JPH0481390B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a luminance signal recording and reproducing apparatus, and more particularly to a luminance signal recording and reproducing apparatus equipped with at least one of a nonlinear pre-emphasis circuit and a nonlinear de-emphasis circuit.

Conventional technology Conventionally, in order to improve the S/N of high frequencies, a non-linear pre-emphasis circuit and a non-linear de-emphasis circuit have been provided in the luminance signal recording system and reproduction system, respectively, and non-linear pre-emphasis is performed on the luminance signal during recording. There is a luminance signal recording and reproducing device that emphasizes the high frequency component and records it on a magnetic recording medium, and when reproducing the reproduced luminance signal, imparts a nonlinear de-emphasis characteristic complementary to the nonlinear pre-emphasis characteristic. A so-called transversal filter or the like is used as such a nonlinear pre-emphasis circuit and a non-linear de-emphasis circuit.

The above transversal filter is a delay circuit,
It consists of multipliers, adders, etc., and subtracts or adds multiple signals that are slightly delayed positionally on the same horizontal scanning line to the pixel information signal on the screen, and performs one horizontal scanning. Pre-emphasis or de-emphasis was performed between signals within a line (for convenience, this will be referred to as "horizontal emphasis"). Therefore, it was only possible to reduce high frequency noise in the horizontal direction of the screen.

Therefore, in order to reduce high-frequency noise in the vertical direction of the screen, a 1H delay circuit that delays by one horizontal scanning period (1H), a nonlinear pre-emphasis circuit consisting of a multiplier, an arithmetic unit, etc.
Other luminance signal recording and reproducing devices provided with a de-emphasis circuit have been proposed in the past (for example, Japanese Patent Laid-Open No. 60-30285). Such non-linear pre-emphasis circuits and non-linear de-emphasis circuits subtract multiple signals before integral multiples of 1H, such as points P' and P'' in the figure, from the signal at point P on the screen shown in FIG. or addition, to perform pre-emphasis and de-emphasis between signals in the vertical direction on the screen (for convenience, this will be referred to as "vertical emphasis").

Problems to be Solved by the Invention In general, noise reduction circuits for VTRs are logically analyzed by considering the noise to be random noise. However, video signals recorded by a VTR have strong correlations in the horizontal, vertical, or frame directions on the screen. Therefore, it is thought that noise also has a correlation.

Therefore, when performing the above vertical emphasis,
As shown in FIG. 11, due to the vertical correlation between pixels, noise is arranged vertically due to the circuit configuration, giving the viewer the impression that rain is falling on the screen. In addition, although we are used to seeing horizontal noise on monitor screens, vertical noise is new and stands out, which is another problem.

Therefore, in place of the 1H delay circuit, the present invention provides
Using a delay circuit configured to separately add a first delay time that is longer than one horizontal scanning period and a second delay time that is shorter than one horizontal scanning period by a certain period of time to the input signal, and then add them together, A luminance signal recording and reproducing device which solves the above problems by being equipped with a non-linear circuit and configured to perform non-linear pre-emphasis and de-emphasis of the luminance signal in a direction inclined at a required angle with respect to the vertical direction of the screen. The purpose is to provide

Means for Solving the Problems A luminance signal recording/reproducing device according to the present invention uses at least one of a nonlinear pre-emphasis circuit and a non-linear de-emphasis circuit each configured of a cyclic filter having a delay circuit and a non-linear circuit. A luminance signal recording/reproducing device equipped with a delay circuit at a time Δt shorter than one horizontal scanning period (However, Δt is a fixed time smaller than one horizontal scanning period)
Longer first delay time and Δt than one horizontal scanning period
The configuration is such that a short second delay time is added to the input signals separately and then added. Further, in addition to the first and second delay times, a third delay time equal to one horizontal scanning period may be separately added to the input signal and then added.

Function The above delay circuit adds the first delay time (1H + Δt), the second delay time (1H - Δt) and the third delay time 1H to the input signal separately, so that the 1H delay Compared to vertical emphasis using a circuit, the direction of emphasis is tilted left and right by Δt. That is, the apparatus of the present invention equipped with the delay circuit and nonlinear circuit performs nonlinear pre-emphasis and de-emphasis of the luminance signal in a direction inclined at an angle θ (however, 0°≦θ≦90°) with respect to the vertical direction of the screen. It will be done.

