Image processing device

In this image processing device, an image processing portion 102 performs a predetermined pre-processing on first image data and outputs it as second image data. A judging portion 104 that judges the degree of importance of the first image data on the basis of the characteristics of a subject that is included in the first image data. A reducing portion 105 reduces the data amount of the second image data in accordance with that degree of importance and outputs it as third image data. According to this image processing device, by reducing the data amount of the second image data in accordance with the degree of importance of the first image data, it is possible to achieve greater reductions in the data amount as the degree of importance decreases. As a result, it is possible to more efficiently reduce the power consumption and time required when transferring image data after data reduction.

BACKGROUND ART

In conventional capsule endoscopes that are inserted in a body for observing organs, images are picked up by a charge coupled device (CCD) or the like, and after image processing such as white balance processing and gamma processing is performed on the images, the same compression is carried out on any image.

In contrast, in the image encoding device disclosed for example in Patent Document 1, a compression method is disclosed in which the center of the image is defined as a important region, and the periphery of the image is defined as a non-important region, whereby compression of differing extents is performed on the respective regions.

Patent Document 1: Japanese Unexamined Patent Application No. H06-334985

DISCLOSURE OF THE INVENTION

The present invention is an image processing device that includes a pre-processing portion that performs a predetermined pre-processing on first image data and outputs it as second image data; a judging portion that judges the degree of importance of the first image data on the basis of the characteristics of a subject that is included in the first image data; and a reducing portion that reduces the data amount of the second image data in accordance with the degree of importance and outputs it as third image data.

Also, the image processing device of the present invention is further provided with a dividing portion that divides the first image data into a plurality of areas, wherein the judging portion judges the degree of importance of each of the areas, and the reducing portion reduces the data amount of a corresponding region of the second image data in accordance with the degree of importance of each of the areas.

Also, the image processing device of the present invention is further provided with an image data cutout portion that cuts out a specified area from the first image data, wherein the judging portion judges the degree of importance of the specified area, and the reducing portion reduces the data amount of a corresponding region of the second image data in accordance with the degree of importance of the specified area.

Also, in the image processing device of the present invention, the judging portion is provided with a judging original data generating portion that generates judging original data for judging the degree of importance of the first image data and an importance judging portion that judges the degree of importance by comparing the judging original data and a threshold value.

Also, in the image processing device of the present invention, the judging original data generating portion generates the judging original data based on an average level of green in the first image data.

Also, in the image processing device of the present invention, the reducing portion is provided with a reduction processing portion that reduces the data amount of the second image data and a reduction rate setting portion that sets a reduction rate of the data amount corresponding to the degree of importance for the reduction processing portion.

Also, in the image processing device of the present invention, the reduction processing portion thins the second image data at a predetermined ratio, and the reduction rate setting portion sets the predetermined ratio.

Also, in the image processing device of the present invention, the reduction processing portion performs low-pass filter processing on the second image data, and the reduction rate setting portion sets a coefficient according to the low-pass filter processing.

Also, in the image processing device of the present invention, the reduction rate setting portion gradually changes the reduction rate from the periphery of an image to the center.

DESCRIPTION OF THE REFERENCE NUMERALS

102,1202image processing portion (pre-processing portion);104,1206judging portion;105,1207reducing portion;201judgment image data cutout portion;202,1501importance index generating portion (judging original data generating portion);203,1502importance judging portion;301,1601reduction rate control signal generating portion (reduction rate setting portion);302,1602reduction processing portion;1205dividing portion;1704LPF coefficient generating portion (reduction rate setting portion)

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, embodiments of the present invention shall be described with reference to the appended drawings.

First, a first embodiment of the present invention shall be described. An image processing device according to the present embodiment is an image processing device for a capsule endoscope. Based on the picked-up image of one field (partial region of a picked-up image in the present embodiment) among the picked-up images that are continuously imaged by the imaging element (imaging means) such as a CCD, it judges whether or not the picked-up image is important as an endoscope image for each field, and performs pixel thinning at a thinning rate in accordance with the judgment result.FIG. 1shows the constitution of the image processing device according to the present embodiment. Hereinbelow, the general functions of the constitution of the present image processing device shall be described.

