JP2013034127A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide-field and high-resolution imaging apparatus provided with a technique capable of performing satisfactory aberration correction over the whole visual field.SOLUTION: The imaging apparatus comprises; an imaging unit; an image-forming optical system which magnifies an image of a sample and guides the image to the imaging unit; and control means. The imaging unit comprises plural imaging element units for taking the image of the sample as plural small sections. Each of the imaging element units comprises: aberration correction means for correcting aberration included in the image of a small section to be imaged; and an imaging element for taking the image corrected by the aberration correction means. The control means separately controls a correction amount of the aberration correction means of each imaging element unit in accordance with the position of the small section to be imaged.

Description

  The present invention relates to an imaging apparatus that captures a sample to acquire a wide-field and high-definition digital image, and more particularly to a technique for correcting aberrations of the imaging apparatus.

2. Description of the Related Art In recent years, in the field of pathological diagnosis, an imaging apparatus that captures a microscopic image of a human tissue piece or the like and enables accumulation and observation using digital image data has attracted attention. In this type of imaging apparatus, generally, a preparation (specimen) in which a sample to be observed is covered and fixed by a translucent protective member (cover glass) is used as a subject. When such a subject is imaged, a cover glass is interposed between the sample and the imaging optical system, so that the observation image is degraded due to various aberration variations caused by the cover glass (decrease in contrast and blurring). there is a possibility.
Therefore, conventionally, a method for correcting the aberration as described above has been proposed. For example, in the imaging apparatus of Patent Document 1, spherical aberration caused by the thickness of the cover glass being different from the reference value is obtained by moving the movable lens group inserted on the image side of the objective lens in the optical axis direction. It is corrected. Patent Document 2 proposes a method of measuring the difference between the thickness of the cover glass and a reference value and estimating the correction amount of aberration from the measured value.
Recently, for the purpose of collectively acquiring images used for pathological diagnosis, a large number of specimens are frequently imaged and imaged. Due to such continuous imaging for a long time, a new problem arises that heat due to illumination light accumulates in the imaging optical system and aberrations occur.
As an aberration correction method for an optical system, for example, a method using an optical element called an Alvarez lens as in Patent Document 3 and a method using adaptive optics as in Patent Document 4 are also known.

JP 2001-264637 A JP 2007-101579 A Japanese Patent Laid-Open No. 10-242048 Japanese Patent Application Laid-Open No. 11-101942

  As described above, various methods for correcting aberrations have been proposed. However, all of these conventional methods uniformly correct the entire field of view of the imaging optical system. For this reason, if the surface shape (height) and thickness of the cover glass are not uniform within the field of view, or if thermal changes due to imaging vary greatly in location, the conventional method cannot correct the aberration (within the field of view). Overcorrected or undercorrected areas may remain). Conventionally, since the field of view of the imaging device was narrow and the resolution was low, such a correction defect was not so much a problem. However, with the recent demand for wider field of view and higher definition, this problem cannot be ignored. .

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a technique capable of performing good aberration correction over the entire field of view in a wide-field and high-resolution imaging apparatus. To do.

The present invention includes an imaging unit, an imaging optical system that enlarges an image of a sample and guides the image to the imaging unit, and a control unit. The imaging unit divides the sample image into a plurality of small sections. A plurality of image sensor units for imaging, and each of the plurality of image sensor units is corrected by an aberration correction unit that corrects an aberration included in an image of a small section to be imaged, and the aberration correction unit; An image pickup device that picks up an image, and the control means provides an image pickup apparatus that individually controls the correction amount of the aberration correction means of each image pickup element unit in accordance with the position of the small section to be picked up.

  According to the present invention, in a wide-field and high-resolution imaging apparatus, it is possible to perform good aberration correction over the entire field of view, and a high-quality image can be acquired.

1 is a diagram illustrating a schematic configuration of an imaging apparatus. The figure which shows schematic structure of an image pick-up element and an aberration correction part. The figure which shows the example of the procedure which divides | segments an imaging area into a some small division, and images it. 6 is a flowchart showing a flow of image acquisition processing by the imaging apparatus. FIG. 3 is a diagram illustrating a schematic configuration of an image sensor and an aberration correction unit according to the first embodiment. The figure which shows the example of the aberration correction using an Alvarez lens. FIG. 6 is a diagram illustrating a schematic configuration of an image sensor and an aberration correction unit in Embodiment 3. The figure which shows the example of a correction | amendment optical system. The figure which shows the example of a correction | amendment optical system. The figure which shows the example of a correction | amendment optical system. The figure which shows the example of the surface shape of a sample. The figure which shows the example of the inclination correction of the surface shape of a sample, and the focal plane of an optical system. The figure which shows the example of arrangement | positioning of an image pick-up element and an Alvarez lens.

  The present invention relates to a thickness variation of a protective member that protects a sample such as a tissue piece, a surface shape (unevenness) of the sample or the protective member, a thermal change at the time of imaging, etc. The present invention relates to a technique for accurately and automatically correcting the aberration caused by the above. More specifically, the present invention has one feature in that the imaging unit is composed of a plurality of imaging elements, and aberration correction means (correcting optical system) capable of controlling the correction amount independently for each imaging element is provided. Have. As a result, the correction amount can be adjusted for each image sensor in accordance with the distribution in the field of view such as the thickness of the protective member, the surface shape, and the temperature, so that it is possible to achieve good aberration correction over the entire field of view. Therefore, the present invention is of a type that generates a wide field of view and a high resolution overall image by dividing the field of view of the imaging optical system with a plurality of image sensors and combining the obtained partial images. The present invention can be particularly preferably applied to an imaging device.

  The present invention can be embodied as an imaging device, or can be embodied as an imaging system that combines an imaging device and an image processing computer (and also a display device and an image storage device). Such an imaging apparatus or imaging system can be suitably used for a virtual slide creation system, a digital microscope, and the like, and is very useful for applications such as pathological diagnosis.

(Device configuration)
FIG. 1 shows a schematic configuration of an imaging apparatus according to an embodiment of the present invention. As illustrated in FIG. 1, the imaging apparatus according to the present embodiment includes a measurement unit 100 that performs pre-measurement of a specimen before imaging, and an imaging unit 300 that acquires a digital image by capturing the specimen using a result of the pre-measurement. And a control unit 400 for controlling them.

