JP2010020523A - Image processor and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor and an imaging system for improving noise reduction performance while suppressing the increase in a hardware scale. <P>SOLUTION: This image processor includes: a processor 250 for performing noise reduction processing to a prescribed band signal created from an original image; noise reduction parts 204 and 214 for operating noise reduction processing to a band signal created from the original image, whose frequency band is higher than that of the prescribed band signal; and a means for synthesizing the band signals after the noise reduction processing has been performed by the processor 250 and the noise reduction parts 204 and 214, and for creating an original image whose noise reduction processing has been completed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an imaging system, and more particularly to a noise reduction method.

  As a noise reduction method for removing a noise signal included in an image, a noise reduction method using multi-resolution conversion is known. In this method, a filter bank or Laplacian pyramid method is used to divide an image into signals of a plurality of frequency bands, and after applying some noise reduction processing to each band signal, these are recombined. . According to this method, it is possible to perform noise reduction processing having an intensity suitable for each divided band.

  FIG. 12 shows an example of multi-resolution conversion using a Laplacian pyramid and a noise reduction method using the same. In FIG. 12, the input image 100 is reduced after the low-pass filter processing by the filter / reduction processing unit 101. By this processing, the image size is halved in both the horizontal direction and the vertical direction. The reduced image is supplied to the filtering unit 111 in the next stage and is sequentially reduced.

  The image reduced by the filter / reduction processing unit 101 is enlarged to the original image size by the enlargement processing unit 102 and then supplied to the subtraction unit 103. In the subtraction unit 103, a difference signal between the input image 100 and the image supplied from the enlargement processing unit 102 is generated. This difference signal corresponds to a high-frequency component blocked by the low-pass filter characteristic used in the filter / reduction processing unit 101. The difference signal containing a lot of high frequency components is supplied to the noise reduction unit 104 and subjected to noise reduction processing.

  The same process is performed in the second and subsequent stages. That is, the filter / reduction processing unit 111, the enlargement processing unit 112, and the subtraction unit 113 generate a band signal corresponding to the second stage, and the noise reduction unit 114 performs noise reduction processing on the band signal. In this way, noise reduction processing is sequentially applied to the band-divided signal.

The output of the noise reduction unit 134 in the lowest frequency band is added to the low frequency side signal and the addition unit 136 and then sent to the high frequency processing. In this way, the signals are sequentially recombined from the low frequency side, and finally the highest frequency signal is added by the adding unit 106 to form an output image 121.
In the example illustrated in FIG. 11, after the low-pass filter processing and the reduction processing are performed in the last-stage filter / reduction processing unit 131, the enlargement processing unit 132 and the enlargement processing unit 135 perform the enlargement processing. The reduction processing in the filter / reduction processing unit 131 and the enlargement processing units 132 and 135 may be omitted.

Patent Document 1 discloses a configuration (for example, refer to Patent Document 2) in which filter processing having directionality is applied to processing corresponding to the noise reduction units 104, 114,. Patent Document 3 discloses a method of performing coring processing in which wavelet transform is used as frequency division, and a signal equal to or lower than a threshold is set to 0 for each divided band signal.
JP 2001-57677 A JP 55-133179 A JP-A-9-212623

  The noise reduction method using multi-resolution conversion as described above has an advantage that noise reduction processing having an intensity suitable for each divided band signal can be performed, and can increase the number of bands to be divided by increasing the number of stages of multi-resolution conversion. For example, a noise component existing at a lower frequency can be an object of noise reduction.

  However, when the number of stages of multi-resolution conversion is increased, there is a problem that the amount of calculation required increases accordingly. In particular, assuming hardware implementation by LSI, etc., the number of stages of multi-resolution conversion may be limited due to hardware scale limitations, and this can provide the desired noise reduction performance when the amount of noise is large. There was a problem that it was not possible.

  The present invention has been made to solve the above-described problem, and an object thereof is to provide an image processing apparatus and an imaging system capable of improving noise reduction performance while suppressing an increase in hardware scale. .

In order to solve the above problems, the present invention employs the following means.
According to a first aspect of the present invention, there is provided filtering means for blocking a signal in a part of a frequency band in an image signal by filtering and outputting a signal in another frequency band, and the first frequency band of the image signal A first band signal generating unit that generates a signal included in the first frequency band, a first noise reducing unit that reduces a noise amount of the signal included in the first frequency band, and a second frequency band of the image signal. First storage means for storing a signal that is included and has a reduced noise amount, and a signal in the first frequency band in which the noise amount is reduced by the first noise reduction means and the input signal are combined. And a signal based on a signal output from the first filtering unit and a signal output from the first storage unit as the signal input to the first image synthesizing unit and the first image synthesizing unit. An image processing apparatus characterized by comprising a first selection means for selecting one of the signal included in the second frequency band.

  According to this aspect, the signal included in the first frequency band acquired by the first band signal generation unit and reduced in the noise amount by the first noise reduction unit and the first storage unit stored in the first storage unit. 2 is configured to synthesize a signal with a reduced amount of noise, so that both the signal included in the first frequency band and the signal included in the second frequency band are respectively Compared with a configuration in which noise is reduced by using a corresponding separate band signal generation unit and noise reduction unit, the scale of hardware can be suppressed.

