Image correction method and image correction apparatus

Abstract

To provide an image correction method capable of easily correcting, even if brightness of a background of an object image is uneven, the image to reduce influence of the brightness unevenness.SOLUTION: An image correction method includes: an image acquisition step S1 of acquiring an object image 10a in which an object 20 appears; a background generation step S2 of generating a plurality of background component images 12a-12c with different degrees of blurring, the background component images being generated by extracting distributions of brightness components of the background from the object image 10a by changing a degree of blurring multiple times on the acquired object image 10a so as to reduce difference between brightness of the object 20 and brightness of a part other than the object; selection steps S3, S3a-S3c of selecting one background component image 12c based on index values that indicate the degrees of blurring and are obtained based on the plurality of background component images 12a to 12c; and an image correction step S4 of generating a corrected object image 14 with reduced brightness unevenness.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an image correction method. [Background technology]

[0002] Conventionally, a method for acquiring an image of an object captured by an imaging device in order to analyze the target object has been known (see, for example, Patent Document 1). Patent Document 1 discloses a configuration for acquiring an image of the object by capturing images of cells cultured in a culture plate using an imaging device such as a microscope. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 171546 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, although not disclosed in the above Patent Document 1, when cells are cultured using a culture plate (culture vessel), the height of the liquid level of the culture solution increases due to surface tension as it approaches the edge of the culture vessel. When the height of the liquid level of the culture solution changes, luminance unevenness occurs in the background of the object image. When luminance unevenness occurs in the background of the object image, the degree (strength) of the correction process must be changed according to the size of the object and the degree of luminance unevenness of the image in order to correct the image to reduce the luminance unevenness. Therefore, in addition to the trouble of the operator having to set the degree of correction process one by one, the degree of correction process also depends on the experience of the operator who corrects the image. Therefore, there is a demand for an image correction method that can easily perform image correction that suppresses the influence of luminance unevenness even when luminance unevenness occurs in the background of the object image.

[0005] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide an image correction method that can easily perform image correction that suppresses the effects of brightness unevenness even when brightness unevenness occurs in the background of an object image. [Means for solving the problem]

[0006] In order to achieve the above object, an image correction method according to a first aspect of the present invention comprises: an image acquisition step of acquiring an object image showing an object to be observed; a background generation step of generating a plurality of background component images with different degrees of blurring by extracting a distribution of background luminance components from the object image by performing a blurring process on the acquired object image multiple times with different degrees of blurring so as to reduce the difference between the luminance of the object in the object image and the luminance of parts other than the object; a selection step of selecting one background component image based on an index value indicating the degree of blurring obtained based on the multiple background component images generated in the background generation step; and an image correction step of generating a corrected object image in which the object image has been corrected so as to reduce luminance unevenness, based on the object image and the selected background component image.

[0007] An object image correction device according to a second aspect of the present invention comprises an image acquisition unit that acquires an object image showing an object to be observed; a background generation unit that generates a plurality of background component images with different degrees of blurring by extracting a distribution of background luminance components from the object image by performing a blurring process on the acquired object image multiple times with different degrees of blurring so as to reduce the difference between the luminance of the object in the object image and the luminance of parts other than the object; a selection unit that selects one background component image based on an index value indicating the degree of blurring obtained based on the multiple background component images generated by the background generation unit; and an image correction unit that generates a corrected object image by correcting the object image so as to reduce luminance unevenness, based on the object image and the selected background component image. Effect of the Invention

[0008] The image correction method according to the first aspect of the present invention and the image correction device according to the second aspect of the present invention include a background generation step of performing blurring processing on an acquired object image multiple times with different degrees of blurring processing to reduce the difference between the luminance of the object in the object image and the luminance of the portion other than the object, thereby extracting the distribution of the background luminance component from the object image, thereby generating multiple background component images with different degrees of blurring processing, and a selection step of selecting one background component image based on an index value indicating the degree of blurring processing obtained based on the multiple background component images generated in the background generation step. As a result, the background component image is automatically selected from the multiple background component images based on the index value indicating the degree of blurring processing obtained based on the multiple background component images, so that the object image can be corrected based on the object image and the selected background component image. As a result, even if luminance unevenness occurs in the background of the object image, image correction that suppresses the influence of the luminance unevenness can be easily performed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the overall configuration of an object image correcting device according to first to fourth embodiments. [Diagram 2] FIG. 2 is a schematic diagram for explaining an object image. [Diagram 3] 10 is a schematic diagram for explaining the occurrence of luminance unevenness in the background of an object image due to a culture solution filled in a culture container. FIG. [Figure 4] This is an image of an object near the edge of a culture vessel, where uneven brightness occurs in the background. [Diagram 5] This is an object image in the center of a culture vessel, with no uneven brightness in the background. [Figure 6] 4 is a flowchart illustrating a process of an image correction method according to the first embodiment. [Figure 7] FIG. 2 is a schematic diagram for explaining a method for generating a background component image according to the first to fourth embodiments. [Figure 8]5A to 5C are schematic diagrams for explaining a method of acquiring an index value based on a difference image according to the first embodiment. [Figure 9] FIG. 2 is a schematic diagram for explaining a method for generating a corrected object image according to the first to fourth embodiments. [Figure 10] 10 is a flowchart illustrating a process of an image correction method according to a second embodiment. [Figure 11] FIG. 11 is a schematic diagram for explaining a method for selecting a background component image based on a differential value according to the second embodiment. [Figure 12] 13 is a flowchart illustrating a process of an image correction method according to a third embodiment. [Figure 13] FIG. 13 is a schematic diagram for explaining a method for selecting a background component image based on a standard deviation according to the third embodiment. [Figure 14] 13 is a flowchart illustrating a process of an image correction method according to a fourth embodiment. [Figure 15] FIG. 13 is a schematic diagram for explaining a configuration for acquiring index values ​​from a power spectrum image according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] With reference to FIG. 1, an image correcting method using an object image correcting device 100 according to the first embodiment will be described.