The specimen (preparation) used in the present embodiment is a sample to be observed (a living tissue piece or the like) placed on a slide glass, which is covered and fixed with a translucent protective member (a cover glass or the like). Is. Since it is difficult to produce a sample with a uniform thickness, minute irregularities are generated on the surface of the sample (the surface on the protective member side) and the surface of the protective member. Also, the protective member itself has uneven thickness of several μm to several tens of μm.

  In FIG. 1, the measurement unit 100 includes a measurement illumination unit 101, a measurement stage 102, a measurement optical system 104, and a measurement unit 105. The measurement illumination unit 101 includes an illumination optical system that guides light from a light source to a preparation (specimen) 103 installed on the measurement stage 102. The measurement stage 102 is a support unit that holds the preparation 103 and adjusts the position of the preparation 103 with respect to the measurement optical system 104.

  The measurement optical system 104 is an optical system that guides the light transmitted through the preparation 103 to the measurement unit 105. Since the measurement unit 100 is intended to measure the entire preparation, the measurement optical system 104 may have a low magnification. Based on the light received via the measurement optical system 104, the measurement unit 105 determines the size of the sample (observation target) on the preparation 103, the shape of the surface of the sample or the protection member, and the thickness of the protection member. It is a means to measure. Data measured by the measurement unit 105 is transmitted to the control unit 400 and used for aberration correction and focus position correction described later.

  Various sensors can be used for the measurement unit 105 according to the measurement purpose. For example, for the purpose of measuring the size of the sample, the brightness and color of the sample image may be acquired with an imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). For the purpose of measuring the unevenness (surface shape) of the sample or the protection member, or the thickness of the protection member, various sensors using reflected light or interference light can be used. For example, an optical distance measurement method using a triangulation method as disclosed in JP-A-6-011341 or a confocal optical system as disclosed in JP-A-2005-98833 uses a glass boundary surface. There is a method for measuring the difference in the distance of the laser beam reflected by the laser beam. The thickness of the protective member can also be measured by a laser interferometer or the like. In FIG. 1, a transmission type measurement unit is illustrated, but depending on the physical quantity to be measured and the type of sensor, a reflection type measurement unit that irradiates light from the protective member side and measures reflected light may be used. A unit or a sensor may be used in combination.

In FIG. 1, the imaging unit 300 includes an imaging illumination unit 301, an imaging stage 302, an imaging optical system 304, and an imaging unit 305.
The imaging illumination unit 301 includes an illumination optical system that guides light from the light source to a preparation 303 installed on the imaging stage 302. The imaging illumination unit 301 includes a light source 201 and an illumination optical system 202. As the light source, for example, a halogen lamp, a xenon lamp, or an LED (Light Emitting Diode) can be used.
The imaging optical system 304 is an optical system that enlarges the image of the sample illuminated on the surface A and guides it to the imaging surface B of the imaging unit 305 in order to capture the sample on the preparation 303 with a wide field of view and high resolution. .

The imaging stage 302 is a support unit that holds the preparation 303 and adjusts the relative position of the preparation 303 with respect to the imaging unit 305 or the imaging optical system 304. The imaging stage 302 can be translated or tilted independently in the X and Y directions orthogonal to the optical axis (Z direction). FIG. 1 shows a coordinate system, and the X axis is a direction perpendicular to the paper surface.
The preparation is moved from the measurement stage 102 to the imaging stage 302 by a transport unit (not shown). As a mechanism of the transport unit, for example, a mechanism in which the measurement stage 102 itself moves to function as the imaging stage 302 may be used, or a mechanism in which a preparation is gripped or sucked and moved onto the stage. In addition, when continuously imaging a plurality of slides, the slides stored in a stocker (not shown) are transported one by one to the measurement stage 102 and the imaging stage 302 one by one by the transport unit. Note that different preparations may be simultaneously installed on the measurement stage 102 and the imaging stage 302, and the measurement processing by the measurement unit 100 and the imaging processing by the imaging unit 300 may be performed in parallel.

  A temperature sensor 308 as temperature measuring means is installed on the imaging stage 302 or near the sample inside the stage 302. The temperature sensor 308 measures the temperature in the vicinity of the preparation 303 during imaging. The temperature sensor 308 may be installed inside the specimen (for example, between the cover glass and the slide glass), or may be installed inside the imaging optical system 304, the imaging illumination unit 301, or the like. Alternatively, a plurality of sensors can be installed at different positions in order to obtain an in-plane distribution of temperature. Data measured by the temperature sensor 308 is transmitted to the control unit 400 and used for aberration correction described later.

  The imaging unit 305 is a unit that photoelectrically converts light (an optical image of a sample) received through the imaging optical system 304 to generate and output image data. The obtained image data is transmitted to an image processing unit (not shown), and image processing such as development, gamma correction, noise removal, synthesis, and compression is performed.

  For example, when imaging an imaging region of 10 mm × 10 mm on a slide with an optical magnification of 10 times, the size of the imaging region on the imaging surface B is 100 mm × 100 mm, that is, about 141 mm in diameter. A large image sensor capable of capturing an image of such an area at a time is costly due to the influence of yield reduction due to pixel defects or the like. Therefore, in the present embodiment, the imaging region is divided into a plurality of small sections, images are captured in units of small sections using a plurality of image sensors, and the obtained partial images are combined (joined), so that a wide field of view and A configuration that generates a high-definition whole image is adopted.

  FIG. 2A illustrates a configuration example of the imaging unit 305. The imaging unit 305 includes 19 imaging elements 306 that are two-dimensionally arranged in the field of view 304 a of the imaging optical system 304. Each image sensor 306 is composed of an image sensor such as a CCD or CMOS. Here, the imaging elements 306 are discretely arranged because the circuit board 306b existing around the effective light receiving surface 306a of the imaging element 306 physically interferes and the light receiving surfaces 306a are arranged without gaps. This is because it cannot be done. For the convenience of illustration, only the light receiving surface 306a is shown except for the elements in the upper two rows. The size of the light receiving surface 306a of each image sensor 306 corresponds to the size of a small section, which is an imaging unit, and each image sensor 306 has its light receiving surface 306a aligned with the focal plane of the imaging optical system 304. Be placed. The number and arrangement of the image sensors 306 are arbitrary, but it is preferable to determine so that all the small sections can be imaged with a smaller number of times of imaging.

