JP7625904B2 - Autofocus device and microscope device - Google Patents

Description

The present invention relates to an autofocus device and a microscope device.

In recent years, attention has been focused on technology that uses microscope systems equipped with epifluorescence microscopes, confocal microscopes, and other microscopes to create two-dimensional or three-dimensional images of samples such as biological tissues, organs, and cells. These microscope systems are systems that irradiate a sample to which a fluorescent dye has been added with illumination light (excitation light), obtain the resulting fluorescence using a microscope, and then capture the image using a camera. Such microscope systems are capable of analyzing the behavior of biological tissues, organs, cells, and other samples, and are therefore widely used in fields ranging from basic biological research to applied development in drug discovery.

Since such microscope systems are often used to sequentially observe samples contained in multiple depressions (wells) formed in a well plate, many of them are equipped with an autofocus device that automatically focuses the objective lens on the sample. The following Patent Document 1 discloses a conventional autofocus device that determines the focus error from the detection signal of a four-segment photodiode and focuses the objective lens to the position where the focus error is minimized.

Patent No. 4974062

The conventional autofocus device disclosed in the above-mentioned Patent Document 1 first sequentially detects focus errors while moving the objective lens in a direction approaching the well plate. Next, it finds the position (focus position) where the detected focus error is minimal, and moves the objective lens in the reverse direction so that the objective lens focuses on that position. In this way, conventionally, the objective lens is moved so that its focus passes through the well plate (overrun), and then the objective lens is moved in the reverse direction by the amount of the overrun, which results in a problem of a long time being required to focus the objective lens on the sample.

The present invention has been made in consideration of the above circumstances, and aims to provide an autofocus device and microscope device that can shorten the time required to focus an objective lens on an object.

In order to solve the above problem, an autofocus device (20, 30, 40) according to one aspect of the present invention includes a drive unit (25) that moves an objective lens (11) in the optical axis (AX) direction, a detection unit (27, 28, 31, 32, SN) that detects whether an object (WP) is placed at a detection position (DP) that is shifted from the focal plane (PL) of the objective lens by a predetermined reference distance (d), and a control unit (29) that drives the drive unit to move the objective lens by the reference distance and control the objective lens to focus on the object when the detection unit detects that the object is placed at the detection position.

In addition, in an autofocus device according to one aspect of the present invention, the detection position is a position on the optical axis of the objective lens, which is a position away from the focal plane by the reference distance in a forward direction, which is a direction from the objective lens toward the focal plane.

In addition, in an autofocus device according to one aspect of the present invention, the control unit drives the drive unit to move the objective lens in the forward direction until the detection unit detects that the object is placed at the detection position.

In one aspect of the present invention, the autofocus device includes a detection unit arranged at a position optically conjugate with the detection position via the objective lens, a split photodiode (28) whose detection surface is divided into multiple parts, and a cylindrical lens (27) arranged on the optical path between the objective lens and the split photodiode.

Alternatively, in one aspect of the present invention, the autofocus device includes a pinhole plate (31) in which the detection unit has a pinhole (31a) positioned at a position optically conjugate with the detection position via the objective lens, and a photodiode (32) that receives light passing through the pinhole.

The autofocus device according to one aspect of the present invention also includes a light source unit (21) that emits light that is focused at the focal point of the objective lens.

Alternatively, in an autofocus device according to one aspect of the present invention, the detection unit includes a triangulation type displacement sensor (SN).

A microscope device (1) according to one aspect of the present invention includes an objective lens (11), a microscope (12) to which light from a target object (WP) is guided via the objective lens, and an autofocus device (20, 30, 40) described above that focuses the objective lens on the target object.

The present invention has the advantage of being able to reduce the time it takes to focus the objective lens on the object.