An imaging portion101performs image capture with a CCD or the like, and generates captured image data that is data of pixels that constitute the captured image. An image processing portion102performs spatial image processing (pre-processing) such as white balance processing and gamma processing on the captured image data, and generates processing image data that is data of the pixels that constitute the processing image. A processing image data storage portion103temporarily stores processing image data. A judging portion104judges the field importance on the basis of the characteristics of the subject using a portion of the captured image data as judgment image data for judging the field importance that shows whether or not the captured image of one field is important as an endoscope image.

A reducing portion105reduces the data amount of the processing image data by performing pixel thinning of the processing image data that is read from the processing image data storage portion103in accordance with the field importance and obtains reduced image data. A compression portion106compresses the reduced image data to obtain compressed image data. A transfer portion107transfers the compressed image data to the outside.

FIG. 2shows the constitution of the judging portion104. A judgment image data cutout portion201cuts out judgment image data from the captured image data. An importance index generating portion202generates a field importance index that is an index when judging the field importance of the captured image from the judgment image data. An importance judging portion203judges the field importance based on the field importance index.

FIG. 3shows the constitution of the reducing portion105. A reduction rate control signal generating portion301generates enable in relation to the pixel thinning of the processing image data, and outputs it as a reduction rate control signal. A reduction processing portion302performs pixel thinning of the processing image data according to the reduction rate control signal, and generates reduced image data. The thinning rate of the pixel thinning is set by the reduction rate control signal.

FIG. 4shows the constitution of the reduction rate control signal generating portion301. An H direction pixel counter401counts the number of pixels in the H direction (horizontal direction) of the processing image. An H enable generating portion402generates an enable in relation to pixel thinning in the H direction of a processing image. A V direction pixel counter403counts the number of pixels in the V direction (perpendicular direction) of a processing image. A V enable generating portion404generates an enable in relation to pixel thinning in the V direction of a processing image.

Next, the field importance in the present embodiment shall be described. In endoscope images, those which include many bubbles in the image are considered non-important images, while those which include few are considered important images. Also, there tends to be more G (green) components in images which contain many bubbles than images which contain few bubbles. Moreover, for example Japanese Unexamined Patent Application No. 2004-321603 and Japanese Unexamined Patent Application No. 2004-337596 disclose art that judges which organ is in an image that is currently being captured by calculating the average color of the image that is being captured. Therefore, by calculating the ratio of the average G level (green component level) of the picked-up image of one field and the average G level that is expected for the organ that is currently being imaged, it is possible to estimate the amount of bubbles that are contained in the picked-up image. For that reason, the present embodiment judges the field importance by this method.

Next, the operation of the image processing device according to the present embodiment shall be described. The image processing portion102generates the processing image data by performing predetermined image processing on the captured image data that is obtained by the imaging portion101, and once writes the processing image data in the processing image data storage portion103. The judgment image data cutout portion201of the judging portion104generates judgment image data that is pixel data of a judgment image in which for example the periphery of the captured image has been as shown inFIG. 5.

The importance index generating portion202, after calculating the average G level of the judgment image data of one field, calculates the ratio with the average G level that is expected for an organ to be observed that is set in advance, and outputs it as a field importance index (judging original data). The importance judging portion203, by comparing the field importance index and a plurality of importance judgment threshold values set in advance, outputs the field importance by judging the field importance of the captured image (for example, one of the three levels of low, medium, high) at the end of one field and generates and outputs a judgment notification signal that shows that the field importance judgment of the captured image is complete.

The reduction rate control signal generating portion301in the reducing portion105generates a reduction rate control signal as follows in parallel with the processing image data being read out from the processing image data storage portion103. When processing image data are read, pixel data of one line are read out in sequence from the pixel at the upper left of a captured image, after which the pixel data of the next line is read out in sequence from the pixel at the left end, and so on, whereby the pixel data of each line are read one by one.

The H direction pixel counter401in the reduction rate control signal generating portion301generates an H direction pixel count value that counts the pixels in the H direction in the processing image by performing a count for each reference timing with the judgment notification signal serving as a start trigger, and performing a reset at each counting of the number of pixels in the H direction of the processing image data. The V direction pixel counter403in the same manner generates a V direction pixel count value that is a count of the pixels in the V direction in the processing image by counting at the timing at which the H direction pixel count value is reset with the judgment notification signal serving as a start trigger, and performing a reset each time the V direction pixel number of the processing image is counted.