  An example of the imaging procedure by the imaging unit 305 will be described with reference to FIGS. FIG. 3A shows the positions of the field of view 304a of the imaging optical system 304 and the imaging element 306 on the imaging surface. A gray rectangle indicates the light receiving surface 306a of the image sensor 306, that is, a small section (region of a partial image) that can be imaged at one time. Positions 1, 2, 3, and 4 in FIG. 3A indicate the center position of the field of view of the imaging optical system 304 in the first, second, third, and fourth imaging, respectively. FIG. 3B shows an imaging area on the imaging surface. A small section captured at the first time is represented by a small section captured at the first and second times, and a small section captured at the second and third times. 3 and 4 indicate the small sections imaged at the fourth time. For example, by fixing the center position of the imaging optical system 304 and sequentially moving the reference position of the imaging stage 302 in the order of positions 1, 2, 3, and 4 in FIG. As shown in FIG. 3B, 76 partial images that fill the imaging region can be acquired.

As shown in FIG. 1, the imaging unit 305 of this embodiment includes an aberration correction unit 307 for correcting aberration with respect to a light beam 310 incident on the imaging element 306 from the imaging optical system 304. The aberration correction unit 307 is individually provided for each image sensor 306, and the correction amount of each aberration correction unit 307 can be controlled independently (hereinafter, the paired image sensor 306 and the aberration correction unit 307 are connected). These are collectively referred to as an image sensor unit). In the present embodiment, all the image sensor units are arranged on the same electric board, but each image sensor unit may be arranged on a different electric board.

2B and 2C schematically show the arrangement and configuration of the image sensor 306 and the aberration correction unit 307. 2B and 2C are views of the imaging unit 305 viewed from a direction orthogonal to the optical axis.
FIG. 2B illustrates an example in which the aberration correction unit 307 includes a correction optical system 307a and a drive unit 307b that drives the correction optical system 307a. The image sensor 306 is fixed on the substrate 309, and a correction optical system 307a is disposed in the optical path between the image sensor 306 and the imaging optical system 304. The drive unit 307b is electrically connected to the substrate 309 through a drive wiring, and changes the correction amount of the correction optical system 307a according to the correction command value from the control unit 400. As the correction optical system 307a, either an optical system that changes an optical characteristic by a mechanical action or an optical system that changes an optical characteristic by an electric action can be used. An example of the former is an Alvarez lens driven by a piezoelectric element or the like, and an example of the latter is adaptive optics such as a liquid lens or a liquid crystal lens.

  FIG. 2C illustrates an example in which the aberration correction unit 307 includes a posture adjustment unit 307c for adjusting the position and inclination of the image sensor 306 in the optical axis direction in addition to the correction optical system 307a. The operation of the posture adjustment unit 307 c is also controlled by a correction command value from the control unit 400. The posture adjustment unit 307c may be configured to adjust only the posture of the image sensor 306, but as illustrated in FIG. 2C, the correction optical system 307a and the image sensor 306 are integrated and the postures of both are integrally adjusted. Is preferred. By fixing the relative position of the correction optical system 307a and the image sensor 306, the correction of the aberration by the correction optical system 307a and the correction of the aberration by the posture adjustment unit 307c can be considered independently, and the correction amount can be easily controlled. Because.

  The attitude adjustment unit 307c can be used for correction of focus shift (defocus) and distortion. For example, the posture adjustment unit 307c corrects the focus shift caused by the unevenness of the sample surface by moving the imaging element 306 from the reference imaging surface B by a minute amount in the optical axis direction, and the correction optical system 307a focuses by thermal aberration. The shift may be corrected. Alternatively, the focus shift may be corrected only by the attitude adjustment unit 307c, and another aberration may be corrected by the correction optical system 307a. Furthermore, the image pickup element 306 may be tilted with respect to the optical axis direction by the attitude adjustment unit 307c, and the correction optical system 307a may also adjust the tilt of the light beam 310 to correct distortion aberration. Alternatively, the distortion aberration may be corrected only by the posture adjustment unit 307c, and another aberration may be corrected by the correction optical system 307a.

  Based on the measurement data obtained from the measurement unit 100 and the temperature sensor 308, the control unit 400 calculates an aberration amount for each position on the slide (for each small section), and sets a correction command value for the corresponding image sensor unit. It is a means for sending out. The control unit 400 also has a function of controlling each block constituting the imaging apparatus, such as the measurement unit 100, the imaging unit 300, the conveyance unit, and the image processing unit. Specific examples of the operation of the control unit 400 and aberration correction and focus position correction will be described later.

(Operation of imaging device)
Next, the procedure of image acquisition processing by the imaging apparatus will be described with reference to the flowchart of FIG.
First, the control unit 400 controls the transport unit (not shown) and installs the preparation 103 on the measurement stage 102 (S101). The installation on the measurement stage 102 may be performed not by the operator but by the operator himself.

  Thereafter, the measurement illumination unit 101 illuminates the preparation 103 installed on the measurement stage 102. The measurement unit 105 receives light from the measurement optical system 104 and measures the shape and size of the sample, the surface shape of the sample or the protective member, and the like (S102). The measurement unit 105 transmits measurement data to the control unit 400. Further, the temperature sensor 308 measures the temperature of the imaging unit 300 and transmits the measurement data to the control unit 400 (S103).

  Next, the control unit 400 determines the imaging area on the slide based on the measurement data acquired in S102 and S103, calculates the aberration amount in each small section in the imaging area, and corrects the aberration. A correction amount for this is determined (S104). Note that when a large number of slides are continuously imaged (that is, when the flow of FIG. 4 is repeatedly executed), the temperature or the amount of aberration is not measured using temperature measurement every time, but using a prepared prediction formula or table. The amount of correction may be obtained by estimating the change in.

  The aberrations that can be generated here are broadly classified into aberrations caused by the preparation (sample, protection member) and aberrations caused by the imaging optical system 304. Examples of the former are due to spherical aberration caused by the thickness of the protective member being thicker or thinner than the reference value (design value), unevenness of the surface of the sample or the protective member, or uneven thickness of the protective member. This is a focus position shift (focus shift) or a tilt of the focal plane. In addition, aberration variations caused by the deformation of the preparation due to the heat of the illumination light and the environmental temperature also correspond to the former example. On the other hand, examples of the latter include a change in the refractive index of a substance constituting the imaging optical system 304 due to the heat of illumination light and the environmental temperature, and aberration fluctuations caused by deformation of the optical element. Aberration fluctuations appear in spherical aberration, coma, astigmatism, curvature of field, and the like. Among the above-mentioned aberrations, focus position shift, spherical aberration, magnification error, and distortion are problems, but the aberration correction unit 307 may correct at least one of these aberrations.

