JP2798562B2 - Signal correction circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal correction circuit, and more particularly, to a video signal correction circuit in a VTR.

[0002]

2. Description of the Related Art Conventionally, a video signal correction circuit which uses a field or frame correlation is very similar to that of a video signal correction circuit, and FIG. 3 is a block diagram showing an example thereof.
It uses field correlation.

In FIG. 3, a video signal input 10 is connected to a plus side input of a subtraction circuit 12 and a plus side input of a subtraction circuit 13, and an output of the subtraction circuit 12 is connected to a storage circuit 15. Is connected to the minus input of the subtraction circuit 13, the output of the subtraction circuit 13 is connected to the amplification circuit 14, the output of the amplification circuit 14 is connected to the minus input of the subtraction circuit 12, and the output of the subtraction circuit 12 is connected to the video signal. The output is 11.

Next, the operation of this conventional example will be described. The subtraction circuit 13 has a video signal input 10
, And the video signal obtained by delaying the output of the subtraction circuit 12 by one field by the storage circuit 15 is input to the minus side input. The subtraction circuit 12 supplies the video signal input 10 to the plus side input.
, And a video signal whose output from the subtraction circuit 13 is multiplied by K by the amplifier circuit 14 is input to the minus side input. The video signal output 11 is obtained from the subtraction circuit 12. Thus, the following relational expression is obtained.

Output 11 = input 10− (input 10−output 11 ′) K = input 10 (1-K) + output 11′K where input 11 ′ is a value delayed by one field. Since the input 10 is the current video signal and the output 11 'is the video signal of one field before, the correlated signal component of the video signal of one field before and the current is emphasized and the uncorrelated video signal is attenuated. Is done.

[0006]

As described above, in the case of the conventional example , the current video signal level and the immediately preceding video signal level are used.
Since only the correlation with the signal level is considered,
Error signal is lost in areas where there is no sudden change in signal level
Error signal can be corrected if
For example, a large contrast or other
Even in the case of a normal video signal that changes in a
Signal level is low, so signal
The original normal signal level is attenuated,
It has the disadvantage of causing blurring and blurring in the vicinity.
Was.

An object of the present invention is to provide a <br/> signal correction circuit for solving the disadvantages mentioned above.

[0008]

According to the present invention, there is provided a signal correction circuit comprising: an input terminal to which a signal input at an N + 1 time point is input;
Is connected to the input terminal and enters the input terminal at the time point N.
A first holding circuit for holding the input signal;
Wherein a second holding circuit for holding a signal inputted to the input terminal, a first differential signal detection circuit for detecting an output a difference signal between the input signal and the N-1 time point of the input signal N times to, N out detecting a difference signal between the input signal and the (N + 1) time of the input signal at the time
A second difference signal detection circuit for force, the difference signal output level of said first difference signal detection circuit, first indicates whether larger than a predetermined <br/> reference signal input level inputted from the outside 1 comparison of
A first comparison circuit that outputs a signal and a difference signal output level of the second difference signal detection circuit are input from the outside.
A second indicating whether or not it is greater than a predetermined reference signal input level;
A second comparison circuit for outputting a comparison signal, receiving said first and <br/> second comparison signal output, comparison of the first and second
Check that both signal outputs are higher than the reference signal input level.
Signal output levels of the first and second comparison circuits shown in FIG.
When that, it is determined that correction is necessary, the input of N times
Instruction signal, so replace with the input signal of N-1 time
A determination circuit that outputs a control signal to be performed, and an input signal at the N time held in the first holding circuit or an input signal at the N-1 time held in the second holding circuit.
Or, the switching by the control signal of the decision circuit first
And a changeover switch for inputting the signal to the second holding circuit, wherein the holding signal output of the second holding circuit is corrected.
It is output as the signal.

[0009]

FIG. 1 is a block diagram showing a signal correction circuit according to an embodiment of the present invention. In FIG. 1, in this embodiment, the video signal input 10 is connected to the register 1, the output of the register 1 is connected to one of the changeover switches 9, the output of the changeover switch 9 is connected to the register 2, and the output of the register 2 Is connected to the other end of the changeover switch 9, the output of the register 1 is connected to one of the inputs of the difference detection circuit 3, the video signal input 10 is connected to the other, and the output of the register 2 is connected to one of the inputs of the difference detection circuit 4 to the other. The output of the register 1 is connected, the output of the difference detection circuit 3 is connected to one of the comparison circuits 5 and the reference level signal 7 is connected to the other, and the output of the difference detection circuit 4 is connected to one of the comparison circuits 6 and the reference level signal 7 is connected to the other. The output of the comparison circuit 5 and the output of the comparison circuit 6 are connected to the judgment circuit 8, the output of the judgment circuit 8 is connected to the control input of the changeover switch 9, and the output of the register 2 is used as the video signal output 11. .

Next, the operation of the embodiment of FIG. 1 will be described. The register 1 receives the video signal input 10 and inputs the output of the register 1 to one of the changeover switches 9. The register 2 receives the output of the changeover switch 9 and outputs it to the other input of the same changeover switch 9. Changeover switch 9
Selects whether to update or hold the data in the register 2 by this. The difference detection circuit 3 receives the output of the register 1 on one side and the video signal input 10 on the other side, detects the difference between the data amount of the register 1 and the data amount of the video signal input 10, and outputs the difference. The difference detection circuit 4 receives the output of the register 2 on one side and the output of the register 1 on the other side, and detects and outputs the difference between the data amount of the register 2 and the data amount of the register 1.

The comparison circuit 5 compares whether the data amount obtained by the difference detection circuit 3 is larger or smaller than the data amount of the reference level signal 7 and outputs the result. Further, the comparison circuit 6 compares and outputs whether the data amount obtained by the difference detection circuit 4 is larger or smaller than the data amount of the reference level signal 7.