The H enable generating portion402generates an enable in relation to pixel thinning of H direction pixel data (called an H enable) from the field importance and H direction pixel count value for each pixel of the captured image.FIG. 6Ashows the H enable generation conditions. In the case of the field importance being “low”, when the remainder of dividing the H direction pixel count value by 4 is “0”, the H enable is “1”, and when other than that the H enable is “0”. Also, in the case of the field importance being “medium”, when the remainder of dividing the H direction pixel count value by 2 is “0”, the H enable is “1”, and when other than that the H enable is “0”. Also, in the case of the field importance being “high”, the H enable is “1” regardless of the H direction pixel count value.

The V enable generating portion404generates an enable (called a V enable) in relation to pixel thinning of V direction pixel data from the field importance and V direction pixel count value.FIG. 6Bshows the V enable generation conditions. The V enable generation conditions are the same as the H enable generation conditions. By following the conditions forFIG. 6AandFIG. 6B, the enable is generated such that the lower the field importance, the higher the thinning rate.

The reduction processing portion302reads the processing image data from the processing image data storage portion103by having the judgment notification signal serve as a start trigger and sifts through the processing image data by validating processing image data when both the H enable and V enable are “1” and otherwise invalidating the processing image data. Thereby, data reduction is performed by pixel thinning of the processing image data to obtain reduced image data. The compression portion106generates compressed image data by compressing the reduced image data using JPEG or the like. The transfer portion107transfers the compressed image data from inside the body to outside the body. Outside the body, when expanding and playing back the compressed image data, the image data of the thinned pixel positions is found by interpolation.

As described above, in the present embodiment, the reduction rate of the processing image data is controlled according to the degree of importance of the captured image. By reducing greater amounts of data the lower the degree of importance of the data as in the present embodiment, it is possible to more efficiently reduce the power consumption and time required for transferring the image data to the outside after data reduction.

Also, by cutting out the judgment image data of a specified area from the captured image data and judging the degree of importance of the captured image using the judgment image data, it is possible to achieve a greater reduction in the amount of computation required for judging the degree of importance than the case of using all of the captured image data for judgment of the degree of importance. Also, it is possible to qualitatively judge degree of importance by generating a field importance index (judging original data) used for judgment of degree of importance and judging the degree of importance based on the result of comparing the field importance index and importance judgment threshold value.

Next, a second embodiment of the present invention shall be described. With respect to the image processing device according to the first embodiment that judges the degree of importance for each field of a captured image and performs pixel thinning at a thinning rate in accordance with the judgment result, the image processing device according to the present embodiment is one that combines the functions of performing pixel thinning at a thinning rate that differs at the center portion and peripheral portion of the captured image.

Hereinbelow, pixel thinning of the processing image data in the present embodiment shall be described. A known characteristic of human visual perception is to focus more on the center portion of an image than the periphery thereof. Therefore, by utilizing this visual perception characteristic in the present embodiment, the center portion of a processing image is regarded as an important region while the periphery is regarded as a non-important region. Pixel thinning of the processing image data is then performed by varying the pixel thinning rate of the important region and the non-important region. When performing pixel thinning of a processing image, in order to perform pixel thinning at a thinning rate that differs between the center portion and periphery of a processing image, the processing image is divided into 5×5 regions as shown inFIG. 8, with each division unit being called a unit.

The image processing device according to the present embodiment replaces the constitution of the reduction rate control signal generating portion301in the first embodiment shown inFIG. 3with constitution shown inFIG. 7, and in other respects is similar to the first embodiment. Therefore, descriptions of constitutions that are the same as the first embodiment shall be omitted, and the function of the constitution of only the reduction rate control signal generating portion301shall be described. InFIG. 7, an H direction position counter701counts information in relation to the position in the H direction of the processing image.

An H enable generating portion702generates an enable in relation to pixel thinning in the H direction of the processing image. A V direction position counter703counts information in relation to the position in the V direction of the processing image. A V enable generating portion704generates an enable in relation to pixel thinning in the V direction of the processing image.

Next, the operation of the image processing device according to the present embodiment shall be described. The reading of processing image data from the processing image data storage portion103is the same as in the first embodiment, and the reduction rate control signal generating portion301generates a reduction rate control signal as shown below in parallel with processing image data being read from the processing image data storage portion103.