1 is a diagram showing a configuration of a main part of a microscope system according to a first embodiment. 1 is an enlarged view of an autofocus device according to a first embodiment of the present invention; 4A to 4C are diagrams for explaining an optical image formed on a four-segment photodiode and a detection signal output from the four-segment photodiode in the first embodiment of the present invention. 5 is a flowchart showing an example of the operation of the autofocus device according to the first embodiment of the present invention. 5A to 5C are diagrams for explaining the operation of the autofocus device according to the first embodiment of the present invention. FIG. 11 is a diagram showing a configuration of a main part of an autofocus device according to a second embodiment of the present invention. FIG. 13 is a diagram showing a configuration of a main part of an autofocus device according to a third embodiment of the present invention. FIG. 13 is a block diagram showing a configuration of a main part of a displacement sensor according to a third embodiment of the present invention.

The autofocus device and microscope device according to the embodiment of the present invention will be described in detail below with reference to the drawings. First, an overview of the embodiment of the present invention will be described, followed by a detailed description of the embodiment of the present invention.

〔overview〕
An embodiment of the present invention provides an autofocus device and a microscope device that can shorten the time required to focus an objective lens on an object. Specifically, the time required to focus an objective lens on an object is shortened by reducing the movement of the objective lens.

The autofocus device disclosed in the above-mentioned Patent Document 1 calculates the focus error from the detection signal of the four-segment photodiode, and focuses the objective lens at the position where the focus error is minimal. Here, when the objective lens is focused on the object (in-focus state), the focus error is small, and when the objective lens is not focused on the object (out-of-focus state), the focus error is large.

The autofocus device disclosed in the above-mentioned Patent Document 1 moves (overruns) the focal point of the objective lens so that it passes through the object in order to detect the in-focus position. Then, once the in-focus position (the position where the focus error is minimal) is detected, the objective lens is moved in the opposite direction by the amount of overrun. Thus, in the past, it was necessary to overrun the objective lens and then move it in the opposite direction, which lengthened the time required to focus the objective lens on the object.

In an embodiment of the present invention, a detection unit is provided that detects whether an object has been placed at a detection position that is shifted a predetermined reference distance from the focal plane of the objective lens, and when the detection unit detects that an object has been placed at the detection position, the objective lens is moved the reference distance to adjust the focus of the objective lens to the object. This allows the movement of the objective lens to be reduced compared to conventional techniques, and shortens the time required to adjust the focus of the objective lens to the object.

First Embodiment
Microscope System
Fig. 1 is a diagram showing the main components of a microscope system according to the first embodiment. As shown in Fig. 1, the microscope system MS of this embodiment includes a microscope device 1, a confocal scanner 2, and a camera 3. Such a microscope system MS irradiates a sample SP contained in a well plate WP (object) with excitation light, and captures the resulting fluorescence with the camera 3 via the confocal scanner 2, thereby obtaining a confocal image of the sample SP.

The well plate WP is a transparent plate-like device in which a large number of wells W (wells) are formed to hold the samples SP. The well plate WP is placed on an XY stage (not shown) with the surface in which the wells W are formed facing upward, and is movable within a horizontal plane. The samples SP are, for example, biological tissues, organs, cells, etc. to which a fluorescent dye has been added.

The microscope device 1 includes an observation optical system 10 and an autofocus device 20. The observation optical system 10 is an optical system for observing a sample SP, and includes an objective lens 11 and a microscope 12. The observation optical system 10 is preferably an infinity-corrected optical system. The objective lens 11 is disposed near the bottom surface of the well plate WP, and irradiates the sample SP with excitation light, while outputting the fluorescence obtained by irradiating the sample SP with the excitation light toward the microscope 12. The microscope 12 guides the fluorescence output from the objective lens 11 and transmitted through a dichroic mirror 24 (described in detail later) to the confocal scanner 2. Details of the autofocus device 20 will be described later.

The confocal scanner 2 constitutes a confocal optical system together with the observation optical system 10 provided in the microscope device 1. The confocal scanner 2 includes, for example, a rotating disk having a microlens array disk and a pinhole array disk attached to a rotating shaft, and scans the fluorescence guided by the microscope 12 by rotating the rotating disk.

The camera 3 obtains a confocal image of the sample SP by capturing the fluorescence output from the confocal scanner 2. The camera 3 is equipped with a solid-state imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and is capable of capturing two-dimensional still images or videos. The confocal image of the sample SP obtained by the camera 3 may be displayed, for example, on a display device (not shown).

