JPH08331422A - Video signal noise removing device - Google Patents

Abstract

PURPOSE: To minimize the degradation of resolution and to provide an image having no influence of a noise component by selectively removing the noise component concerning the noise component of a digital video signal outputted from an A/D converter while using a digital filter. CONSTITUTION: Concerning the noise component of the digital video signal outputted from an A/D converter 5 discriminated as a noise by a noise discriminating means 11 to the digital video signal outputted from the A/D converter 5, the noise component is removed by a digital filter 6. Besides, the digital video signal outputted from the A/D converter 5 not discriminated as a noise is not passed through the digital filter 6 but outputted to a camera process circuit 13 so that the resolution can not be degraded by the digital filter 6. Therefore, the image reducing the degradation of resolution and having no influence of the noise component can be provided on a monitor screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to analog / digital video signals.
Regarding a video signal processing circuit such as a video camera for digital (A / D) conversion, when the digital video signal of the A / D converter output contains a noise component, the noise of the noise is minimized after the deterioration of the resolution is minimized. The present invention relates to a video signal noise eliminator configured to improve the influence of components on a monitor screen and obtain a high quality video.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram showing the configuration of a conventional video signal processing circuit. A CCD (charge coupled device) image pickup device 1 converts the amount of light into an electric signal. The CDS (correlation double sampling) circuit 2 removes the noise component of the analog video signal output from the CCD image pickup device 1 by the correlation double sampling. The AGC (automatic gain control unit) circuit 3 adjusts the amplitude of the analog video signal from which the noise component is removed so that the analog video signal holds a constant signal level. Then, the clamp circuit 4 clamps the amplitude-adjusted analog video signal for A / D conversion. A for the clamped analog video signal
The / D converter 5 converts into a digital video signal. A camera process circuit for a digital video signal which is digitally converted and input through the digital filter 6.
In 13, video signal processing such as gamma correction and contour correction is performed and output as a final digital video signal.

As described above, in the conventional video signal processing circuit, the noise component of the analog video signal output from the CCD image pickup device 1 can be removed by the correlated double sampling of the CDS circuit 2.

However, when the GND and the power supply of the CDS circuit 2, the AGC circuit 3, the clamp circuit 4, or the input / output of these circuits are affected by other circuits and picked up as noise, the A / D converter 5 is used. In some cases, a noise component may be superimposed on the input analog video signal.

FIG. 12 shows a state in which a noise component is superimposed on the analog video signal input to the A / D converter 5.

In FIG. 12, the digital output level is 5
An example of bits is shown, and MSB (Most Significant Bi
t) indicates the most significant bit, and LSB (Least Significant B
it) indicates the least significant bit.

FIG. 12 (a) shows a waveform diagram of an analog video signal input to the A / D converter 5, which has a digital value "0010".
It is a constant level input waveform corresponding to "0". At this time, if a noise component synchronized with the clock of the A / D converter 5 is superimposed, as shown in FIG.
The digital video signal output from the converter 5 does not have the digital value "00100", but is digital values "00101", "00011", "0010" for each pixel in synchronization with the clock.
The signal will fluctuate between 1 ”and“ 00011 ”.

In this case, the difference in digital value between adjacent pixels is "1", but it may be "2" depending on the magnitude of the noise component.

Since the camera process circuit 13 performs various digital signal processing based on the digital video signal output from the A / D converter 5, finally, as shown in FIG. 12 (c), vertical stripes appear on the monitor screen. It becomes a pattern. That is, so-called fixed pattern noise occurs. In order to remove such a noise component, it is possible to remove the noise component by always passing the digital video signal output from the A / D converter 5 through the digital filter 6 as shown in FIG.

[0010]

However, in the conventional technique, the digital video signal output from the A / D converter 5 is always passed through the digital filter 6 in order to remove the noise component. Since the digital video signal output from the D converter 5 is also passed through the digital filter 6, there is a problem that the resolution deteriorates even if the noise component can be removed.

When the noise component of the digital video signal output from the A / D converter 5 is viewed on the monitor screen, the noise component is more noticeable in the low luminance region, but the noise component is less noticeable in the high luminance region. Since there is A in the high brightness range
The noise component of the digital video signal output from the A / D converter 5 is the same as the noise component of the digital video signal output from the A / D converter 5 in the low luminance range,
Although it is not necessary to remove the noise by degrading the resolution through the conventional technique, in the conventional technique, the noise component is removed in order to remove the noise component regardless of the brightness level of the digital video signal output from the A / D converter 5. Since the digital video signal of the output of the A / D converter 5 which is inconspicuous on the monitor screen in the luminance range is also passed through the digital filter 6, it becomes a factor of extra deterioration of the resolution.

Therefore, according to the present invention, it is determined whether or not there is noise according to the brightness level of the digital video signal,
A first object of the present invention is to provide a video signal noise eliminator capable of removing a noise component by selectively passing a digital filter and obtaining an image with less deterioration of resolution due to the digital filter.

Further, according to the present invention, in order to further minimize the deterioration of the resolution due to the digital video signal passing through the digital filter, it is possible to improve the accuracy in determining whether the digital video signal is noise or not, and further to improve the luminance of the digital video signal. A second object is to provide a video signal noise removing device capable of removing noise according to the level.

A third aspect of the present invention is to provide a video signal noise removing device capable of effectively removing noise according to the frequency characteristics of the noise component of a digital video signal in advance.
The purpose of.