[0012] (Configuration of Object Image Correction Device) 1, the object image correcting device 100 includes an image acquiring unit 1, a control unit 5 including a background generating unit 2, a selecting unit 3 and an image correcting unit 4, a display unit 6, and an input receiving unit 7. The object image correcting device 100 is an example of the "image correcting device" in the claims.

[0013] The image acquiring unit 1 is configured to acquire an object image 10. In this first embodiment, the object image 10 is an image showing a cell 20 (see FIG. 2). Specifically, the object image 10 is an image of the cell 20 cultured in a culture solution 31 (see FIG. 3) filled in a culture container 30 (see FIG. 3). In the first embodiment, the image acquiring unit 1 is configured to acquire the object image 10 from a device that captures the object image 10, such as a microscope 8 equipped with an imaging device. The image acquiring unit 1 includes, for example, an input / output interface.

[0014] The background generating unit 2 is configured to generate a background component image 12 (see FIG. 7) by extracting the distribution of luminance components of a background 21 (see FIG. 3) from the object image 10. The background generating unit 2 performs a filter process (blurring process) on the object image 10 to reduce the difference between the luminance of the cells 20 as the subject in the object image 10 and the luminance of the background 21, which is a portion other than the object. When performing a filter process on the object image 10, the background generating unit 2 generates a plurality of background component images 12 using a plurality of filters with different filter sizes. The process by which the background generating unit 2 generates the background component image 12 will be described in detail later.

[0015] The selection unit 3 is configured to select one background component image 12 having an index value indicating the degree of blurring obtained based on the luminance value of each of the plurality of background component images 12 generated by the background generation unit 2 that is smaller than a predetermined threshold value from among the plurality of background component images 12. Note that the process of the selection unit 3 selecting one background component image 12 from among the plurality of background component images 12 will be described in detail later.

[0016] The image correction unit 4 generates a corrected object image 14 by correcting the object image 10 so as to reduce luminance unevenness, based on the object image 10 and the background component image 12 selected by the selection unit 3. The process by which the image correction unit 4 generates the corrected object image 14 will be described in detail later.

[0017] The control unit 5 is configured to control the object image correction device 100, and includes a background generation unit 2, a selection unit 3, and an image correction unit 4, which are control blocks. The control unit 5 includes a processor such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a GPU (Graphics Processing Unit), or an FPGA (Field-Programmable Gate Array) configured for image processing. The control unit 5 is also configured to control the display unit 6 to display the object image 10, the corrected object image 14, and the like.

[0018] The display unit 6 is configured to display the object image 10 acquired by the image acquisition unit 1, the corrected object image 14 generated by the image correction unit 4, etc. The display unit 6 includes a display device such as a liquid crystal monitor, for example.

[0019] The input reception unit 7 is configured to be able to receive operation input from an operator, and includes input devices such as a mouse and a keyboard.

[0020] (Object image) The object image 10 will be described with reference to Fig. 2. In this first embodiment, the object image 10 is an image in which a cell 20 is captured. Note that in this first embodiment, the object image 10 is a microscope image captured by a microscope 8 equipped with an imaging device. The cell 20 is an image captured of a cell 20 having differentiation potential. For example, the cell 20 includes an iPS cell (induced pluripotent stem cell), an ES cell (embryonic stem cell), etc.

[0021] (Uneven background brightness caused by culture solution) 3 to 5, a case where brightness unevenness occurs in the background 21 of the object image 10 due to the culture solution 31 will be described. In the first embodiment, among the object images 10, an image in which brightness unevenness occurs in the background 21 is referred to as object image 10a (see FIG. 4), and an image in which brightness unevenness does not occur in the background 21 is referred to as object image 10b (see FIG. 5).

[0022] As shown in FIG. 3, the cells 20 are cultured in a culture solution 31 filled in a culture vessel 30. The height of the liquid surface 31a of the culture solution 31 gradually changes due to surface tension in the vicinity 40 of the end of the culture vessel 30. In the example shown in FIG. 3, the height of the liquid surface 31a of the culture solution 31 increases as it approaches the end 30a of the culture vessel 30. In this case, due to the difference in height of the culture solution 31, luminance unevenness occurs in the background 21 as in the object image 10a shown in FIG. 4. Note that the object image 10a is an image including the cells 20 in the vicinity 40 of the end of the culture vessel 30. In the object image 10a shown in FIG. 4, the luminance unevenness of the background 21 is expressed by applying hatching with different intervals. The object image 10a shown in FIG. 3 is an example in which luminance unevenness occurs in which the luminance value (pixel value) of the background 21 decreases from the left side to the right side of the image. Moreover, the vicinity 40 of the end of the culture vessel 30 includes both the position of the end 30a of the culture vessel 30 itself and the vicinity of the position of the end 30a of the culture vessel 30.