  In the case of aberration due to a preparation, the amount of aberration can vary depending on the position on the preparation. Therefore, in S104, the control unit 400 needs to calculate an aberration amount or a correction amount for each small section shown in FIG. 3B. On the other hand, in the case of aberration caused by the imaging optical system 304, the amount of aberration varies depending on the position of the imaging optical system 304 in the field of view. When the relative position of the imaging device 306 and the field of view 304a of the imaging optical system 304 is fixed as shown in FIGS. 3A and 3B, the aberration amount and the correction amount are calculated for each imaging device 306. Good. Therefore, when correcting both the aberration caused by the preparation and the aberration caused by the imaging optical system 304, the control unit 400 determines the position of the small section (position on the preparation) and the position in the field of view (position of the image sensor). The aberration correction amount may be determined based on the above.

  For example, the control unit 400 obtains the inclination of the focal plane of each small section based on information such as the surface shape (surface irregularities) obtained by the pre-measurement, and determines a correction amount for correcting this inclination. . In addition, the control unit 400 obtains the amount of aberration variation based on the temperature information measured by the temperature sensor 308, and determines the amount of focal position correction, magnification correction, and distortion correction. At this time, the control unit 400 may calculate the correction amount by calculating the aberration or the variation of the aberration by simulation from the information on the structure and physical properties of the optical system and the lens barrel and the measured temperature information. Alternatively, an approximate expression or table representing the relationship between the temperature change and the aberration correction amount is stored in advance in a memory or the like, and the control unit 400 can obtain the correction amount from the measured temperature information.

In the present embodiment, the temperature measurement result is used, but a configuration in which the aberration amount is estimated by another method may be employed. For example, before imaging a specimen (preparation), a test chart is placed at the imaging position, imaging is performed, and the obtained test chart image is analyzed to obtain focus shift, magnification error, distortion, etc. Good. The imaging of the test chart may be performed every time the preparation is imaged, or may be performed at a predetermined interval (for example, after a plurality of preparations are imaged or after a predetermined time has elapsed). Alternatively, when a large number of slides are continuously imaged, the relationship between the elapsed time from the start of imaging and the correction amount of aberration can be stored in advance as an aberration correction table, and the correction amount can be determined from the elapsed time. In other words, the correction amount may be determined by calculation from the measurement result such as temperature, the aberration amount may be directly measured to obtain the correction amount, and the correction amount based on the aberration information obtained in advance. May be determined. When the temperature measurement result is not used for calculating the aberration, the temperature sensor 308 can be omitted.

  The preparation 103 is transported from the measurement stage 102 to the imaging stage 302 by a transport unit (not shown) using the time for which the control unit 400 calculates the correction amount (S105). In order to shorten the processing time, the processes of S104 and S105 are performed in parallel.

  Thereafter, the control unit 400 sends a correction command value (drive signal) to each image sensor unit based on the determined correction amount, and causes the correction optical system 307a and / or the posture adjustment unit 307c of the aberration correction unit 307 to be transmitted. Drive (S106). At this time, the control unit 400 selects a correction amount corresponding to the small section imaged by the image sensor 306 for each image sensor unit.

  Then, the imaging illumination unit 301 illuminates the preparation 303 installed on the imaging stage 302 and performs imaging (S107). At this time, the sample image on the preparation 303 is magnified by the imaging optical system 304, and after appropriate aberration correction is performed by the aberration correction unit 307, an image is formed on the imaging surface (light receiving surface) of the image sensor 306. To do. The partial image data output from each image sensor 306 is temporarily stored in an internal or external storage device.

  Subsequently, the control unit 400 determines whether or not imaging of all the small sections has been completed (S108). If there are remaining small sections that are not imaged, either the stage 302 or the imaging unit 305 or Both are moved, and the image sensor 306 is adjusted to the position of the small section to be imaged next (S109). Since the amount of aberration also changes when the small section to be imaged changes, the control unit 400 drives the aberration correction unit 307 so that the correction amount corresponds to the position of the small section after the change (S106), and then performs imaging (S106). S107).

  After acquiring the partial image data of all the small sections by repeating the processing of S106 to S109, the image processing unit synthesizes these partial image data to generate image data of the entire specimen with a wide field of view and high definition. (S110). At this time, image processing such as gamma correction, noise removal, and compression is also performed as necessary. The image processing apparatus stores the generated image data in an internal or external storage device (S111).

(Advantages of this embodiment)
In the imaging apparatus of the present embodiment, the imaging unit 305 includes a plurality of imaging elements 306, and an aberration correction unit 307 that can be controlled independently for each imaging element 306 is provided. As a result, the amount of aberration correction can be individually adjusted for each image sensor 306. Therefore, even when there is variation in the amount of aberration within the field of view, good aberration correction can be achieved over the entire field of view, and a high-quality digital image can be obtained. Can be acquired. In addition, since the correction amount of the aberration is calculated based on the measurement result of the measurement unit 100, it is possible to suitably correct the aberration caused by the surface shape (unevenness) of the sample or the protection member and the uneven thickness of the protection member. it can. Furthermore, by using the measurement result of the temperature sensor 308, the aberration of the imaging optical system 304 caused by the environmental temperature, the heat of the illumination light, or the like can be corrected appropriately.

<Example 1>
In Example 1, an example in which an Alvarez lens is used as the correction optical system 307a of the aberration correction unit 307 will be described. An Alvarez lens is a pair of optical elements having an aspheric surface of the same shape,
This is an optical system arranged close to each other so that the aspheric surfaces face each other. By relatively moving the pair of optical elements in the direction orthogonal to the optical axis, the optical characteristics can be changed.

  5A and 5B each show one image sensor unit (a set of the image sensor 306 and the aberration correction unit 307). The aberration correction unit 307 in FIG. 5A includes a correction optical system 307a composed of an Alvarez lens composed of two optical elements O1 and O2, and a drive unit 307b that drives each optical element. FIG. 5B is an example of an Alvarez lens composed of three optical elements O1, O2, and O3, which is a combination of two Albarez lenses, O1 and O2, and O2 and O3. It corresponds to. In this way, two or more Alvarez lenses can be combined.

  First, an aberration correction method will be described based on an example in which optical power (focal length) is generated by laterally shifting an optical element with reference to FIGS. 6A and 6B schematically show a cross section of the Alvarez lens in FIG. 5A on the XZ plane.