[0015]

In order to achieve the first object, according to the invention of claim 1, adjacent pixel difference detecting means for detecting a difference in brightness level between adjacent pixels of a digital video signal, and digital Reference luminance level setting means for presetting a luminance level for a video signal, and a digital video signal divided into two luminance regions with the luminance level as a boundary, a noise level for a difference in luminance level for each adjacent image difference is preset. Whether or not the digital video signal is noise is compared by comparing the noise level setting means to be set with the digital video signal with the luminance level, and by comparing the noise level with respect to the difference in the brightness level of each adjacent pixel of the digital video signal. After discriminating the noise, a noise discriminating and removing means for selectively removing only the noise by the digital filter is provided. By kicking it, it is obtained so as to perform the less noise removal resolution degradation depending on the luminance levels of the digital video signal.

In order to achieve the second object, the method according to claim 2
In the described invention, N (N
The integer) and N the standard brightness level setting means for previously setting the luminance level (Y ₁ to Y _N) of the boundary luminance level _{(Y 1 ~Y N), N} + 1 pieces of luminance region (T ₁ ~ In the digital video signal previously divided into T _{N + 1} ), the luminance region (T ₁ ~
T N _{+ 1} noise level (H ₁ for the difference in luminance level for each adjacent pixel for each luminance area of) to H N + ₁₎ noise region setting means for setting N + a 1 provided that the, in the noise discrimination removing means The noise discrimination accuracy with respect to the digital video signal can be improved, and the noise can be removed with a smaller resolution.

In order to achieve the third object, claim 3
In the invention described above, in order to remove noise in the digital video signal in advance, digital filters having different characteristics are provided in M (M
The number of types is set so that the noise discrimination / removal means can effectively remove noise according to the frequency characteristics of the noise component of the digital video signal.

[0018]

According to the image signal noise eliminating device of the first aspect,
After determining whether or not the digital video signal is noise by the noise discrimination / removal means, if it is noise, the digital video signal from which the noise is removed through the digital filter and the noise component of the digital video signal are replaced. , Remove noise.

At this time, the noise discrimination / removal means serves as a reference noise for discriminating whether or not the noise is a difference between the luminance level of the digital video signal and the luminance level of each adjacent pixel obtained by the adjacent pixel difference detecting means. By setting the level in advance, the reference area for discriminating the digital video signal from the noise component can be set arbitrarily, so that the noise component of the digital video signal in the low-luminance region that is noticeable on the monitor screen can be set. Only the noise component of the digital video signal in the high brightness range that is not noticeable on the monitor screen is removed by the digital filter.
By not removing the noise, it is possible to minimize the deterioration of resolution due to the digital filter and improve the influence of noise components appearing on the monitor screen.

In the video signal noise eliminator according to the second aspect of the present invention, the reference area for discriminating the noise component of the digital video signal by the noise discrimination removing means for discriminating the noise component of the digital video signal and eliminating the noise component is subdivided. For this reason, by providing N reference brightness level setting means and N + 1 noise level setting means, the accuracy in discriminating the digital video signal from noise can be further improved, so that a more appropriate digital video signal can be obtained. It is possible to remove noise according to the brightness level, and it is possible to remove the influence of noise components appearing on the monitor screen while minimizing the deterioration of resolution due to the digital filter.

According to a third aspect of the present invention, there is provided a video signal noise removing device, wherein M kinds of digital filters having different characteristics are provided in order to remove noise components of the digital video signal in advance, and the digital filters are provided according to the noise components of the digital video signal. By properly using, it is possible to effectively remove noise according to the frequency characteristics of noise of the digital video signal.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the entire apparatus in the first embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of adjacent pixel difference detection means, and FIG. 3 is a block diagram showing the configuration of noise discrimination means. FIG. 4 is a block diagram showing the configuration of the video signal register section. The components having the same numbers and names as those described in the prior art in FIG.

As shown in FIG. 2, the adjacent pixel difference detecting means 7 delays the digital video signal output from the A / D converter 5 by one pixel by the register 14 and outputs the digital video signal from the A / D converter 5. A video signal without delay
The subtractor 15 subtracts from the digital video signal output from the A / D converter 5 to detect the difference in brightness level between adjacent pixels.
For the digital video signal output from the D converter 5,
A luminance level Y is set as a reference for determining whether or not noise is detected. The first noise area setting means 9 sets a noise level H ₁ for discriminating noise with respect to a difference in luminance level between adjacent pixels detected by the adjacent pixel difference detecting means 7 at a luminance level lower than the luminance level Y, and The two-noise area setting means 10 sets a noise level H ₂ for discriminating noise, with respect to the difference in luminance level between adjacent pixels detected by the adjacent pixel difference detecting means 7 at a luminance level equal to or higher than the luminance level Y.

The noise discrimination means 11 is the A / D converter 5
When the digital video signal of the output of is at a luminance level lower than the luminance level Y and the difference between the luminance levels detected by the adjacent pixel difference detecting means 7 is within the noise level H ₁ , or the output of the A / D converter 5 The digital video signal has a luminance level equal to or higher than the luminance level Y, and the difference between the luminance levels detected by the adjacent pixel difference detecting means 7 is the noise level H.
A / D converter 5 at any time within ₂
The digital video signal output by is discriminated as noise, and the noise discrimination signal 24 according to the presence or absence of noise is output.

The video signal register section 12 removes noise from the digital video signal output from the A / D converter 5 based on the noise discrimination signal 24. The video signal register unit 12 is composed of a first register 25, a second register 26, and a selector circuit 27. The first register 25 adjusts the difference in delay time due to the difference in circuit scale between the noise discrimination signal 24 and the digital video signal output from the A / D converter 5, and then the digital video signal output from the A / D converter 5. And the second register 26 similarly stores the noise discrimination signal 24
And the digital video signal output from the A / D converter 5 is stored after adjusting the difference in delay time due to the difference in circuit scale from the digital video signal passed through the digital filter 6.