As a result, the noise correlation also occurs in a direction inclined at the angle θ with respect to the vertical direction of the screen, and the direction of noise correlation is diffused, resulting in a reproduced image having substantially no noise correlation.

Embodiment FIG. 1 shows a block system diagram of a first embodiment of a luminance signal recording/reproducing apparatus according to the present invention. This first
The embodiment has a configuration in which the functions of both the nonlinear pre-emphasis circuit and the non-linear de-emphasis circuit can be shared. The operation of this first embodiment will be explained with reference to the signal waveform diagram shown in FIG. First, to explain the case where it operates as a nonlinear pre-emphasis circuit,
A luminance signal a as shown in FIG. 2A (for convenience of explanation, expressed as a signal of one vertical scanning period (1V)) inputted to an input terminal 1 is supplied to a delay circuit 3 through an arithmetic unit 2.

FIG. 3 shows a detailed block system diagram of a first embodiment of the delay circuit 3 which is the main part of the apparatus of the present invention in the block system shown in FIG. Here, the luminance signal a supplied through the arithmetic unit 2 is supplied to the delay line 4. The delay line 4 has a delay time characteristic of (t _H - Δt) consisting of one horizontal scanning period t _H and a minute time Δt, and the incoming luminance signal a is delayed for the above time (t _H - Δt).
After the delay, the signal is supplied to one input terminal of a delay line 5 having a delay time of 2×Δt and an adder 6, respectively. The delay line 5 delays the incoming signal by a time of 2×Δt and then supplies it to the other input terminal of the adder 6.
Here, it is added to the signal from delay line 4.

Therefore, for example, the signal at _one point P on _the screen shown in _FIG .
A further time 2Δt before the signal at _two points P, that is,
P ₃ time (T _H + Δt) before the signal at P ₁ point above
The signal is the sum of the point signal and the point signal.

Returning to FIG. 1 again, the arithmetic unit 7 converts the luminance signal a from the input terminal 1 into the adder 6.
The output luminance signal of is subtracted to obtain a signal b as shown in FIG.
It is supplied to the arithmetic unit 2 via a coefficient circuit 9 which multiplies it by a coefficient k ₁ (for example, 0.5). The arithmetic unit 2 subtracts the signal supplied from the coefficient circuit 9 from the luminance signal a from the input terminal 1 and supplies the obtained signal to the delay circuit 3 again.

On the other hand, the coefficient circuit 10 multiplies the output signal c of the limiter 8 by a coefficient k ₂ (for example, 0.65) and outputs the result to the adder 1.
1, and a signal d as shown in FIG. 2D obtained by adding the luminance signal a from the input terminal 1 is outputted to the output terminal 12.

The luminance signal d output to this output terminal 12 is
For example, P ₁ on the n-th horizontal scanning line counting from the horizontal scanning line at the top of the screen on the screen shown in FIG.
For the signal at the point, in the signal on the (n-1)th horizontal scanning line 1H before, P ₂ points before the time (t _H - Δt) and P ₃ points before the time (t _H +Δt) Add each signal little by little, and then add (n-2) signals 2H before
In the signal on the th horizontal scanning line, P ₄ , P ₅ and
Add the signals of ₆ points P little by little, and in the same way, 3H,
This is a signal obtained by adding little by little the signals at a predetermined point on the horizontal scanning line 4H, ..., nH before. In this way, a nonlinear pre-emphasis characteristic in which the high-frequency components of spatial frequencies in the vertical and diagonal directions of the screen are enhanced in level compared to the low-frequency components is imparted to the luminance signal a input to the input terminal 1. luminance signal d
is obtained. By the way, the time required to horizontally scan two adjacent horizontal scanning lines of the same field by the vertical distance (interval) on the screen is 180ns, which is compared to 1H (=63.5μs). It's a short amount of time. Here, the minute time Δt is, for example,
When set to 200 ns, the inclination angle θ at which nonlinear pre-emphasis is performed with respect to the vertical direction of the screen shown in FIG. 4 becomes about 50°.