[0023] 5, the height of the liquid surface 31a of the culture solution 31 is constant in the central portion 41 of the culture vessel 30. When the height of the liquid surface 31a of the culture solution 31 is constant, no luminance unevenness occurs in the background 21. That is, as shown in the object image 10b, in an image including the cells 20 in the central portion 41 of the culture vessel 30, no luminance unevenness occurs in the background 21. Note that the object image 10b is an image in which only the cells 20 in the central portion 41 of the culture vessel 30 are captured.

[0024] (Image correction method processing) Next, a method for correcting an object image 10 using an image correction method according to a first embodiment will be described with reference to Fig. 1 and Fig. 6 to Fig. 9. As shown in Fig. 6, in this first embodiment, the image correction method includes an image acquisition step S1, a background generation step S2, a selection step S3, and an image correction step S4.

[0025] (Acquisition of object image) In the first embodiment, first, in step S1, an object image 10 is acquired. Specifically, the image acquisition unit 1 acquires, by communication, an object image 10 captured by, for example, a microscope 8 equipped with an imaging device. Then, the process proceeds to step S2.

[0026] (Generation of background component image) Next, in step S2, the background generating unit 2 acquires a background component image 12 from the object image 10a. A method for generating the background component image 12 by the background generating unit 2 will be described with reference to FIG. 7. In the first embodiment, the background generating unit 2 performs a filter process on the object image 10a acquired by the image acquiring unit 1 to generate the background component image 12 by extracting the distribution of the luminance component of the background 21 from the object image 10a. Specifically, the background generating unit 2 generates the background component image 12 by applying a median filter to the object image 10a. In the first embodiment, the background generating unit 2 blurs the image by applying the median filter so as to reduce the difference in luminance between the cells 20, which are the subject of the object image 10a, and the background 21, which is the portion other than the cells 20.

[0027] Note that the filtering process using a median filter obtains the median value of the pixel values ​​of each pixel in a region (filter) that is set to a predetermined size with the pixel of interest at its center. Specifically, the filtering process using a median filter obtains the pixel values ​​of each pixel in the filter that is centered on the pixel of interest, rearranges them in pixel value order, and obtains the median value. The obtained median value is then set as the pixel value of the pixel of interest. This process is performed on each pixel of the object image 10a by changing the pixel of interest. Therefore, the filtering process using a median filter increases the processing load.

[0028] Therefore, in the first embodiment, the background generating unit 2 (see FIG. 1) generates the reduced reduced object image 10c shown in FIG. 7(B) by reducing the object image 10a in which uneven brightness occurs in the background 21 shown in FIG. 7(A). Specifically, the background generating unit 2 generates the reduced object image 10c by performing lossless compression processing on the object image 10a. In the first embodiment, the background generating unit 2 generates the reduced reduced object image 10c by reducing the object image 10a to 1 / 8 of its size, for example.

[0029] Then, as shown in FIG. 7(C), the background generating unit 2 generates a reduced reduced background component image 11 by filtering the reduced object image 10c after the reduction. In the first embodiment, the background generating unit 2 applies a median filter to the reduced object image 10c, which is an image obtained by reducing the object image 10a. The reduced reduced background component image 11 is an image in which the luminance unevenness (background component) of the background 21 is extracted by filtering. In the reduced reduced background component image 11, the position of the cell 20 in the object image 10a is represented by a dashed line. The reduced background component image 11 shown in FIG. 7(C) is an example in which blurring is performed to such an extent that the cell 20 and the background 21 cannot be clearly distinguished from each other.

[0030] 7(D), the background generating unit 2 enlarges the reduced background component image 11 to generate a background component image 12. Specifically, the background generating unit 2 enlarges the reduced background component image 11 so that the size of the background component image 12 becomes the same as the size of the object image 10a. In the first embodiment, for example, the background generating unit 2 enlarges the reduced background component image 11 to eight times its size to generate the background component image 12.

[0031] In the background generating step S2, a plurality of filter sizes of the median filter are applied to the reduced object image 10c. As a result, the background generating unit 2 generates a plurality of reduced background component images 11, and enlarges each of the reduced background component images 11 to generate a plurality of background component images 12. For example, in this first embodiment, as shown in the upper part of FIG. 8, a plurality of background component images 12a to 12c are obtained. In addition, the larger the filter size, the stronger the degree of blurring (strength of blurring process) can be. Thereafter, the process proceeds to step S3.

[0032] (Select background component image) In step S3, the selection unit 3 selects one background component image 12c from among the plurality of background component images 12a to 12c. A configuration in which the background generation unit 2 selects the background component image 12c will be described with reference to FIG. 8. The selection unit 3 performs a process of taking a difference in luminance values ​​of each of the plurality of background component images 12a to 12c generated by the background generation unit 2. At this time, a process of taking a difference in luminance values ​​of two adjacent background component images 12a to 12c having different blurring intensities among the background component images 12a to 12c having different blurring intensities due to differences in filter sizes is performed. Specifically, a difference image 13b is obtained by taking a difference in luminance values ​​of the background component images 12a and 12b. Also, a difference image 13c is obtained by taking a difference in luminance values ​​of two adjacent background component images 12b and 12c having different blurring intensities. The selection unit 3 is also configured to select the background component image 12c on the basis that an index value indicating the degree of blurring obtained based on all acquired difference images 13 including the difference images 13b and 13c is smaller than a predetermined threshold value.

