Autofocus device and microscope device

Abstract

To provide an autofocus device and a microscope device that can reduce time required for adjusting a focus of an objective lens to an object.SOLUTION: An autofocus device 20 comprises: a driving unit 25 that moves an objective lens 11 in an optical axis direction; a detection unit 28 that detects whether an object is arranged at a detection position DP shifted by a predefined reference distance from a focal plane of the objective lens 11; and a control unit 29 that, when the detection unit 28 detects that the object is arranged at the detection position DP, performs control of driving the driving unit 25 to move the objective lens 11 by the reference distance to adjust the focus of the objective lens 11 to the object.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an autofocus device and a microscope device. [Background technology]

[0002] 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 with a microscope, and capture the image with a camera. Such microscope systems are capable of analyzing the behavior of samples such as biological tissues, organs, and cells, and are therefore widely used in fields ranging from basic biological research to applied development in drug discovery.

[0003] Such microscope systems are often used to sequentially observe samples contained in a number of depressions (wells) formed in a well plate, and so 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 finds a focus error from a detection signal from a four-segment photodiode and focuses the objective lens to a position where the focus error is minimized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4974062 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, 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, the position (focus position) where the detected focus error is minimum is obtained, and the objective lens is moved in the reverse direction so that the objective lens is focused at that position. In this way, conventionally, the objective lens is moved so that the 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 causes a problem that it takes a long time to focus the objective lens on the sample.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide an autofocus device and a microscope apparatus that can shorten the time required to focus an objective lens on an object. [Means for solving the problem]

[0007] In order to solve the above problem, an autofocus device (20, 30, 40) according to one embodiment 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 a predetermined reference distance (d) from a focal plane (PL) of the objective lens, and a control unit (29) that, when the detection unit detects that the object has been placed at the detection position, drives the drive unit to move the objective lens by the reference distance and control the objective lens to focus on the object.

[0008] 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, away from the focal plane by the reference distance in a forward direction, which is the direction from the objective lens toward the focal plane.

[0009] 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 has been placed at the detection position.

[0010] In addition, an autofocus device according to one embodiment of the present invention includes a detection unit arranged at a position optically conjugate with the detection position via the objective lens, a split photodiode (28) having a detection surface divided into multiple parts, and a cylindrical lens (27) arranged on the optical path between the objective lens and the split photodiode.

[0011] Alternatively, an autofocus device according to one embodiment of the present invention 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.

[0012] Moreover, the autofocus device according to one aspect of the present invention includes a light source unit (21) that emits light that is condensed at the focal point of the objective lens.

[0013] Alternatively, in the autofocus device according to one aspect of the present invention, the detection unit includes a triangulation type displacement sensor (SN).

[0014] A microscope apparatus (1) according to one embodiment of the present invention comprises an objective lens (11), a microscope (12) to which light from an object (WP) is guided via the objective lens, and an autofocus device (20, 30, 40) described above that focuses the objective lens on the object. Effect of the Invention

[0015] According to the present invention, it is possible to reduce the time required to focus the objective lens on the object. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram showing a configuration of a main part of a microscope system according to a first embodiment. [Diagram 2] 1 is an enlarged view of an autofocus device according to a first embodiment of the present invention. FIG. [Diagram 3] 4 is a diagram 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. FIG. [Figure 4] 5 is a flowchart showing an example of the operation of the autofocus device according to the first embodiment of the present invention. [Diagram 5] FIG. 2 is a diagram for explaining the operation of the autofocus device according to the first embodiment of the present invention. [Figure 6] FIG. 4 is a diagram showing a configuration of a main part of an autofocus device according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a diagram showing a configuration of a main part of an autofocus device according to a third embodiment of the present invention. [Figure 8] FIG. 11 is a block diagram showing a configuration of a main part of a displacement sensor according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an autofocus device and a microscope device according to an embodiment of the present invention will be described in detail with reference to the drawings. First, an overview of the embodiment of the present invention will be described, and then the embodiment of the present invention will be described in detail.

[0018] 〔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.

[0019] The autofocus device disclosed in the above-mentioned Patent Document 1 obtains a focus error from a detection signal of a four-segment photodiode, and focuses the objective lens at a position where the focus error is minimized. 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.

[0020] 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 position where the in-focus state is achieved. Then, when the in-focus position (the position where the focus error is minimized) is detected, the objective lens is moved in the reverse direction by the amount of overrun. Thus, in the past, it was necessary to overrun the objective lens and then move it in the reverse direction, which lengthened the time required to focus the objective lens on the object.

[0021] In an embodiment of the present invention, a detection unit is provided that detects whether or not an object is 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 is placed at the detection position, the objective lens is moved the reference distance to focus the objective lens on the object. This makes it possible to reduce the movement of the objective lens compared to conventional methods, and shorten the time required to focus the objective lens on the object.

[0022] [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 excitation light onto a sample SP contained in a well plate WP (object), and captures the resulting fluorescence with the camera 3 via the confocal scanner 2, thereby obtaining a confocal image of the sample SP.