Next, the block system shown in Figure 1 is non-linear.
To explain the case where it operates as a de-emphasis circuit, the output signal c of the limiter 8 has a coefficient
k ₂ / (k ₂ + 1) (for example, 0.65 / (0.65 + 1) ≒
0.394) via the coefficient circuit 13
4. The arithmetic unit 14 subtracts the output signal of the coefficient circuit 13 from the luminance signal a input from the input terminal 1, and outputs a luminance signal e as shown in FIG. 2E to the output terminal 15.

The luminance signal e output to this output terminal 15 is
Similar to the above, this is a signal obtained by little by little subtracting a predetermined signal on the horizontal scanning line 1H, 2H, . . . , nH before that. In this way, a luminance signal e having a nonlinear de-emphasis characteristic in which high-frequency components of spatial frequencies in the vertical and diagonal directions of the screen are attenuated in level compared to low-frequency components is obtained.

The luminance signals d and e have mutually complementary characteristics as shown in FIG. Therefore, when the luminance signal d with non-linear pre-emphasis characteristics is applied to the input terminal 1 in FIG. 1 during reproduction, the non-linear de-emphasis characteristics are applied from the output terminal 15, and the original characteristics are reproduced. A luminance signal a as shown in FIG. 2A is obtained.
In this way, the signal at _point P on the n-th horizontal scanning line shown in FIG.
In the figure, non-linear pre-emphasis and non-linear de-emphasis are performed, which are added or subtracted from the signal at a predetermined point on the horizontal scanning line that is an integer multiple of 1H, such as points _{P 2 to} P 6 (hereinafter referred to as For convenience, "Nonlinear Diffusion Vertical Emphasis"
). As a result, the flow of information is diffused as shown in FIG. 4, and the vertical correlation of noise as shown in FIG. 11 is reduced.

Furthermore, when the non-linear diffusion vertical emphasis is performed, for example, the signal at point _P5 on the (n-2)th horizontal scanning line will be 2H later in the vertical direction of the screen.
_For example, n
Since the information on the line has an effect on lines such as (n+2), (n+4), etc., it is also possible to avoid poor complementarity when the above-mentioned nonlinear pre-emphasis and non-linear de-emphasis are configured in an open-loop circuit configuration. effective.

Further, the S/N improvement effect of the nonlinear diffusion vertical emphasis is the same as that of the vertical emphasis as long as the setting constants of the emphasis such as the coefficients k ₁ and k ₂ are the same. However, the screen on which non-linear diffusion vertical emphasis was actually applied had no noticeable noise and the S/N was visually excellent.
It was a very impressive screen that I had never seen before. That is, non-linear diffusion vertical emphasis reduces noise visually or data and improves S/N.
It can be said to be a very effective means of improving.

Figure 5 shows the delay circuit 3 in the block system shown in Figure 1.
2 shows a detailed block system diagram of the second embodiment of the invention. In the figure, the delay line 16 is similar to the delay line 4 (t _H −
Δt), and has a delay time characteristic of 1H delay line 1
7 has a delay time characteristic of t _H , and the delay line 18
has a delay time characteristic of 2×Δt similarly to the delay line 5. Here, the delay line 16 delays the incoming luminance signal a by a time (t _H -Δt) and then supplies the signal to a delay line 18 and an adder 19, respectively. The delay line 18 delays the incoming signal by a time of 2×Δt, and then
Output to adder 19. On the other hand, the 1H delay line 17 delays the incoming luminance signal a by a time _tH , and then
Output to adder 19. The adder 19 adds and outputs the three input signals mentioned above. The output signal of the adder 19 is the output signal of the adder 6.
Since this is a signal obtained by adding the output signal of the 1H delay line 17, if this output addition signal is supplied to the arithmetic unit 7 shown in FIG. The screen, as shown in FIG. 6, is a reproduced screen that is the same as the nonlinear diffusion vertical emphasis screen shown in FIG. 4 and the vertical emphasis screen shown in FIG. 11. In this way, a reproduced screen in which the correlation of the noises is diffused in a complicated manner can be obtained.