When the noise discriminating means 11 discriminates that the digital video signal output from the A / D converter 5 is not noise, the selector circuit 27 causes the digital filter 6 which stores the noise component in the first register 25. It is replaced with a digital video signal that does not pass through and is output to the camera process circuit 13. In addition, the noise discriminating means 11 is an A / D
When it is determined that the digital video signal output from the converter 5 is noise, the selector circuit 27 causes the second register 24
It is replaced with the digital video signal that has passed through the digital filter 6 and is output to the camera process circuit 13 that performs various video signal processing such as gamma correction. As a result, the camera process circuit 13 performs various video signal processing such as gamma correction and contour correction on the basis of the digital video signal output from the A / D converter 5 from which noise components have been removed. No good image is obtained.

Next, the operation of the video signal noise eliminator in the first embodiment having the above construction will be described. Until the digital video signal is generated, the operation is the same as that of the conventional circuit shown in FIG.

In the first embodiment, as shown in FIG.
The digital video signal output from the converter 5 is converted into a digital filter 6, an adjacent pixel difference detection means 7, and a noise discrimination means.
11 and the video signal register section 12 are input to four circuit blocks. Then, the digital filter 6 removes the noise component contained in the digital video signal output from the A / D converter 5, and the adjacent pixel difference detection means 7 outputs A
Whether or not the reference brightness level setting means 8 detects the difference in brightness level between adjacent pixels of the digital video signal output from the A / D converter 5 and determines that the digital video signal output from the A / D converter 5 is noise. A brightness level Y which is a reference of whether or not to set is set.

The noise discriminating means 11 discriminates whether or not the digital video signal output from the A / D converter 5 is noise. That is, the noise determination means 11 includes the brightness level Y preset in the reference brightness level setting means 8 and the noise level H set in the first noise area setting means 9.
Noise discrimination is performed based on ₁ and the noise level H ₂ set in the second noise area setting means 10. In the first noise area setting means 9, the adjacent pixel difference detection means 7 is at a brightness level lower than the brightness level Y set by the reference brightness level setting means 8.
The noise level H ₁ for discriminating noise is set for the difference between the brightness levels of the adjacent pixels detected in step 2, and the second noise area setting means 10 sets the noise level H ₁ or higher to the brightness level Y or higher set by the reference brightness level setting means 8. A noise level H ₂ for discriminating noise is set for the difference in brightness level between adjacent pixels detected by the adjacent pixel difference detection means 7 at the brightness level.

As shown in FIG. 3, the noise discriminating means 11 compares the digital video signal output from the A / D converter 5 with the brightness level Y set by the reference brightness level setting means 8 in the comparator circuit 16 and compares them. As a result, when the brightness level of the digital video signal output from the A / D converter 5 is lower than the brightness level Y, the output signal 17 of the comparator circuit 16 is "H". Further, the comparator circuit 18 compares the difference in luminance level for each adjacent pixel detected by the adjacent pixel difference detection means 7 with the noise level H ₁ ,
As a result of the comparison, it is assumed that the output signal 19 of the comparator circuit 18 becomes "L" when the difference between the brightness levels of the adjacent pixels detected by the adjacent pixel difference detecting means 7 is within the noise level H ₁ . Further, in the comparator circuit 20, the difference in luminance level for each adjacent pixel detected by the adjacent pixel difference detecting means 7 is compared with the noise level H _2, and as a result of comparison, for each adjacent pixel detected by the adjacent pixel difference detecting means 7. When the difference between the brightness levels of the _{two is} within the noise level H ₂ , the comparator circuit 20
It is assumed that the output signal 21 of "L" becomes "L".

Therefore, the output signal 17 of the comparator circuit 16
If the logical product of the output signal 19 of the comparator circuit 18 and the logical negation of the output signal 19 of the comparator circuit 18 is taken, the output signal 22 indicates that the digital video signal of the output of the A / D converter 5 has a brightness level lower than the brightness level Y ₁ and the adjacent pixel. When the difference between the brightness levels of the adjacent pixels detected by the difference detecting means 7 is within the noise level H _1, it becomes "H". Similarly, if the logical NOT of the output signal 17 of the comparator circuit 16 and the logical NOT of the output signal 21 of the comparator circuit 20 is taken, the output signal 23 is
The digital video signal output from the / D converter 5 has a brightness level of Y or higher and the adjacent pixel difference detection means 7
When the difference between the brightness levels of the adjacent pixels detected in step _{2 is} within the noise level H _2, it becomes "H".

Therefore, finally, if the logical sum of the output signal 22 and the output signal 23 is taken, the digital video signal of the output of the A / D converter 5 has a luminance level lower than the luminance level Y and the adjacent pixel difference detecting means. If the difference between the brightness levels of the adjacent pixels detected in 7 is within the noise level H ₁ , or if the digital video signal output from the A / D converter 5 has a brightness level of the brightness level Y or higher and the adjacent pixel difference detecting means. The difference between the brightness levels detected in 7 is the noise level H ₂
The noise discrimination signal 24 which becomes "H" in any of the cases below is generated. As a result, the noise discrimination means 11 can discriminate, for each pixel, whether or not the digital video signal output from the A / D converter 5 is noise.

The video signal register section 12 removes noise from the digital video signal output from the A / D converter 5 based on the noise discrimination signal 24. Video signal register section 12
Is a first register 25, a second register 26 and a selector circuit 27.
The first register 25 is provided with a noise discrimination signal 24
After adjusting the difference in delay time due to the difference in circuit scale between the digital video signal output from the A / D converter 5 and the A / D converter 5,
The digital video signal output from the A / D converter 5 is stored, and the second register 26 stores the noise discrimination signal 24 and the A / D signal.
The difference in delay time due to the difference in circuit scale from the output digital video signal of the converter 5 is adjusted, and then the digital video signal output from the A / D converter 5 is passed through the digital filter 6 to be stored.