  In FIG. 6A, the two optical elements O1 and O2 are arranged to face each other. The facing surfaces (inner surfaces) of the optical elements O1 and O2 are aspherical surfaces having the same shape. The outer surfaces of the optical elements O1 and O2 are flat surfaces. If the outer surface is flat, there is an advantage that the aberration correction unit can be easily controlled because no aberration is generated from the outer surface when the surface is shifted laterally. However, the outer surface does not necessarily have to be a flat surface.

In the figure, the Z axis is the optical axis. The X and Y axes are taken perpendicular to the optical axis. The aspherical shape of the optical element O1 is f ₁ (x, y), and the aspherical shape of the optical element O2 is f ₂ (x, y). Assuming that the shifting direction is the x direction, the aspheric shapes of the two are given by the following formulas that differ by a constant term. In order to generate optical power (focal length) by laterally shifting the element in the x direction, x is used up to the third order term, and y is used up to the second order term.
f ₁ (x, y) = a (x ³ + 3xy ² ) + c ₁
f ₂ (x, y) = a (x ³ + 3xy ² ) + c ₂ (1)
Here, a is a coefficient representing the size of the aspherical undulation, and the larger the a, the larger the undulation, and the smaller a, the closer to the plane.

  In the Alvarez lens, as shown in FIG. 6A, two lenses having a central thickness d are arranged with a gap s therebetween. In the drawing, for convenience of explanation, the aspherical undulation and the interval s are exaggerated, but the actual undulation a and the interval s are very small. The interval s is preferably small, and is preferably about several μm to several hundred μm. FIG. 6B shows a state in which only one element is laterally shifted in the x direction.

Aspheric _f 1 (x, y) and the aspherical shape _f 2 (x, y) of the optical element O2 of the optical element O1 in the initial state shown in FIG. 6 (A) for the unevenness of the match completely, the optical element The optical system composed of O1 and the optical element O2 functions in the same manner as a plane-parallel plate having no optical power. Here, when the optical element O2 is moved in the x direction by a distance Δ as shown in FIG. 6B, the optical path length difference from the initial state is as follows. n is the refractive index of the lens.
Optical path length difference = (n · d ′ + s ′) − (n · d + s)
= (1-n) (f ₁ (x + Δ, y) −f ₂ (x, y)) (2)

Here, if the influence of the second and higher order terms of Δ is small and ignored, the result is as follows.
Optical path length difference = (1−n) (3aΔ (x ² + y ² ) + (c ₁ −c ₂ )) (3)
Therefore, a term of (x ² + y ² ) is generated by the lateral shift amount Δ, and thus the optical system composed of the optical elements O1 and O2 has a rotationally symmetric power with respect to the optical axis. Moreover, the power can be freely controlled by the lateral shift amount Δ.

For example, when the size of one side of the image sensor 306 is 20 mm, the radius of the visual field of the correction optical system 307a is 10 mm. If the amount to be generated as a power component is 1 mm, the shift amount Δ at this time is 1 mm, and the refractive index of the lens is 1.5, a = 6.7 × 10 ⁻³ from Equation (3).
In such an optical element, when the optical element is laterally shifted by 1 mm (Δ = 1), a power component is generated by 1 mm, and when the optical element is laterally shifted by 2 mm (Δ = 2), a power component is generated by 2 mm.
In this example, only one optical element is moved, but the same result can be obtained by moving both elements in the opposite direction by Δ / 2.

  Next, an example in which two types of aberration correction are performed independently by combining a plurality of Alvarez lenses will be described with reference to FIGS. In the following example, the focus position is corrected using the optical elements O1 and O2, and the magnification change is corrected using the optical elements O2 and O3.

In the Alvarez lens shown in FIG. 6C, three optical elements O1 to O3 having a central thickness d are arranged with an interval s. The surfaces of the optical elements O1 and O2 facing each other are aspherical surfaces having the same shape, and the shape is the same as that shown in FIG. That is, the aspherical shape of the optical element O1 on the optical element O2 side is f ₁ (x, y), and the aspherical shape of the optical element O2 on the optical element O1 side is f ₂ (x, y). Further, the faces of the optical elements O2 and O3 facing each other are also aspherical surfaces having the same shape. The aspherical shape on the optical element O3 side of the optical element O2 is f ₃ (x, y), and the aspherical shape on the optical element O2 side of the optical element O3 is f ₄ (x, y). That is, both surfaces of the middle optical element O2 are aspheric.

The optical characteristics and functions of the optical elements O1 and O2 are the same as those described with reference to FIGS. On the other hand, the optical characteristics and functions of the optical elements O2 and O3 are as follows. Assuming that the shifting direction is the x direction, the aspherical shapes of the optical elements O2 and O3 are given by the following equations that differ by a constant term. In order to change the magnification by laterally shifting the element in the x direction, x is used up to the fourth order term, and y is used up to the third order term. For simplicity, the constant term is omitted.
f ₃ (x, y) = b (x ⁴ + 4xy ³ )
f ₄ (x, y) = b (x ⁴ + 4xy ³ ) (4)

Here, when the optical element O3 is moved in the x direction by the distance Δ ′ without moving the optical element O2 as shown in FIG. 6D, the optical path length difference from the initial state is as follows. n is the refractive index of the lens. Here, the influence of the second and higher order terms of Δ ′ is neglected because it is small.
Optical path length difference = (1−n) (4bΔ ′ (x ³ + y ³ )) (5)
Accordingly, a term of (x ³ + y ³ ) is generated by the lateral shift amount Δ ′, and thus the optical elements O2 and O3 change in magnification. Moreover, the amount can be freely controlled by the lateral shift amount Δ ′.

As an example, if the size of one side of the image sensor is 20 mm, the field radius of the correction optical system is 10 mm. Assuming that the amount of change in magnification is 1 mm, the shift amount Δ ′ at this time is 1 mm, and the refractive index of the lens is 1.5, b = 5.0 × 10 ⁻⁴ from equation (5).

