WO2017056599A1

WO2017056599A1 - Image generation device and image generation method

Info

Publication number: WO2017056599A1
Application number: PCT/JP2016/069135
Authority: WO
Inventors: 拓矢安田
Original assignee: 株式会社Ｓｃｒｅｅｎホールディングス
Priority date: 2015-09-28
Filing date: 2016-06-28
Publication date: 2017-04-06
Also published as: JP2017068302A

Abstract

A compositing technique for joining multiple original images together, with which a composite image is generated while suppressing the influence of image quality deterioration attributable to optical characteristics of an imaging system. Weights to be assigned to respective pixels of the images to be captured are set in advance in accordance with the optical characteristics of the imaging system. By using a mask M, that is, an extracted area having weights equal to or greater than a certain threshold value, a mask arrangement for entirely masking an imaging object region within a well W is determined. The multiple original images are captured using a layout corresponding to the mask arrangement, and the original images are composited after the pixels of the respective images are weighted.

Description

Image creating apparatus and image creating method

The present invention relates to a technique for synthesizing a plurality of original images to create an image of an imaging target area that is larger than an imaging field of view of an imaging means.
Cross-reference of related applications The disclosures in the specification, drawings and claims of each of the following Japanese applications are incorporated herein by reference in their entirety:
Japanese Patent Application No. 2015-189251 (filed on Sep. 28, 2015).

When a wider image than the imaging field of view of the imaging means is required, a composite image may be created from the original image captured by dividing the imaging target area into a plurality of areas. In this case, how to combine a plurality of original images greatly affects the image quality of the combined image. In general, a part of the adjacent original images is imaged by overlapping each other, and an appropriate image processing is performed on the overlapping portions so that the original images are joined together to make the seam of the images less noticeable. Yes.

For example, in the technique described in Patent Document 1, when two images provided with overlapping portions are combined, the pixel data of the pixels corresponding to the overlapping portions in each image are weighted and added, and the end portion of the image By reducing the weight as much as possible, the joint is made inconspicuous. In the technique described in Patent Document 2, when a plurality of images captured with a minute time interval are aligned and combined, one image is a reference image, and the other plurality of images are a reference image. Is done. Then, the unnaturalness of the combined image is eliminated by changing the region for alignment with the reference image for each reference image.

Japanese Patent Laid-Open No. 62-140174 JP 2011-176777 A

Although not particularly taken into consideration in the above-described prior art, in the case where a wide imaging target region is divided into a plurality of original images and synthesized, for example, when the original image is imaged under special imaging conditions, the imaging optical system Image quality non-uniformities due to the optical properties of the individual original images can be included. For example, image quality deterioration such as uneven brightness, blurring, and distortion is particularly likely to appear at the periphery of an image. Examples of such special imaging include imaging in a wide-angle imaging field of view and imaging using an imaging optical system having a high percentic characteristic. For this reason, if the method of superimposing the field of view for capturing the original image is not set appropriately, the deteriorated images will be stitched together, and a composite image with the desired image quality will always be obtained. There is a problem that can not be.

The present invention has been made in view of the above problems, and in a technique for combining a plurality of original images together, it is possible to create a composite image in which the influence of image quality degradation caused by the optical characteristics of the imaging system is suppressed. The purpose is to provide technology that can be used.

In order to solve the above-described problem, an aspect of the image creating apparatus according to the present invention has a two-dimensional imaging field of view, the imaging field of view with respect to the imaging target region is different from each other, and the imaging fields of adjacent positions are The image capturing means that divides the image area into a plurality of original images and composites the plurality of original images by capturing the image several times by partially overlapping each other and combining the plurality of original images An image composition unit that creates a single composite image representing a region, and the image composition unit associates a position in the original image and a weight given to a pixel at the position in accordance with the optical characteristics of the imaging unit. Based on the weighting rule, each pixel in each original image is weighted, and a plurality of weighted original images are synthesized so that pixels corresponding to the same position in the imaging target region overlap each other, and imaging means As all positions of the imaging target region is represented as an active pixel in at least one of the original images, perform imaging with overlapping imaging field in the imaging target region.

According to another aspect of the image creating method of the present invention, in order to solve the above-described problem, the position of the imaging field of view relative to the imaging target region is made different from each other by an imaging unit having a two-dimensional imaging field of view. An imaging process for dividing an imaging target area wider than the imaging field of view into a plurality of original images and synthesizing the plurality of original images by performing imaging a plurality of times by partially overlapping adjacent imaging fields of view. A composite step of creating a single composite image representing the imaging target region, and in the composite step, the position in the original image and the weight given to the pixel at the position are associated according to the optical characteristics of the image pickup means. Based on the assigned weighting rule, weighting is performed on each pixel in each original image so that pixels corresponding to the same position in the imaging target region overlap each other in the plurality of weighted original images. It is combined, in the imaging process, all positions in the imaging target region as represented as an effective pixel in at least one of the original image, the imaging is performed with overlapping imaging field in the imaging target region.

In these inventions, the “effective pixel” is defined as a pixel that is given a weight equal to or higher than a predetermined threshold by the above-described weighting rule among the pixels constituting the original image. In the invention configured as described above, a weight based on a weighting rule corresponding to the optical characteristics of the imaging unit is given to each pixel of a plurality of original images captured so as to partially overlap. Thereby, the weight which each pixel in an original image has can be varied. For this reason, if the weight of the pixel in the portion that causes degradation or loss of the image information due to the optical characteristics of the imaging means is made smaller than the other portions, the portion is less likely to be reflected in the composite image.

On the other hand, even if a single weighting rule is applied to a plurality of original images, the weights given to the pixels corresponding to the same position in the imaging target region are not necessarily the same between a plurality of original images having different imaging positions. Not. For this reason, if the overlapping portion is not appropriate at the stage of capturing the original image, image information may be partially lost in the composite image. That is, even if the pixels to which only a small weight is given are overlapped, effective image information is not reflected in the composite image. Therefore, in the present invention, weighting rules at the time of composition are taken into consideration at the imaging stage. That is, the entire imaging target area is covered with pixels having a weight equal to or greater than a predetermined threshold in at least one original image. More precisely, the imaging field of view for each imaging is set according to the weighting rule so as to have such a relationship.

Therefore, a pixel having a weight less than the threshold in one original image is given a weight greater than or equal to the threshold in any of the other original images. For this reason, when the original image is synthesized, the image information of the pixel to which a large weight is given is strongly reflected in the synthesized image in all the pixels, and the omission of the image information is avoided.