When the noise discriminating means 11 discriminates that the digital video signal output from the A / D converter 5 is noise by the noise discriminating means 24, the selector circuit 27 discriminates noise. A /
The digital video signal output from the D converter 5 is stored in the second register 26, and the digital video signal output from the A / D converter 5 is passed through a digital filter 6 to be replaced with a digital video signal from which noise has been removed. And the digital video signal output from the A / D converter 5 is not discriminated by the noise discriminating means 11 as noise, the digital video signal output from the A / D converter 5 that does not pass through the digital filter 6 stored in the first register 25 is output. The signal is output to the camera process circuit 13. As a result, A / that is determined to be noise by the noise determination means 11
Only the digital video signal output from the D converter 5 is A /
The digital video signal output from the D converter 5 can be replaced with the digital video signal output from the A / D converter 5 from which noise has been removed through the digital filter 6 and output to the camera process circuit 13.

Regarding the portion which is not discriminated as noise by the noise discriminating means 11, the output of the A / D converter 5 which does not pass the digital filter 6 stored in the first register 25 can be outputted to the camera process circuit 13. Therefore, the deterioration of the resolution due to the digital filter 6 can be minimized.

Further, FIG. 5 shows a concrete example of the circuit operation in the first embodiment. Here, the case where the characteristic of the digital filter 6 is (1 + Z ~ ¹ ) / 2 in the Z conversion formula is shown. Note that FIG. 5 shows an example in which the digital output level is 5 bits, MSB (Most Significant Bit) indicates the most significant bit, and LSB (Least Significant Bit) indicates
The least significant bit is shown.

As shown in FIG. 5A, in the first embodiment, A / D
For the digital video signal output from the converter 5, the area for noise discrimination by the noise discrimination means 11 is set in advance to an arbitrary value, and the reference luminance level setting means 8 is set to the digital video signal output from the A / D converter 5. In, the brightness level Y is preset to "7".

Next, in the first noise area setting means 9, at a luminance level lower than the luminance level Y, the difference in luminance level detected by the adjacent pixel difference detecting means 7 is set to a noise level H ₁ which is determined as noise. Set "1" and similarly
In the second noise area setting means 10, a noise level H that is determined to be noise with respect to a difference in brightness level detected by the adjacent pixel difference detection means 7 at a brightness level equal to or higher than the brightness level Y.
"2" is set to _2.

As a result, in the noise discrimination means 11, A /
The digital video signal output from the D converter 5 is lower than "7" set at the brightness level Y, and the difference in brightness level between adjacent pixels detected by the adjacent pixel difference detection means 7 is set to the noise level H _1. A digital video signal of 1 "or less is discriminated as noise, the digital video signal of the output of the A / D converter 5 is" 7 "or more set by the brightness level Y, and each adjacent pixel detected by the adjacent pixel difference detection means 7 The difference in the brightness level of "2" is set to the noise level H _2.
The following digital video signals are also determined as noise.

Noise discriminated by the noise discrimination means 11 is A
The digital video signal output from the A / D converter 5 is replaced in the video signal register section 12 with the digital video signal from which noise has been removed through the digital filter 6 and output to the camera process circuit 13. To be done. As a result, as shown in FIG. 5B, at the output of the video signal register unit 12, the noise component of the digital video signal of the output of the A / D converter 5 is the digital video signal whose noise component has been removed by the digital filter 6. The digital video signal output from the A / D converter 5 which has not been discriminated as noise by the noise discrimination means 11 is output to the camera process circuit 13 without passing through the digital filter 6. There is no loss of resolution. Therefore, it is possible to obtain a digital video signal with less deterioration of resolution after removing noise.

FIG. 6 is a block diagram showing the configuration of the second embodiment of the present invention. Here, the case where three reference luminance level setting means and four noise area setting means are used will be described (claim) 2. When the value of N described in 2 is "3"). The members having the same numbers and the same names as those of the members described in the first embodiment have the same construction operation, and thus detailed description thereof will be omitted.

The second embodiment differs from the first embodiment shown in FIG. 1 in that two types of noise discriminating means 11 and 31 are provided for A / D.
In order to improve the accuracy of noise discrimination for the digital video signal output from the converter 5, a second reference luminance level setting means 28, a third noise area setting means 29, a fourth noise area setting means 30, and a second That is, the noise discrimination means 31, the third reference luminance level setting means 33, the comparator circuit 35, and the selector circuit 34 are provided.

The first noise discriminating means 11 shown in FIG.
First noise discrimination signal 24, first reference luminance level setting means 8
Is the noise discrimination means 11 and the noise discrimination signal 2 shown in FIG.
4. Same as the reference brightness level setting means 8, but
Here, for convenience, the names are referred to as the first noise discrimination means 11, the first noise discrimination signal 24, and the first reference luminance level setting means 8.

In the second embodiment, with respect to the digital video signal output from the A / D converter 5, the brightness levels Y ₁ to Y are supplied to the first reference brightness level setting means 8 to the third reference brightness level setting means 33. Set ₃ in advance. At this time, at a brightness level lower than the brightness level Y ₃ with reference to the brightness level Y ₃ ,
Set the brightness level Y ₁ as a reference noise discrimination for the digital video signal of the output of the A / D converter 5, a luminance level Y ₃ or more luminance levels based on the luminance level Y _3, A / D converter 5 The luminance level Y ₂ which is a reference for noise discrimination with respect to the digital video signal output by the above is set.