[0033] Specifically, for each of all the acquired difference images 13 including the difference images 13b and 13c, the average value of the luminance value of the entire image is acquired, and the difference value is acquired as an index value. For example, as shown in FIG. 6, it is acquired from the difference image 13b that the difference value is "8", and from the difference image 13c that the difference value is "4". Then, when this difference value becomes smaller than a predetermined threshold value, the background component image 12c with the larger filter size is selected from the background component images 12b and 12c used to generate the difference image 13c. The predetermined threshold value based on which the selection is made can be arbitrarily changed by setting, but is "5" in this first embodiment. Note that, when there are a plurality of difference images 13 with difference values ​​smaller than the predetermined threshold value, the background component image 12 is selected using the difference image 13 with the largest difference value. Then, the process proceeds to step S4.

[0034] (Generating a corrected object image) In step S4, the image correction unit 4 generates a corrected object image 14 by correcting the object image 10a so as to reduce luminance unevenness based on the object image 10a and the background component image 12c selected by the selection unit 3. A configuration for generating the corrected object image 14 will be described with reference to FIG. 9. As shown in FIG. 9, the image correction unit 4 subtracts the background component image 12c from the object image 10a. When the background component image 12c is subtracted from the object image 10a, the pixel value of the entire image may become smaller, and the contrast of the image may decrease. Therefore, in the first embodiment, the image correction unit 4 generates the corrected object image 14 by subtracting the background component image 12c from the object image 10a and then adding a predetermined luminance value. The predetermined pixel value is, for example, half the gradation of the pixel value of the object image 10a. In the first embodiment, for example, when the pixel value of the object image 10a is 256 gradations, the background generation unit 2 adds 128 as the predetermined pixel value.

[0035] As shown in Fig. 9, the corrected object image 14 has reduced luminance unevenness in the background 21. In the corrected object image 14 shown in Fig. 9, the reduced luminance unevenness in the background 21 is expressed by not hatching the background 21.

[0036] As described above, even if the object image 10a has luminance unevenness, the object image correcting device 100 selects an appropriate background component image 12c and corrects the image, thereby obtaining a corrected object image 14 with reduced luminance unevenness.

[0037] (Effects of the first embodiment) In the first embodiment, the following effects can be obtained.

[0038] The image correction method of the first embodiment includes an image acquisition step S1 for acquiring an object image 10a including a cell 20 as an observation target, a background generation step S2 for performing a blurring process on the acquired object image 10a multiple times with different degrees of blurring to reduce the difference between the luminance of the cell 20 in the object image 10a and the luminance of the background 21, which is the part other than the cell 20, thereby generating multiple background component images 12a-12c with different degrees of blurring by extracting the distribution of the luminance component of the background 21 from the object image 10a, a selection step S3 for selecting one background component image 12c based on an index value indicating the degree of blurring obtained based on the multiple background component images 12a-12c generated in the background generation step S2, and an image correction step S4 for generating a corrected object image 14 by correcting the object image 10a so as to reduce luminance unevenness, based on the object image 10a and the selected background component image 12c. In this way, the background component image 12c is automatically selected from the plurality of background component images 12a-12c based on the index value indicating the degree of blurring obtained based on the plurality of background component images 12c, so that the object image 10a can be corrected based on the object image 10a and the selected background component image 12c. As a result, even if brightness unevenness occurs in the background 21 of the object image 10a, image correction that suppresses the influence of the brightness unevenness can be easily performed.

[0039] In the first embodiment, the index value is acquired based on the luminance values ​​of the background component images 12a to 12c, and the selection step S3 selects one background component image 12c corresponding to an index value smaller than a predetermined threshold value from among the background component images 12a to 12c generated in the background generation step S2. This automatically selects the background component image 12c whose index value based on the luminance values ​​of the background component images 12a to 12c is smaller than the predetermined threshold value. That is, since the background component image 12c that has been sufficiently blurred is automatically selected, the object image 10a can be corrected based on the object image 10a and the selected background component image 12c that has been sufficiently blurred. As a result, image correction that suppresses the influence of luminance unevenness on the object image 10a can be easily and appropriately performed.

[0040] In the first embodiment, when there are a plurality of index values ​​smaller than a predetermined threshold value among the plurality of background component images 12a to 12c generated in the background generating step S2, the selection step S3 selects one background component image 12c corresponding to the largest index value among the index values ​​smaller than the predetermined threshold value. As a result, even when a plurality of index values ​​smaller than the predetermined threshold value are obtained, a more appropriate background component image 12c is selected. Here, the background component image 12 corresponding to the largest index value among the index values ​​smaller than the predetermined threshold value has a weaker degree of blurring compared to the background component image 12 corresponding to other index values ​​smaller than the predetermined threshold value, and the luminance value of the background 21 in the object image 10a and the luminance value of the background component image 12 generated based on the object image 10a are close to each other. Therefore, by selecting the background component image 12 corresponding to the largest index value among the index values ​​smaller than the predetermined threshold value, it is possible to suppress the divergence between the luminance value of the background 21 in the object image 10a and the luminance value of the background component image 12 generated based on the object image 10a. As a result, it is possible to more appropriately select the background component image 12 to be used when performing image correction on the object image 10a to suppress the effects of luminance unevenness.

