JP3158781B2 - Noise reduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise reduction device used for improving the S / N ratio in video equipment such as a video camera.

[0002]

2. Description of the Related Art In recent years, a camera-integrated VTR or the like has been equipped with a function of performing zooming by performing signal processing on a video signal output from a CCD.

[0003] This processing is called electronic zoom in distinction from optical zoom using a lens, and is used in combination with optical zoom to improve the overall zoom magnification. Hereinafter, the electronic zoom will be briefly described.

FIG. 3 is a diagram for explaining the outline of the vertical electronic zoom processing. In FIG.
Reference numerals 1, a2, and a3 represent three consecutive scanning lines in the same field of the video signal. Now, the input signals a1,
Consider a case in which double vertical zoom processing is performed on a2 and a3.

As shown in the figure, the scanning lines inserted between a1 and a2 and between a2 and a3 are interpolated to (a1 + a2) / 2 and (a2 + a3), respectively.
If the output is obtained as / 2, an image in which the vertical direction of the input image is doubled on the monitor is displayed.

However, the biggest disadvantage of this process is that
As shown in the figure, the vertical resolution, that is, the spatial frequency characteristic in the vertical direction is deteriorated. In the case of the NTSC system, the vertical resolution is 525/2 [cph]. However, when the double zoom process is performed, the half resolution is 525/4 [cp].
h].

As one method for improving this,
A method is considered in which the density of scanning lines is increased to increase the sampling frequency in the vertical direction. This is shown in FIG. FIG. 3B shows a case in which double-zoom is performed without interpolation processing by obtaining scanning lines for one frame. In this case, the vertical resolution after the zoom processing is 525/2 [cph].

Although the vertical zoom has been described above, the same holds true for the horizontal zoom.

Next, a method of increasing the sampling frequency in the vertical direction as described above will be described. The first conceivable method is to obtain a signal for one frame from an input signal and a signal obtained by delaying the input signal by one field using a field memory. This method is fine for still images,
In the case of a moving image, since there is a difference in sampling time between the two fields, a very unsightly screen is obtained when the moving part is zoomed.

One possible method is to obtain a signal of two fields having the same sampling time. This method can be realized by using, for example, two CCDs. FIG. 4 shows this state.

FIG. 4 shows the spatial positions of the scanning lines of the video signals output from the two CCDs located at the same spatial position, wherein a1 to a3 represent the output signals of the CCD1. , B1 to b3 indicate output signals of the CCD 2. In the diagram (a), a1 to a3 are the first fields and b1 to b3 are the first fields.
The case where the signal is a signal of the second field is shown, and (b) shows the reverse case. It is possible to make the two CCD output signals have mutually opposite fields by controlling the reading of the CCD, and this is known as a vertical pixel shifting method.

A zoom process is performed using the scanning lines for one frame obtained in this way, and finally a signal for one field is obtained. However, recently, the downsizing of the home camera-integrated VTR has been progressing, and the downsizing of the CCD has been progressing accordingly. Naturally, the light receiving area per pixel is also small, so that the S / N tends to be worse, and it is necessary to improve the S / N by some means.

For this reason, improvement of S / N by a cyclic noise reduction device using a field memory or a frame memory conventionally mounted on a home VTR or the like is being studied.

Here, the operation of the cyclic noise reduction device will be briefly described. FIG. 5 shows a configuration example of a cyclic noise reduction device using a field memory. A difference signal between the input video signal and the output signal of the field memory 7 is obtained by the first subtraction means 10a. If the input video signal is a still image, the difference signal hardly contains a video signal, and only noise is extracted. The difference signal is subtracted from the input signal by the second subtracting means 10b to reduce noise. This process can be regarded as an averaging process of two fields.

However, in the above-described recursive noise reduction apparatus, since a moving image contains a large amount of video signals in the differential signal, the subtraction of the differential signal from the input signal as it is causes degradation of the afterimage. . Therefore, based on the statistical reason that “generally noise has smaller amplitude than signal”, the difference signal is multiplied by a coefficient k (0 ≦ k ≦ 1) by the multiplication means 11 in FIG. Only the part is extracted as noise. More specifically, noise is extracted by controlling k to a value close to 1 for a portion having a small amplitude in the difference signal and controlling k to a value close to 0 for a portion having a large amplitude. By subtracting the extracted noise from the input signal, it is possible to reduce the noise while suppressing the afterimage.

[0016]

However, in the above-mentioned recursive noise reduction apparatus, a problem may occur not only in a moving image but also in a still image. This is shown below.

FIG. 6A is an enlarged view of a boundary portion when a diagonal line exists in the screen. When such a signal is processed by the above-described cyclic noise reduction apparatus, the averaging processing of the two fields is performed by a1 and b, respectively.
1, always between a2 and b2, a3 and b3. Therefore, as the noise reduction effect is strengthened, the uncorrelated portions are averaged, and the phenomenon that the contrast of the uncorrelated portions is reduced and the boundary of the oblique line becomes rough as shown in FIG.