As a result, the area of the digital video signal output from the A / D converter 5 is divided into four brightness areas T ₁ to T ₄ as shown in FIG. Here, the brightness area T ₁ has a digital video signal output from the A / D converter 5 whose brightness level is lower than the brightness level Y ₁ as an area, and the brightness area T ₂ has a brightness level equal to or higher than the brightness level Y ₁ and A / D converter 5 with brightness level lower than Y ₃
A digital video signal to a region of the output luminance area T ₃
Is a digital video signal of the output of the A / D converter 5 whose brightness level is higher than the brightness level Y ₃ and lower than the brightness level Y ₂ , and the brightness region T ₄ is A where the brightness level is the brightness level Y ₂ or higher. The area of the digital video signal output from the / D converter 5 is used.

Next, noise level H ₁ to noise for discriminating as noise with respect to the brightness level difference between adjacent pixels of the digital video signal output from the A / D converter 5 in the brightness range T ₁ to brightness range T ₄ . The level H ₄ is preset by the first noise area setting means 9 to the fourth noise area setting means 30.

In the first noise discrimination means 11, the luminance region T ₁
In the luminance region T ₂ , noise discrimination is performed on the digital video signal output from the A / D converter 5. First noise discrimination means 11, in the luminance area T _1, when the difference between the brightness level of each adjacent pixels detected in the adjacent pixel difference detecting means 7 is within the noise level H _1, or in a luminance region T _2, adjacent pixels difference When the difference between the brightness levels of the adjacent pixels detected by the detecting means 7 is within the noise level H ₂ , the digital video signal output from the A / D converter 5 is discriminated as noise and the first noise discrimination is performed. Output signal 24.

In the second noise discrimination means 31, the luminance region T ₃
In the luminance region T ₄ , noise discrimination is performed on the digital video signal output from the A / D converter 5 in the same manner as the first noise discrimination means 11. Second noise discrimination means 31, in the luminance region T _3, when the difference in luminance level for each neighboring pixels detected in the adjacent pixel difference detecting means 7 is within the noise level H _3, or in a luminance area T _4, adjacent pixels When the difference between the brightness levels of the adjacent pixels detected by the difference detection means 7 is within the noise level H ₄ , the A / D
The digital video signal output from the converter 5 is discriminated as noise, and the second noise discrimination signal 32 is output.

The first noise discrimination signal 24 from the first noise discrimination means 11 and the second noise discrimination signal 32 from the second noise discrimination means 31 are the digital video signals output from the A / D converter 5. When the brightness level is lower than the brightness level set by the third reference brightness level setting means 33, by outputting "L" to the comparator circuit 35,
In the selector circuit 34, the first noise discrimination signal 11 from the first noise discrimination means 11 is based on the output of the comparator circuit 35.
Is selected by the selector circuit 34 and the luminance level of the digital video signal output from the A / D converter 5 is equal to or higher than the luminance level Y ₃ set by the third reference luminance level setting means 33, the comparator circuit 35 By outputting "H", the selector circuit 34 selects the second noise discrimination signal 32 from the second noise discrimination means 31 on the basis of the output of the comparator circuit 35. As a result, the noise discrimination for the digital video signal output from the A / D converter 5 can be performed without overlapping the region discriminated as noise by the first noise discrimination means 24 and the region discriminated as noise by the second noise discrimination means 31. it can.

In the subsequent processing, the video signal register unit 12 performs the first operation based on the output signal from the selector circuit 34.
Since the processing as described in the embodiment is performed, the description thereof will be omitted.

Further, FIG. 7 shows a concrete example of the circuit operation in the second embodiment. Here, the case where the characteristic of the digital filter 6 is (1 + Z ~ ¹ ) / 2 in the Z conversion formula is shown. Note that FIG. 7 shows an example in which the digital output level is 5 bits, MSB (Most Significant Bit) shows the most significant bit, and LSB (Least Significant Bit) shows the least significant bit.

That is, in the second embodiment, the digital video signal output from the A / D converter 5 is set to "1" as the brightness level Y ₁ by the first reference brightness level setting means 8.
"0" is arbitrarily set in advance, and the second reference luminance level setting means 2
The brightness level Y ₂ is set to “24” by 8 and the third reference brightness level setting means 33 sets the brightness level Y ₃ to “1”.
4 ”is set.

As a result, the area of the digital video signal output from the A / D converter 5 is the brightness area T ₁ to the brightness area T _4.
It is divided into four. Here, in the brightness area T ₁ , the A / D whose brightness level is lower than “10” set to the brightness level Y ₁ is set.
The digital video signal output from the converter 5 is set as a region,
The luminance region T ₂ has a region where the digital video signal of the output of 5 of the A / D converter has a luminance level of “10” or more set to the luminance level Y ₁ and lower than “14” set to the luminance level Y _3. The luminance region T ₃ is a region where the digital video signal output from the A / D converter 5 has a luminance level of “14” or higher set to the luminance level Y ₃ and lower than “24” set to the luminance level Y _2. The luminance region T ₄ is assumed to be a region where the digital video signal output from the A / D converter 5 whose luminance level is set to the luminance level Y ₂ and is “24” or more.

Next, a noise level H ₁ to noise for discriminating noise from a luminance level difference between adjacent pixels of the digital video signal output from the A / D converter 5 in the luminance region T ₁ to the luminance region T ₄ . The level H ₄ is preset by the first noise area setting means 9 to the fourth noise area setting means 30. Here, in the luminance region T _1, the noise level H ₁
To set to "1", and sets "2" to the noise level H ₂ in the luminance region T _2, "1" is set to the noise level H ₃ in the brightness region T _3, the noise level H in the luminance region T ₄ Set ₄ to “0” in advance.