As described above, according to the present invention, in the technique for combining a plurality of original images together, each pixel constituting the plurality of original images is weighted according to the optical characteristics of the imaging means. In addition, the method of superimposing the imaging fields during imaging of the original image is determined so that the entire imaging target region is represented by pixels having a weight equal to or greater than the threshold in at least one original image. Therefore, it is possible to create a composite image in which the influence of image quality deterioration caused by the optical characteristics of the imaging system is suppressed.

The above and other objects and novel features of the present invention will become more fully apparent when the following detailed description is read with reference to the accompanying drawings. However, the drawings are for explanation only and do not limit the scope of the present invention.

It is a figure which shows schematic structure of the imaging device which can apply the image preparation method concerning this invention. It is a 1st figure which shows well imaging by this imaging device. It is a 2nd figure which shows well imaging by this imaging device. It is a figure which shows imaging when an imaging object area | region is larger than an imaging visual field. It is a 1st figure which shows the actual example of the image quality fall in the peripheral part of an image. It is a 2nd figure which shows the actual example of the image quality fall in the peripheral part of an image. It is a 1st figure which shows how to give the weight to a pixel. It is a 2nd figure which shows how to give the weight to a pixel. It is a 3rd figure which shows how to give the weight to a pixel. It is a 1st figure which shows the example of expression of a weighting map. It is a 2nd figure which shows the example of expression of a weighting map. It is a 1st figure which illustrates the mask produced from a weighting map. It is a 2nd figure which illustrates the mask produced from a weighting map. It is a figure which shows the example of allocation of an original image. It is a flowchart which shows the imaging process in this embodiment. It is a flowchart which shows the composition process of an image. It is a figure for demonstrating extraction of a well area | region.

FIG. 1 is a diagram showing a schematic configuration of an imaging apparatus to which an image creating method according to the present invention can be applied. This imaging device 1 is a cell, cell colony, bacteria, etc. (hereinafter referred to as “cell etc.”) cultured in a liquid injected into a recess called a well W formed on the upper surface of the well plate WP. This is an apparatus for imaging a raw sample.

The well plate WP is generally used in the fields of drug discovery and biological science. The well plate WP is formed in a cylindrical shape with a substantially circular cross section on the top surface of a flat plate, and the bottom surface is transparent and flat. Are provided. Although the number of wells W in one well plate WP is arbitrary, for example, 96 (12 × 8 matrix arrangement) can be used. The diameter and depth of each well W is typically about several mm. The size of the well plate and the number of wells targeted by the imaging apparatus 1 are not limited to these, and are arbitrary, for example, those having 6 to 384 holes are generally used. The imaging apparatus 1 can be used not only for imaging a well plate having a plurality of wells but also for imaging cells or the like cultured in a flat container called a dish.

A predetermined amount of liquid as the medium M is injected into each well W of the well plate WP, and cells or the like cultured under predetermined culture conditions in the liquid are imaging objects of the imaging apparatus 1. The medium may be one to which an appropriate reagent has been added, or it may be in a liquid state and gelled after being placed in the well W. As will be described later, in the imaging apparatus 1, for example, cells cultured on the inner bottom surface of the well W can be targeted for imaging. Commonly used liquid volume is about 50 to 200 microliters.

The imaging apparatus 1 includes a holder 11 that holds the well plate WP, an illumination unit 12 that is disposed above the holder 11, an imaging unit 13 that is disposed below the holder 11, and a CPU 141 that controls the operations of these units. The control part 14 which has. The holder 11 is in contact with the peripheral edge of the lower surface of the well plate WP carrying the sample together with the medium M in each well W, and holds the well plate WP in a substantially horizontal posture.

The illumination unit 12 emits illumination light toward the well plate WP held by the holder 11. As a light source of illumination light, for example, a white LED (Light Emitting Diode) can be used. A combination of a light source and an appropriate illumination optical system is used as the illumination unit 12. The illumination unit 12 illuminates cells and the like in the well W provided on the well plate WP from above.

An imaging unit 13 is provided below the well plate WP held by the holder 11. The imaging unit 13 is provided with an imaging optical system (not shown) at a position directly below the well plate WP. The optical axis of the imaging optical system is oriented in the vertical direction. FIG. 1 is a side view, and the vertical direction in the figure represents the vertical direction.

The cell etc. in the well W are imaged by the imaging unit 13. Specifically, light emitted from the illumination unit 12 and incident on the liquid from above the well W illuminates the imaging target. Light transmitted downward from the bottom surface of the well W is incident on the light receiving surface of the image sensor 132 through the imaging optical system of the imaging unit 13 including the objective lens 131. An image of the imaging target imaged on the light receiving surface of the imaging device 132 by the imaging optical system is captured by the imaging device 132. The image sensor 132 is an area image sensor having a two-dimensional light receiving surface, and for example, a CCD sensor or a CMOS sensor can be used.

The imaging unit 13 can be moved in the horizontal direction and the vertical direction by a mechanical control unit 146 provided in the control unit 14. Specifically, the mechanical control unit 146 operates the drive mechanism 15 based on a control command from the CPU 141 to move the imaging unit 13 in the horizontal direction. Thereby, the imaging unit 13 moves in the horizontal direction with respect to the well W. The focus is adjusted by moving in the vertical direction. When imaging is performed in a state where the entire well W is accommodated in the imaging field, the mechanical control unit 146 positions the imaging unit 13 in the horizontal direction so that the optical axis coincides with the center of the well W. .

Further, when moving the imaging unit 13 in the horizontal direction, the driving mechanism 15 moves the illumination unit 12 integrally with the imaging unit 13 as indicated by a dotted arrow in the drawing. That is, the illuminating unit 12 is arranged so that the optical center thereof substantially coincides with the optical axis of the imaging unit 13, and moves in conjunction with the imaging unit 13 when moving in the horizontal direction. Thereby, no matter which well W is imaged, the center of the well W and the light center of the illumination unit 12 are always located on the optical axis of the imaging unit 13. Therefore, it is possible to maintain the imaging condition favorably while keeping the illumination condition for each well W constant.

The image signal output from the imaging device 132 of the imaging unit 13 is sent to the control unit 14. That is, the image signal is input to an AD converter (A / D) 143 provided in the control unit 14 and converted into digital image data. The CPU 141 executes image processing as appropriate based on the received image data. The control unit 14 further includes an image memory 144 for storing and storing image data, and a memory 145 for storing and storing programs to be executed by the CPU 141 and data generated by the CPU 141. It may be integral. The CPU 141 executes various control processes described later by executing a control program stored in the memory 145.