Next, the second to fifth embodiments of the device of the present invention are shown in Figs.
This will be explained with reference to FIG. Similar to the first embodiment of the device of the present invention, these embodiments have a configuration in which the circuit functions of the nonlinear pre-emphasis circuit and the non-linear de-emphasis circuit can be shared, and the delay circuit 3 which is the main part thereof By using the configuration as shown in FIGS. 3 and 5, it is possible to obtain a reproduced screen in which diffused vertical emphasis is applied as shown in FIGS. 4 and 6. In FIGS. 7 to 10, the same components as those in FIG. 1 are denoted by the same reference numerals, and the explanation thereof will be omitted as appropriate.

FIGS. 7 and 8 show block diagrams of second and third embodiments of the apparatus of the present invention, respectively. The second and third embodiments are characterized in that they are provided with a changeover switch 20 for arbitrarily selecting one of the nonlinear pre-emphasis circuit and the non-linear de-emphasis circuit. Therefore, most of the circuitry can be shared by the nonlinear pre-emphasis circuit and the nonlinear de-emphasis circuit.

Now, we will convert the block system shown in Figure 7 into a non-linear
When operating as a pre-emphasis circuit, the changeover switch 20 is connected to the terminal 20a side.
Here, the input luminance signal that enters the input terminal 21 is supplied to the arithmetic unit 23 via the arithmetic unit 22 and the delay circuit 3. The arithmetic unit 23 limits the amplitude of the signal obtained by subtracting the output signal of the delay circuit 3 from the input luminance signal via the limiter 24, and then calculates the coefficient
The terminals 20a and 20 of the changeover switch 20 are connected in parallel through coefficient circuits 25 and 26 that multiply k ₃ and k ₄ , respectively.
b. Since the changeover switch 20 is connected to the terminal 20a side, the output signal of the coefficient circuit 25 is supplied to the arithmetic unit 22 via the terminal 20a of the changeover switch 20. The arithmetic unit 22 subtracts the output signal of the coefficient circuit 25 from the input luminance signal and supplies the obtained signal to the delay circuit 3 again.

On the other hand, the coefficient circuit 27 multiplies the output signal of the limiter 24 by a coefficient k ₅ and supplies the obtained signal to the adder 28 , where it is added to the input luminance signal and outputted to the output terminal 29 .

Next, when operating the second embodiment as a nonlinear de-emphasis circuit, the changeover switch 20 is connected to the terminal 20b side. Thereby, the arithmetic unit 22 supplies a signal obtained by subtracting the output signal of the coefficient circuit 26 from the input reproduced luminance signal supplied to the terminal 21 to the delay circuit 3. In this case, the output signal of the coefficient circuit 27 is supplied to the arithmetic unit 30, where it is subtracted from the input reproduced luminance signal, and then output to the output terminal 31.

As described above, the output terminals 29 and 31 provide a luminance signal with non-linear pre-emphasis characteristics and a reproduced luminance signal with non-linear de-emphasis characteristics, respectively.

Next, a third embodiment will be described. In FIG. 8, the same components as those in FIG. Note that the limiter 24a has the same function as the limiter 24 described above. This third embodiment is different from the second embodiment in that the coefficient circuits 25, 26 and 27 are replaced by coefficients k ₆ , k ₇ and k _{8 .}
As coefficient circuits 32, 33 and 34 having respectively
Furthermore, a limiter 24b and a coefficient circuit 35 having a coefficient _k9 are newly provided between the arithmetic unit 23 and the adder 28, so that the adder 28 adds the input luminance signal and the output signal of the coefficient circuit 35. They differ in their composition.

That is, when the third embodiment operates as a nonlinear pre-emphasis circuit, the arithmetic unit 2
The output signal of 3 is the coefficient circuit 32 and the changeover switch 2.
The signal is supplied to the arithmetic unit 22 through the terminal 20a of 0, and is also supplied to the adder 28 through the limiter 24b and the coefficient circuit 35, where it is added with the input luminance signal, and then non-linear pre-emphasis characteristics are imparted thereto. The brightness signal is output to the output terminal 29 as a luminance signal. Next, the third embodiment described above is non-linear.
When operating as a de-emphasis circuit, the output signal of the arithmetic unit 23 is sent to the limiter 24a and the coefficient circuit 3.
3 and the terminal 20b of the changeover switch 20, and is also supplied to the calculator 30 via the limiter 24a and the coefficient circuit 34, where it is subtracted from the input reproduced luminance signal. , is outputted to the output terminal 31 as a reproduced luminance signal imparted with non-linear de-emphasis characteristics.