  According to a second aspect of the present invention, there is provided first band signal generation means for generating a signal included in a first frequency band of an image signal, and a first amount of noise reduced in the signal included in the first frequency band. 1 noise reduction means and the first frequency band of the first frequency band that is included in the second frequency band of the image signal, the noise amount of which is reduced by the signal of which the noise amount is reduced, and the first noise reduction means. A first image synthesizing unit that synthesizes the signal, and the first band signal generating unit includes a first filtering unit that blocks a signal in a part of the frequency band in the image signal by filtering. In the image processing apparatus, the signal included in the second frequency band input to the first image synthesizing unit is not a signal based on the signal output from the first filtering unit. That.

  According to a third aspect of the present invention, band signal generation means for generating a signal included in the first frequency band of the image signal, and noise reduction means for reducing the noise amount of the signal included in the first frequency band, A processor for reducing a noise amount of a signal included in the second frequency band of the image signal, a signal included in the first frequency band in which the noise amount is reduced by the noise reduction unit, and a noise amount by the processor An image synthesizing unit that synthesizes a signal included in the second frequency band in which the frequency is reduced.

  According to a fourth aspect of the present invention, there is provided an imaging system including an imaging unit that captures an image of a subject and the image processing apparatus according to any one of the above that processes an image signal acquired by the imaging unit.

  According to a fifth aspect of the present invention, the amount of noise is reduced using noise reduction means for a signal included in the first frequency band of the image signal, and the signal included in the second frequency band of the image signal is detected. An image processing method comprising: reducing a noise amount using the noise reduction unit; and synthesizing a signal included in the first frequency band and the signal included in the second frequency band in which the noise amount is reduced. It is.

  According to a sixth aspect of the present invention, an image signal is input, and a first band signal generating unit that generates a high band signal and a low band signal from the input image signal, and the band signal generating unit First storage means for storing a low-band signal, first noise reduction means for reducing noise in the high-band signal generated by the band signal generation means, and high band in which noise is reduced by the first noise reduction means A first image synthesizing unit that synthesizes the signal and the low-band signal, a second storage unit that stores the synthesized image signal synthesized by the first image synthesizing unit, and an input to the first band signal generating unit. A first switching means for switching the image signal to either an original image signal or a low-band signal stored in the first storage means; and a signal input to the first image synthesizing means, Bandwidth An image processing apparatus having a second switching means for switching to one of the stored combined image signal in the low band signal and the second storage means to be output from the generation means.

According to this aspect, the high-band signal and the low-band signal are generated from the input image signal by the first band signal generation unit, and the low-band signal is stored in the first storage unit. In this case, since the low-band signal stored in the first storage means can be input again to the first-band signal generation means via the first switching means, the low-band signal is A low-frequency signal is further generated. In this way, by repeatedly using the first band signal generating means, it becomes possible to generate signals of a plurality of bands from the original image signal, and to demonstrate the capability beyond the capability of the first band signal generating means. It becomes possible.
For the high-band signal generated by the first band signal generation unit, noise is reduced by the noise reduction unit, and the high-band signal after the noise reduction and the low-band signal generated by the first band signal generation unit are the first. The images are synthesized by the image synthesis means. In this case, the synthesized image signal synthesized by the first image synthesizing unit is stored in the second storage unit, and can be further input to the first image synthesizing unit via the second switching unit. Therefore, as described above, even when the first band signal generation unit is repeatedly used to generate a plurality of band signals, the low band signal paired with the high band signal output from the noise reduction unit is generated. It is possible to input the first image composition means.
As described above, according to the present invention, since the first band signal generation unit, the noise reduction unit, and the first image synthesis unit can be repeatedly used, high noise reduction performance can be achieved while suppressing an increase in hardware scale. Can be obtained.
The high-band signal means, for example, a signal flowing from each filtering unit to the enlargement processing unit in the first embodiment described later. The low-band signal means a signal stored in the frame memory 223 in the first embodiment described later, for example.

  According to a seventh aspect of the present invention, an image signal is input, a band signal generating unit that generates a high band signal and a low band signal from the input image signal, and a high band generated by the band signal generating unit First noise reduction means for reducing signal noise, second noise reduction means for reducing noise of a low-band signal generated by the band signal generation means, and high noise reduced by the first noise reduction means An image synthesizing unit that synthesizes the band signal and the low-band signal whose noise is reduced by the second noise reduction unit, and the second noise reduction unit reduces the noise of the low-band signal by program control by a processor. An image processing apparatus.

  According to this aspect, since the noise reduction processing by software is adopted for the low-band signal noise reduction processing with a low processing burden, the apparatus can be downsized while reducing the processing burden compared to the case where a dedicated circuit is provided. It becomes possible to plan.

  An eighth aspect of the present invention generates a first frequency band signal and a second frequency band signal from an input image signal, and is included in the first frequency band signal and the second frequency band signal. The image processing method is characterized in that the generated noise is removed using a common noise reduction means, and the first frequency band signal and the second frequency band signal after noise reduction are synthesized.

  According to the present invention, it is possible to improve noise reduction performance while suppressing an increase in hardware scale.

