JPS5920310B2 - 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 mutually equal delay amounts τ and a subtraction circuit 3. A luminance signal is supplied via 6.

Now, for convenience, the luminance signal E supplied to the terminal 7 is delayed by a delay amount τ
If E( is +τ) (see FIG. 2A, the same applies hereinafter), this luminance signal +τ) passes through delay line 1 and becomes the first luminance signal E(+τ) delayed by τ. ) will be obtained at terminal 8.

Furthermore, by supplying this signal E() to the delay line 2 in the subsequent stage, a second luminance signal E() delayed by 2τ is obtained.
−τ) is obtained. Here, the signal E (+τ) changes the most from the black level to the white level, or vice versa, and the sharpness is required the most. The delay time τ is selected so that the rise time (or fall time) is 2τ.

Actually, τ is about 0.1 μsec. Incidentally, the first signal E 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 is supplied to the matrix circuit M to which the color difference signals (R-Y) and (B-Y) are supplied. stomach. Then, the original signal E (+τ) and the second
By supplying the signal E (-τ) to the subtractor 3, the terminal 9 receives the signal Ev () as shown in FIG. −τ) ・・・
...(1) is obtained, but this signal Ev () is the beam scanning velocity modulation signal (contour signal), and this is the third
As shown in the figure, the light is supplied to a deflection means 13 for scanning speed modulation, which is provided separately from the horizontal and vertical deflection means 12 present in the picture tube 11.

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.

Various methods of supplying the signal Ev(t) are conceivable, so the explanation thereof will be omitted. Such a signal Ev(t) is deflected by deflection means 1
3, the scanning speed of the electron beam on the screen is modulated by this signal Ev(t), and although a detailed explanation thereof will be omitted, it corresponds to the rising and falling edges of the signal E(t). The amount of light emitted at a position on the screen changes rapidly, thus 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 to a step function. Now, the transmission band of the video signal (0
A step signal that can pass through a frequency range of up to 4.5 MHz and has the fastest rise is applied to the picture tube as a luminance signal, the luminance distribution of the step image on the screen at that time is measured, and its rise time and overshoot are calculated. The sharpness of the step-like image caused by the step signal will be considered by observing the Utes and the like. 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, where 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. Curve 20 is the 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. and,
When speed modulation is performed as described above, the curve becomes as shown by curve 22, and it can be seen that the rise 5 is also earlier 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 objective using the speed modulation method, it is sufficient to increase the supply amount of the speed modulation signal Ev(t). As the amount of supply of the speed modulation signal Ev(t) increases, the amount of overshoot increases. A step response with an overshoot of several percent is obtained. However, in this method, as shown in the figure, the ideal curve 20
As the positional shift becomes noticeable, the rise of the image,
It feels like the falling position has moved. It goes without saying that this phenomenon is not limited to step signals, but 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, further improves sharpness, and makes it possible to effectively correct image positional deviations.

That is, in the present invention, density modulation of the electron beam is performed by forming an aperture-corrected signal and supplying it to the picture tube 11, and a velocity modulation signal is also generated based on this aperture-corrected signal. It is configured to modulate the scanning speed of the beam by forming a beam.
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. FIG. 5 shows an example of a television receiver according to the present invention. In the present invention, a first delay circuit 30 consisting of a pair of delay means 31 and 32 is provided, and an aperture-corrected signal Ep(t) for density modulating the electron beam is formed here. Delay means 3
1 and 32 use delay lines as before. However, the delay amount is selected as τp(τ?τ), which is the signal delay amount involved in aperture correction, and is 0.25
It is selected within the range of ~0.5 μsec. In this example, τ,=0.
The time is selected to be 294 μsec. Here, the previous delay line 3
1 is conveniently expressed as E(t+τ.). The signal E(t+τ,) is made into the first signal E(t) delayed by τ by the first delay line 31, and p
Furthermore, by passing this signal E(t) through the next delay line 32, a second signal E(t-τ.

) is obtained. In this example, signal E(t) is used as a reference signal. Here, the following equation is used as the aperture-corrected signal Ep(t).

To obtain the signal EA(t), first provide an adder 35 as shown in FIG. 5, and add the signals E(t+τp) and E(t-
τ.

) to obtain a sum signal, and after supplying this to the level control circuit 36 and lowering the level to 1, supplying it to the subtracter 37 together with the signal E(t), the signal EA(
t) is calculated. In addition, 38 is the aperture correction amount α
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 signal EA(t) is further sent to the adder 3 together with the signal E(t).
9, and from a terminal 40, the desired sum signal, that is, the aperture-corrected signal Ep(t) is obtained. This sum signal Ep(t) is used as a luminance signal. However, in reality, the speed modulation signal Ep(t) described later
In order to match the phase with the modulated signal Ep(t), a signal delayed by a predetermined time is used. Signal Ep(t
) is illustrated by a curve 41 in FIG.