<Autofocus device>
Fig. 2 is an enlarged view of the autofocus device according to the first embodiment of the present invention. As shown in Figs. 1 and 2, the autofocus device 20 includes a laser 21 (light source unit), a lens group 22, a half mirror 23, a dichroic mirror 24, an actuator 25 (drive unit), a collimator lens 26, a cylindrical lens 27 (detection unit), a four-segment photodiode 28 (detection unit, segmented photodiode), and a control unit 29. Note that the control unit 29 is not shown in Fig. 1.

The laser 21 emits laser light (hereinafter, referred to as detection light) that is focused at the focal point FP of the objective lens 11. The detection light emitted from the laser 21 is used to achieve autofocus (automatically aligning the focal point FP of the objective lens 11 with the target object). In the following, to simplify the explanation and make it easier to understand, it is assumed that the focal point of the objective lens 11 is aligned with the bottom surface of the well plate WP by the autofocus device 20.

The lens group 22 converts the detection light emitted from the laser 21 into parallel light. The half mirror 23 reflects a portion (e.g., half) of the detection light converted into parallel light by the lens group 22 toward the dichroic mirror 24, and transmits a portion (e.g., half) of the detection light reflected from the dichroic mirror 24.

The dichroic mirror 24 is disposed on the optical path between the objective lens 11 and the microscope 12 provided in the observation optical system 10, and transmits the excitation light irradiated to the sample SP and the fluorescence obtained from the sample SP, and reflects the detection light used for autofocus. Under the control of the control unit 29, the actuator 25 moves the objective lens 11 in a direction along the optical axis AX (e.g., vertically). As the objective lens 11 moves, the focus FP and focal plane PL of the objective lens 11 also move in a direction along the optical axis AX.

The collimating lens 26 focuses the detection light that is reflected from the dichroic mirror 24 and transmitted through the half mirror 23. The cylindrical lens 27 is a lens with a flat entrance surface and a cylindrical exit surface, and focuses the detection light only in a specific direction (the direction in which the exit surface has a curvature). The four-segment photodiode 28 is a photodiode whose detection surface is divided into four regions. The cylindrical lens 27 and the four-segment photodiode 28 are provided to detect focus errors by the astigmatism method.

The positions of the collimator lens 26 and the cylindrical lens 27 are adjusted so that the detection light reflected at the detection position DP shown in FIG. 2 is irradiated onto the center of the four-segment photodiode 28. In other words, the four-segment photodiode 28 is disposed at a position where the center of its detection surface is optically conjugate with the detection position DP via the objective lens 11. Thus, in this embodiment, the detection position DP, which is the reference when the autofocus device 20 detects a focus error, is set at a position different from the focus FP of the objective lens 11.

The detection position DP is set in this manner in order to detect whether or not the bottom surface of the well plate WP is located at the detection position DP before the focus FP of the objective lens 11 reaches the bottom surface of the well plate WP. In addition, by reducing the movement of the objective lens 11 compared to conventional techniques, the time required to align the focus FP of the objective lens 11 with the bottom surface of the well plate WP is shortened.

The detection position DP is a position that is shifted from the focal plane PL of the objective lens 11 by a predetermined reference distance d. More specifically, the detection position DP is a position on the optical axis AX of the objective lens 11 that is shifted from the focal plane PL by the reference distance d in the forward direction, which is the direction from the objective lens 11 toward the focal plane PL. Note that the reference distance d is not limited to a specific distance and can be set to any distance.

Figure 3 is a diagram for explaining the optical image formed on the four-segment photodiode and the detection signal output from the four-segment photodiode in the first embodiment of the present invention. Note that Figures 3(a) and (b) are diagrams showing an example of the optical image of the detection light formed on the detection surface of the four-segment photodiode 28, and Figure 3(c) is a diagram showing an example of the detection signal output from the four-segment photodiode 28.