  Hereinafter, an image processing apparatus, an image processing method, and an imaging system according to the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of an image processing apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the image processing apparatus 1 according to the present embodiment employs a system that performs multi-resolution conversion using a Laplacian pyramid and reduces noise for each band signal.
Specifically, the image processing apparatus 1 includes a filtering unit (filtering unit) that blocks a signal of a part of the frequency band in the image signal by filtering and outputs a signal of the other frequency band. A band signal generation unit (first band signal generation means) 2 that generates a signal included in the first frequency band, a noise reduction processing unit 3 that reduces the noise amount of the signal included in the first frequency band, An image synthesizing unit (first image synthesizing unit) 4 that synthesizes the signal of the first frequency band in which the amount of noise is reduced by the noise reduction processing unit 3 and the input signal is provided.
The image processing apparatus 1 is further input to a frame memory 224 (first storage unit) that stores a signal that is included in the second frequency band of the image signal and has a reduced amount of noise, and the image composition unit 4. A first selection unit (first selection unit) 222 that selects one of a signal based on a signal output from the filtering unit included in the band signal generation unit 2 and a signal output from the frame memory 224 as the signal; Among the signals stored in the input image 200 and the frame memory 223 as signals input to the frame memory (second storage means) 223 that stores the signal output from the filtering unit and the band signal generation unit 2 A second selection unit (second selection means) 225 for selecting any one of the above, and a connection for switching between connection and non-connection between the filtering unit and the frame memory 223. Switching unit and a (connection switching means) 220.

The band signal generation unit 2 includes N (N is an integer equal to or greater than 1) stages of filtering units 201 and 211, and enlargement processing units 202 and 212 provided corresponding to the filtering units 201 and 211, respectively, and subtraction Parts 203 and 213 are provided.
The noise reduction processing unit 3 includes N noise reduction units 204 and 214 provided corresponding to the filtering units 201 and 211, respectively. The image composition unit 4 includes N stages of composition units 209 and 219 provided corresponding to the filtering units 201 and 211, respectively. Each of the combining units 209 and 219 includes enlargement processing units 205 and 215 and addition units 206 and 216, respectively. In the present embodiment, the case where N = 2 is described as an example.

The first-stage filtering unit 201 performs low-pass filter processing on the input image 200 and then reduces it to a predetermined size. Thereby, for example, the image size of the input image 200 is halved in both the horizontal direction and the vertical direction. The reduced image generated by the filtering unit 201 can be supplied to the enlargement processing unit 202 and the subsequent filtering unit 211.
The enlargement processing unit 202 enlarges the reduced image from the filtering unit 201 to a size before the reduction processing by the filtering unit 201, that is, here, enlarges the reduced image to the size of the input image 200 and outputs it to the subtracting unit 203. To do. The subtraction unit 203 generates a band signal by calculating a difference signal between the image input from the enlargement processing unit 202 and the image input to the filtering unit 201, that is, the input image 200, and reduces this noise. Output to the unit 204. The noise reduction unit 204 performs predetermined noise reduction processing on the input band signal and outputs it.

The second-stage filtering unit 211 performs a reduction process after performing a low-pass filter process on the reduced image from the filtering unit 201. In this way, each filtering unit 201, 211 generates and outputs a reduced image obtained by further reducing the image output from the preceding filtering unit (the input image 200 for the first filtering unit 201).
The reduced image generated by the reduction processing 211 can be supplied to the enlargement processing unit 212, the connection switching unit 220, and the first selection unit 222.

  The enlargement processing unit 212 enlarges the input reduced image to a size before the reduction processing by the filtering unit 211 and outputs the reduced image to the subtraction unit 213. The subtraction unit 213 generates a band signal by taking the difference between the image supplied from the enlargement processing unit 212 and the image input to the filtering unit 211, and outputs the band signal to the noise reduction unit 214. The noise reduction unit 214 performs a predetermined noise reduction process on the input band signal and outputs it.

The connection switching unit 220 is means for switching connection and disconnection between the filtering unit 211 and the frame memory 223. Specifically, when the wirings at both ends of the connection switching unit 220 are in a connected state, the reduced image output from the filtering unit 211 is supplied to the frame memory 223, and the wirings at both ends of the connection switching unit 220 are in a disconnected state. In some cases, the reduced image output from the filtering unit 211 is not supplied to the frame memory 223.
The first selection unit 222 is means for switching the supply source of the reduced image input to the N-th combining unit 219 of the image combining unit 4. Specifically, the reduced image from the filtering unit 211 or the reduced image 400 with reduced noise held in the frame memory 224 is supplied to the combining unit 219.
The second selection unit 225 is means for switching a signal input to the band signal generation unit 2. Specifically, either one of the input image 200 and the signal stored in the frame memory 223 is selected as a signal to be input to the band signal generation unit 2, and one of the signals is one stage of the band signal generation unit 2. Supplied to the eye filtering unit 201.

The enlargement processing unit 215 of the N-th synthesis unit 219 enlarges the input reduced image to the size of the reduced image input to the corresponding filtering unit 211 and outputs the reduced image to the addition unit 216. The adding unit 216 adds the noise-reduced band signal supplied from the noise reducing unit 214 and the reduced image supplied from the enlargement processing unit 215, and outputs the result to the (N-1) th combining unit 209.
The enlargement processing unit 205 of the synthesis unit 209 enlarges the reduced image from the synthesis unit 219 and outputs the reduced image to the addition unit 206. The adding unit 206 adds the noise-reduced band signal supplied from the noise reducing unit 204 and the reduced image supplied from the enlargement processing unit 205 and outputs the result. As a result, a noise-reduced image returned to a predetermined size is output.