The H direction position counter701generates an H pixel count value that counts the pixels in the H direction in a unit by performing a count for each reference timing with the judgment notification signal serving as a start trigger and performing a reset at each counting of the number of pixels in the H direction of the unit. Also, the H direction position counter701in parallel with this generates an H unit count value that counts the units in the H direction in the processing image by performing a count at the timing at which the H pixel count value is reset with the judgment notification signal serving as a start trigger, with the H pixel count value being reset at each counting of the total number of pixels in the H direction of the processing image. Also, the H direction position counter701generates an increment signal that shows that the counting of the pixel number in the H direction of the processing image has been completed during resetting of the H unit count value.

The H enable generating portion702generates an enable in relation to pixel thinning of H direction pixel data (called the H enable) from the field importance, the H unit count value and the H pixel count value.FIG. 9Ashows the H enable generation conditions.FIG. 10AtoFIG. 10Cshow the waveform of the H enable that is generated according to the conditions ofFIG. 9A.FIG. 10Ashows the waveform of the H enable in the case of the field importance being “low”,FIG. 10Bshows the waveform of the H enable in the case of the field importance being “medium”, andFIG. 10Cshows the waveform of the H enable in the case of the field importance being “high”.

The V direction position counter703generates a V pixel count value that counts the pixels in the V direction in a unit by performing a count at each increment with the judgment notification signal serving as a start trigger and performing a reset at each counting of the number of pixels in the V direction of the unit. Also, the V direction position counter703in parallel with this generates a V unit count value that counts the units in the V direction in the processing image by performing a count at the timing at which the V pixel count value is reset with the judgment notification signal serving as a start trigger, with the V pixel count value being reset at each counting of the total number of pixels in the V direction of the processing image.

The V enable generating portion704generates an enable in relation to pixel thinning of V direction pixel data (called the V enable) from the field importance, the V unit count value and the V pixel count value.FIG. 9Bshows the H enable generation conditions.FIG. 11AtoFIG. 11Cshow the waveform of the V enable that is generated according to the conditions ofFIG. 9B.FIG. 11Ashows the waveform of the V enable in the case of the field importance being “low”,FIG. 11Bshows the waveform of the V enable in the case of the field importance being “medium”, andFIG. 11Cshows the waveform of the V enable in the case of the field importance being “high”.

By generating enables according to the conditions ofFIG. 9AandFIG. 9B, enables are generated so that the thinning rate of the overall image increases as the field importance decreases, and in the case of the degree of importance of the image not being high, the thinning rate gradually decreases from the periphery to the center of the image. Thereafter, pixel thinning of the processing image data, generation of compressed image data, and transfer of the compressed data are performed in the same process as the first embodiment.

According to the aforementioned embodiment, it is possible to more efficiently reduce the power consumption and time required for transferring the image data to the outside after data reduction, similarly to the first embodiment. Also, in the case of the important region and non-important region in the captured image being known in advance (with the center portion being the important region and the periphery being the non-important region in the present embodiment), it is possible to control the reduction rate of data in accordance with the degree of importance of the captured image itself and also set a reduction rates that differ at the important region and non-important region, and so it is possible to even more efficiently reduce the power consumption and time required for transferring the image data to the outside after data reduction. Also, by gradually changing the reduction rate of the data, it is possible to smoothly alter the image quality and possible to prevent visual unnaturalness.

Next, a third embodiment of the present invention shall be described. The image processing device according to the present embodiment judges whether or not the capture image is important as an endoscope image for each region that divides the captured image of one field, and performs strong low pass filter (LPF) processing in accordance with the Judgment result at each region.

FIG. 12shows the constitution of the image processing device according to the present embodiment. Hereinbelow, the general functions of the constitution of the present image processing device shall be described. An imaging portion1201performs image capture with a CCD or the like, and generates captured image data that is data of pixels that constitute the captured image. An image processing portion1202performs spatial image processing such as white balance processing and gamma processing on the captured image data, and generates processing image data that is data of the pixels that constitute the processing image. A processing image data storage portion1203temporarily stores processing image data.