As another example, an example in which spherical aberration is corrected using optical elements O2 and O3 will be described. The aspherical shape of the optical element O2 is f ₃ (x, y), and the aspherical shape of the optical element O3 is f ₄ (x, y). Assuming that the shifting direction is the x direction, the aspheric shapes of the two are given by the following formulas that differ by a constant term. In order to generate spherical aberration by laterally shifting the element in the x direction, x is used up to the fifth order term and y is used up to the fourth order term. For simplicity, the constant term is omitted.
f ₃ (x, y) = b (x ⁵ + 5xy ⁴ )
f ₄ (x, y) = b (x ⁵ + 5xy ⁴ ) (6)

Here, when the optical element O3 is moved in the x direction by the distance Δ ′ without moving the optical element O2 as shown in FIG. 6D, the optical path length difference from the initial state is as follows. n is the refractive index of the lens. Here, the influence of the higher-order terms of Δ ′ or higher is ignored because it is small.
Optical path length difference = (1−n) (5bΔ ′ (x ⁴ + y ⁴ )) (7)

Therefore, the term (x ⁴ + y ⁴ ) is generated by the lateral shift amount Δ ′, and thus the optical elements O2 and O3 generate spherical aberration. Moreover, the amount can be freely controlled by the lateral shift amount Δ ′.
As an example, assuming that the amount of spherical aberration to be generated is 1 mm, the field radius of the correction optical system is 10 mm, the shift amount Δ ′ at this time is 1 mm, and the refractive index of the lens is 1.5, b = 4 from equation (7). 0.0 × 10 ⁻⁵ .

The lateral shift direction of the optical elements O1 and O2 may be orthogonal to the lateral shift direction of the optical elements O2 and O3. Examples thereof are shown in FIGS. 6 (E) to (G).
As described above, the optical elements O1 and O2 can correct the focal position, the magnification error, or the spherical aberration by laterally shifting the element in the x direction. On the other hand, the optical elements O2 and O3 correct the distortion change by shifting the element in the y direction.

In order to correct distortion by shifting the element in the y direction, x uses up to the fifth order term and y uses up to the sixth order term. The constant term is omitted.
f ₃ (x, y) = b (y ⁶ + 6yx ⁵ )
f ₄ (x, y) = b (y ⁶ + 6yx ⁵ ) (8)

Here, when the optical element O3 is moved in the y direction by a distance Δ ′ as shown in FIG. 6G, the optical path length difference from the initial state is as follows. n is the refractive index of the lens. Here, the influence of the higher-order terms of Δ ′ or higher is ignored because it is small.
Optical path length difference = (1−n) (6bΔ ′ (x ⁵ + y ⁵ )) (9)

Accordingly, the term (x ⁵ + y ⁵ ) is generated by the lateral shift amount Δ ′, and thus the optical elements O2 and O3 generate distortion. Moreover, the amount can be freely controlled by the lateral shift amount Δ ′.
As an example, if the amount of distortion is 1 mm, the radius of the visual field of the correction optical system is 10 mm, the shift amount Δ ′ at this time is 1 mm, and the refractive index of the lens is 1.5, b = 3.3 × 10 ⁻⁶ .

  Since the work of shifting and taking the difference is differentiation itself, the (n + 1) th order term is inserted in the direction of shifting as an aspherical shape, and the nth order term is inserted in the direction orthogonal to the shifting direction. If the component is output, it is possible to correct the n-th order aberration. In these examples, an aspherical surface that corrects symmetrical aberrations in the x and y directions is given, but aberration correction in only one direction can also be performed in the x and y directions. It is also possible to correct aberrations that are different in the x and y directions.

FIGS. 13A and 13B show preferable examples of the arrangement of the image sensor 306 and the aberration correction unit 307. FIGS. 13A and 13B are plan views of the imaging unit 305 as viewed from the imaging optical system 304 side. Here, an Alvarez lens composed of optical elements O1 and O2 is shown as the aberration correction unit 307, and it is assumed that the imaging element 306, the optical element O1, and the optical element O2 are arranged in this order from the back of the drawing. FIG. 13A shows an initial state (a state before driving the Alvarez lens). In each of the aberration correction units 307, a pair of optical elements O having an aspheric surface having the same shape.
1 and O2 face each other with their centers aligned, and no aberration correction is performed. FIG. 13B shows a state in which aberration is generated by relatively shifting the optical elements O1 and O2 in the lateral direction. As shown in FIG. 13B, when the image sensor units are alternately arranged for each row, the interval between the image sensor units in the same column can be increased, and the movement distance of the optical element in the column direction can be increased. If the movement distance, that is, the relative shift amount of the optical elements O1 and O2 can be increased, the aberration correction amount can be easily controlled, and the aspherical amount can be reduced, so that aberration other than the intended aberration occurs. There is an advantage that it is difficult to do.

  By arranging a plurality of image sensor units including the aberration correction unit 307 as described above in the field of view of the imaging optical system 304 and independently controlling each of the aberration correction units 307, aberrations can be independently made in place. Correction can be performed. That is, by individually controlling the aberration correction unit 307 provided for each image sensor 306, it is possible to individually correct aberrations for light incident on the plurality of image sensors 306.

<Example 2>
In the second embodiment, an example will be described in which aberrations and focal position deviations due to uneven thickness of the cover glass are corrected.
Depending on the uneven thickness of the cover glass, the imaging position may move in the optical axis direction, or the light beam (focal plane) may be tilted, so that the imaging surface of the imaging element 306 may be out of the focal depth. In order to solve this, as shown in FIG. 2C, the correction optical system performs correction similar to moving or tilting the image sensor 306 in the optical axis direction according to the surface shape (unevenness) of the cover glass. Can also be realized.

  The first embodiment shows that the imaging position can be moved in the optical axis direction by changing the optical power (focal length) by an optical system called an Alvarez lens. Similarly, the light beam (focal plane) can be tilted as follows.

  FIG. 8A shows an Alvarez lens composed of four optical elements O1, O2, O3 and O4. The optical elements O1 and O2 form a pair, and the faces of the two elements facing each other are aspherical surfaces having the same shape, and the outer faces are flat. Further, the optical elements O3 and O4 are paired, and the faces of the two elements facing each other are aspherical surfaces having the same shape, and the outer faces are flat. If the outer surface is a flat surface, there is an advantage that the control of the correction optical system 307a is simplified because no aberration occurs from the outer surface when the surface is shifted laterally. However, the outer surface does not necessarily have to be a flat surface.

In the figure, the Z axis is the optical axis. The X and Y axes are taken perpendicular to the optical axis. The aspherical shape of the optical element O1 is f ₁ (x, y), the aspherical shape of the optical element O2 is f ₂ (x, y), the aspherical shape of the optical element O3 is f ₃ (x, y), and the optical element Let the aspherical shape of O4 be f ₄ (x, y). Assuming that the direction in which the optical element O1 or O2 is shifted is the x direction, the aspheric shapes of the two are given by the following formulas that differ by a constant term. In order to generate an inclination in the x direction by laterally shifting the element in the x direction, x uses up to a quadratic term. The constant term is omitted.
f ₁ (x, y) = ax ²
f ₂ (x, y) = ax ² (10)

Since the optical element O3 or O4 is inclined in the y direction by shifting in the y direction, y uses up to the second order term. If the constant term is omitted, the aspheric shapes of the optical elements O3 and O4 are given by the following equations.
f ₃ (x, y) = by ²
f ₄ (x, y) = by ² (11)
The coefficients a and b of the optical elements and the interval s between the optical elements are small as in the first embodiment.