  Next, an image processing method realized by the image processing apparatus 1 according to the present embodiment having the above-described configuration will be described. First, the image processing method according to the present embodiment includes three modes according to the settings of the connection switching unit 220, the first selection unit 222, and the second selection unit 225.

[First mode]
First, in the first mode, as shown in FIG. 2, the input image 200 is supplied to the filtering unit 201 by the second selection unit 225, and the filtering unit 211 is connected to the frame memory 223 by the connection switching unit 220. The first selection unit 222 is in an open state, or the synthesis unit 219 is connected to the output line of the filtering unit 211 or the frame memory 224 by the first selection unit.

By connecting in this way, the input image 200 is reduced in stages by the filtering units 201 and 211 provided in N stages. The reduced image 300 output from the filtering unit 211 is stored in the frame memory 223 via the connection switching unit 220.
The purpose of this first mode is to obtain a reduced image 300. Therefore, it is not necessary to operate the components unnecessary for obtaining the reduced image 300.
However, in the case where the synthesis unit 219 is connected to the output line of the filtering unit 211 by the first selection unit 222 and other blocks are also operated, in addition to the reduced image 300 described above, it corresponds to two stages. It is possible to obtain an output image to which the noise reduction processing is applied.

[Second mode]
Next, in the second mode, as shown in FIG. 3, the filtering unit 201 is connected to the frame memory 223 by the second selection unit 225, and the connection switching unit 220 is opened. Further, the synthesis unit 219 is connected to the output line of the filtering unit 211 by the first selection unit 222.
By connecting in this way, in the second mode, the reduced image 300 stored in the frame memory 223 in the first mode is input to the band signal generation unit 2, specifically, the first-stage filtering unit 201. .
The input reduced image 300 is further reduced by the filtering units 201 and 211, and the reduced image 301 is output to the synthesis unit 219 via the first selection unit 222.

  On the other hand, the reduced images generated by the filtering units 201 and 211 are supplied to the enlargement processing units 202 and 212 and the subtraction units 203 and 213, respectively, thereby generating each band signal. Each band signal is supplied to the noise reduction units 204 and 214, whereby noise reduction processing is performed, and the band signal after noise reduction is output to the synthesis units 209 and 219, respectively.

  In the synthesis unit 219, the reduced image 301 is enlarged and then synthesized with the band signal from the noise reduction unit 214. This synthesized image is supplied to the synthesizing unit 209, synthesized with the band signal from the noise reducing unit 204 after enlarging processing, and output as a reduced image 400 with reduced noise. The noise-reduced reduced image 400 is stored in the frame memory 224.

  As described above, in the second mode, the reduced image 300 is input again to the band signal generation unit 2, so that the reduced image 301 output from the band signal generation unit 2 passes through the 2 × N-stage filtering unit. This corresponds to a reduced image when it is created. Thereby, it becomes possible to demonstrate the capability more than the capability originally provided in the band signal generation unit 2.

[Third mode]
Subsequently, in the third mode, as illustrated in FIG. 4, the input image 200 is input to the filtering unit 201 by the second selection unit 225, the connection switching unit 220 is opened, and the first selection unit 222 The combining unit 219 is connected to the frame memory 224.
By being connected in this way, the input image 200 is supplied to the band signal generation unit 2, and the reduction units 201 and 211 are subjected to the stepwise reduction process, and the respective reduction images are subtracted from the enlargement processing units 202 and 212. Each band signal is generated by being supplied to the units 203 and 213. Each band signal is subjected to noise reduction processing by the noise processing units 204 and 214 and then output to the corresponding combining units 209 and 219.

  In addition, since the synthesis unit 219 is connected to the frame memory 224 by the first selection unit 222, the reduced noise reduced image 400 stored in the frame memory 224 is synthesized via the first selection unit 222. To the unit 219. As a result, by performing the enlargement and synthesis processing on the reduced noise reduced image 400, a composite image with the band signal from the noise reduction unit 214 is created, and the enlargement and synthesis processing is also performed in the synthesis unit 209. As a result, a noise-reduced original image 500 having a size substantially the same as that of the input image 200 is finally output.

  As described above, according to the image processing device 1 and the image processing method according to the present embodiment, the common band signal generation unit 2, the noise reduction processing unit 3, and the image synthesis unit 4 are performed a plurality of times (the above-described implementation). Since it is used twice in the form, it is possible to exhibit the ability more than the ability of the band signal generation unit 2 and the like. As a result, it is possible to improve noise reduction performance while suppressing an increase in hardware scale.

  In the present embodiment, the device configuration having the multi-resolution conversion capability for two stages is used twice to obtain a noise reduction performance equivalent to four stages. It is also possible to obtain noise reduction performance equivalent to 3 × N stages and 4 × N stages by recursively inputting images.