A captured image data storage portion1204temporarily stores captured image data. A dividing portion1205divides the captured image data that is read from the captured image data storage portion1204and, in order to judge the degree of importance of each division region, generates a division control signal for dividing the captured image into, for example, 5×5 regions (areas) as shown inFIG. 13. A judging portion1206judges the area importance that shows whether or not the captured image of the area unit is important as an endoscope image from the captured image data that is read from the captured image data storage portion1204and a division control signal.

A reducing portion1207reduces the data amount of the processing image data by performing LPF processing of the processing image data that is read from the processing image data storage portion1203according to the area importance and obtains reduced image data. A compression portion1208compresses the reduced image data to obtain compressed image data. A transfer portion1209transfers the compressed image data to the outside.

FIG. 14shows the constitution of the dividing portion1205. An H area pixel counter1401generates an H area pixel count value that counts the pixels in the H direction of the area. A V area pixel counter1402generates a V area pixel count value that counts the pixels in the V direction of the area. An H area counter1403generates an H area count value that counts the areas in the H direction of the captured imaged. A V area counter1404generates a V area count value that counts the areas in the V direction of the captured image. A count value decoder1405decodes the H area pixel count value, the V area pixel count value, the H area count value and the V area count value, and generates a write area coordinate signal and a read address signal described below.

FIG. 15shows the constitution of the judging portion1206. An importance index generating portion1501generates an area importance index that is an index when judging the area importance of the captured image from the judgment image data. An importance judging portion1502judges the area importance based on the area importance index.

FIG. 16shows the constitution of the reducing portion1207. A reduction rate control signal generating portion1601generates an LPF coefficient when performing LPF processing on the processing image data based on the area importance, and outputs it as a reduction rate control signal. A reduction processing portion1602performs LPF processing of the processing image data in accordance with the reduction rate control signal, and generates reduced image data.

FIG. 17shows the constitution of the reduction rate control signal generating portion1601. An importance storage portion1701stores the area importance corresponding to the write area coordinate signal. An H direction position counter1702generates an H direction position count value that counts the pixels in the H direction of the processing image. An V direction position counter1703generates a V direction position count value that counts the pixels in the V direction of the processing image. An LPF coefficient generating portion1704generates an LPF coefficient from the H direction position count value and the V direction position count value.

Next, the operation of the image processing device according to the present embodiment shall be described. The image processing portion1202generates the processing image data by performing predetermined image processing on the captured image data that is obtained by the imaging portion1201, and once writes the processing image data in the processing image data storage portion1203. At this time, the captured image data is also written in the captured image data storage portion1204, and after the writing of the captured image data is completed, the captured image data storage portion1204generates a write complete notification signal that indicates that the writing of the captured image data has been completed.

Then, the dividing portion1205operates as shown below in parallel with the captured image data being read from the captured image data storage portion1204. When the captured image data is read, the data of each pixel is read in sequence as shown inFIG. 18. The H area pixel counter1401in the dividing portion1205generates an H area pixel count value that counts the pixels in the H direction in the area by performing a count for each reference timing with the write complete notification signal serving as a start trigger, and performing a reset at each counting of the number of pixels in the H direction of the area. The V area pixel counter1402in the same manner generates a V area pixel count value that counts the pixels in the V direction in the area by performing a count for each reference timing with the write complete notification signal serving as a start trigger, and performing a reset at each counting of the number of pixels in the V direction of the area.

The H area counter1403generates an H area count value that counts the areas in the H direction in the captured image by performing a count at the timing at which the V area pixel count value is reset with the write complete notification signal serving as a start trigger, and resetting at each counting of the number of areas in the H direction. The V area counter1404in the same manner generates a V area count value that counts the areas in the V direction in the captured image by performing a count at the timing at which the H area count value is reset with the write complete notification signal serving as a start trigger, and resetting at each counting of the number of areas in the V direction.

The count value decoder1405generates a read address signal for reading processing image data from the processing image data storage portion1203at every area similarly toFIG. 18and a write area coordinate signal that shows the area in the captured image from the H area pixel count value, the H area count value, the V area pixel count value, and the V area count value. The write area coordinate signal changes at every area.