3A and 3B, the detection surface of the four-segment photodiode 28 is divided into four regions 28a to 28d. If the signals output from these four regions 28a to 28d are designated A to D, respectively, the detection signal V output from the four-segment photodiode 28 is expressed by the following formula (1).
V=(A+C)-(B+D)...(1)
In other words, the magnitude of the detection signal V is calculated from the difference between the sum of the signals output from two non-adjacent regions (e.g., regions 28a and 28c) among the four regions 28a to 28d and the sum of the signals output from the remaining two regions (e.g., regions 28b and 28d).

The optical system on the light receiving side of the autofocus device 20 is an optical system having astigmatism due to the cylindrical lens 27. As described above, the four-segment photodiode 28 is disposed at a position where the center of its detection surface is optically conjugate with the detection position DP via the objective lens 11. Therefore, the optical image of the detection light formed on the detection surface of the four-segment photodiode 28 changes according to the position of the objective lens 11 (e.g., vertical position: Z-direction position). As a result, the detection signal V output from the four-segment photodiode 28 changes according to the position (Z) of the objective lens 11, as shown in FIG. 3(c).

For example, consider the case where the objective lens 11 is positioned so that the detection position DP shown in FIG. 2 is located vertically below the bottom surface of the well plate WP (the case where the objective lens 11 is positioned at position Z1 in FIG. 3(c)). In this case, as shown in FIG. 3(a), the elliptical detection light is imaged on the detection surface of the four-segment photodiode 28. As a result, the magnitude of the detection signal V output from the four-segment photodiode 28 becomes, for example, V1, as shown in FIG. 3(c).

In contrast, consider the case where the objective lens 11 is positioned so that the detection position DP shown in FIG. 2 is located on the bottom surface of the well plate WP (the case where the objective lens 11 is positioned at position Z2 in FIG. 3(c)). In this case, as shown in FIG. 3(b), the circular detection light is imaged on the detection surface of the four-segment photodiode 28. As a result, the magnitude of the detection signal V output from the four-segment photodiode 28 becomes, for example, zero (or nearly zero), as shown in FIG. 3(c).

The control unit 29 uses the detection signal output from the four-segment photodiode 28 to control the focus FP of the objective lens 11 to be aligned with the bottom surface of the well plate WP. Specifically, the control unit 29 drives the actuator 25 to move the objective lens 11 forward until the absolute value of the detection signal output from the four-segment photodiode 28 becomes minimum (e.g., until it becomes zero). Note that the absolute value of the detection signal output from the four-segment photodiode 28 becomes minimum when the bottom surface of the well plate WP is positioned at the detection position DP.

When the absolute value of the detection signal output from the four-segment photodiode 28 becomes minimum, the control unit 29 drives the actuator 25 to control the objective lens 11 to move forward by a reference distance d. By performing such control, the focus of the objective lens 11 can be adjusted to the bottom surface of the well plate WP. The reference distance d is stored in advance in the control unit 29.

<Autofocus Device Operation>
Fig. 4 is a flowchart showing an example of the operation of the autofocus device according to the first embodiment of the present invention. Fig. 5 is a diagram for explaining the operation of the autofocus device according to the first embodiment of the present invention. The flowchart shown in Fig. 4 is started every time a sample SP to be observed, among the samples SP contained in the well plate WP, is placed above the objective lens 11 by driving the XY stage.

When the process of the flowchart shown in FIG. 4 is started, first, the objective lens 11 is moved under the control of the control unit 29 while referring to the detection signal output from the four-segment photodiode 28 (step S11). Specifically, when the objective lens 11 is placed in the initial position, the control unit 29 starts driving the actuator 25. This starts the movement of the objective lens 11 in a direction along the optical axis AX (e.g., vertically upward: Z direction). Then, the objective lens 11 is moved while referring to the detection signal output from the four-segment photodiode 28 (see FIG. 5(a)).