  In the present embodiment, the purpose is only to obtain the reduced image 300 in the first mode, and the generation of the band signal and the noise reduction processing are performed on the input image 200 in the third mode. However, instead of this mode, in the first mode, the band signal generation unit 2 and the noise reduction processing unit 3 are operated to generate and store each band signal with reduced noise. The stored noise-reduced band signal and the noise-reduced reduced image 400 may be combined.

  In this embodiment, the reduced image 300 is input again to the first-stage filtering unit 201 in the second mode. Instead, the output signal of the filtering unit 211 is input to the band signal generation unit 2. It is also possible to input again, and the output of the combining unit 219 may be the noise-reduced reduced image 400. In this way, it is possible to obtain noise reduction performance equivalent to three stages.

  Further, for example, there is an image reduction function in image processing other than noise reduction, and a reduced image of the input image 200 is created. This can be regarded as substantially the same as the reduced image 300 created by the filtering units 201 and 211. If it is an image, the processing speed can be improved by making this image an input image in the second mode without implementing the first mode.

[Second Embodiment]
Next, an image processing apparatus and an image processing method according to the second embodiment of the present invention will be described. As shown in FIG. 5, the image processing apparatus of this embodiment is different from that of the first embodiment in that M (M is the output side of the connection switching unit 220 ′ and the input side of the first selection unit 222 ′. 1 or more stages) band signal generation unit (second band signal generation unit) 5, noise reduction processing unit (second noise reduction unit) 6 including M noise reduction units, M stage image synthesis unit (Second image composition means) 7 is provided.
Hereinafter, the image processing apparatus according to the present embodiment will not be described with respect to the points common to the first embodiment, and different points will be mainly described. In the present embodiment, the case where M = 1 is described as an example, but the number of M is not limited.

  FIG. 5 is a diagram illustrating a schematic configuration of the image processing apparatus according to the present embodiment. As shown in this figure, a band signal generation unit 5, a noise reduction processing unit 6, and an image synthesis unit 7 are provided on the output side of the connection switching unit 220 ′ and the input side of the first selection unit 222 ′. Yes. The configurations of the band signal generation unit 5, the noise reduction processing unit 6, and the image synthesis unit 7 are substantially the same as those of the band signal generation unit 2, the noise reduction processing unit 3, and the image synthesis unit 4 described above. As for the reduction processing unit 6, the noise reduction processing method is simplified compared to the noise reduction processing unit 3.

A reduced image output from the filtering unit 211 can be input to the band signal generation unit 5 via the connection switching unit 220 ′.
The filtering unit 612 performs a reduction process after performing a low-pass filter process on the input reduced image. The reduced image generated by the filtering unit 612 can be input to the enlargement processing unit 622 and the combining unit 629 of the image combining unit 7.

  The enlargement processing unit 622 of the band signal generation unit 5 enlarges the input reduced image to a size before the reduction processing by the filtering unit 612, and outputs it to the subtraction unit 623. The subtraction unit 623 generates a band signal by taking the difference between the image supplied from the enlargement processing unit 622 and the reduced image input to the filtering unit 612, and outputs the band signal to the noise reduction unit 624. The noise reduction unit 624 performs predetermined noise reduction processing on the input band signal and outputs it. Here, the function of the noise reduction unit 624 is simplified compared to the noise reduction units 204 and 214. For example, when the noise reduction units 204 and 214 perform a noise reduction process that combines a filtering process with a direction determination process and a coring process, the noise reduction unit 624 performs, for example, a noise reduction process by a coring process. Only do. Thus, by simplifying the function of the noise reduction unit 624, it is possible to improve the processing speed.

  The band signal subjected to the noise reduction processing by the noise reduction unit 624 is supplied to the synthesis unit 629 of the image synthesis unit 7. The enlargement processing unit 625 of the synthesis unit 629 enlarges the reduced image from the filtering unit 612 to the size of the reduced image input to the filtering unit 612 and outputs the reduced image to the addition unit 626. The adder 626 adds the noise-reduced band signal supplied from the noise reducer 624 and the reduced image supplied from the enlargement processor 625 and outputs the result.

The connection switching unit 220 ′ is means for switching the supply destination of the reduced image output from the filtering unit 211. Specifically, the reduced image from the filtering unit 211 is supplied to the filtering unit 612 or the frame memory 223. However, the connection switching unit 220 ′ allows the filtering unit 211 to be connected to both the filtering unit 612 and the frame memory 223 at the same time, and outputs a reduced image to both the filtering unit 612 and the frame memory 223. Is possible.
The first selection unit 222 ′ is means for switching the supply source of the reduced image input to the N-th combining unit 219 of the image combining unit 4. Specifically, the reduced noise reduced image output from the adding unit 626 of the synthesizing unit 629 or the reduced noise reduced image 700 held in the frame memory 224 is supplied to the synthesizing unit 219.

  Next, an image processing method realized by the image processing apparatus according to this embodiment having the above-described configuration will be described. First, the image processing method according to the present embodiment includes three modes according to the settings of the second selection unit 225, the connection switching unit 220 ′, and the first selection unit 222 ′.