[0041] In the first embodiment, in the image correction method for selecting one of the background component images 12a-12c corresponding to an index value smaller than a predetermined threshold, the selection step S3 preferably generates difference images 13a-13c of luminance values ​​based on two adjacent background component images 12a-12c with different degrees of blurring among the plurality of background component images 12a-12c with different degrees of blurring, obtains a difference value as an index value according to the difference image 13, and selects one of the background component images 12c used to generate the difference image 13c with a difference value smaller than a predetermined difference value threshold. As a result, the background component image 12c with a difference value, which is a quantitative value based on the luminance values ​​of the plurality of background component images 12a-12c, smaller than the difference value threshold is automatically selected, so that the object image 10a can be corrected based on the object image 10a and the background component image 12c corresponding to the difference image 13c with a small difference value. As a result, image correction for suppressing the influence of luminance unevenness on the object image 10 can be easily and appropriately performed using the background component image 12c that is automatically selected based on the difference value.

[0042] In the first embodiment, the blurring process is a filter process that performs a correction process by applying a filter to the object image 10a, and a filter size for changing the degree of blurring is changed to generate a plurality of background component images 12a to 12c with different degrees of blurring. This makes it possible to generate a plurality of background component images 12a to 12c with different degrees of blurring according to the filter size. As a result, it is possible to perform image correction on the object image 10a to suppress the influence of brightness unevenness by using the background component image 12c selected from the plurality of background component images 12a to 12c generated according to the filter size.

[0043] In the first embodiment, the filter used in the filtering process in the background generating step S2 is a median filter, and a plurality of background component images 12a to 12c are generated from the object image 10a by using the median filter. Here, when a Gaussian filter or an averaging filter is applied as the filtering process, it may not be possible to accurately obtain the luminance component of the background 21 due to stray light with an extremely high pixel value or foreign matter with an extremely low luminance value. Therefore, by applying a median filter that smoothes the luminance value of each pixel in a predetermined region, it is possible to obtain a background component image 12 that accurately obtains the luminance component of the background 21 even when stray light or foreign matter is mixed in. As a result, the luminance unevenness of the background 21 can be corrected based on the accurate background component image 12c, and therefore a corrected object image 14 in which the luminance unevenness of the background 21 is accurately corrected can be obtained.

[0044] [Second embodiment] Next, an image correction method according to the second embodiment will be described. The device configuration of an object image correction device 100 used in the image correction method according to the second embodiment is the same as that of the object image correction device 100 shown in FIG. 1. In the second embodiment, a case will be described in which the selection unit 3 performs differentiation processing on the luminance values ​​of each of a plurality of background component images 12a to 12c in the selection step S3a shown in FIG. 10. Note that a description of the points common to the first embodiment in the second embodiment will be omitted.

[0045] In the second embodiment, in step S3a shown in FIG. 10, the selection unit 3 is configured to perform differentiation processing on the luminance values ​​of each of the multiple background component images 12a to 12c generated by the background generation unit 2. Specifically, as shown in FIG. 11, a Sobel filter (an example of a differentiation filter) is applied to the luminance values ​​of the background component images 12a to 12c from two directions, the vertical direction and the horizontal direction, to obtain a differential image, and the average value of the luminance values ​​of the differential image is obtained as the differential value. For example, in the second embodiment, the differential value obtained from the background component image 12a is "10", the differential value obtained from the background component image 12b is "6", and the differential value obtained from the background component image 12c is "4". The predetermined threshold value based on which the selection is performed can also be arbitrarily changed by setting, but is "5" in this second embodiment. Then, when this differential value becomes smaller than the predetermined threshold value "5", the background component image 12c based on which the differential value was obtained is selected. Thereafter, the process proceeds to step S4, and the corrected object image 14 is generated.

[0046] (Effects of the second embodiment) Next, the effects of the second embodiment will be described.

[0047] In the image correction method of the second embodiment, the selection step S3a obtains a differential value as an index value based on the luminance value of each of the background component images 12a to 12c having different degrees of blurring, and selects one background component image 12c corresponding to a differential value smaller than a predetermined differential value threshold. This automatically selects the background component image 12c having a differential value, which is a quantitative value based on the luminance values ​​of the background component images 12a to 12c, smaller than the differential value threshold, so that the object image 10a can be corrected based on the object image 10a and the selected background component image 12c having a small differential value. As a result, image correction that suppresses the influence of luminance unevenness on the object image 10a can be easily and appropriately performed using the background component image 12c automatically selected based on the differential value.

[0048] Other effects of the second embodiment are similar to those of the first embodiment.