Besides, the control unit 14 is provided with an interface (IF) unit 142. The interface unit 142 accepts operation input from the user and presents information such as processing results to the user, and exchanges data with an external device connected via a communication line. It has a function. In order to realize the user interface function, the interface unit 142 is connected to an input receiving unit 147 that receives an operation input from the user and a display unit 148 that displays and outputs a message to the user, a processing result, and the like.

The control unit 14 may be a dedicated device equipped with the hardware described above, and a control program for realizing processing functions to be described later is incorporated into a general-purpose processing device such as a personal computer or a workstation. It may be. That is, a general-purpose computer device can be used as the control unit 14 of the imaging device 1. In the case of using a general-purpose processing device, it is sufficient that the imaging device 1 has a minimum control function for operating each unit such as the imaging unit 13.

2A and 2B are diagrams showing well imaging by this imaging apparatus. More specifically, FIG. 2A is a diagram showing the path of light during well imaging, and FIG. 2B is a diagram showing the relationship between the well and the imaging field of view. A well W that carries cells or the like as an imaging object contains a medium M injected in a liquid state. Accordingly, the illumination light L that enters from above the well W enters the imaging object via the liquid level of the culture medium M. The liquid surface generally forms a downwardly convex meniscus, whereby the illumination light L is refracted and bent outward from the center of the well W. When the illumination light L is telecentric illumination widely used in this type of imaging apparatus, the principal ray of the illumination light is bent in an outward direction away from the optical center except for the optical center. In the vicinity of the center of the well W, the refraction is small, and the closer to the peripheral edge of the well W, the larger the refraction.

In order to efficiently collect the light bent outward in this way and guide it to the imaging device 132, the optical characteristic of the imaging optical system including the objective lens 131 in this embodiment is that the principal ray is a general meniscus. It is assumed that the inclination of the principal ray of the illumination light that is bent by the inclination is approximately the same. Such an optical characteristic is also called an object-side high percentic characteristic. In this imaging optical system, even light whose chief ray is obliquely outward at a position away from the optical axis of the objective lens 131 can be efficiently condensed and imaged on the imaging element 132. For this reason, this imaging optical system is suitable for imaging an entire well W in the imaging field of view V as shown in FIG. 2B. This point is also described in, for example, Japanese Patent Application Laid-Open No. 2015-118036 previously disclosed by the applicant of the present application.

As shown in FIG. 2B, the entire well W can be included in the imaging field of view V when imaging a well W having a relatively small diameter at a low magnification. On the other hand, when imaging an imaging object carried by a well having a larger diameter (for example, a well in a 6-well plate) or when imaging at a high magnification, the size of the area to be imaged is the imaging field of view. It becomes relatively large with respect to the size of. There may be a case where the entire well W that is the imaging target region cannot be included in the imaging visual field V.

FIG. 3 is a diagram showing imaging when the size of the imaging target area is larger than the size of the imaging visual field. Here, a case will be described in which the entire well W having a larger diameter than that described so far is used as an imaging target region and the imaging target inside thereof is imaged. The same idea can be applied when the size of the imaging target region is relatively larger than the size of the imaging visual field V. This corresponds to the case of imaging an imaging object carried in a shallow container having a large diameter called a dish, or the case of imaging at a higher magnification even for a small-diameter well.

When the imaging target area is wider than the imaging field of view V, the imaging target area is divided into a plurality of images, and an image representing the entire area to be imaged is created by combining the images by image processing. It is possible. In this case, in order to ensure the desired image quality in the created image, it is necessary to improve the quality of the individual images before synthesis. Items to be noted for this purpose will be described next.

As shown in FIG. 3, when the imaging region V includes only the central region away from the peripheral portion Wp of the well W, the influence of the meniscus on the surface of the medium M on the optical path is sufficiently small. For this reason, in telecentric illumination, light incident near the optical axis C of the objective lens 131 is collected and incident on the image sensor 132. On the other hand, at a position away from the optical axis C, a mismatch due to the difference in the chief ray inclination between the incident light and the optical system occurs.

That is, at a position away from the optical axis C, the objective lens 131 side is configured to receive light whose principal ray is inclined outward as shown by the dotted line in the drawing, on the premise of refraction at the liquid surface. On the other hand, the light passing through the well W goes straight without being refracted by the meniscus. For this reason, the inclination of the principal ray in the incident light does not match the inclination of the principal ray on the light receiving side. As a result, the image quality may be deteriorated, particularly at the peripheral edge of the imaging field of view V. Specifically, the image may become dark or uneven brightness may occur.

The area where the required image quality can be ensured in the physical imaging field V of the imaging unit 13 is considered as an effective imaging field. Then, as described above, the physical imaging visual field V that can be used as an effective imaging visual field is mainly the central portion, and compared with this, deterioration in image quality can be a problem at the peripheral portion. That is, in the image captured in such a state, the image quality is good in the central region of the image, more strictly in the region extending around the position corresponding to the optical axis C of the objective lens 131 in the image. . On the other hand, there is a possibility that the image quality is deteriorated in the outer region.

FIG. 4A and FIG. 4B are diagrams showing examples of image quality degradation at the peripheral edge of an image. FIG. 4A shows an example of an image obtained by imaging a grid pattern for image quality evaluation in which small dots are regularly arranged on a glass plate instead of the well plate WP as an imaging object, and a partially enlarged view thereof. Indicates. In the central portion of the image, each dot appears clearly and at a constant arrangement pitch. On the other hand, at the periphery of the image, particularly at the corner of the rectangular image region, the image is dark, the outline of the dots is unclear, and the shape and arrangement pitch are also disturbed.

FIG. 4B shows a problem when such images are simply stitched together. As shown in FIG. 4A, it is assumed that, for example, four images including an area where the image quality is reduced are joined at the peripheral edge, particularly at the corner. At this time, there may be a case where the areas where the image quality is lowered are adjacent to each other, such as the area surrounded by a circle in FIG. 4B, and the desired image quality cannot be obtained in the synthesized image. As in the above-described prior art, it is conceivable that a plurality of images are captured so that a part thereof overlaps, and the overlapping part is synthesized by an appropriate image processing to make the joint inconspicuous. However, this also does not compensate for image quality degradation in the original image.

In terms of post-combination image quality, it is only necessary to extract and combine only the central portion where there is no deterioration in image quality from multiple images. However, when this is done, the effective area extracted from one image becomes narrower and more images are required. For this reason, the time required for imaging and composition processing becomes long, which is not realistic. Further, there is no particular quantitative index as to how much overlap between images should be taken during imaging.