If the noise reduction effect is weakened to avoid this phenomenon, the S / N cannot be improved much. Although the above phenomenon does not basically occur if the frame cyclic noise reduction processing is performed, since the sampling frequency in the time axis direction is の of that in the case of the field, the afterimage degradation is smaller than in the case of the field cyclic type. There is a problem that it becomes larger.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide a noise reduction apparatus which basically has no deterioration at a boundary portion of an oblique line and whose afterimage deterioration is equivalent to that of a field recursive noise reduction apparatus. Aim.

[0020]

In order to achieve the above object, a noise reduction apparatus according to the present invention uses an interlaced video signal.
A first video signal which is a signal, and the first video signal
An interlaced video signal with a reversed spatial position
An apparatus for receiving a second video signal as input, wherein the first and second delay means delay the video signal by one field ;
The first video signal and the second delay means provide one filter.
A first noise reduction circuit that receives a video signal that has been subjected to a field delay, performs a noise reduction process, and outputs the processed signal to the first delay unit; and a second video signal and the first noise reduction circuit .
The video signal delayed by one field by the delay means is input signal
And a configuration of a second noise reduction circuit that performs a noise reduction process and outputs the result to the second delay unit.

Further, the noise reduction apparatus of the present invention, inter
A first video signal which is a video signal of a race system;
Interlacing method in which the spatial position is opposite to that of the first video signal
For inputting a second video signal, which is a video signal of the formula
Wherein the first video signal or the second video signal
First selecting means for selecting the second video signal;
At the opposite timing to the selection means,
A second video signal for selecting one video signal or the second video signal
Selecting means, first and second delay means for delaying the video signal by one field, and using the output signal of the first selecting means and the output signal of the first delay means as input signals, performing noise reduction processing A first noise reduction circuit that outputs the signal to the first delay means, and an output signal of the second selection means and an output signal of the second delay means as input signals. 2 has a configuration of a second noise reduction circuit for outputting to the delay means.

[0022]

According to the present invention, a noise reduction process using the correlation between two fields existing at the same position spatially is performed by the above-described configuration.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a noise reduction device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a noise reduction apparatus according to a first embodiment of the present invention.

The signal source 1 comprises two systems of first video signals and b1 to b3 as shown in FIG.
And video signals Y1 and Y2 corresponding to the first and second noise reduction units, respectively.
Output to Examples of the signal source 1 include a plurality of CCDs having a vertical pixel shift structure.

The first and second noise reduction units 3 and 4
It comprises first and second noise reduction circuits 6a and 6b and first and second field memories 7a and 7b, respectively. Each of the first and second noise reduction circuits 6a and 6b has a circuit configuration as shown in FIG. In the first noise reduction circuit 6a, the input video signal Y1
Is subtracted from the output signal of the second field memory 7b to obtain a difference signal, a portion having a small amplitude is extracted as noise, the noise is reduced by subtracting from the input video signal Y1, the noise is reduced, and output to the zoom circuit 5. The data is also output to the first field memory 7a.

Similarly, the second noise reduction circuit 6b extracts noise from the input video signal Y2 and the output signal of the first field memory 7a and subtracts the noise from the input video signal Y2 to reduce the noise. To the second field memory 7b.

As a result, a video signal whose sampling frequency in the vertical direction is twice is input to the zoom circuit 5, and zoom processing with a high vertical resolution is performed.

Here, the reason why a difference signal is obtained from the input video signal Y1 and the output signal of the second field memory 7b in the first noise reduction circuit 6a will be described. Assuming that a video signal as shown in FIG. 4A is output from the signal source 1 at an arbitrary time, one field period ago, as shown in FIG. 4B, a1 to a3 and b1 ~ B3
Are output. From this, the reason why the Y1 signal currently output from the signal source 1 is spatially at the same position is that the Y2 signal one field period before, that is, the output signal of the second field memory 7b. In the second noise reduction circuit 6b, the input video signal Y2 and the first
From the output signal of the field memory 7a.

As described above, two fields having different fields from each other are used.
If one of the video signals of the system and a signal obtained by delaying the other video signal by one field are input to the cyclic noise reduction circuit, two fields existing at the same position spatially can be obtained. Noise reduction can be performed by using the frame cyclic noise reduction process spatially,
In principle, the oblique line boundary portion deterioration peculiar to the field recursive processing is eliminated. Further, since the processing is a field cyclic processing in terms of time, the afterimage degradation is smaller than that of the frame cyclic processing.

FIG. 2 is a block diagram showing a noise reduction apparatus according to a second embodiment of the present invention. The signal source 1 converts two systems of a first video signal and a second video signal as shown by a1 to a3 and b1 to b3 in FIG.
The corresponding video signals Y1 and Y2 are generated and output to the first and second selecting means 2a and 2b, respectively.

The first and second selecting means 2a and 2b select either Y1 or Y2 in response to the control signal from the control signal input terminal 8, and select the first and second noise reduction sections 3 and 2. 4 respectively.

The components of the first and second noise reduction units 3 and 4 are the same as those of the first embodiment, and the description is omitted. In the first noise reduction circuit 6a, the first selecting means 2
The difference signal is obtained by subtracting the output signal of the first field memory 7a from the output signal of a, and a portion having a small amplitude is extracted as noise, and the noise is reduced by subtracting from the output signal of the first selecting means 2a. Then, the data is output to the zoom circuit 5 and also to the first field memory 7a.