The importance index generating portion151in the judging portion1206generates an area importance index from the captured image data that is read from the captured image data storage portion1204, and notifies the generated area importance index to the importance judging portion1502at the timing at which the write area coordinate signal changes. Also, the importance index generating portion1501resets the generated area importance index when notifying the area importance index to the importance judging portion1502. The importance judging portion1502judges the area importance (for example, one of the three levels of low, medium, high) by comparing the area importance index that is notified from the importance index generating portion1501and a plurality of importance judgment threshold values set in advance and generates a judgment notification signal that shows that the importance judgment of all the areas is complete simultaneously with the judgment of the last area.

The importance storage portion1701in the reduction rate control signal generating portion1601that the reducing portion1207is provided with stores the area importance and the write area coordinate signal in correspondence with each other. Then, the reduction rate control signal generating portion1601generates an LPF coefficient in the following manner in parallel with the reading of the processing image data from the processing image data storage portion1203in accordance with the read address signal.

The H direction position counter1702generates an H pixel count value that counts the pixels in the H direction in the processing image by performing a count for each reference timing with the judgment notification signal serving as a start trigger, and performing a reset at each counting of the number of pixels in the H direction of the processing image. The V direction position counter1703in the same manner generates a V pixel count value that counts the pixels in the V direction in the processing image by performing a count at the timing at which the H pixel count value is reset with the judgment notification signal serving as a start trigger, and performing a reset at each counting of the number of pixels in the V direction of the processing image.

The LPF coefficient generating portion1704generates a read area coordinate signal that shows the coordinates of the area based on the H pixel count value and the V pixel count value and reads the corresponding area importance from the importance storage portion1701. Also, the LPF coefficient generating portion1704generates an in-area coordinate signal that shows the coordinates in an area based on the H pixel count value and the V pixel count value and, based on the area importance and in-area coordinate signal, generates an LPF signal that sharply changes from weak to strong from the edge to the center of the area when the area importance is “low”, generates an LPF signal that gradually changes from weak to strong from the edge to the center of the area when the area importance is “medium”, and generates an LPF signal that is uniformly weak over the entire area when the area importance is “high” (refer toFIG. 19).

The reduction processing portion1602in the reducing portion1207performs data reduction by reduction of the high-frequency component of the processing image data by starting reading of the processing image data from the processing image data storage portion1203with the judgment notification signal serving as a trigger, and performing LPF processing of the processing image data in accordance with the LPF coefficient, and thereby obtains reduced image data. The compression portion1208generates compressed image data by compressing the reduced image data using JPEG or the like. The transfer portion1209transfers the compressed image data from inside the body to outside the body.

As described above, in the present embodiment, LPF processing of the processing image data is executed in accordance with the degree of importance of the captured image. By further raising the intensity of the LPF processing as the degree of importance decreases as in the present embodiment, it is possible to more efficiently reduce the power consumption and time required for transferring the image data to the outside after data reduction, similarly to the first and second embodiments.

Also, by dividing the captured image data into a plurality of areas and judging the degree of importance of each area and then reducing the data amount of the region of the corresponding processing image data in accordance with the degree of importance of each area, it is possible to carry out flexible processing in accordance with the characteristics of each region of the image even when the degree of importance in each region in the image differs. Also, when judging the area importance, by considering the coordinates in the captured image that are indicated by the H direction area count value and the V direction area count value, it is possible to judge the area importance that incorporates a method which makes the center portion of the captured image the important region and the periphery the non-important region.

While preferred embodiments of the invention have been described above with reference to the drawings, specific constitutions of the present invention are not limited to these embodiments, and design modifications with a range that does not depart from the scope of the present invention are included in the present invention. For example, the range of applications of the image processing device of the present invention is not limited to a capsule endoscope.

Also, in the aforementioned embodiments, the data amount was reduced by pixel thinning and LPF processing, but the data amount may also be reduced by changing the compression rate in the compression portion106,1208in accordance with the degree of importance of the image. Moreover, the data amount may be reduced by lessening the number of bits that express one pixel. For example, a pixel that was expressed with 8 bits may be expressed with 4 bits, and two pixels may be expressed with 8 bits.

INDUSTRIAL APPLICABILITY

According to the present invention, by reducing the data amount of a second image data in accordance with the degree of importance of a first image data in an image processing device that compresses image data, it is possible to achieve greater reductions in the data amount as the degree of importance decreases. As a result, it is possible to more efficiently reduce the power consumption and time required when transferring the image data after data reduction.