In an initial state where the elements are not laterally shifted, the optical system composed of the optical elements O1 and O2, and the optical elements O3 and O4 is a mere plane-parallel plate. Here, the optical element O2 is not moved as shown in FIG. 8A, the optical element O1 is moved in the x direction by the distance Δ, and the optical element O4 is not moved as shown in FIG. 8B. Move in the y direction by a distance Δ ′. Then, the optical path length difference from the initial state is as follows when the second and higher order terms of Δ are omitted. n is the refractive index of the lens.
Optical path length difference in x direction = (1−n) (2aΔx)
Optical path length difference in y direction = (1−n) (2bΔ′y) (12)

Therefore, the tilts of the focal planes in the x and y directions are independently generated by the lateral shift amount Δ in the x direction and the lateral shift amount Δ ′ in the y direction.
As an example, assuming that the radius of the field of view of the correction optical system is 10 mm, the optical path length difference in the x direction is 10 μm at the maximum in order to generate a tilt of 1 mrad, the shift amount Δ at this time is 1 mm, and the refractive index of the lens is Assuming 1.5, a = 10 ⁻³ from Equation (12).

Alternatively, the tilt of the focal plane in the y direction can be controlled by moving the optical element in the x direction as shown in FIG.
In FIG. 8C, the aspheric shapes of the optical elements O1 and O2 are the same as those in the equation (10), but the aspheric shapes of the optical elements O3 and O4 are as follows.
f ₃ (x, y) = 2bxy
f ₄ (x, y) = 2bxy (13)

  Here, as shown in FIG. 8C, when the optical element O1 (or O2) is moved in the x direction by the distance Δ and the optical element O4 (or O3) is moved in the x direction by the distance Δ ′, the equation (12) is obtained. Such focal plane inclination occurs independently. The optical element having an aspherical shape represented by Expression (13) can also control the tilt of the focal plane in the x direction by moving the optical element in the y direction.

  Alternatively, as shown in FIG. 8D, the magnitude of the tilt of the focal plane in the x direction is controlled by moving the set of optical elements in the x direction, and the set of optical elements is rotated around the optical axis. Accordingly, the direction of inclination can be set to an arbitrary direction.

  One set or two sets of Alvarez lenses having a secondary aspherical shape as shown by these formulas (10), (11), and (13), and the formula (1) shown in the first embodiment. And a pair of Alvarez lenses having a third-order aspherical shape as described above. Then, it becomes possible to move the imaging position (focal length) in the optical axis direction and tilt the focal plane.

Here, an example in which the focal position is adjusted in the vicinity of the surface of the specimen will be described with reference to FIGS.
First, the measurement unit 100 measures the approximate shape, size, center position, and the like of the sample (observation object) included in the preparation. In addition, the surface shape (surface irregularities) of the preparation is measured. FIG. 11A shows the surface shape of the preparation measured by the measurement unit 100 as a gray image. The center of the observation object is the origin, the horizontal axis is the position in the X direction, and the vertical axis is the position converted to the size on the image plane in the Y direction (unit: mm). The surface position (height) converted to the size on the image plane is shown. This figure shows that white is the highest and the height is lower as it approaches black. It can be seen that the surface height varies due to uneven thickness of the protective member and unevenness of the sample itself.
The position in the XY direction of the surface shape of this preparation was converted to the size on the image plane by multiplying the actual position of the sample on the preparation by the magnification of the optical system. The magnification of the optical system is 10 times as described above. The amount of unevenness on the surface of the preparation is also converted to the size on the image plane, and the amount of unevenness of the sample on the actual preparation is multiplied by the square of the magnification.

  Next, the control unit 400 calculates the correction amount in each small section using the measurement data in FIG. FIG. 11 (B) shows a dividing line representing a small section which is an imaging unit superimposed on measurement data. The size of the small section is determined by the size of the effective light receiving surface 306a of the image sensor 306. One small section is an area where one image sensor 306 captures an image at a time. Here, the size of the small section is 20 mm × 20 mm on the image plane.

  To focus on a sample surface having an inclination, an image of the sample surface is formed on the light receiving surface of the image sensor 306 by inclining the focal plane of the optical system so as to cancel the inclination of the sample surface. Good. In the present embodiment, the control unit 400 calculates the least square plane of the surface of each small section from the measurement data, and converts the least square plane into parallel with the light receiving surface of the image sensor 306 so that the aberration correction unit 307 performs the conversion. Determine the correction amount.

  FIG. 12A illustrates a surface shape 11 of a certain small section and a least square plane 12 approximated to the surface shape 11. FIG. 12 (A) shows a bird's-eye view of the surface shape of one small section shown in FIG. 11 (B). The height direction of the coordinate system in FIG. 11B is Z, and Z = 0 is the focal position of the imaging optical system 304.

When the least square plane 12 of the surface shape 11 was calculated using a known least square approximation, a plane represented by the following equation was obtained.
Z (x, y) = αx + βy + χ
α = 0.013575, β = 0.007186, χ = 0.856061 (14)
Therefore, the inclination in the X direction is 13.6 mrad, the inclination in the Y direction is 7.2 mrad, and the height of the center position (x = 10, y = −90) is z = 0.345 mm.

  FIG. 12B conceptually illustrates a state in which the surface inclination is corrected by the Alvarez lens. The optical image 13 of the sample surface obtained through the imaging optical system 304 has unevenness and inclination according to the surface shape of the preparation. By controlling the optical elements O1 to O4 so as to cancel the inclination of the least square plane 14 of the light image 13, the light image 13 on the sample surface is corrected to an image 15 substantially parallel to the light receiving surface of the image sensor 306. . That is, the aberration correction unit 307 of the present embodiment makes the focal plane of the optical system parallel to the least square plane of the sample surface by using the optical elements O1 to O4, instead of tilting the imaging element 306 as shown in FIG. It is what you want to do.