The judgment circuit 8 outputs a control signal when the outputs of the comparison circuits 5 and 6 both exceed the data amount of the reference level signal 7 when the data amount obtained by the difference detection circuit 3 and the difference detection circuit 4 both exceed the data amount. The register 2 is output by the changeover switch 9
Switch to the output side to hold the data. If the data amount obtained by the difference detection circuit 3 and the difference detection circuit 4 does not exceed one or both of the data amounts of the reference level signal 7, a control signal is output, and the output of the register 1 is Side to update the data in the register 2.

This embodiment will be described in detail with reference to FIG. When the level of the reference signal input 7 was VR, in the video signal input 10 of figure waveform j, A point, B point, the point C
Signal level, if it is the following relationship with respect to VR, | (signal level at the point B) - (signal at the point A level <br/> Le) |> VR and,, | (C point Signal level ) − ( signal level at point B ) | > VR.

In both cases, the data amount exceeds the reference level signal 7, and the output of the determination circuit 8 is output at a high level as shown by a waveform m in the figure. In response to the output of the register 1 of the waveform k, the data at the point A held in the register 2 is output to the register 2 again.
The point A is output twice as shown in the output of (1). Accordingly, the video signal output 11 has a waveform having no point B as shown by a waveform n in the figure.

[0015] Next, point D, point E, if the point F is in the following relation, | (signal level at the point E) - (point D
Signal level ) | > VR and | ( signal level at point F )
− ( Signal level at point E ) | < VR.

This is because the data amount obtained by the difference detection circuit 4 exceeds the data amount of the reference level signal 7, so that the output of the judgment circuit 8 remains at the low level of the waveform m in FIG. Is the output of the register 1 as it is, and the output of the input register 2 is a continuous output of D, E, and F as shown by the waveform l in the figure. The video signal output 11 at this time becomes D, E, F of the waveform n in the figure, and becomes the same output as the input.

In the embodiment of the present invention, if data is taken into the register at 4 fsc (four times the subcarrier), the signal can be corrected by correlation with the horizontal direction of the screen. Thus, the signal can be corrected based on the correlation with the vertical direction of the screen.

The signal correction based on the correlation with the horizontal direction of the screen can be another embodiment of the present invention in which an analog video signal is input. This embodiment is shown in FIG. In FIG. 4, this embodiment can be realized by using operational amplifiers for the sample and hold circuits 16 and 17 as the holding circuits, the difference detection circuits 3 and 4, and the comparators for the comparison circuits 5 and 6, and inputting the reference level signal. Also becomes an analog input. Other parts are the same as those in FIG.

[0019]

As described above, according to the present invention, an abnormal pulse in a signal flow is detected and removed by comparing a difference between a current signal and a previous signal. There is an effect that the abnormal signal can be completely removed, the visual image quality can be improved and the image can be easily viewed, and since the data other than the abnormal signal is output as it is, the reproducibility of the image is good.

Since the level at which the signal can be corrected from the outside can be set by the reference level signal 7 shown in FIGS. 1 and 4, there is an advantage that an effect corresponding to the system to be incorporated can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a signal correction circuit according to one embodiment of the present invention.

FIG. 2 is a timing chart illustrating the signal correction circuit of FIG. 1;

FIG. 3 is a block diagram showing a conventional signal correction circuit.

FIG. 4 is a block diagram showing a signal correction circuit according to another embodiment of the present invention.

[Explanation of symbols]

 1, 2 shift register 3, 4 difference detection circuit 5, 6 comparison circuit 7 reference level signal 8 determination circuit 9 changeover switch 10 video signal input 11 video signal output 12, 13 subtraction circuit 14 amplification circuit 15 storage circuit 16, 17 sample hold circuit

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) G11B 20/02 G11B 20/24 H04N 5/21 H04N 5/93

Claims (3)

(57) [Claims] 1. A input terminal of N + 1 time signal input is input, the input terminal connected to N times said input terminal
, A first holding circuit for holding a signal input to
A second holding circuit for holding a signal input to the input terminal at a time; a signal input to the input terminal at the time N and a signal input to the input terminal at the time N-1; signal and the first difference signal detection circuit for detecting an output a difference signal, detecting a difference signal between said signal input to the input terminal to the N time N + 1 when the signal input to the input terminal Out
A second difference signal detection circuit for force, the difference signal output level of said first difference signal detection circuit, first indicates whether larger than a predetermined <br/> reference signal input level inputted from the outside 1 comparison
A first comparison circuit that outputs a signal and a difference signal output level of the second difference signal detection circuit are input from the outside.
A second indicating whether or not it is greater than a predetermined reference signal input level;
A second comparison circuit for outputting a comparison signal, receiving said first and <br/> second comparison signal output, comparison of the first and second
Check that both signal outputs are higher than the reference signal input level.
Signal output levels of the first and second comparison circuits shown in FIG.
When that, it is determined that correction is necessary, the N time
The signal input from the input terminal is converted to the N-1 time point.
Instructed to replace at the signal inputted to the input terminal
A determination circuit that outputs a control signal to be performed, and an input signal at the N time held in the first holding circuit or an input signal at the N-1 time held in the second holding circuit.
Or, the switching by the control signal of the decision circuit first
And a changeover switch for inputting the signal to the second holding circuit, wherein the holding signal output of the second holding circuit is corrected.
Signal correction circuit, characterized in that the output as a signal. 2. The signal correction circuit according to claim 1, wherein each of the first and second holding circuits comprises a register. 3. The first and second holding circuits are both sample and hold circuits, the first and second difference detection circuits are both operation amplifiers, and the first and second comparison circuits are both. 2. The signal correction circuit according to claim 1, wherein the signal correction circuit is a comparator.