In the first noise discrimination means 11, the luminance region T ₁
In the luminance region T ₂ , noise discrimination is performed on the digital video signal output from the A / D converter 5. In the luminance region T ₁ , the first noise discriminating unit 11 determines whether the difference between the luminance levels of the adjacent pixels detected by the adjacent pixel difference detecting unit 7 is within “1” set in the noise level H ₁ or in the luminance region. At T ₂ , the difference in brightness level between adjacent pixels detected by the adjacent pixel difference detection means 7 is the noise level H.
_In either case of within 2 set in 2, A /
The digital video signal output from the D converter 5 is discriminated as noise, and the first noise discrimination signal 24 is output.

In the second noise discriminating means 31, the luminance region T ₃
In the luminance region T ₄ , noise discrimination is performed on the digital video signal output from the A / D converter 5. In the luminance region T ₃ , the second noise discriminating unit 31 determines whether the difference between the luminance levels of the adjacent pixels detected by the adjacent pixel difference detecting unit 7 is within “1” set in the noise level H ₃ or in the luminance region. At T ₄ , the difference in brightness level between adjacent pixels detected by the adjacent pixel difference detection means 7 is the noise level H.
_{When the} value is within "0" set to ₄ , A
The digital video signal output from the / D converter 5 is discriminated as noise, and the second noise discrimination signal 32 is output.

As for the first noise discrimination signal 24 from the first noise discrimination means 11 and the second noise discrimination signal 32 from the second noise discrimination means 31, the digital video signal output from the A / D converter 5 has a luminance level. when set to Y ₃ "14" of the lower brightness level than, by outputting "L" to the comparator circuit 35, from the first noise discrimination means 11 based on the output of the selector circuit 34 in the comparator circuit 35 the first noise discrimination signal 24 selector circuit 34 selects, when the digital video signal of the output of the a / D converter 5 is luminance level Y ₃ is set to "14" or higher brightness level, the comparator circuit 35 "H By outputting "," the selector circuit 34
Then, based on the output of the comparator circuit 35, the second noise discrimination signal 32 from the second noise discrimination means 31 is fed to the selector circuit.
34 choose.

As a result, the digital image signal output from the A / D converter 5 does not overlap the area determined by the first noise determination means 11 as noise and the area determined by the second noise determination means 31 as noise. Noise can be discriminated against. Here, the A / D converter 5 determined to be noise
The digital video signal of the output of 1 is replaced by the digital video signal of the output of the A / D converter 5 in the video signal register section 12 through the digital filter 6 to remove the noise, and the camera process circuit 13
Is output to

Therefore, as shown in FIG. 7B, at the output of the video signal register section 12, the noise component of the digital video signal of the output of the A / D converter 5 is the digital video signal whose noise component has been removed by the digital filter 6. It will be replaced by a signal. Moreover, the digital video signal of the output of the A / D converter 5 which is not discriminated as noise by the first noise discriminating means 11 and the second noise discriminating means 31 is output to the camera process circuit 13 without passing through the digital filter 6. Therefore, the resolution will not deteriorate.

Further, by subdividing the luminance region for noise discrimination with respect to the digital video signal output from the A / D converter 5 as described above, the A / D converter 5 as shown in FIG. In the case of the output digital video signal, when it is felt that the noise component is inconspicuous on the monitor screen in the high luminance region, the difference in the luminance level Y ₄ for discriminating the noise in the third noise region setting means 29 is " 0 "
By setting, the digital video signal output from the A / D converter 5 having a brightness level of “24” or higher is not discriminated as a noise component, and therefore the resolution is not deteriorated.

Therefore, since it is possible to perform fine noise removal in accordance with the brightness level of the digital video signal output from the A / D converter 5, the noise is removed and the digital video signal with less deterioration in resolution is obtained. Obtainable.

FIG. 8 is a block diagram showing the structure of the third embodiment, which has the same reference numerals as those of the members described in the first embodiment.
Those having the same name have the same configuration operation, and thus detailed description thereof will be omitted. Although the first digital filter 6 shown in FIG. 8 is similar to the digital filter 6 shown in FIG. 1, it is referred to as a first digital filter here for convenience.

The third embodiment differs from the first embodiment shown in FIG. 1 in that in order to remove the noise component of the digital video signal output from the A / D converter 5, N kinds of digital filters having different characteristics are used. And a selector circuit 37 for arbitrarily switching the digital filter according to the frequency characteristics of the noise component of the digital video signal output from the A / D converter 5,
That is, the digital filter switching means 38 is provided. Here, an example is shown in which two types of digital filters, that is, a first digital filter 6 and a second digital filter 36 having different characteristics are used to remove noise components of the digital video signal output from the A / D converter 5.
(When the value of M in claim 3 is "2").

With the configuration shown in FIG. 8, when the digital image signal output from the A / D converter 5 is determined to be noise by the noise determining means 11, the characteristics of the first digital filter 6 indicate that the output of the A / D converter 5 is the same. Even when the noise component of the digital video signal cannot be sufficiently removed, by selecting the second digital filter 36 by the digital filter switching means 38, the second digital filter 36 is selected.
Depending on the characteristics of, the noise component can be removed. Therefore, the more digital filters having different characteristics are provided, the more noise can be removed according to the noise components of the various digital video signals output from the A / D converter 5.

Therefore, in the case where the A / D converter 5 and the camera process circuit 13 in the conventional circuit configuration as shown in FIG. When the output digital video signal is affected by the noise component, it is necessary to remove the noise with one digital filter regardless of the characteristics of the frequency component of the output noise component of the A / D converter 5. Depending on the characteristics of the frequency component of, the noise component could not be removed.
Even when M kinds of digital filters are set as in the present embodiment and an effective digital filter is used to remove noise to form an LSI, various A /
It is also possible to deal with the noise frequency characteristic of the noise of the digital video signal output from the D converter 5.