Next, the control unit 29 performs a process to determine whether the absolute value of the detection signal output from the four-segment photodiode 28 has reached a minimum (step S12). Specifically, as shown in FIG. 3(c), the control unit 29 determines whether the absolute value of the detection signal output from the four-segment photodiode 28 has reached zero (or nearly zero) after reaching a peak. The absolute value of the detection signal output from the four-segment photodiode 28 reaches a minimum when the detection position DP reaches the bottom surface of the well plate WP (see FIG. 5(b)).

If it is determined that the absolute value of the detection signal output from the four-segment photodiode 28 is not at a minimum (if the result of the determination in step S12 is "NO"), the operation of step S11 continues (see FIG. 5(a)). On the other hand, if it is determined that the absolute value of the detection signal output from the four-segment photodiode 28 is at a minimum (if the result of the determination in step S12 is "YES"), the objective lens 11 is moved forward by the reference distance d under the control of the control unit 29 (step S13).

Specifically, the actuator 25 is driven by the control unit 29, and an operation is performed to move the objective lens 11 forward by a reference distance d stored in the control unit 29 from a state in which the detection position DP is located on the bottom surface of the well plate WP (see FIG. 5(b)). When the above operation is performed, the focal point FP of the objective lens 11 is located on the bottom surface of the well plate WP, and the focal point FP of the objective lens 11 is aligned with the object (see FIG. 5(c)). This completes the series of operations of the autofocus device 20.

The sample SP is observed by the observation optical system 10, the confocal scanner 2, and the camera 3 with the focal point FP of the objective lens 11 aligned with the object. When observation of the sample SP is completed, the actuator 25 is driven by the control unit 29 to return the objective lens 11 to its initial position. Then, the XY stage is driven to position the sample SP, which is the next object of observation, above the objective lens 11.

As described above, in this embodiment, whether or not an object (the bottom surface of the well plate WP) has been placed at the detection position DP is detected based on whether or not the absolute value of the detection signal output from the four-segment photodiode 28 has become a minimum. Then, when it is detected that an object has been placed at the detection position DP, the control unit 29 drives the actuator 25 to move the objective lens 11 by a reference distance d to align the focus FP of the objective lens 11 with the object. This allows the movement of the objective lens 11 to be reduced compared to the conventional method, and shortens the time required to focus the objective lens 11 on the object.

In addition, in this embodiment, the objective lens 11 is moved only in one direction (vertically upward) to align the focus FP of the objective lens 11 with the object. This eliminates the need to move the objective lens in the opposite direction after moving it so that the focus passes through the object (overrunning it), as was done conventionally, and therefore reduces vibration. As a result, not only can the time required to align the objective lens 11 with the object be shortened, but the objective lens 11 can also be aligned with high precision.

Conventionally, the time required for autofocus per cycle was approximately 440 msec. If the present embodiment can reduce the time required for autofocus by 85 msec per cycle, a time reduction of approximately 19% can be achieved. Conventionally, the time required to observe all of the samples SP stored in a well plate WP in which 96 recesses W are formed was approximately 60 seconds. With this embodiment, the time required to observe all of the samples SP stored in the same well plate WP can be reduced to approximately 52 seconds.

Second Embodiment
Microscope System
The microscope system according to this embodiment is configured by providing an autofocus device 30 shown in Fig. 6 instead of the autofocus device 20 shown in Fig. 1, and the configuration other than the autofocus device 30 is the same as that in Fig. 1. Therefore, a detailed description of the microscope system according to this embodiment will be omitted.

<Autofocus device>
Fig. 6 is a diagram showing the main configuration of an autofocus device according to a second embodiment of the present invention. An autofocus device 30 of this embodiment has a configuration in which the cylindrical lens 27 and the four-segment photodiode 28 of the autofocus device 20 shown in Fig. 2 are replaced with a pinhole plate 31 (detection unit) and a photodiode 32 (detection unit).

The pinhole plate 31 is a plate-like member in which a pinhole 31a is formed. The pinhole plate 31 is made of a light-blocking material. The pinhole plate 31 is arranged so that the pinhole 31a is located at a position optically conjugate with the detection position DP via the objective lens 11. The photodiode 32 detects the light that has passed through the pinhole 31a. The pinhole plate 31 and the photodiode 32 are provided to detect a focus error by the confocal method.

