation signal (contour signal), which exists in the picture tube 11 as shown in FIG. It is supplied to deflection means 13 for scanning speed modulation, which is provided separately from the horizontal and vertical deflection means 12.

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

Since various methods of supplying the signal can be considered, 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 the signals 'F and V(t). The amount of light emitted at the positions on the screen corresponding to the rise and fall of E(t) changes rapidly, thereby improving the sharpness of the image.

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

Now, a step signal that passes 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 its rise time, overshoot, etc.

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.

To achieve such purpose with velocity modulation method.

It is only necessary to increase the supply amount of this speed modulation signal Ev(t), and as it increases, the overshoot amount increases.

For example, a step response with an overshoot of more than 10% as shown by curve 23 is obtained.

In this method, as shown in the figure, the positional deviation with respect to the ideal curve 20 becomes noticeable, giving the impression that the rising and falling positions of one image have shifted.

This development is not limited to step signals.

Needless to say, this problem also occurs when displaying a normal video signal, but in this case, especially when reproducing an image that is continuous with the song (black and white, black and white, black and white, etc.), the white image appears thinner. On the other hand, black images tend to become too thick.

The present invention eliminates these drawbacks with a simple structure,
In addition to further improving the sharpness, the positional deviation of the outline of one image is effectively corrected and sharpened.

A television receiver according to the present invention will be described 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.

FIG. 5 shows an example of a television receiver according to the invention.

In the present invention, an electron beam scanning speed and density modulation signal forming circuit 30 comprising a pair of delay means 31 and 32
is provided.

As the delay means 31 and 32, delay lines are used as before.

However, the delay amount is selected to be τ (τ>τ), which becomes the signal delay amount involved in aperture correction as described later, and is selected within the range of 0.25 to 0.5 μsec.

In this example, τ = 0.294 μsec is selected.

Therefore, if the luminance signal supplied to the preceding delay line 31 is illustrated as being obtained from the signal source 33 for convenience, the luminance signal from this can be expressed as E (10τ).

The signal E(t+τ) is transmitted by the first delay line 31.

The first signal E(t) is delayed by τp;

By passing this signal E(t) through the next delay line 32,
A second signal E(t-τ) is obtained.

In this example, the signal E(t) is used as a reference signal, and the delay line 31 is connected to
A tap 11.12 is provided at °32.

Therefore, if the signals E(t+τ) * E (t-τ) derived from the single taps 11 and 132 are supplied to the subtracter 34, the difference signal Ey (t) (By(t)-" E (10r) - E
(t T ), l is obtained, which is used as a signal for beam scanning velocity modulation as described above.

In the present invention, the video signal E P(t) supplied to the picture tube 11
A signal to which a correction signal Ep(t) for aperture correction is added is used.

That is, a signal Ep(t) expressed by a linear equation is used.

Ep(t)=E(t)+αEA(t) To obtain the aperture correction signal EA(t), first provide an adder 35 as shown in FIG.
τ ) and E (-τ ) are supplied to obtain a sum signal, and this is supplied to the level control circuit 36 to step down the level to 10, and then sent to the subtracter 37 together with the signal E(t). Once supplied, an aperture correction signal EA(t) is determined.

Note that 38 is a level control circuit for determining the aperture correction amount α, and the correction amount α is selected within the range of 0.1 to 0.3 in consideration of the aperture effect.

In this example, a case where α=0.15 is shown.

The aperture correction signal E A (t) is further converted into the signal E (t
) is supplied to the adder 39, and the desired sum signal Ep(t) is obtained from the terminal 40.

This sum signal Ep(t) is used as a luminance signal.

In this way, the beam scanning velocity modulation signal E is applied to the deflection means 13.
y(t) and a sum signal Ep(t) to which an aperture correction signal EA(t) is added as a luminance signal to be supplied to the picture tube 11, the response of the step signal is as shown by the curve 41 in FIG. It will be shown as follows.

As is clear from this characteristic curve diagram, it is not only possible to provide sufficient overshoot in the large current range of the electron beam, but also to be able to effectively correct time delays (positional deviations) since it is close to the ideal curve 20. It is.

Note that one curve 41 is a case where the correction amount α is selected to be 0.15 (15%), and in this case, an overshoot of about 24% is obtained.

As described above, in the present invention, the electron beam is velocity-modulated and density-modulated by the sum signal Ep (t) including the correction signal EA (t) for aperture correction, so that sufficient overshoot can be obtained and sharpness can be obtained. In addition to the feature of further improving the image quality, it also has the feature of almost completely correcting the positional deviation of one image.

Therefore, even if continuous black and white images are projected, the white image will not become thin and the black image will not become thick.

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

[Brief explanation of drawings]

FIG. 1 is a connection diagram showing an example of velocity modulating an electron beam, and FIG. 2 is a diagram for explaining the operation. Fig. 3 is a diagram showing an example of a picture tube suitable for applying the present invention, Fig. 4 is a characteristic diagram showing the response of a step signal, and Fig. 5 is an example of the main part of a television receiver according to the present invention. The configuration diagram shown in FIG. 6 is a characteristic diagram similar to FIG. 4 for explaining the present invention. 30 is a speed modulation and density modulation signal forming circuit. 31.32 is a delay line, 35.39 is an adder, 34°37
is the subtractor, Ey(t) is the velocity modulation signal, Ep(t)
is the density modulation signal, and τ and τ are the delay amounts.

Claims (1)

[Claims] 1. First and second delay means having approximately equal delay times are connected in series, and a luminance signal is supplied to the first delay means and the luminance signal is transmitted from the first delay means for a predetermined time. A delayed first luminance signal is obtained, a second luminance signal delayed by approximately twice the predetermined time is obtained from the second delay means, and the luminance signal and the first and second luminances are The signals are combined to form an aperture correction signal, this aperture correction signal and the first brightness signal are combined at a predetermined ratio, and this combined output is supplied to the brightness control electrode of the picture tube to adjust the density of the electron beam. Along with being modulated. A beam scanning velocity modulation signal is formed by subtracting a pair of luminance signals output from intermediate taps provided in each of the first and second delay means. A television receiver characterized in that the modulation signal is supplied to a horizontal deflection velocity modulation means so that the velocity of the electron beam is modulated.