In the subsequent processing, the video signal register section 12 removes the noise component of the digital video signal in the same manner as described in the first embodiment, and the description thereof will be omitted.

A concrete example of the video signal noise removing operation in the third embodiment is shown in FIGS. 9 and 10. Here, FIG.
Represents the characteristics of the first digital filter 6 by the Z conversion formula (1
+ Z ~ ¹ ) / 2 shows the case where noise is removed from the output of the A / D converter 5, and FIG. 10 shows the characteristics of the second digital filter 36 as (1 + Z ~ ¹ + Z ~ ² ) / 3 by the Z conversion formula.
As a case, the case where noise is removed from the output of the A / D converter 5 is shown. 9 and 10 show an example in which the digital output level is 5 bits, and the MSB (Most Si
gnificant Bit) indicates the most significant bit, and LSB (Least S
ignificant Bit) indicates the least significant bit. Also,
9 (a) and 10 (a) show digital video signals output from the same A / D converter 5, and it is assumed that noise is periodically generated in the vicinity of the low luminance region.

First, an area in which noise discrimination is performed by the first noise discriminating means 11 with respect to the digital video signal output from the A / D converter 5 as shown in FIGS. 9A and 10A is arbitrarily set in advance. Set. Here, in order to remove noise components in the low luminance region of the output of the A / D converter 5 and minimize deterioration of resolution, the luminance level Y of the reference luminance level setting means 8 is set.
Is set to “10” in advance. Next, in the digital video signal output from the A / D converter 5 which is lower than the brightness level Y, the noise level H ₁ that is determined as noise with respect to the brightness level difference between adjacent pixels detected by the adjacent pixel difference detection means 7 Is set in advance by the first noise area setting means 9. Similarly, in the digital video signal output from the A / D converter 5 having a luminance level of Y or higher, the noise level H ₂ for discriminating the difference between the luminance levels of the adjacent pixels detected by the adjacent pixel difference detection means 7 as noise is set as the noise level H _2. “0” is set by the second noise area setting means 10.

As a result, in the noise discrimination means 11, A /
The digital video signal output from the D converter 5 has a brightness level lower than “10” set to the brightness level Y, and the difference in brightness level between adjacent pixels detected by the adjacent pixel difference detection means 7 is the noise level H ₁ 2 or less, or when the digital video signal output from the A / D converter 5 has a brightness level Y of 10 or more set to the brightness level Y and the adjacent pixel detected by the adjacent pixel detecting means 7 When the difference in the brightness level for each is less than or equal to “0” set in the noise level H ₂ , the digital video signal output from the A / D converter 5 is determined to be noise.

The noise component of the digital video signal output from the A / D converter 5 which is discriminated as noise by the noise discriminating means 11 is removed by the digital filter.
If the digital filter is one type of digital filter as in the conventional case and has a characteristic of (1 + Z ~ ¹ ) / 2 in the Z conversion type like the first digital filter 6 as shown in FIG. The noise component of the digital video signal output from the A / D converter 5 as shown in FIG. 9 (a) cannot be completely removed, and the noise is output to the video signal register unit 12 as shown in FIG. 9 (b). The components remain, but Fig. 10
As shown in (b), the noise component can be completely removed if the second digital filter 36 has a characteristic of (1 + Z ~ ¹ + Z ~ ² ) / 3 in the Z conversion formula.

Therefore, A as shown in FIGS. 9 (a) and 10 (a)
In the case of the digital video signal output from the / D converter 5,
Since the noise component can be removed by selecting the second digital filter 36 by the digital filter switching means 38, the output of the video signal register unit 12 is the output of the A / D converter 5 as shown in FIG. 10 (b). The noise component of the output digital video signal is replaced with the digital video signal from which the noise component has been removed by the second digital filter 38. Moreover, the digital video signal of the output of the A / D converter 5 which is not discriminated as noise by the noise discriminating means 11 is output to the camera process circuit 13 without passing through either the first digital filter 6 or the second digital filter 38. Resolution does not deteriorate.

As described above, in order to remove the noise component of the digital video signal output from the A / D converter 5, M
A type of digital filter is preset and A / D
By arbitrarily switching the digital filter according to the frequency characteristics of the noise of the digital video signal output from the converter 5, the noise component can be removed more effectively and a digital video signal with less deterioration of resolution can be obtained. You can

[0074]

As described above, according to the structure of the first aspect of the present invention, the video signal noise eliminating apparatus sets the area for discriminating noise in the digital video signal according to the brightness level. Based on this area, it is determined whether or not there is noise in the digital video signal, and the portion that is determined as a noise component is selectively replaced with a digital video signal from which noise has been removed through a digital filter. Since the resolution of the digital video signal is not impaired by the digital filter, it is possible to obtain a digital video signal with less deterioration of resolution after removing noise components.

According to the second aspect of the present invention, the precision of noise discrimination in the noise discrimination removing means can be improved by subdividing the region discriminated as noise in the digital video signal, so that the luminance is further improved. By performing the noise removal according to the level, it is possible to remove the noise component while further minimizing the deterioration of the resolution.

According to the third aspect of the present invention, in order to remove the noise component of the digital video signal, M types of digital filters having different characteristics are preset and set according to the frequency characteristic of the noise component of the digital video signal. Thus, by selectively using an effective digital filter to remove the noise component, it is possible to remove the noise according to the frequency characteristic of the noise of the digital video signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of a video signal noise elimination device of the present invention.