In this embodiment, when an object (the bottom surface of the well plate WP) is placed at the detection position DP, all of the detection light reflected by the object passes through the pinhole 31a. In contrast, when an object is placed at a position other than the detection position DP, the diameter of the detection light incident on the pinhole plate 31 increases, and the amount of light passing through the pinhole 31a decreases. Therefore, whether or not an object (the bottom surface of the well plate WP) is placed at the detection position DP can be detected based on whether or not the amount of light passing through the pinhole 31a is maximized (whether or not the detection signal of the photodiode 32 is maximized).

<Autofocus Device Operation>
The autofocus device 30 of this embodiment differs from the autofocus device 20 of the first embodiment only in the detection method, and performs the same operation as the autofocus device 20 of the first embodiment (the operation described with reference to FIG. 5 ). For this reason, a detailed description of the operation of the autofocus device 30 of this embodiment will be omitted.

As described above, in this embodiment, whether or not an object (the bottom surface of the well plate WP) has been placed at the detection position DP is detected based on whether or not the detection signal output from the photodiode 32 has reached a maximum. Then, when it is detected that an object has been placed at the detection position DP, the control unit 29 drives the actuator 25 to move the objective lens 11 by a reference distance d to align the focus FP of the objective lens 11 with the object. This allows the movement of the objective lens 11 to be reduced compared to the conventional method, and shortens the time required to focus the objective lens 11 on the object.

Furthermore, in this embodiment, as in the first embodiment, the objective lens 11 is moved only in one direction (vertically upward) to align the focus FP of the objective lens 11 with the object. This makes it possible to reduce vibrations as in the first embodiment. As a result, not only can the time required to align the focus of the objective lens 11 with the object be shortened, but the objective lens 11 can also be aligned with high accuracy.

Third Embodiment
Microscope System
The microscope system according to this embodiment is configured with an autofocus device 40 shown in Fig. 7 instead of the autofocus device 20 shown in Fig. 1, and the configuration other than the autofocus device 40 is the same as that in Fig. 1. Therefore, a detailed description of the microscope system according to this embodiment will be omitted.

<Autofocus device>
Fig. 7 is a diagram showing the main configuration of an autofocus device according to a third embodiment of the present invention. An autofocus device 40 of this embodiment is configured by omitting the laser 21, the lens group 22, the half mirror 23, the dichroic mirror 24, the collimator lens 26, the cylindrical lens 27, and the four-segment photodiode 28 of the autofocus device 20 shown in Fig. 2, and by providing a displacement sensor SN (detection unit). The displacement sensor SN includes a light projector 41 and a light receiver 42, and detects whether or not an object (the bottom surface of the well plate WP) is placed at the detection position DP by a triangulation method.

Figure 8 is a block diagram showing the main components of a displacement sensor in a third embodiment of the present invention. As shown in Figure 8, the light projector 41 of the displacement sensor SN is equipped with a laser 41a and a light projecting optical system 41b, and projects the laser light (hereinafter referred to as detection light) emitted from the laser 41a from an oblique direction toward the detection position DP. Note that the oblique direction here means a direction oblique to the optical axis AX of the objective lens 11 (or a direction oblique to the bottom surface of the well plate WP). The light receiver 42 of the displacement sensor SN is equipped with a light receiving optical system 42a and a detector 42b, and detects the detection light reflected by the bottom surface of the well plate WP.

When the bottom surface of the well plate WP is located at the detection position DP, the detection light reflected by the bottom surface of the well plate WP is imaged at the center of the detector 42b, as shown by the solid line in FIG. 8. In contrast, when the bottom surface of the well plate WP is not located at the detection position DP, the detection light reflected by the bottom surface of the well plate WP is imaged at a position different from the center of the detector 42b, as shown by the dashed line in FIG. 8. Therefore, whether or not an object (the bottom surface of the well plate WP) is located at the detection position DP can be detected depending on whether or not the detection light is imaged at the center of the detector 42b.