[0023] The well plate WP is a transparent plate-like device in which a large number of wells W (wells) are formed for accommodating 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, living tissues, organs, cells, etc. to which a fluorescent dye has been added.

[0024] 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, and outputs 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.

[0025] The confocal scanner 2 constitutes a confocal optical system together with an 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 coupled to a rotating shaft, and scans the fluorescence guided by the microscope 12 by rotating the rotating disk.

[0026] 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 image capturing 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 on, for example, a display device (not shown).

[0027] <Autofocus device> Fig. 2 is an enlarged view of an autofocus device according to a first embodiment of the present invention. As shown in Figs. 1 and 2, an 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.

[0028] The laser 21 emits a laser light (hereinafter, referred to as detection light) that is focused on the focal point FP of the objective lens 11. The detection light emitted from the laser 21 is used to realize autofocus (automatically aligning the focal point FP of the objective lens 11 with the target object). In the following, for the sake of simplicity and ease of understanding, 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.

[0029] The lens group 22 converts the detection light emitted from the laser 21 into parallel light. The half mirror 23 reflects a part (e.g., half) of the detection light converted into parallel light by the lens group 22 toward the dichroic mirror 24, and transmits a part (e.g., half) of the detection light reflected from the dichroic mirror 24.

[0030] 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 on the sample SP and the fluorescence obtained from the sample SP, and reflects the detection light used for autofocus. The actuator 25 moves the objective lens 11 in a direction along the optical axis AX (for example, in the vertical direction) under the control of the control unit 29. In addition, 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.

[0031] The collimator lens 26 collects the detection light 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 collects 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 a focus error by an astigmatism method.

[0032] Here, 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 focal point FP of the objective lens 11.

[0033] The reason for setting such a detection position DP is to detect whether the bottom surface of the well plate WP is located at the detection position DP before the focal point FP of the objective lens 11 reaches the bottom surface of the well plate WP, and to shorten the time required to align the focal point FP of the objective lens 11 with the bottom surface of the well plate WP by reducing the movement of the objective lens 11 compared to the conventional method.

[0034] The detection position DP is a position shifted by a predetermined reference distance d from the focal plane PL of the objective lens 11. More specifically, the detection position DP is a position on the optical axis AX of the objective lens 11, which is a position separated by the reference distance d from the focal plane PL 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.

[0035] 3 is a diagram 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. Note that Figs. 3(a) and (b) are diagrams showing an example of an optical image of detection light formed on the detection surface of the four-segment photodiode 28, and Fig. 3(c) is a diagram showing an example of a detection signal output from the four-segment photodiode 28.

[0036] 3(a) and (b), 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 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).

[0037] 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 (for example, the position in the vertical direction: the position in the Z direction). 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).

[0038] For example, consider the case where the objective lens 11 is disposed 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 disposed at position Z1 in Fig. 3(c)). In this case, as shown in Fig. 3(a), an 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).

[0039] In contrast, consider the case where the objective lens 11 is disposed 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 disposed 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).

[0040] The control unit 29 performs control to align the focal point FP of the objective lens 11 with the bottom surface of the well plate WP using the detection signal output from the four-segment photodiode 28. 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 (for example, 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 located at the detection position DP.

[0041] When the absolute value of the detection signal output from the four-segment photodiode 28 becomes minimum, the control unit 29 controls the actuator 25 to move the objective lens 11 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 the control unit 29 in advance.

[0042] <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. Also, 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 accommodated in the well plate WP, is positioned above the objective lens 11 by driving the XY stage.

[0043] When the process of the flowchart shown in Fig. 4 is started, first, an operation of moving the objective lens 11 is performed 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 at 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 (for example, the vertical upward direction: Z direction). Then, an operation of moving the objective lens 11 is performed while referring to the detection signal output from the four-segment photodiode 28 (see Fig. 5(a)).

[0044] Next, the control unit 29 performs a process of determining whether or not the absolute value of the detection signal output from the four-segment photodiode 28 has become a minimum (step S12). Specifically, as shown in Fig. 3(c), the control unit 29 determines whether or not the absolute value of the detection signal output from the four-segment photodiode 28 has become zero (or nearly zero) after reaching a peak. The absolute value of the detection signal output from the four-segment photodiode 28 becomes a minimum when the detection position DP reaches the bottom surface of the well plate WP (see Fig. 5(b)).

[0045] If it is determined that the absolute value of the detection signal output from the four-segment photodiode 28 has not become 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 has become minimum (if the result of the determination in step S12 is "YES"), the operation of moving the objective lens 11 forward by the reference distance d is performed under the control of the control unit 29 (step S13).

[0046] 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 focus FP of the objective lens 11 is located on the bottom surface of the well plate WP, and the focus 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.

[0047] Incidentally, with the focal point FP of the objective lens 11 set on the object, the sample SP is observed by the observation optical system 10, the confocal scanner 2, and the camera 3. When the observation of the sample SP that is the observation target is completed, the actuator 25 is driven by the control unit 29 to perform an operation of returning the objective lens 11 to its initial position. Then, the XY stage is driven to perform an operation of positioning the sample SP, which is the next target for observation, above the objective lens 11.