Here, the aspherical shapes of the optical elements O1 and O2 are as shown by the equation (10), and the aspherical shapes of the optical elements O3 and O4 are as shown by the equation (13). .
Since the size of the image sensor 306 is 20 mm per side, the field radius of the correction optical system 307a is 10 mm. If the aspherical coefficient a = b = 10 ⁻³ and the refractive index of the lens is 1.5, the shift amount Δ = 13.6 mm and Δ ′ = 7 in order to coincide with the plane represented by the equation (14). It is only necessary to drive each optical element by 2 mm. At this time, if the shift amount is measured using a laser interferometer, the relative positional accuracy of the correction optical system 307a can be guaranteed.

Then, the center position of the image sensor 306 is moved by 0.345 mm in the optical axis direction. Alternatively, another set of optical elements whose aspherical shape is represented by the formula (1) may be increased, and movement of the imaging position in the optical axis direction may be realized by the correction optical system 307a. In that case, assuming that the field radius of the correction optical system 307a is 10 mm, the refractive index of the lens is 1.5, and a = 6.7 × 10 ⁻³ , the shift amount Δ is 0.345 mm from the equation (3).

As another example, as shown in FIG. 9A, the opposing surfaces of the pair of optical elements O1 and O2 may have an inclination that can be expressed by a linear function. The tilt can be set in an arbitrary direction by rotating one optical element around the optical axis. When the shapes of the opposing surfaces of the optical elements O1 and O2 match as shown in FIG. 9A, there is no inclination, but one optical element centering on the optical axis as shown in FIG. 9B. When O2 is rotated, the focal plane is tilted, and the tilt direction changes according to the direction of rotation. Such an optical system is known as a wedge prism.
Further, when the optical elements O1 and O2 are shifted and arranged as shown in FIG. 9C, the distance between the elements changes, so that the spherical aberration changes and the focal plane position can be changed in the optical axis direction. However, the magnitude of the tilt cannot be controlled.
As another example, a variable apex angle prism P as shown in FIG. 10A is also known. This optical element has a plane, and the tilt of the focal plane is set to an arbitrary size and direction by tilting an axis perpendicular to the plane with respect to the optical axis as shown in FIGS. 10B and 10C. can do.

<Example 3>
In Example 3, an example in which adaptive optics is used as the aberration correction unit 307 will be described. FIG. 7 shows one image sensor unit.

  The aberration correction unit 307 has a correction optical system 307a made of a liquid lens. By controlling the voltage applied from the drive unit 307b to the correction optical system 307a, the refractive index or shape of the liquid lens can be changed. Similar to the above-described embodiment, the aberration amount is obtained for each small section in accordance with the measurement data obtained from the measurement unit 100 or the temperature sensor 308, and the aberration is controlled by controlling the optical characteristics of the correction optical system 307a so as to cancel the aberration amount. Correction is possible.

  As the adaptive optics, a liquid crystal lens can be used in addition to the liquid lens. Alternatively, an optical element that adjusts the refractive index by filling the liquid lens with fine particles having a refractive index different from that of the liquid and changing the density of the fine particles can also be used.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. For example, although both the measurement unit 100 and the temperature sensor 308 are provided in FIG. 1, only one of them may be provided according to the type of aberration to be corrected. In the above-described embodiment, examples of correction targets include focal position shift, focal plane tilt, spherical aberration, magnification error (chromatic aberration of magnification), distortion aberration, and the like, but other aberrations may be corrected. . As the aberration correction unit 307, a plurality of correction optical systems may be combined, or different types of correction optical systems (for example, an Alvarez lens and adaptive optics) may be combined. Further, if the flatness of the imaging surface of each imaging device 306 is poor (the imaging surface is warped), the image acquired by each imaging device 306 may be distorted. It may be corrected (in conjunction with aberrations).

  304: Imaging optical system, 305: Imaging unit, 306: Imaging device, 307: Aberration correction unit, 400: Control unit

Claims (13)

An imaging unit;
An imaging optical system for enlarging an image of the sample and guiding it to the imaging unit;
Control means,
The imaging unit has a plurality of imaging element units for imaging the sample image divided into a plurality of small sections,
Each of the plurality of image pickup device units includes an aberration correction unit that corrects an aberration included in an image of a small section to be picked up, and an image pickup device that picks up an image corrected by the aberration correction unit.
The image pickup apparatus characterized in that the control means individually controls the correction amount of the aberration correction means of each image pickup device unit in accordance with the position of the small section to be picked up. The imaging unit obtains an entire image of the sample by repeatedly imaging while changing the relative positions of the plurality of image sensor units and the sample,
2. The control unit according to claim 1, wherein each time the relative position between the imaging element unit and the sample changes, the correction amount of each aberration correction unit is changed according to the position of the small section after the change. The imaging device described. The imaging apparatus according to claim 1, wherein the aberration correction unit includes a correction optical system having a variable optical characteristic provided between the imaging optical system and the imaging element. The imaging apparatus according to claim 3, wherein the correction optical system includes a plurality of optical elements that change optical characteristics by relatively moving in a direction orthogonal to the optical axis.   The imaging apparatus according to claim 3, wherein the correction optical system includes an optical element that changes an optical characteristic by an electrical action. The imaging apparatus according to claim 1, wherein the aberration correction unit includes a posture adjustment unit that adjusts a posture of the imaging element. The imaging apparatus according to claim 6, wherein the posture adjustment unit changes a position of the imaging element in an optical axis direction. The imaging apparatus according to claim 6, wherein the posture adjustment unit changes an inclination of an imaging surface of the imaging element. The imaging apparatus according to claim 6, wherein the attitude adjustment unit integrally changes the attitudes of the imaging element and the correction optical system. A measuring means for measuring the shape of the surface of the sample or the shape of the surface of the protective member covering the surface of the sample;
The said control means determines the correction amount with respect to either or both of the shift | offset | difference of a focus position and the inclination of a focal plane based on the measurement result of the said measurement means, The any one of Claims 1-9 characterized by the above-mentioned. The imaging device described in 1. A thickness measuring means for measuring the thickness of the protective member covering the surface of the sample;
The imaging apparatus according to claim 1, wherein the control unit determines a correction amount for spherical aberration based on a measurement result of the thickness measuring unit. A temperature measuring means for measuring the temperature of either or both of the imaging optical system and the sample;
12. The control unit according to claim 1, wherein the control unit determines a correction amount for a focal position shift, spherical aberration, magnification error, or distortion based on a measurement result of the temperature measurement unit. The imaging device according to item. The control means determines a correction amount for a focal position shift, spherical aberration, magnification error, or distortion based on a result of analyzing an image obtained by imaging a test chart by the imaging unit. The imaging device according to any one of claims 1 to 12.

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