<Autofocus Device Operation>
The autofocus device 40 of this embodiment differs from the autofocus device 20 of the first embodiment only in the detection method, and performs the same operation as the autofocus device 20 of the first embodiment (the operation described with reference to FIG. 5 ). For this reason, a detailed description of the operation of the autofocus device 40 of this embodiment will be omitted.

As described above, in this embodiment, whether or not an object (the bottom surface of the well plate WP) has been placed at the detection position DP is detected based on whether or not the detection light has been imaged at the center of the detector 42b. Then, when it is detected that an object has been placed at the detection position DP, the control unit 29 drives the actuator 25 to move the objective lens 11 by a reference distance d to align the focus FP of the objective lens 11 with the object. This allows the movement of the objective lens 11 to be reduced compared to the conventional method, and shortens the time required to focus the objective lens 11 on the object.

Furthermore, in this embodiment, as in the first embodiment, the objective lens 11 is moved only in one direction (vertically upward) to align the focus FP of the objective lens 11 with the object. This makes it possible to reduce vibrations as in the first embodiment. As a result, not only can the time required to align the focus of the objective lens 11 with the object be shortened, but the objective lens 11 can also be aligned with high accuracy.

Although the autofocus device and microscope device according to the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be freely modified within the scope of the present invention. For example, in the above-described embodiments, an example was described in which the detection position DP is set on the optical axis AX of the objective lens 11. However, the detection position DP does not necessarily have to be set on the optical axis AX of the objective lens 11, and may be set at a position offset from the optical axis AX of the objective lens 11.

In the above-described embodiment, an example was described in which the detection position DP was set at a position that was a reference distance d away from the focal plane PL in the forward direction. However, the detection position DP may also be set at a position that was a reference distance d away from the focal plane PL in the direction opposite to the forward direction. When set in this way, for example, the initial position of the objective lens 11 may be set at a position close to the well plate WP, and the objective lens 11 may be moved away from the well plate WP to detect whether or not an object has been placed at the detection position DP.

REFERENCE SIGNS LIST 1 microscope device 11 objective lens 12 microscope 20 autofocus device 21 laser 25 actuator 27 cylindrical lens 28 four-segment photodiode 29 control unit 30 autofocus device 31 pinhole plate 31a pinhole 32 photodiode 40 autofocus device AX optical axis d reference distance DP detection position PL focal plane SN displacement sensor WP well plate

Claims (8)

A drive unit that moves the objective lens in the optical axis direction;
a detection unit that detects whether an object is placed at a detection position, the detection position being a reference for detecting a focus error, set at a position shifted by a predetermined reference distance from a focal plane of the objective lens; and
a control unit that drives the drive unit to move the objective lens by the reference distance and control the objective lens to focus on the object when the detection unit detects that the object is placed at the detection position; and
An autofocus device comprising: The autofocus device according to claim 1, wherein the detection position is a position on the optical axis of the objective lens, the position being spaced from the focal plane by the reference distance in a forward direction, which is a direction from the objective lens toward the focal plane. The autofocus device according to claim 2, wherein the control unit drives the drive unit to move the objective lens in the forward direction until the detection unit detects that the object is placed at the detection position. the detection unit is a split photodiode arranged at a position optically conjugate with the detection position via the objective lens, the split photodiode having a detection surface split into a plurality of parts;
a cylindrical lens disposed on an optical path between the objective lens and the segmented photodiode;
The autofocus device according to claim 1 , further comprising: the detection unit includes a pinhole plate arranged so that a pinhole is located at a position optically conjugate with the detection position via the objective lens;
a photodiode that receives light passing through the pinhole;
The autofocus device according to claim 1 , further comprising: The autofocus device according to any one of claims 1 to 5, further comprising a light source unit that emits light that is focused at the focal point of the objective lens. The autofocus device according to any one of claims 1 to 3, wherein the detection unit is equipped with a triangulation type displacement sensor. An objective lens;
a microscope into which light from an object is guided via the objective lens;
An autofocus device according to any one of claims 1 to 7, which adjusts the focus of the objective lens on the object;
A microscope apparatus comprising:

Images