As described above, there is a trade-off between the number of images to be captured and the image quality when it is assumed that an image covering a whole imaging target region is created by joining a plurality of images. However, a method having a clear standard has not been established so far regarding how much overlap between images should be ensured and how to synthesize the obtained images.

In the imaging device 1 of this embodiment, when the imaging target area is larger than the imaging visual field V of the imaging unit 13, a plurality of original images are acquired by performing imaging a plurality of times at different positions in the imaging target area. . Then, by synthesizing these original images, an image of the entire imaging target area is created. At this time, a plurality of original images are picked up so as to partially overlap, and the degree of the overlap reflects the processing contents in the later synthesis stage. Hereinafter, the principle of image composition and the actual processing contents in the present embodiment will be described.

As described above, in the captured original image, a constant image quality is obtained at the central portion near the optical axis C of the imaging optical system, and the image quality is deteriorated at the peripheral portion. In other words, the image information in the region near the optical axis C in the original image has high reliability, and the reliability of the image information is low in the peripheral portion away from the optical axis C. For this reason, when combining images, a large weight is given to a pixel having reliable image information in an overlapping portion of a plurality of images, while a smaller weight is given to a pixel having unreliable image information. To synthesize. In this way, the image information of highly reliable pixels is more strongly reflected in the combined pixels, and the image quality of the combined image can be improved.

FIG. 5A, FIG. 5B, and FIG. 5C are diagrams showing how to give weights to pixels. In the following drawings, when representing the direction of an image, following the general coordinate setting in a two-dimensional image, the upper left of the image is the origin (0, 0), the horizontal direction is the X coordinate, and the vertical direction is the Y coordinate. Further, the coordinates of the point on the image plane are represented by (x, y).

FIG. 5A is a diagram schematically showing a change in image quality. As shown in the figure, indices representing image quality such as image brightness, distortion, and blur are generally constant up to a certain distance from the optical axis C, but gradually decrease as the distance further increases. Therefore, weighting reflecting such characteristics may be performed. That is, as shown in FIG. 5B, a certain weight (for example, 1) is given to a pixel within a certain distance D from the optical axis C among the pixels in the original image. Further, the weighting coefficient Wt is set so that the weight gradually decreases as the distance from the optical axis C increases, and finally the weight becomes zero.

Due to the nature of the imaging optical system, it is generally considered that the weighting coefficient Wt at each pixel position should be set so that the value of the weighting coefficient Wt is rotationally symmetric with respect to the optical axis C of the imaging optical system. In this way, a weighting map in which the weighting coefficient Wt for each pixel position is mapped is created in advance. The weighting map is obtained by evaluating the imaging optical system in advance. For example, test imaging is performed using a test chart such as the grid pattern shown in FIG. 4A, the degree of deterioration in image quality for each pixel is quantitatively evaluated, and the result is mapped in correspondence with the pixel position. It can be a map. Depending on the configuration of the optical system, the weighting factor Wt may not have rotational symmetry.

For example, even if there is non-uniformity in the optical characteristics on the side of the illumination optical system, for example, the distribution of the amount of illumination light incident on the well W is not uniform, the characteristics of the illumination optical system are also included by the prior evaluation as described above It can be a weighting map. In this case, the weighting map reflects the optical characteristics of both the illumination optical system and the imaging optical system.

Then, as shown in FIG. 5C, the pixel value P (x, y) of each pixel of the original image Im is multiplied by a weight coefficient Wt (x, y) obtained from the weight map Mw according to the pixel position. Thus, the pixel value Pw (x, y) of each pixel in the weighted image Iw is determined. Thereby, an image Iw obtained by assigning weighting to the original image Im based on the optical characteristics of the imaging optical system is obtained. In the weighted image Iw, the pixel value P (x, y) of the original image Im is maintained as it is in the central portion near the optical axis C. On the other hand, in the peripheral portion, the pixel value weight of the original image Im is reduced to a small value. The weighted pixel value Pw (x, y) of each pixel can be expressed by the following (Equation 1).

FIG. 6A and FIG. 6B are diagrams showing examples of expression of weighting maps. FIG. 6A represents the value of the weighting factor Wt for the XY plane (image plane) as a three-dimensional map. In general, it is possible to express a weight coefficient Wt having an arbitrary distribution shape as a curved surface in the map space using such a three-dimensional map. Even when the optical characteristic of the imaging optical system does not have rotational symmetry, it can be expressed as an asymmetric curved surface. In order to store and use the map in the memory 145, the map may be stored as a lookup table for the X coordinate value and the Y coordinate value.

FIG. 6B shows an example in which the weight coefficient Wt is quantized in multiple stages and expressed as a two-dimensional map. A value 1 is set for the weighting factor Wt in a region within a predetermined distance centered on the optical axis C. A smaller value is set as the weighting coefficient Wt in a region farther from the optical axis C, such as 0.7 for the outer region and 0.5 for the outer region. In this case, the weighting factor Wt corresponding to each pixel in the original image Im is set stepwise according to the distance from the optical axis C of the pixel position. It may also be expressed as a function of distance. In such an aspect, the amount of information to be stored in the memory 145 can be greatly reduced.

As long as the weight given to the pixel at the position can be derived from the coordinate position in the image, the map can be expressed in an arbitrary format and stored in the memory 145. When a plurality of original images are captured under the same imaging condition, the weighting map Mw may be one set for them. However, it may be desirable to prepare the weighting map Mw for each condition, for example, when a plurality of original images are captured under different illumination conditions or imaging conditions.

Based on this weighting concept, the degree of image overlap when the original image is captured and the calculation method during image composition are determined. First, how to overlay the original images at the time of imaging will be described. Pixels with higher reliability of image information are given greater weight. Therefore, when the entire imaging target area is occupied by only pixels given a weight of a certain value or more, the entire imaging target area is determined by extracting those pixels and reconstructing the image. Images expressed in image quality can be created.

That is, a virtual mask obtained by extracting an area where the weighting coefficient Wt is equal to or greater than a predetermined threshold in the weighting map Mw is set. Then, it is only necessary to determine the arrangement of the mask so that the entire imaging target area can be covered with the mask. The number and arrangement of masks at this time represent the number and arrangement of original images necessary for representing the entire imaging target region. Such a mask is obtained, for example, by binarizing the weighting map Mw using the above threshold value.