[0049] [Third embodiment] Next, an image correction method according to the third embodiment will be described. The device configuration of an object image correction device 100 used in the image correction method according to the third embodiment is the same as that of the object image correction device 100 shown in FIG. 1. In the third embodiment, a case will be described in which the selector 3 acquires a standard deviation value for each luminance value of a plurality of background component images 12a to 12c in the selection step S3b shown in FIG. 12. Note that a description of the points common to the first and second embodiments will be omitted in the third embodiment.

[0050] In the third embodiment, in step S3b shown in Fig. 12, the selection unit 3 performs a process of acquiring a standard deviation value for the luminance value of each of the plurality of background component images 12a to 12c generated by the background generation unit 2, as shown in Fig. 13. Specifically, the luminance values ​​of the background component images 12a to 12c are applied to the following formula to acquire the standard deviation. In the following formula, the image size is M × N, src(i, j) is the luminance value at the position (i, j) of the image, and μ is the average value of the luminance values.

number

[0051] (Effects of the third embodiment) Next, the effects of the third embodiment will be described.

[0052] In the image correction method of the third embodiment, the selection step S3b acquires a standard deviation as an index value based on the luminance values ​​of the background component images 12a to 12c having different degrees of blurring, and selects one background component image 12c corresponding to a standard deviation smaller than a predetermined threshold value. This automatically selects the background component image 12c whose standard deviation, which is a quantitative value based on the luminance values ​​of the background component images 12a to 12c, is smaller than the standard deviation threshold value, so that the object image 10a can be corrected based on the object image 10a and the selected background component image 12c having the small standard deviation. As a result, image correction that suppresses the influence of luminance unevenness on the object image 10a can be easily and appropriately performed using the background component image 12c automatically selected based on the standard deviation.

[0053] Other effects of the third embodiment are similar to those of the first and second embodiments.

[0054] [Fourth embodiment] Next, an image correction method according to the fourth embodiment will be described. The device configuration of an object image correction device 100 used in the image correction method according to the fourth embodiment is the same as that of the object image correction device 100 shown in FIG. 1. In the fourth embodiment, a case will be described in which, in the selection step S3c shown in FIG. 14, the selector 3 generates power spectrum images 15a to 15c based on the luminance values ​​of the plurality of background component images 12a to 12c, and selects one background component image 12c using a specific value as an index value based on the power spectrum images 15a to 15c. Note that, in the fourth embodiment, a description of points common to the first to third embodiments will be omitted.

[0055] In the fourth embodiment, in step S3c shown in FIG. 14, the selection unit 3 performs Fourier transform on each of the multiple background component images 12a to 12c generated by the background generation unit 2, as shown in FIG. 15, to obtain power spectrum images 15a to 15c. The power spectrum images 15a to 15c are images in which the vertical y-axis and the horizontal x-axis of the images are both expressed by frequency. The selection unit 3 obtains a specific value, which is an average value of luminance values ​​on a circumference at a specific frequency, for each of the power spectrum images 15a to 15c. For example, in the fourth embodiment, the specific value obtained from the power spectrum image 15a is "10", the specific value obtained from the power spectrum image 15b is "6", and the specific value obtained from the power spectrum image 15c is "4". The predetermined threshold value based on which the selection is made can also be arbitrarily changed by setting, but in this fourth embodiment, it is "5". Then, when the specific value becomes smaller than the predetermined threshold value "5", the background component image 12c based on which the specific value was obtained is selected. Thereafter, the process proceeds to step S4, where the corrected object image 14 is generated.

[0056] (Effects of the fourth embodiment) Next, the effects of the fourth embodiment will be described.

[0057] In the image correction method of the fourth embodiment, the selection step S3c performs Fourier transform processing on each of a plurality of background component images 12a to 12c having different degrees of blurring processing to generate power spectrum images 15a to 15c showing the intensity of the spectrum according to the frequency components, obtains a specific value that is an average of the luminance values ​​at a specific frequency of the power spectrum images 15a to 15c as an index value, and selects one of the background component images 12c used to generate the power spectrum image 15c whose specific value is smaller than a predetermined specific value threshold value. As a result, the background component image 12c having a specific value that is a quantitative value based on the luminance values ​​of the plurality of background component images 12a to 12c and is smaller than the specific value threshold value is automatically selected, so that the object image 10a can be corrected based on the object image 10a and the selected background component image 12c. As a result, image correction that suppresses the influence of luminance unevenness on the object image 10a can be easily and appropriately performed using the background component image 12c automatically selected based on the specific value.

[0058] Other effects of the fourth embodiment are similar to those of the first to third embodiments.

[0059] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications (variations) within the meaning and scope of the claims.

[0060] For example, in the above first to fourth embodiments, the object in the object image 10 is a cell 20, but the present invention is not limited to this. An object image 10a in which an arbitrary subject to be observed appears may be acquired, and a corrected object image 14 may be generated.

[0061] In the above first to fourth embodiments, an example of a configuration in which the image acquisition unit 1 acquires the object image 10 has been shown, but the present invention is not limited to this. For example, the background generation unit 2 may be configured to acquire the object image 10 that has been acquired in advance by the image acquisition unit 1 and stored in a storage unit (not shown).