[First mode]
First, in the first mode, as shown in FIG. 6, the input image 200 is input to the filtering unit 201 by the second selection unit 225, and the frame memory 223 is connected to the filtering unit 211 by the connection switching unit 220 ′. The first selection unit 222 ′ is in an open state or connects the output line of the addition unit 626 and the synthesis unit 219. Note that the connection switching unit 220 ′ may connect the filtering unit 211 to both the filtering unit 612 and the frame memory 223.
By connecting in this way, the input image 200 is reduced stepwise by the filtering unit 201 and the filtering unit 211 provided in N stages. The reduced image 600 output from the filtering unit 211 is stored in the frame memory 223 via the connection switching unit 220.
The purpose of this first mode is to obtain a reduced image 600. Therefore, it is not necessary to operate the components that are not necessary for obtaining the reduced image 600.

  However, the connection switching unit 220 ′ connects the filtering unit 211 to both the filtering unit 612 and the frame memory 223, and the first selection unit 222 ′ connects the combining unit 219 to the output line of the adding unit 626. When the block is also operated, it is possible to obtain an output image to which noise reduction corresponding to three stages is applied in addition to the reduced image 600 described above.

[Second mode]
Next, in the second mode, as shown in FIG. 7, the filtering unit 201 is connected to the frame memory 223 by the second selection unit 225, and the filtering unit 211 is connected to the filtering unit 612 by the connection switching unit 220 ′. The combining unit 219 is connected to the combining unit 629 by the first selection unit 222 ′.
Thereby, the image processing apparatus according to the second mode functions as an apparatus having a three-stage frequency band dividing function.

Specifically, in the second mode, the reduced image 600 stored in the frame memory 223 in the first mode is input to the first-stage filtering unit 201 of the band signal generation unit 2 by the second selection unit 225.
The reduced image 600 is reduced stepwise by the filtering units 201 and 211, input to the filtering unit 612 via the connection switching unit 220 ′, further reduced, and supplied to the combining unit 629.
The reduced images reduced by the filtering units 201, 211, and 612 are supplied to the enlargement processing units 202, 212, and 622. Further, the subtraction units 203, 213, 623, and the noise reduction units 204, 214, and 624 are supplied. Each band signal is output to the respective combining units 209, 219, and 629 by passing through the respective band signals. Then, the image synthesis is performed in stages by the synthesis units 629, 219, and 209, whereby the reduced image 700 with reduced noise is output from the synthesis unit 209. The noise-reduced reduced image 700 is stored in the frame memory 224.

[Third mode]
Subsequently, in the third mode, as shown in FIG. 8, the input image 200 is input to the filtering unit 201 by the second selection unit 225, the connection switching unit 220 ′ is opened, and the first selection unit 222. ′ Connects the combining unit 219 to the frame memory 224.
Thus, the input image 200 is subjected to stepwise reduction processing by the filtering units 201 and 211, and the respective reduced signals are supplied to the enlargement processing units 202 and 212 and the subtraction units 203 and 213, so that each band signal is changed. Generated. Each band signal is subjected to noise reduction processing by the noise processing units 204 and 214 and then output to the corresponding combining units 209 and 219.

  Further, since the synthesis unit 219 is connected to the frame memory 224 by the first selection unit 222 ′, the noise-reduced reduced image 700 stored in the frame memory 224 is supplied to the synthesis unit 219. As a result, by performing enlargement and synthesis processing on the reduced noise reduced image 700, a composite image with the band signal from the noise reduction unit 214 is created. Further, the synthesis unit 209 also performs enlargement and synthesis processing. As a result, the noise-reduced original image 800 having the same size as the input image 200 is finally output from the synthesis unit 209.

  As described above, according to the image processing apparatus according to the present embodiment, since one component is used multiple times to perform band signal creation, noise reduction processing, image synthesis, and the like, It becomes possible to demonstrate the capability beyond the capability with which the composition is provided. As a result, it is possible to improve noise reduction performance while suppressing an increase in hardware scale.

Furthermore, according to the image processing apparatus according to the present embodiment, it is necessary to increase the processing speed, the first to third modes cannot be performed, and it is necessary to obtain an output image only in the first mode. Even in some cases, noise reduction processing with a large number of stages can be realized with a simple configuration in which a simplified noise reduction processing unit 6 is added to the noise reduction processing unit 3.
In addition, before and after the connection switching unit 220 ′ and the first selection unit 222 ′, the noise reduction units (noise reduction processing unit 3 and noise reduction processing unit 6) having different noise reduction performance are arranged separately, so that the first When the first to third modes are performed, it is possible to prevent the band signals having different noise reduction performance from being irregularly combined, and to obtain a natural image.

[Third Embodiment]
Next, an image processing apparatus and an image processing method according to the third embodiment of the present invention will be described. In the first embodiment and the second embodiment described above, processing by a dedicated circuit is assumed. However, in the image processing apparatus according to the present embodiment, program control by a processor is adopted for some noise reduction processing. .

Usually, an image processing apparatus often has a processor in charge of processing such as control. If noise reduction processing can be performed by a processor, it can be expected that flexible and complicated processing by program control is possible compared to the case of a dedicated circuit.
By the way, since the number of pixels to be processed is enormous in image processing, there is a problem that a large amount of processing time is required for a normal processor. Therefore, in the image processing apparatus according to the present embodiment, the processing corresponding to the above-described second mode processing for performing noise reduction processing on the reduced image is realized by program control by the processor, and other processing, that is, The noise reduction processing for the original image is realized using a dedicated circuit.
As described above, the processing by the software is applied to the second mode processing for handling the reduced image having a smaller number of pixels than the original image, and the first mode and the third mode processing for handling the original image having a large number of pixels are dedicated. By performing processing using a circuit, it is possible to obtain an advantage that flexible and complicated noise reduction processing can be realized while suppressing an increase in processing time and an increase in size of the apparatus.