7A and 7B are diagrams illustrating a mask created from the weighting map. The mask M1 illustrated in FIG. 7A is an example in which a relatively large threshold Th1 (for example, 0.9) is set for the weighting factor Wt. On the other hand, FIG. 7B shows an example of the mask M2 in which a smaller threshold Th2 (for example, 0.7) is set. In these drawings, a hatched portion indicates a portion having a weight greater than or equal to a threshold, and this portion masks the imaging target region.

When the set value of the threshold is large, the image quality is guaranteed to be high in the masked area, but the masked area is small. This means that many images are required to cover the entire imaging area. For example, if the threshold value is set to 1, the image quality deterioration can be ignored, but the number of necessary images increases and the processing time becomes longer.

On the other hand, when the set value of the threshold is small, the area to be masked is large, so that the number of necessary images is small. However, the part where the image quality is slightly lowered is also used for the synthesized image, and this is reflected in the quality of the synthesized image. The threshold value may be determined according to the required image quality. In the following description, it is assumed that the mask M2 shown in FIG.

FIG. 8 is a diagram showing an example of original image allocation. There can be innumerable mask arrangements for covering the entire well W, which is the imaging target area, with the mask M created from the weighting map Mw. However, it is desirable that the area of the overlapping portion between the masks is as small as possible. Considering that the original image is sequentially captured while changing the position of the imaging unit 13 with respect to the well W, it is desirable that the moving path of the imaging unit 13 is as simple as possible and the length is as short as possible.

If the imaging apparatus 1 moves the imaging unit 13 in the X direction and the Y direction, which are the side directions of the mask M (or original image), the arrangement of the mask M is also along these directions. Is preferred. From such a viewpoint, for example, an arrangement as shown in FIG. 8 can be considered.

In FIG. 8, points P1 to P10 indicated by black circles indicate the barycentric positions of the plurality of masks M (or original images) arranged. In a general imaging method, the position of the center of gravity of the original image coincides with the position of the optical axis C when the original image is captured. A solid line arrow indicates a trajectory of scanning movement of the imaging unit 13, more precisely, a trajectory of the optical axis C of the imaging unit 13 on the imaging target region of the well W. White circles Ps and Pe indicate the start point and the end point of the scanning movement of the imaging unit 13.

In the example shown in FIG. 8, the entire inner region of the well W, which is the imaging target region, is covered by ten masks M. The 10 masks M are arranged in 3 rows in the X direction, the left side, ie, the most (−X) side row is 3, the center row is 4, the right side, ie, the (+ X) side row is 3 rows. Each is constituted by a mask. In each column, adjacent masks M partially overlap each other. The mask shape is isotropic in the X direction and the Y direction, and the arrangement pitch of the mask M is the same in the X direction and the Y direction.

Further, the arrangement in the Y direction of each mask M in the center column is shifted in the Y direction by half the arrangement pitch with respect to the Y direction arrangement of each mask M in each of the left and right columns. Therefore, when a barycentric position (for example, point P3) of one mask included in one column and a barycentric position (for example, points P4 and P5) of two nearest masks included in the adjacent column are connected to each other, an equilateral triangle is obtained. become. In other words, the distance between the centroid position of one mask and the centroid position of each of the plurality of masks partially overlapping the mask is the same among the plurality of masks.

With such an arrangement, it is possible to effectively cover, with another original image, a portion of the original image having a reduced image quality that appears at the corner of the original image by imaging with a rotationally symmetric imaging optical system. More generally, by changing the position of the original image along the direction in which the original images are arranged in each column between adjacent columns, the corners of the original image overlap between adjacent columns. Can be prevented. By arranging the original image corresponding to the mask quantitatively obtained from the weighting result based on the image quality evaluation, it is possible to avoid the concentration of the degraded image quality in the overlay, and an image of a certain level or higher. It is possible to ensure quality.

The mask arrangement in FIG. 8 shows the allocation of the original image at the time of imaging. Accordingly, the scanning movement recipe of the imaging unit 13 may be set so that the optical axis C of the imaging optical system sequentially passes through the points P1 to P10 corresponding to the center of gravity of each mask M during imaging. If imaging is performed every time the optical axis C of the imaging optical system reaches any one of the points P1 to P10 while scanning and moving the imaging unit 13 according to the set scanning movement recipe, the imaging target region is obtained. An original image covering the whole well W is acquired. In this sense, the position of the imaging unit 13 corresponding to each of the points P1 to P10, that is, when the optical axis C coincides with each of the points P1 to P10, is hereinafter referred to as “imaging position”.

FIG. 9 is a flowchart showing the imaging process in this embodiment. The CPU 141 causes each unit of the apparatus to perform a predetermined operation based on a control program created in advance, and executes an imaging process illustrated in FIG. 9, thereby acquiring a plurality of original images. First, the imaging unit 13 is positioned at a predetermined start position by the drive mechanism 15 that operates according to a control command from the mechanical control unit 146 (step S101). The start point Ps shown in FIG. 8 corresponds to the optical axis position of the objective lens 131 at this time. Although only the scanning movement of the imaging unit 13 will be described here, as described above, the illumination unit is moved along with the movement of the imaging unit 13 so that the optical center of the illumination light and the optical axis of the objective lens 131 always coincide with each other. 12 also moves.

Subsequently, the scanning movement of the imaging unit 13 with respect to the well W is started based on a preset scanning movement recipe (step S102). If the imaging unit 13 reaches the end position corresponding to the end point Pe, the process ends (step S103). Until the end position is reached, every time the imaging unit 13 reaches one of the imaging positions corresponding to the points P1 to P10 (step S104), steps S105 and S106 are executed to perform imaging. The position where the imaging unit 13 is located can be detected based on, for example, an output signal from a position sensor (not shown) mounted on the imaging unit 13.

When the imaging unit 13 reaches the imaging position, the light source of the illuminating unit 12 is turned on for a predetermined time, so that the imaging target is stroboscopically illuminated. Is acquired (step S105). Image data obtained by digitizing the image signal output from the image sensor 132 by the AD converter 143 is stored and saved in the image memory 144 (step S106). By repeating the above process until the imaging unit 13 reaches the end position, imaging is performed at imaging positions corresponding to the points P1 to P10, and 10 original images are acquired.

Since imaging is performed under strobe illumination, there is no need to temporarily stop the scanning movement of the imaging unit 13 for imaging, and the mechanical control unit 146 scans and moves the imaging unit 13 at a constant speed according to the scanning movement recipe. Just do it. By optimizing the scanning movement recipe so that the path connecting the points P1 to P10 is as short as possible, the time required for imaging can be shortened.