[0062] Furthermore, in the above first to fourth embodiments, examples have been shown in which the object image 10 is an image captured by the microscope 8, but the present invention is not limited to this. The object image 10 may be any image showing an object, and may be, for example, an image acquired using a scanning probe microscope (SPM). Even when an image is acquired using an SPM, for example, when the stage on which the cell 20 is placed is tilted, the object image 10 will have luminance unevenness, as in the object image 10a shown in FIG. 4, and therefore it is effective to apply the image correction method of the present invention.

[0063] In the above first to fourth embodiments, the selection steps S3 and S3a to S3c select one background component image 12c corresponding to an index value smaller than a predetermined threshold value from among the plurality of background component images 12a to 12c generated in the background generation step S2, but the present invention is not limited to this. The selection step S3 may select one background component image 12 corresponding to an index value equal to a predetermined threshold value from among the plurality of background component images 12 generated in the background generation step S2.

[0064] In the above first to fourth embodiments, the blurring process is performed using filter sizes of different sizes to generate three background component images 12a to 12c, but the present invention is not limited to this. Any number of background component images 12 may be generated as long as it is two or more, and the blurring process may be performed using a plurality of filter sizes of different sizes according to the number of background component images 12 to be generated.

[0065] In the above first to fourth embodiments, the background generating unit 2 generates the background component image 12 by applying a median filter to the object image 10a, but the present invention is not limited to this. For example, the background generating unit 2 may be configured to generate the background component image 12 by applying a Gaussian filter or an averaging filter to the object image 10a. However, when the background generating unit 2 generates the background component image 12 by applying a Gaussian filter or an averaging filter, the components of the background 21 may not be accurately obtained due to stray light with extremely high pixel values ​​or foreign matter with extremely low pixel values. Therefore, it is preferable that the background generating unit 2 is configured to generate the background component image 12 by applying a median filter.

[0066] In the above first to fourth embodiments, the background generating unit 2 reduces the object image 10a and applies a filter to the reduced object image 10c resulting from the reduction to generate the background component image 12, but the present invention is not limited to this. The background generating unit 2 may be configured to generate the background component image 12 by applying a blurring process to the object image 10a without reducing the object image 10a.

[0067] In the above first to fourth embodiments, an example has been shown in which the background generating unit 2 generates the corrected object image 14 by performing a correction process on the object image 10a in which the background 21 has luminance unevenness, but the present invention is not limited to this. The background generating unit 2 may be configured to perform a correction process on the object image 10a regardless of whether or not the background 21 has luminance unevenness.

[0068] In the above first to fourth embodiments, the background generating unit 2 generates the corrected object image 14 by subtracting the background component image 12 from the object image 10a, but the present invention is not limited to this. For example, the background generating unit 2 may generate the corrected object image 14 by subtracting the background component image 12 from the object image 10a. The background generating unit 2 may use any method for generating the corrected object image 14.

[0069] In the above first to fourth embodiments, the background generating unit 2 subtracts the background component image 12 from the object image 10a and adds a predetermined luminance value to generate the corrected object image 14, but the present invention is not limited to this. For example, the background generating unit 2 may be configured to generate the corrected object image 14 without adding a predetermined luminance value after subtracting the background component image 12 from the object image 10a.

[0070] [Aspects] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0071] (Item 1) an image acquisition step of acquiring an object image including an object to be observed; a background generating step of performing blurring processing on the acquired object image multiple times with different degrees of blurring processing to reduce a difference between the luminance of the object in the object image and the luminance of a portion other than the object, thereby generating multiple background component images with different degrees of blurring processing by extracting a distribution of background luminance components from the object image; a selection step of selecting one of the background component images based on an index value indicating a degree of blurring obtained based on the plurality of background component images generated in the background generating step; and generating a corrected object image by correcting the object image so as to reduce luminance unevenness, based on the object image and the selected background component image.

[0072] (Item 2) the index value is obtained based on luminance values ​​of the plurality of background component images; 2. The image correction method according to claim 1, wherein the selection step selects one of the background component images generated in the background generation step, the background component image corresponding to the index value smaller than a predetermined threshold value.

[0073] (Item 3) 3. The image correction method according to claim 2, wherein, in the selection step, when there are a plurality of index values ​​smaller than a predetermined threshold value among the plurality of background component images generated in the background generation step, one of the background component images corresponding to the largest index value among the index values ​​smaller than a predetermined threshold value is selected.

[0074] (Item 4) 3. The image correction method according to claim 2, wherein the selection step generates a difference image of luminance values ​​based on two adjacent background component images having different degrees of blurring among the plurality of background component images having different degrees of blurring, obtains a difference value as the index value according to the difference image, and selects one of the background component images used to generate the difference image having the difference value smaller than a predetermined difference value threshold value.

[0075] (Item 5) 3. The image correction method according to claim 2, wherein the selection step obtains a differential value as the index value based on a luminance value of each of the plurality of background component images having different degrees of blurring, and selects one of the background component images corresponding to the differential value smaller than a predetermined differential value threshold value.

[0076] (Item 6) 3. The image correction method according to claim 2, wherein the selection step obtains a standard deviation as the index value based on the luminance values ​​of each of the plurality of background component images having different degrees of blurring, and selects one of the background component images corresponding to the standard deviation smaller than a predetermined threshold value.