The image processing apparatus according to this embodiment will be described below with reference to the drawings.
FIG. 9 is a block diagram illustrating a schematic configuration of the image processing apparatus according to the present embodiment. In FIG. 9, the same code | symbol is attached | subjected about the same component as 1st Embodiment mentioned above.

[First mode]
In the first mode, as in the first embodiment described above, the reduced image 300 is generated by inputting the input image 200 to the filtering units 201 and 211 in stages, and the reduced image 300 passes through the connection switching unit 220. And stored in the frame memory 223.

[Second mode]
In the second mode, the reduced image 300 is supplied from the frame memory 223 to the processor 250, and noise reduction processing by the processor 250 is performed. The noise reduction processing realized by the processor 250 is processing corresponding to noise reduction processing using multi-resolution conversion corresponding to two stages as shown in FIG. 3, for example. Thereby, the noise-reduced reduced image 400 obtained in the first embodiment is created, and the noise-reduced reduced image 400 is stored in the frame memory 224.

[Third mode]
In the third mode, when the input image 200 is input, reduced images are generated in stages by the filtering units 201 and 211, and the reduced images are supplied to the enlargement processing units 202 and 212 and the subtraction units 203 and 213, respectively. Thus, each band signal is generated. Each band signal is subjected to noise reduction processing by the noise reduction units 204 and 214 and then output to the corresponding synthesis units 209 and 219.
In addition, the noise reduction reduced image 400 stored in the frame memory 224 is input to the synthesis unit 219. As a result, by performing the enlargement and synthesis processing on the reduced noise reduced image 400, a composite image with the band signal from the noise reduction unit 214 is created, and the enlargement and synthesis processing is also performed in the synthesis unit 209. As a result, a noise-reduced original image 500 having a size substantially the same as that of the input image 200 is finally output from the synthesizing unit 209.

In the case of a dedicated circuit, it is often difficult to realize a noise reduction method using information of the entire image such as a histogram of the entire image due to the limitation of the memory amount in the circuit. On the other hand, in the case of processing by the processor 250, information on the entire image stored in a frame memory (not shown) in which the original image and the like are stored can be accessed relatively easily. It is also possible to adopt a noise reduction method for reducing noise.
As described above, according to the image processing apparatus and the image processing method according to the present embodiment, the processing corresponding to the second mode in the first embodiment or the second embodiment is realized by the program processing by the processor 250. As a result, it is possible to obtain high noise reduction performance while suppressing an increase in hardware scale, and it is possible to perform flexible and complex noise reduction processing by program control.

  In the present embodiment, the noise reduction process realized by the processor 250 is not limited to the noise reduction process using the multi-resolution conversion described above, and a noise reduction process suitable for the program process by the processor 250 is adopted. Is also possible. For example, noise reduction processing based on a histogram or the like of the entire image may be employed.

  The input to the processor 250 is not limited to the reduced image 300 obtained by the filtering units 201 and 211. For example, a reduced image of the input image 200 is created in image processing other than noise reduction. If the image can be regarded as substantially the same as the reduced image 300 created by the filtering units 201 and 211, instead of the reduced image 300 stored in the frame memory 223, as shown in FIG. The reduced image obtained by the above may be used as an input image to the processor 250.

[Application example]
FIG. 11 is a diagram illustrating an overall configuration example when the image processing apparatus according to any one of the above-described embodiments is applied to an imaging system such as a digital camera.
As illustrated in FIG. 11, the imaging system includes an imaging unit 900 that captures a subject and a processing device 901 that processes an image acquired by the imaging unit 900. The imaging unit 900 includes a lens system 910 and an imaging element 911 such as a CCD. The processing device 901 includes an image processing unit 912, an image compression unit 913, a recording medium 914, and the like.
The image processing unit 912 has normal image processing functions such as white balance processing, edge enhancement processing, and color signal processing, and noise reduction included in the image processing device according to any of the first to third embodiments described above. It has a function.

  In the imaging system having such a configuration, an image captured by the imaging element 911 through the lens system 910 is transferred to the image processing unit 912. The image processing unit 912 performs normal image processing such as white balance processing, edge enhancement processing, and color signal processing on the input image, and noise using multi-resolution conversion according to any of the above-described embodiments. Apply reduction processing. The image after the noise reduction processing is compressed into a JPEG format or the like by the image compression unit 913 and then stored in a recording medium 914 such as a memory card.