In the scanning movement recipe of this embodiment, the imaging unit 13 moves in the Y direction by a predetermined distance from the start position corresponding to the start point Ps to capture an original image for one column (left column), and then a certain amount in the X direction. The original image for one column (center column) is captured while moving in the Y direction again. Further, it moves a certain amount in the X direction, captures one row (right column) of original images while moving in the Y direction, and finally reaches the end position corresponding to the end point Pe. As described above, in this embodiment, the imaging unit 13 acquires the necessary number of original images by alternately performing the movement in the Y direction and the movement in the X direction.

Next, a process for synthesizing a plurality of original images thus obtained and creating an image corresponding to the entire imaging target area will be described. In this allocation example, ten original images are acquired. However, in the case of further generalization, the number of original images is set to K (K is an integer of 2 or more), and each original image is represented by a code Ik (k = 1, 2, ..., K). In this example, K = 10.

FIG. 10 is a flowchart showing image composition processing. First, various correction processes that can be executed for each single original image, such as shading correction, distortion correction, and deconvolution correction, are performed on the acquired K original images (step S201). These corrections are performed as necessary and may be omitted. Subsequently, the corrected plurality of original images Ik are superimposed on a virtual two-dimensional map plane so that the positions of the pixels corresponding to the same position of the well W coincide with each other (step S202). Of these, a well region covering the entire well W is cut out (step S203).

FIG. 11 is a diagram for explaining the extraction of the well region. Of the area occupied by the original image Ik (k = 1 to 10 in this example) superimposed on the virtual map plane, a rectangular area including the entire well W and a minimum area outside the well is cut out as the well area Rw. . For the purpose of creating an image representing the entire well W, the subsequent processing is performed in the well region Rw, and other regions are unnecessary. For convenience of explanation, a new coordinate system is set for the well region Rw. In order to distinguish from the XY coordinate system, the new coordinate system is the X′Y ′ coordinate system, and points in the coordinate system are represented by coordinates (x ′, y ′).

Referring back to FIG. 10, the synthesis process will be described. Subsequent to the extraction of the well region, a synthesis process for each pixel is executed. First, the initial value of the coordinates (x ′, y ′) of the pixel to be processed in the well region Rw is set to the origin (0, 0) of the upper left corner of the well region Rw (steps S204 and S205). Then, the pixel value of the pixel corresponding to the coordinate point (x ′, y ′) in the combined image is calculated (step S206). When there is only one original image having pixels occupying the coordinate point (x ′, y ′), the pixel value of the pixel in the original image (not weighted) is directly used as the combined pixel value. On the other hand, when there are a plurality of original images having pixels that occupy the coordinate point (x ′, y ′), the combined pixel values are obtained by calculation based on the pixel values of the pixels extracted from the original images. It is done.

Each pixel of the original image Ik is given a weight according to the reliability of the image information of the pixel. Therefore, when a plurality of original images are overlapped, the pixel value of the pixel having a larger weight may be reflected more strongly in the combined pixel value. In principle, the combined pixel value Po (x ′, y ′) can be expressed by a weighted sum of pixel values of overlapping pixels. Specifically, according to the following (Formula 2).

In (Expression 2), the code Pwk (x ′, y ′) is a pixel value Pw (x ′, y ′) weighted by (Expression 1) with respect to the pixel of the original image Ik at the coordinate point (x ′, y ′). y ′). Note that the pixel value Pwk (x ′, y ′) of the original image Ik that does not have a pixel at the coordinate position is set to 0.

In this case, for example, in a region where pixels having relatively large weights overlap each other, the pixel value may be too large compared to other regions. Therefore, it is more preferable that the pixel value is normalized by the total value of the weighting factors Wt of the overlapping pixels as in (Equation 3) below.

In (Equation 3), a symbol Pk (x ′, y ′) is a pixel value of a pixel extracted from the original image Ik as a pixel located at the coordinate point (x ′, y ′). If the original image Ik does not have a pixel at that position, the value is 0. A symbol Wtk (x ′, y ′) is a weighting factor that acts on the pixel value Pk (x ′, y ′) based on the weighting map Mw. Although the weighting map Mw itself is common to each original image, since each original image Ik is mapped to a different position on the virtual map plane, the weighting map Mw applied to each original image Ik is also on the virtual map plane. It is necessary to link with the position of the original image.

The weighting map Mw is converted to the original image Ik on the X′Y ′ map plane by performing the coordinate transformation necessary for mapping the original image Ik on the XY map plane on the X′Y ′ map plane. Can be adjusted to the position. As a result, the value of the weighting factor Wt at the coordinate point (x ′, y ′) is not necessarily unique, and when a plurality of original images occupy the coordinate point, each corresponding original image Ik is individually Value exists. In order to distinguish these, a subscript k is used to express a weighting coefficient corresponding to the pixel value Pk (x ′, y ′) of the pixel occupying the coordinate point (x ′, y ′) in the original image Ik. It is expressed by Wtk (x ′, y ′). When the original image Ik has no pixel at the coordinate point (x ′, y ′), the value of the corresponding weight coefficient Wtk (x ′, y ′) is set to 0.

When normalization based on (Expression 3) is performed, in a case where pixels given weights that are small (for example, sufficiently small with respect to the threshold) overlap, the denominator value of (Expression 3) decreases and the pixel value is neglected. May be emphasized. However, in the present embodiment, since the assignment of the original images is determined so that at least one of the overlapping original images has a weight equal to or greater than the threshold value, such a problem does not occur.

Thus, when the pixel value of the coordinate point (x ′, y ′) in the well region Rw is obtained by either (Expression 2) or (Expression 3), the coordinate value x ′ is incremented by one. Shift the target pixel to the right. The calculation of the pixel value Po (x ′, y ′) is repeated until the coordinate position reaches the right end of the well region Rw (steps S207 and S208). Thereby, the pixel value for one pixel column in the horizontal direction (X ′ direction) in the combined image is obtained.

The calculation of pixel values for one column as described above is repeated until the lower end of the well region Rw is reached while the coordinate value y ′ is incremented by one (steps S209 and S210). Thereby, the pixel values of all the pixels in the well region Rw in the combined image are determined. By reconstructing an image corresponding to the well region Rw based on the pixel value thus calculated (step S211), a composite image representing the entire well W is created from a plurality of original images obtained by partially imaging the well W. Can do.

When the images are synthesized, methods other than those described above are also conceivable for processing the portion where the original images overlap. For example, it is conceivable to use the pixel value of the overlapping pixel that is given the highest weight. However, in this case, the connection of the image contents becomes unnatural at the end of the overlapping portion, and the joint may be noticeable.