FIGS. 9 and 10 show block diagrams of fourth and fifth embodiments of the apparatus of the present invention, respectively. This fourth
The fifth embodiment is characterized in that a switch (hereinafter referred to as "switch") 36 for switching functions as the non-linear pre-emphasis circuit and the non-linear de-emphasis circuit is provided, Compared to the third embodiment, the switch has fewer contact points and has a simpler configuration.

Now, we will convert the block system shown in Figure 9 into a non-linear
When operating as a pre-emphasis circuit, the switch 36 is turned on. Here, the input luminance signal that enters the input terminal 37 is supplied to the delay circuit 3 through the adder 38 and the arithmetic unit 39, and after being delayed for a predetermined time at 1H and its vicinity as described above, is supplied to the arithmetic unit 40. Ru. The arithmetic unit 40 limits the amplitude of a signal obtained by subtracting the output signal of the delay circuit 3 from the output signal of the adder 38 via a limiter 41, and then sends the signal to the arithmetic unit 39 via a coefficient circuit 42 that multiplies it by a coefficient _k10 . supply Arithmetic unit 39 is adder 3
A signal obtained by subtracting the output signal of the coefficient circuit 42 from the output signal of 8 is supplied to the delay circuit 3 again. On the other hand, the output signal of the limiter 41 has a coefficient
The signal is supplied to an adder 38 via a coefficient circuit 43 for multiplying by k ₁₁ and a switch 36, respectively. Adder 38
The addition output signal obtained by adding the input luminance signal and the output signal of the coefficient circuit 43 is sent to the arithmetic unit 3 again.
9 and 40 respectively, and the output terminal 44
Output to. In this way, the luminance signal subjected to non-linear pre-emphasis is transmitted to the output terminal 4.
Obtained from 4.

Next, when the fourth embodiment is operated as a nonlinear de-emphasis circuit, the switch 36 is turned off, and the adder 38 does not perform the addition operation as described above. In this case, the input reproduced luminance signal entering the input terminal 37 is input to the adder 3
8 to computing units 39, 40 and 45, respectively. Arithmetic unit 45 outputs a signal obtained by subtracting the output signal of coefficient circuit 43 from the input reproduced luminance signal to output terminal 46 . In this way, a reproduced luminance signal subjected to non-linear de-emphasis is obtained from the output terminal 46.

Next, the fifth embodiment will be described. In FIG. 10, the same components as those in FIG. This fifth embodiment uses a coefficient circuit 47 for multiplying by a coefficient k ₁₂ in place of the coefficient circuit 43 used in the fourth embodiment, and furthermore,
The coefficient circuit 42 is not provided in the feedback loop from the limiter 41 to the arithmetic unit 39, and the arithmetic unit 40 and the limiter 4
It is characterized by being placed between 1 and 1. Here, the output signal of the arithmetic unit 40 is supplied to the arithmetic unit 39 via the coefficient circuit 42 and the limiter 41 in series, and to the arithmetic unit 45 via the coefficient circuit 42, the limiter 41, and the coefficient circuit 47 in series. Supplied. The coefficient multiplied by the coefficient circuit 45 is k ₁₂ = k ₁₁ /
Since k ₁₀ , the output signal of the coefficient circuit 47 is sent to the arithmetic unit 40.
The output signal is multiplied by k ₁₀ × k ₁₂ = k ₁₁ , and
In the end, the functions of the fifth embodiment are the same as those of the fourth embodiment.

Note that the configuration of the delay circuit 3 is not limited to the configuration shown in FIGS. 3 and 5, and the configuration of the device of the present invention is not limited to the first to fifth embodiments. , various configurations can be achieved by changing the combinations of coefficient circuits, arithmetic units, and adders. Therefore, in the embodiment of the device of the present invention described above, the directions of diffusion are left and right, but the angle θ is between 0° and
Any angle within the range of 90° may be used, and configurations such as a combination of the horizontal direction and the vertical direction, a combination of the vertical direction and any one of the left and right directions as shown in FIG. 6 are also possible.