Next, the speed modulation signal Evp(t) will be explained.
In the present invention, the aperture-corrected signal Ep(
t) is used as the original signal.

Therefore, as shown in FIG.
A second delay circuit 45 consisting of 3 is provided. delay line 4
The delay amounts of 2 and 43 are respectively τ as shown in FIG. Now, if the connection point t1 is the reference time axis, the sum signal Fp
(t) can be expressed as Ep(t+τ), so this signal Ep(t+τ) and the delayed signal (fourth signal) Ep(t-0) obtained through the delay line 43 are subtracted by the subtracter 46.
, a difference signal Evp(t) for speed modulation as shown by a curve 48 in FIG. 7 is obtained at the terminal 47.

Here, since the difference signal Evp(t) obtained at the terminal 47 uses equation (2) as its original signal, it can be expressed by the following equation.

Although the curve 48 shows only the rising portion of the signal E(t), the same applies to the falling portion.

In addition, the density modulation of the electron beam is performed using the velocity modulation signal Evp(t).
The signal (voltage) obtained at the terminal 40 derived from the connection point of the delay lines 42 and 43 in FIG.
This is done at EpO(t). If the electron beam is velocity-modulated using the difference signal Evp(t) shown by this curve 48, the electron beam will be decelerated between time points t1 and T2 and between T3 and T4 shown in FIG. 7, but between time points T2 and T3. And, between T4 and T5, it is accelerated in the opposite direction.

Therefore, the amount of light emitted increases in the part where the signal changes rapidly, and the luminance signal is aperture-corrected and delayed for a predetermined time (third signal) EpO (
t) and the aperture-corrected signal E
When a velocity modulation signal Evp(t) is obtained based on p(t) and is supplied to the deflection means 13, the response of the step signal becomes as shown by a curve 50 in FIG. As is clear from this characteristic curve diagram, it is possible to provide sufficient overshoot in the large current range of the electron beam.
Since it is close to the ideal curve 20, positional deviation can be effectively corrected.

Note that the curve 50 shows the case where the correction amount α is selected to be 0.15 (15%), and in this case, an overshoot of about 40% is obtained. Moreover, the smear is small. In addition, the 8th
The curve 51 shown in the figure is the aperture-corrected signal Ep(
This is a case where the beam is density-modulated after delaying t), but the signal Ev(t) shown in FIG. 1 is used instead of the signal Evp(t) as the velocity modulation signal.

Therefore, as is clear from comparing both curves 50 and 51, the present invention has the feature that both positional deviation and smear can be reduced. As explained above, in the present invention, the electron beam is density-modulated using the aperture-corrected signal Ep(t), and the aperture-corrected signal Ep(t) is used to density-modulate the electron beam.
The configuration is such that the electron beam is velocity-modulated using a signal Evp(t) formed based on p(t). In this way, not only can sufficient overshoot be obtained, but also the smear can be reduced compared to the conventional method, so in addition to the characteristic that the sharpness can be further improved,
It also has the feature of being able to almost completely correct image positional deviations.
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. In addition,
The aperture-corrected signal Ep(t) mentioned above is
The point is that the frequency characteristics in the high frequency range of about 1 to 2 MBz are emphasized (frequency boosted), so in addition to the above-mentioned embodiments, the first and second delay circuits 30 and 45 are used. It goes without saying that the lever signal Ep(t) can be obtained.

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, FIG. 5 is a configuration diagram showing an example of the main part of the television receiver according to the present invention, and FIGS. 6 to 8 are diagrams for explaining the present invention. It is a characteristic curve diagram. 30 is the first delay circuit, 45 is the second delay circuit, 31, 32, 4
2, 43 is a delay line, Evp(t) is a velocity modulation signal, Ep
O(t) is a density modulation signal, and τ and τp are delay amounts.

Claims (1)

[Claims] 1 It has a first delay circuit consisting of a pair of delay means, and supplies a luminance signal to the first delay circuit, so that the first luminance signal is delayed by a certain period of time, and the second luminance signal is delayed by approximately twice the time. The input brightness signal and the second brightness signal are supplied to a level control circuit, and the levels of each of the input brightness signal and the second brightness signal are gradually reduced by approximately 1/2, and the first brightness signal is Subtract the output signal of the above level control circuit from
The aperture-corrected signal formed by adding this subtracted output and the first luminance signal was supplied to a second delay circuit comprising a pair of delay means, and the aperture-corrected signal was delayed for a certain period of time. The third luminance signal and approximately 2
A fourth luminance signal delayed by twice the time is obtained, the third luminance signal is supplied to the picture tube to perform density modulation of the electron beam, and the aperture-corrected signal and the fourth luminance signal are
A television receiver configured to modulate the scanning speed of the electron beam by supplying a difference signal between the brightness signal and the brightness signal to a beam scanning speed modulating deflection means provided in the picture tube.