Similarly, the second noise reduction circuit 6b extracts noise from the output signal of the second selector 2b and the output signal of the second field memory 7b, and subtracts it from the output signal of the second selector 2b. To reduce the noise and output the noise to the zoom circuit 5 and the second field memory 7
Also output to b.

As a result, a video signal whose sampling frequency in the vertical direction is double is input to the zoom circuit 5, and zoom processing with a high vertical resolution is performed.

Here, the first and second selecting means 2a,
The same processing as in the first embodiment can be performed by inverting the control signal input to 2b every field period and switching the output signal. This is the first
The noise reduction unit 3 will be described as an example. Assuming that Y1 is selected by the first selection signal 2a at an arbitrary time and input to the first noise reduction circuit 6a, Y1 is written in the field memory 7a at that time, but 1 field Later, in the first selection signal 2a, Y
2 is selected and Y1 is output from the field memory 7a, so that Y1 and Y2 are supplied to the first noise reduction circuit 6a.
Will be input. Therefore, in this case, FIG.
As is clear from the above, the cyclic noise reduction processing is performed using the signal of the field having the same spatial position as the input. The second noise reduction unit 4 can be described in exactly the same way.

As described in the above two embodiments, in the present invention, a signal having a scanning line for one frame in one field period is applied to a cyclic type using two fields existing at the same position in space. It is possible to perform noise reduction processing, and spatially it becomes a frame cyclic type, and there is basically no deterioration at the boundary of diagonal lines, and temporally it becomes a field cyclic type and the afterimage degradation is lower than that of the frame cyclic type. It is possible to configure a small noise reduction device. It should be noted that the present invention
In the embodiment, the first noise reduction circuit and the second noise reduction circuit are used.
The output of the noise reduction circuit is used as the output signal of the noise reduction device.
, A first noise reduction circuit and a second noise reduction circuit
Output of the first field
Noise reduction of output of memory and second field memory
It may be an output signal of a circuit. Further, in the embodiment of the present invention,
In this case, the signal source 1 has a plurality of vertical pixel shift structures.
Although the case of using the CCD described above has been described, it is not limited to this.
Instead of one of the two video signals Y1 and Y2.
For the interlaced video signal, the other
Output the video signal so that the spatial position of the video signal is reversed.
If it is.

[0037]

As described above, according to the present invention, the noise is reduced by utilizing the correlation between two fields existing at the same position spatially, whereby the frame is cyclic in space and time is reduced in time. Field cyclic noise reduction processing can be realized, and as a result, there is no deterioration of the oblique line boundary part peculiar to the field cyclic noise reduction processing, and processing with less residual image degradation than the frame cyclic noise reduction processing is possible. A noise reduction device can be realized, and its practical effect is great.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a noise reduction device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a noise reduction device according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram and a frequency characteristic diagram for explaining an operation of a vertical electronic zoom process.

FIG. 4 is a schematic diagram for explaining vertical pixel shifting.

FIG. 5 is a block diagram showing a configuration of a field recursive noise reduction device.

FIG. 6 is an enlarged view of a screen for explaining deterioration of an oblique line boundary portion due to field cyclic noise reduction processing.

[Explanation of symbols]

 2 selection means 3 first noise reduction unit 4 second noise reduction unit 6 noise reduction circuit 7 field memory (delay means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/222-5/257 H04N 5/21

Claims (2)

(57) [Claims] 1. An interlaced video signal,
1 video signal and the first video signal and the spatial position are
A second video signal that is a reverse interlaced video signal
And a first and second delay means for delaying the video signal by one field, and one filter by the first video signal and the second delay means.
A first noise reduction circuit that performs a noise reduction process on the video signal that has been field-delayed as an input signal and outputs the resultant signal to the first delay unit; and a second filter that includes the second video signal and the first delay unit.
And a second noise reduction circuit that performs a noise reduction process on the video signal that has been subjected to a field delay and that outputs the video signal to the second delay unit. The first and second noise reduction circuits, or 1
And the output signal of the second delay means is output at the same timing.
A noise reduction device characterized by applying force . 2. An interlaced video signal,
1 video signal and the first video signal and the spatial position are
A second video signal that is a reverse interlaced video signal
And inputting the first video signal or the second video signal for each field.
The first selection means for selecting a signal and the field selection signal are output at a timing opposite to that of the first selection means.
Select the first video signal or the second video signal each time.
Second selecting means, first and second delay means for delaying the video signal by one field , an output signal of the first selecting means and an output signal of the first delay means as input signals, A first noise reduction circuit that performs a noise reduction process and outputs the result to the first delay unit; and an output signal of the second selection unit and an output signal of the second delay unit as input signals. And a second noise reduction circuit that outputs the first and second noise reduction circuits to the second delay means.
And the output signal of the second delay means is output at the same timing.
And force, the noise reduction apparatus characterized by switching the control signal of the first and second selecting means every predetermined period.