[0077] (Item 7) 3. The image correction method according to item 2, wherein the selection step generates a power spectrum image indicating a spectral intensity according to a frequency component by performing a Fourier transform process on each of the plurality of background component images having different degrees of blurring, obtains a specific value that is an average of luminance values ​​at a specific frequency of the power spectrum image as the index value, and selects one of the background component images used for generating the power spectrum image in which the specific value is smaller than a predetermined specific value threshold value.

[0078] (Item 8) 2. The image correction method according to claim 1, wherein the blurring process is a filtering process that performs a correction process by applying a filter to the object image, and a filter size for changing the degree of the blurring process is changed in a plurality of ways to generate a plurality of background component images with different degrees of blurring.

[0079] (Item 9) 9. The image correction method according to item 8, wherein the filter used in the filter processing in the background generating step is a median filter, and the background component image is extracted from the object image by using the median filter to generate a plurality of the background component images.

[0080] (Item 10) an image acquisition unit for acquiring an object image showing an object to be observed; a background generating unit that performs blurring processing on the acquired object image multiple times while changing the degree of blurring processing to reduce a difference between the luminance of the object in the object image and the luminance of a portion other than the object, thereby generating multiple background component images with different degrees of blurring processing by extracting a distribution of background luminance components from the object image; a selection unit that selects one of the background component images based on an index value that indicates a degree of blurring obtained based on the plurality of background component images generated by the background generation unit; and an image correction section that generates a corrected object image by correcting the object image so as to reduce luminance unevenness, based on the object image and the selected background component image. [Explanation of symbols]

[0081] 1 Image acquisition section 2 Background generation section 3 Selection section 4 Image Correction Section 5. Control section 6 Display section 7 Input reception section 8. Imaging device 10, 10a-10c Object images 12, 12a to 12c Background component images 13, 13a-13c Difference images 14 Corrected object image 15, 15a-15c Power spectrum images 20 cells (objects) 21 Background 100 Object image correction device (image correction device)

Claims

1. an image acquisition step of acquiring an object image including an object to be observed; a background generating step of performing blurring processing on the acquired object image multiple times with different degrees of blurring processing to reduce a difference between the luminance of the object in the object image and the luminance of a portion other than the object, thereby generating multiple background component images with different degrees of blurring processing by extracting a distribution of background luminance components from the object image; a selection step of selecting one of the background component images based on an index value indicating a degree of blurring obtained based on the plurality of background component images generated in the background generating step; and generating a corrected object image by correcting the object image so as to reduce luminance unevenness, based on the object image and the selected background component image.

2. the index value is obtained based on luminance values ​​of the plurality of background component images; 2. The image correction method according to claim 1, wherein the selection step selects one of the background component images generated in the background generation step, the background component image corresponding to the index value smaller than a predetermined threshold value.

3. 3. The image correction method according to claim 2, wherein, when there are a plurality of index values ​​smaller than a predetermined threshold value among the plurality of background component images generated in the background generating step, the selection step selects one of the background component images corresponding to the largest index value among the index values ​​smaller than a predetermined threshold value.

4. 3. The image correction method according to claim 2, wherein the selection step generates a difference image of luminance values ​​based on two adjacent background component images having different degrees of blurring among the plurality of background component images having different degrees of blurring, obtains a difference value as the index value according to the difference image, and selects one of the background component images used to generate the difference image having the difference value smaller than a predetermined difference value threshold value.

5. 3. The image correction method according to claim 2, wherein the selection step obtains a differential value as the index value based on a luminance value of each of the plurality of background component images having different degrees of blurring, and selects one of the background component images corresponding to the differential value smaller than a predetermined differential value threshold value.

6. 3. The image correction method according to claim 2, wherein the selection step obtains a standard deviation as the index value based on luminance values ​​of each of the plurality of background component images having different degrees of blurring, and selects one of the background component images corresponding to the standard deviation smaller than a predetermined threshold value.

7. 3. The image correction method according to claim 2, wherein the selection step generates a power spectrum image indicating a spectral intensity according to a frequency component by performing a Fourier transform process on each of the plurality of background component images having different degrees of blurring, obtains a specific value that is an average of luminance values ​​at a specific frequency of the power spectrum image as the index value, and selects one of the background component images used for generating the power spectrum image in which the specific value is smaller than a predetermined specific value threshold value.

8. 2. The image correction method according to claim 1, wherein the blurring process is a filtering process that performs a correction process by applying a filter to the object image, and a filter size for changing a degree of the blurring process is changed in a plurality of sizes to generate a plurality of the background component images having different degrees of blurring.

9. 9. The image correction method according to claim 8, wherein the filter used in the filtering process in the background generating step is a median filter, and the background component image is extracted from the object image by using the median filter to generate a plurality of the background component images.

10. an image acquisition unit for acquiring an object image showing an object to be observed; a background generating unit that performs blurring processing on the acquired object image multiple times while changing the degree of blurring processing to reduce a difference between the luminance of the object in the object image and the luminance of a portion other than the object, thereby generating multiple background component images with different degrees of blurring processing by extracting a distribution of background luminance components from the object image; a selection unit that selects one of the background component images based on an index value that indicates a degree of blurring obtained based on the plurality of background component images generated by the background generation unit; and an image correction section that generates a corrected object image by correcting the object image so as to reduce luminance unevenness, based on the object image and the selected background component image.

Images