  According to such an imaging system, high noise reduction performance can be realized while suppressing the apparatus cost.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

1 is a block diagram illustrating a schematic configuration of an image processing apparatus according to a first embodiment of the present invention. It is a figure for demonstrating the 1st mode of the image processing apparatus which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the 2nd mode of the image processing apparatus which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the 3rd mode of the image processing apparatus which concerns on the 1st Embodiment of this invention. It is the block diagram which showed schematic structure of the image processing apparatus which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the 1st mode of the image processing apparatus which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the 2nd mode of the image processing apparatus which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the 3rd mode of the image processing apparatus which concerns on the 2nd Embodiment of this invention. It is the block diagram which showed schematic structure of the image processing apparatus which concerns on the 3rd Embodiment of this invention. It is the block diagram which showed the modification of schematic structure of the image processing apparatus which concerns on the 3rd Embodiment of this invention. 1 is a block diagram illustrating a schematic configuration example of an imaging system according to an embodiment of the present invention. It is the figure which showed an example of the multiresolution conversion by the conventional Laplacian pyramid, and the image processing method using the same.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 2 Band signal generation part 3 Noise reduction process part 4 Image synthetic | combination part 201, 211, 612 Filtering part 202,212,622,205,215,625 Enlargement process part 203,213,623 Subtraction part 204,214, 624 Noise reduction unit 206, 216, 626 Addition unit 209, 219, 629 Composition unit 220, 220 ′ Connection switching unit 222, 222 ′ First selection unit 223, 224 Frame memory 225 Second selection unit

Claims (13)

A first filtering unit that includes a filtering unit that blocks a signal in a part of a frequency band in the image signal and outputs a signal in another frequency band, and generates a signal included in the first frequency band of the image signal. Band signal generation means,
First noise reduction means for reducing a noise amount of a signal included in the first frequency band;
First storage means for storing a signal included in a second frequency band of the image signal and having a reduced amount of noise;
First image synthesizing means for synthesizing the signal of the first frequency band in which the amount of noise is reduced by the first noise reducing means and the input signal;
As the signal input to the first image synthesizing unit, a signal based on the signal output from the first filtering unit and a signal included in the second frequency band output from the first storage unit An image processing apparatus comprising: a first selecting unit that selects any one of the above.   2. The image processing apparatus according to claim 1, wherein a noise amount of the signal output from the first filtering unit and selected by the first selection unit is not reduced by the first noise reduction unit. .   2. The signal stored in the first storage means and included in the second frequency band is a signal based on a signal whose amount of noise has been reduced by the first noise reduction means. Alternatively, the image processing apparatus according to claim 2. Second storage means for storing a signal output from the first filtering means;
And a second selection unit that selects one of the image signal and the signal stored in the second storage unit as a signal input to the first band signal generation unit. The image processing apparatus according to claim 1.   The image processing apparatus according to claim 4, further comprising a connection switching unit that switches connection and non-connection between the first filtering unit and the second storage unit. Second band signal generating means for generating a signal included in the third frequency band and a signal included in the fourth frequency band from the signal output from the first filtering means;
Second noise reduction means for reducing the amount of noise in the signal included in the third frequency band;
A second image synthesizing unit that synthesizes a signal included in the third frequency band in which the amount of noise is reduced by the second noise reducing unit and a signal included in the fourth frequency band;
The first selection means includes the signal output from the second image composition means and the second output from the first storage means as the signal input to the first image composition means. 6. The image processing apparatus according to claim 1, wherein any one of signals included in the frequency band is selected. First band signal generation means for generating a signal included in the first frequency band of the image signal;
First noise reduction means for reducing a noise amount of a signal included in the first frequency band;
A first signal that is included in the second frequency band of the image signal and has a reduced amount of noise and a signal in the first frequency band in which the amount of noise is reduced by the first noise reduction unit. And image synthesizing means
The first band signal generation means includes first filtering means for blocking a signal of a part of the frequency band in the image signal by filtering,
The image processing apparatus according to claim 1, wherein the signal included in the second frequency band input to the first image synthesizing unit is not a signal based on the signal output from the first filtering unit. Band signal generation means for generating a signal included in the first frequency band of the image signal;
Noise reduction means for reducing the amount of noise of a signal included in the first frequency band;
A processor for reducing a noise amount of a signal included in a second frequency band of the image signal;
Image synthesizing means for synthesizing the signal included in the first frequency band in which the noise amount is reduced by the noise reducing means and the signal included in the second frequency band in which the noise amount is reduced by the processor; An image processing apparatus comprising:   The image processing apparatus according to claim 8, wherein a signal output from the band signal generation unit is not input to the processor. A second noise reduction means;
Second image composition means,
The first band signal generating means has second filtering means,
The second noise reduction unit performs a noise reduction process on a signal included in the third frequency band generated by using the second filtering unit,
The second image synthesizing unit synthesizes the signal output from the first image synthesizing unit and the signal included in the third frequency band in which the amount of noise is reduced by the second noise reducing unit. The image processing apparatus according to any one of claims 1 to 5, 7, and 8. Imaging means for photographing a subject;
An imaging system comprising the image processing apparatus according to claim 1, which processes an image signal acquired by the imaging unit. Reducing the amount of noise using a noise reduction processing means for a signal included in the first frequency band of the image signal;
Reducing the amount of noise using the noise reduction processing means for the signal included in the second frequency band of the image signal;
An image processing method comprising: synthesizing a signal included in a first frequency band in which the amount of noise is reduced and a signal included in a second frequency band. The noise reduction processing means has a filtering means for blocking a signal of a part of the frequency band in the image signal by filtering,
The image processing method according to claim 12, wherein an output signal from the filtering unit is input to the filtering unit again.

Images