On the other hand, for example, when there is a pixel having a weight of 1 in an overlapping portion, it is possible to adopt the pixel value having a weight of 1 as it is without processing the pixel value. This method is effective in terms of preserving image information to the maximum extent because image quality degradation does not become a problem when viewing the pixels. In this case as well, connection with surrounding pixels can be a problem. The composition method can be selected as appropriate depending on which of the preservation of image information and the smoothness of the composite image is given priority.

As described above, in this embodiment, when an image of an imaging target area that is wider than the imaging visual field V of the imaging device 1 is required, imaging is performed by dividing the imaging target area into a plurality of parts. At this time, in order to smoothly stitch together a plurality of original images, images are taken so that adjacent original images partially overlap. The overlap between the original images reflects the processing contents in the subsequent image composition.

That is, in this embodiment, the weighting map Mw that represents the weighting factor Wt that gives weight to each pixel of the original image in consideration of the image quality degradation that occurs at the peripheral edge of each original image due to the optical characteristics of the imaging unit 13. Is prepared. In a portion where a plurality of original images overlap, the combined pixel value is calculated according to the weight of the pixel extracted from each original image. Specifically, by multiplying the pixel value of each pixel by a weighting coefficient, the pixel value of a pixel to which a greater weight is given is reflected more strongly in the combined pixel value.

Then, the allocation of the original image when the divided images are taken is determined so that the entire imaging region is occupied by pixels to which a weight equal to or higher than a predetermined threshold is given in at least one original image. By doing so, it is possible to determine the image information of the entire imaging region using image information of pixels having image quality of a certain level or higher in the original image. Therefore, there is no pixel reconstructed only from pixels having a small weight, that is, low reliability with respect to the image information, and the quality of the combined image can be improved.

As described above, in the above embodiment, the illumination unit 12 is the “illumination unit” of the present invention, the imaging unit 13 is the “imaging unit” of the present invention, and the drive mechanism 15 is the “moving unit” of the present invention. Each is functioning. These functions integrally as “imaging means” of the present invention. The imaging element 132 corresponds to the “area image sensor” of the present invention, and the imaging optical system including the objective lens 131 corresponds to the “high percentic optical system”. In addition, the control unit 14 functions as the “image composition unit” of the present invention.

In the above embodiment, the movement direction of the imaging unit 13 corresponding to the Y direction of the image corresponds to the “first scanning direction” of the present invention, and the movement of the imaging unit 13 in this direction and the imaging in the middle thereof are the main directions. This corresponds to the “main scanning process” of the invention. The direction corresponding to the X direction corresponds to the “second scanning direction” of the present invention, and the movement of the imaging unit 13 in this direction corresponds to the “sub-scanning process” of the present invention.

Note that the present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, the imaging unit 13 of the above embodiment has a high percentric optical system. In the imaging unit 13, when there is no influence of the meniscus, the image quality is likely to be deteriorated at the peripheral portion of the image. Therefore, the effect of the present invention is particularly effective. However, the problem that image quality is likely to deteriorate at the peripheral edge of an image due to, for example, lens aberration, vignetting, illumination light unevenness, etc. also occurs in various optical systems other than such an imaging optical system. The present invention can be applied to an apparatus having such various imaging optical systems.

Further, the above embodiment is an imaging device that images a living sample such as a cell carried in the well W. However, what the imaging apparatus according to the present invention uses as an imaging target is not limited to these and is arbitrary. Even if the image is not picked up via the liquid surface, for example, an image picked up using a wide-angle lens tends to have a large distortion at the peripheral portion, so that it can be said that this is an example in which the present invention functions particularly effectively.

Also, the above-described assignment of the original image is merely an example, and should be appropriately set according to the purpose and in accordance with the gist of the present invention.

In the above-described embodiment, a set of imaging units 13 captures a plurality of original images while scanning and moving with respect to the imaging target region. However, the plurality of original images may be captured by different imaging means. In this case, since there is a difference in characteristics for each imaging unit, it is desirable to prepare a weighting map for each imaging unit.

In the description of the above-described embodiment, the “weighting rule” according to the present invention is described as the weighting map Mw. However, it is arbitrary how the weighting rule is expressed and implemented in the apparatus. As described above, in addition to the lookup table and the function, a configuration in which the weight coefficient is derived by conditional branching according to case classification may be used.

As described above, the specific embodiment has been exemplified and described. In the present invention, the weight given by the weighting rule is set to be larger in the central pixel of the original image than in the peripheral pixel. Also good. In a general imaging optical system, the image quality is the best at the center of the image, and the image quality is lower at the periphery. By performing weighting that reflects such properties, it is possible to effectively suppress the influence of the deterioration in image quality caused by the characteristics of the imaging optical system.

Further, for example, the weight given by the weighting rule is a constant value equal to or greater than the threshold for pixels within a predetermined distance from the position corresponding to the optical center of the imaging unit in the original image, while for pixels far from the predetermined distance. You may set so that it may become so small that it leaves | separates from an optical center. By giving a constant weight to the central portion of the image, unnecessary image processing is suppressed, and the image quality of the original image can be maintained.

In this case, the magnitude of the weight given by the weighting rule may be rotationally symmetric with respect to the optical center, for example. When the imaging optical system is configured by a combination of lenses having rotationally symmetric characteristics with respect to the optical axis, the optical characteristics also have rotational symmetry with respect to the optical axis. By performing weighting that reflects this, the weighting rule can be described with simpler expressions, and the processing for weighting can be simplified.

Further, for example, in image composition, when there are a plurality of original images including pixels corresponding to the same position in the imaging target region, the pixel value of the pixel corresponding to the position in each of the original images is weighted based on the weighting rule. A value obtained by multiplying the coefficients according to the sum may be used as the pixel value of the pixel corresponding to the position in the composite image. According to such a configuration, a pixel to which a greater weight is given reflects the pixel value more strongly in the result. Thereby, it is possible to suppress the influence of a pixel having a small weight and therefore a large image quality degradation.

Further, for example, the imaging means may include an area image sensor that converts an optical image in the imaging field of view into an electrical signal. In a configuration in which an area image sensor captures a two-dimensional imaging field at a time, the imaging optical system also needs a function to form a two-dimensional optical image. In such a configuration, the image quality deteriorates at the periphery of the imaging field. Easy to appear. In such a case, by applying the technical idea of the present invention, it becomes possible to create a composite image in which the influence of image quality deterioration is suppressed.