FIG. 2 is a block diagram showing a configuration of adjacent pixel difference detection means in the first to third embodiments of the present invention.

FIG. 3 is a block diagram showing a configuration of noise determining means in the first to third embodiments of the present invention.

FIG. 4 is a block diagram showing a configuration of a video signal register section in the first to third embodiments of the present invention.

5A is a digital video signal waveform diagram at the output of the A / D converter of the first embodiment of the present invention, and FIG. 5B is a digital video signal at the output of the video signal register section of the first embodiment of the present invention. It is a signal waveform diagram.

FIG. 6 is a block diagram showing the configuration of a second embodiment of the video signal noise eliminator of the present invention.

7A is a digital video signal waveform diagram at the output of the A / D converter of the second embodiment of the present invention, and FIG. 7B is a digital video signal at the output of the video signal register section of the second embodiment of the present invention. It is a signal waveform diagram.

FIG. 8 is a block diagram showing a configuration of a video signal noise removing apparatus according to a third embodiment of the present invention.

9A is a waveform diagram of a digital video signal at the output of the A / D converter of the third embodiment of the present invention, and FIG. 9B shows characteristics of the first digital filter in the third embodiment of the present invention. FIG. 3 is a digital video signal waveform diagram at the output of the video signal register section when noise removal is performed as 1 + Z ¹ ) / 2.

10 (a) is a waveform diagram of a digital video signal at the output of the A / D converter of the third embodiment of the present invention, and FIG. 10 (b) shows the characteristics of the second digital filter in the third embodiment of the present invention ( as ^{1 + Z ~ 1 + Z ~} 2) / 3, a digital video signal waveform diagram at the output of the video signal register section when performing the noise removal.

FIG. 11 is a block diagram showing a configuration of a conventional video signal processing circuit.

FIG. 12 (a) is an analog video signal waveform diagram of an input of a conventional A / D converter, (b) is a digital video signal waveform diagram of an output of an A / D converter affected by a conventional noise component, c) is an explanatory diagram of a monitor screen showing the influence of noise.

[Explanation of symbols]

1 ... CCD image sensor, 2 ... CDS circuit, 3 ... AGC
Circuit, 4 ... Clamp circuit, 5 ... A / D converter,
6 ... Digital filter, 7 ... Adjacent pixel difference detection means, 8 ... Reference brightness level setting means, 9 ... First noise area setting means, 10 ... Second noise area setting means, 11 ...
Noise discrimination means, 12 ... video signal register section, 13 ... camera process circuit, 14 ... register, 15 ... subtractor,
16, 18, 20, 35 ... Comparator circuit, 24 ... Noise discrimination signal, 25 ... First register, 26 ... Second register, 2
7, 34, 37 ... Selector circuit, 28 ... Second reference luminance level setting means, 29 ... Third noise area setting means, 30 ... Fourth noise area setting means, 31 ... Second noise determining means, 32
... second noise discrimination signal, 33 ... third reference luminance level setting means, 36 ... second digital filter, 38 ... digital filter switching means.

Claims (3)

[Claims] 1. An analog video signal is input from an imaging unit,
Adjacent pixel difference detection means for detecting a difference in brightness level between adjacent pixels of the digitally converted digital video signal; reference brightness level setting means for presetting a brightness level for the digital video signal; As noise area setting means for presetting a noise level for a difference in brightness level between adjacent pixels for each brightness area of the digital video signal divided into two brightness areas, two brightnesses with the brightness level as a boundary Noise discrimination / removal means for discriminating the digital video signal as noise and eliminating the noise by a digital filter when the difference in luminance level between adjacent pixels is within the noise level in the digital video signal divided into regions. A video signal noise eliminator comprising: 2. An analog video signal is input from the image pickup section,
Adjacent pixel difference detection means for detecting a difference in brightness level between adjacent pixels of the digitally converted digital video signal, and N (N is an integer) brightness levels (Y _{1 to} Y _N ) for the digital video signal. And N reference brightness level setting means, and the digital image pre-divided into _{N + 1} brightness regions (T _{1 to} T _{N + 1} ) with the brightness level (Y _{1 to} Y _N ) as a boundary. In the luminance region of the signal, _{N + 1} noises that set the noise level (H _{1 to} H _{N + 1} ) for the luminance level difference between adjacent pixels for each luminance region of the luminance region (T _{1 to} T _{N + 1} ). With the area setting means and the brightness level (Y _{1 to} Y _N ) as a boundary, the brightness area (T _{1 to} T
_{In the} digital video signal divided into ( _{N + 1} ), the difference in luminance level between adjacent pixels is the noise level (H _{1 to} H).
_A video signal noise eliminator comprising: a noise discrimination / removal unit that discriminates the digital video signal as noise when it is within _{N + 1} ) and removes the noise by a digital filter. 3. An analog video signal is inputted from the image pickup section,
Adjacent pixel difference detection means for detecting a difference in luminance level between adjacent pixels of the digitally converted digital video signal, and M for removing a noise component of the digital video signal in advance.
(M is an integer) digital filters having different characteristics, reference luminance level setting means for presetting a luminance level for the digital video signal, and the digital divided into two luminance regions with the luminance level as a boundary. Noise region setting means for presetting a noise level corresponding to a difference in luminance level between adjacent pixels for each luminance region of the video signal; and the digital video signal divided into two luminance regions with the luminance level as a boundary, When the difference in brightness level between adjacent pixels is within the noise level, the digital video signal is discriminated as noise, and one kind of digital filter is selected from the M digital filters having different characteristics to remove the noise. The digital discrimination filter to remove noise by the digital filter. Video signal noise reduction apparatus according to claim.