In addition, the limiters 8, 24, 24a, 24b
and 41 may be other nonlinear circuits. Also,
In a VTR equipped with only either a nonlinear pre-emphasis circuit or a non-linear de-emphasis circuit, the video signal (i.e.
Since the amplitude of the luminance signal (luminance signal) is not so emphasized during recording and playback, the video signal played back from the magnetic tape recorded by the existing VTR, which does not have a non-linear pre-emphasis circuit, is
Even through a de-emphasis circuit, the original signal waveform can be restored with virtually no problems; on the other hand, when a magnetic tape on which a video signal has been recorded through a non-linear pre-emphasis circuit is played back on an existing VTR that does not have a non-linear de-emphasis circuit. It also has the advantage of being able to reproduce the original signal with almost no practical problems. Therefore,
A non-linear pre-emphasis circuit may be provided only in the recording system, or a non-linear de-emphasis circuit may be provided only in the reproduction system.

Effects of the Invention As described above, according to the present invention, since nonlinear diffusion vertical emphasis is performed, the present invention has the following numerous features.

Since noise in the vertical direction on the playback screen due to the conventional vertical emphasis can be reduced, and the correlation between the noise in the horizontal and vertical directions is diffused, the S/N ratio can be visually significantly improved.

Since it is configured to include at least one of a nonlinear pre-emphasis circuit and a non-linear de-emphasis circuit,
By changing the amount of pre-emphasis and de-emphasis according to the amplitude of the luminance signal,
Non-linear pre-emphasis or de-emphasis can be performed on the luminance signal, and therefore an effect of improving the S/N of the reproduced luminance signal can be obtained while maintaining compatibility with existing VTRs.

As described above, it is possible to obtain a reproduced luminance signal that does not deteriorate in image quality due to passing through the recording/reproducing system and is visually good.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing a first embodiment of the luminance signal recording/reproducing device according to the present invention, and FIG.
FIGS. 3 and 5 are signal waveform diagrams for explaining the operation of the illustrated block system, and FIGS. 6 is a diagram showing an example of the nonlinear diffusion vertical emphasis method using the apparatus of the present invention, and FIGS.
Block system diagram showing examples to fifth examples, first
FIG. 1 is a diagram showing an example of a conventional vertical emphasis method. 1, 21, 37... Brightness signal or reproduced brightness signal input terminal, 2, 7, 14, 22, 23, 30, 3
9, 40, 45... Arithmetic unit, 3... Delay circuit,
4, 5, 16, 18...delay line, 6, 11, 1
9, 28, 38...adder, 8, 24, 24a,
24b, 41...Limitsuta, 9, 10, 13, 2
5-27, 32-35, 42, 43, 47... Coefficient circuit, 12, 29, 44... Luminance signal output terminal, 15, 31, 46... Reproduction luminance signal output terminal, 17... 1H delay line, 20...changeover switch,
36... Open/close switch.

Claims (1)

[Scope of Claims] 1. A luminance signal recording and reproducing device comprising at least one of a non-linear pre-emphasis circuit and a non-linear de-emphasis circuit configured of a cyclic filter having a delay circuit and a non-linear circuit, the device comprising: The circuit has a first delay time that is longer than one horizontal scanning period by Δt (however, Δt is a fixed time smaller than one horizontal scanning period) and a second delay time that is shorter than one horizontal scanning period by Δt. 1. A luminance signal recording and reproducing device characterized in that the luminance signal is added after being added to the luminance signal. 2. A luminance signal recording and reproducing device equipped with at least one of a nonlinear pre-emphasis circuit and a non-linear de-emphasis circuit configured with a cyclic filter having a delay circuit and a non-linear circuit, wherein the delay circuit is used for one horizontal scanning period. A first delay time longer than Δt (where Δt is a constant time smaller than one horizontal scanning period), a second delay time shorter than one horizontal scanning period by Δt, and a third delay equal to one horizontal scanning period. 1. A luminance signal recording and reproducing device characterized in that the luminance signal recording and reproducing device is configured to separately add time and time to an input signal and then add them.