In this case, the imaging means may have a high percentic optical system that guides the light emitted from the imaging target region in the imaging field of view to the area image sensor. In such an imaging optical system, image quality deterioration is likely to occur particularly in the peripheral portion of the image, so that the effect of the present invention becomes remarkable.

For example, the imaging unit may include an imaging unit that captures an image within the imaging field of view, and a moving unit that moves the imaging unit relative to the imaging target region. According to such a configuration, a plurality of original images can be captured by a set of imaging units.

In this case, the imaging unit may further include an illuminating unit that illuminates the imaging target region intermittently in synchronization with the relative movement of the imaging unit with respect to the imaging target region by the moving unit. In such a configuration, since the optical image is received by the imaging unit only while the illumination unit is lit, a still image can be acquired without stopping the movement of the imaging unit by the moving unit. Therefore, it is possible to shorten the time required for imaging compared to a configuration in which imaging is performed by temporarily stopping the imaging unit.

In the imaging method according to the present invention, in the imaging step, the imaging means intermittently captures an image while scanning and moving at a constant speed relative to the imaging target area in the first scanning direction. The main scanning process for acquiring a plurality of original images arranged along the line and the sub-scanning process in which the imaging unit moves in the second scanning direction orthogonal to the first scanning direction relative to the imaging target region are alternately performed. When executed, a plurality of original images are acquired in each of the first scanning direction and the second scanning direction, and positions in the first scanning direction may be different between adjacent original images in the second scanning direction. In such a configuration, by changing the positions of the original images adjacent in the second scanning direction in the first scanning direction, it is possible to prevent the corners of the original image having large image quality deterioration from overlapping.

Although the invention has been described with reference to specific embodiments, this description is not intended to be construed in a limiting sense. Reference to the description of the invention, as well as other embodiments of the present invention, various modifications of the disclosed embodiments will become apparent to those skilled in the art. Accordingly, the appended claims are intended to include such modifications or embodiments without departing from the true scope of the invention.

The present invention can be applied to all techniques for imaging an area wider than the imaging field of view of the imaging means by dividing it into a plurality of images and creating an image obtained by synthesizing them, and the imaging object is not particularly limited.

1 Imaging device (image creation device)
12 Illumination unit (imaging means, illumination unit)
13 Imaging unit (imaging means, imaging unit)
14 Control unit (image composition means)
15 Drive mechanism (imaging means, moving part)
131 Objective lens 132 Image sensor (area image sensor)
Mw weighting map Rw well region W well WP well plate Wt weighting factor

Claims

The imaging field of view has a two-dimensional imaging field of view, the positions of the imaging field of view relative to the imaging target region are different from each other, and the imaging fields of view adjacent to each other are partially overlapped with each other to perform imaging a plurality of times. An imaging means for dividing and imaging a wider area of the imaging target area into a plurality of original images;
Image combining means for combining the plurality of original images and creating a single combined image representing the imaging target region;
The image synthesizing unit is configured to assign each pixel in the original image based on a weighting rule in which a position in the original image and a weight given to the pixel at the position are associated according to optical characteristics of the imaging unit. Weighting is performed, and the plurality of weighted original images are combined so that pixels corresponding to the same position in the imaging target region overlap each other,
When a pixel that is given a weight equal to or higher than a predetermined threshold by the weighting rule among the pixels in the original image is defined as an effective pixel,
The imaging means performs image generation in which the imaging field of view is overlapped in the imaging target region so that all positions in the imaging target region are represented as the effective pixels in at least one of the original images. apparatus.
2. The image creating apparatus according to claim 1, wherein a weight given by the weighting rule is larger in a central pixel of the original image than in a peripheral pixel.
The weight given by the weighting rule is a constant value greater than or equal to the threshold for pixels within a predetermined distance from the position corresponding to the optical center of the imaging means in the original image, while pixels farther than the predetermined distance. The image creating apparatus according to claim 1, wherein the smaller the distance from the optical center.
4. The image creating apparatus according to claim 3, wherein the weight given by the weighting rule has rotational symmetry with respect to the optical center.
When there are a plurality of original images including pixels corresponding to the same position in the imaging target region, the image composition unit weights the pixel values of the pixels corresponding to the position in each of the original images based on the weighting rule. 5. The image creating apparatus according to claim 1, wherein a value obtained by multiplying a coefficient corresponding to the size of the pixel is a pixel value of a pixel corresponding to the position in the composite image.
6. The image creating apparatus according to claim 1, wherein the imaging unit includes an area image sensor that converts an optical image in the imaging field of view into an electrical signal.
The image creating apparatus according to claim 6, wherein the imaging unit includes a high-percentric optical system that guides light emitted from the imaging target region in the imaging visual field to the area image sensor.
The image creating apparatus according to any one of claims 1 to 7, wherein the imaging unit includes an imaging unit that images the imaging field of view and a moving unit that moves the imaging unit relative to the imaging target region.
The image creating apparatus according to claim 8, wherein the imaging unit includes an illuminating unit that illuminates the imaging target region by intermittently lighting in synchronization with relative movement of the imaging unit with respect to the imaging target region by the moving unit.
The imaging means having a two-dimensional imaging field of view makes the position of the imaging field of view different from the region to be imaged and performs imaging a plurality of times by partially overlapping the imaging fields of view adjacent to each other, An imaging step of imaging by dividing the imaging target area in a wider range than the imaging field of view into a plurality of original images;
Combining the plurality of original images to create a single composite image representing the imaging target region, and
In the compositing step, a position in the original image and a weight given to the pixel at the position are based on a weighting rule associated according to the optical characteristics of the imaging unit, for each pixel in the individual original image. Weighting is performed, and the plurality of weighted original images are combined so that pixels corresponding to the same position in the imaging target region overlap each other,
When a pixel that is given a weight equal to or higher than a predetermined threshold by the weighting rule among the pixels in the original image is defined as an effective pixel,
In the imaging step, an image is captured by overlapping the imaging field of view in the imaging target region so that all positions in the imaging target region are represented as the effective pixels in at least one of the original images. How to make.
In the imaging step,
The imaging unit intermittently captures images while scanning and moving at a constant speed in the first scanning direction relative to the imaging target region, so that a plurality of the original images arranged along the first scanning direction are captured. Main scanning processing to be acquired;
The first scanning direction and the second scanning are alternately performed by the imaging unit alternately with a sub-scanning process that moves in a second scanning direction orthogonal to the first scanning direction relative to the imaging target region. A plurality of the original images are acquired in each of the directions,
The image creation method according to claim 10, wherein positions in the first scanning direction are different between the original images adjacent in the second scanning direction.