[0048] 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 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 makes it possible to reduce the movement of the objective lens 11 compared to the conventional method, and shorten the time required to focus the objective lens 11 on the object.

[0049] Furthermore, in this embodiment, the objective lens 11 is moved only in one direction (vertically upward) to adjust the focus FP of the objective lens 11 to the object. This eliminates the need to move the objective lens in the opposite direction after moving the objective lens so that the focus passes through the object (overrunning it), as in the conventional method, and therefore reduces vibration. As a result, not only can the time required to adjust the focus of the objective lens 11 to the object be shortened, but the objective lens 11 can also be aligned with high accuracy.

[0050] Incidentally, it is assumed that the time required for autofocus per cycle was conventionally about 440 [msec]. If the time required for autofocus can be reduced by 85 [msec] per cycle by this embodiment, a time reduction of about 19% can be achieved. It is assumed that the time required for observing all the samples SP stored in a well plate WP having 96 recesses W formed therein was conventionally about 60 seconds. By this embodiment, the time required for observing all the samples SP stored in the same well plate WP can be reduced to about 52 seconds.

[0051] Second Embodiment Microscope System The microscope system according to this embodiment is configured with 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.

[0052] <Autofocus device> Fig. 6 is a diagram showing the main configuration of an autofocus device according to a second embodiment of the present invention. Autofocus device 30 of this embodiment has a configuration in which cylindrical lens 27 and four-segment photodiode 28 of autofocus device 20 shown in Fig. 2 are replaced with a pinhole plate 31 (detection unit) and a photodiode 32 (detection unit).

[0053] The pinhole plate 31 is a plate-like member in which a pinhole 31a is formed. The pinhole plate 31 is formed using a material having light-shielding properties. The pinhole plate 31 is disposed 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 light transmitted through the pinhole 31a. The pinhole plate 31 and the photodiode 32 are provided to detect a focus error by a confocal method.

[0054] In this embodiment, when the object (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 the object is placed at a position different from the detection position DP, the light diameter of the detection light incident on the pinhole plate 31 becomes large, and the amount of light passing through the pinhole 31a decreases. Therefore, whether or not the object (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).

[0055] <Autofocus Device Operation> Autofocus device 30 of this embodiment differs from autofocus device 20 of the first embodiment only in the detection method, and performs the same operation as autofocus device 20 of the first embodiment (the operation described using FIG. 5). Therefore, a detailed description of the operation of autofocus device 30 of this embodiment will be omitted.

[0056] 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 adjust the focus FP of the objective lens 11 to the object. This makes it possible to reduce the movement of the objective lens 11 compared to the conventional method, and shorten the time required to adjust the focus of the objective lens 11 to the object.

[0057] In this embodiment, similar to the first embodiment, the objective lens 11 is moved only in one direction (vertically upward) to adjust the focus FP of the objective lens 11 to the object. This makes it possible to reduce vibrations similar to the first embodiment. As a result, not only can the time required to adjust the focus of the objective lens 11 to the object be shortened, but also the objective lens 11 can be aligned with high accuracy.

[0058] 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.

[0059] <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 omits the laser 21, lens group 22, half mirror 23, dichroic mirror 24, collimator lens 26, cylindrical lens 27, and four-segment photodiode 28 of the autofocus device 20 shown in Fig. 2, and is provided with 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 a well plate WP) is placed at a detection position DP by a triangulation method.

[0060] Fig. 8 is a block diagram showing the main configuration of a displacement sensor in a third embodiment of the present invention. As shown in Fig. 8, a light projector 41 of the displacement sensor SN includes a laser 41a and a light projecting optical system 41b, and projects a laser light (hereinafter, called detection light) emitted from the laser 41a toward a detection position DP from an oblique direction. 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). A light receiver 42 of the displacement sensor SN includes 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.

[0061] When the bottom surface of the well plate WP is placed at the detection position DP, the detection light reflected by the bottom surface of the well plate WP forms an image 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 placed at the detection position DP, the detection light reflected by the bottom surface of the well plate WP forms an image 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 placed at the detection position DP can be detected depending on whether or not the detection light forms an image at the center of the detector 42b.

[0062] <Autofocus Device Operation> Autofocus device 40 of this embodiment differs from autofocus device 20 of the first embodiment only in the detection method, and performs the same operation as autofocus device 20 of the first embodiment (the operation described using FIG. 5). Therefore, a detailed description of the operation of autofocus device 40 of this embodiment will be omitted.

[0063] As described above, in this embodiment, whether or not an object (the bottom surface of the well plate WP) is placed at the detection position DP is detected based on whether or not the detection light is imaged at the center of the detector 42b. Then, when it is detected that the object is 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 adjust the focus FP of the objective lens 11 to the object. This makes it possible to reduce the movement of the objective lens 11 compared to the conventional method, and shorten the time required to adjust the focus of the objective lens 11 to the object.

[0064] In this embodiment, similar to the first embodiment, the objective lens 11 is moved only in one direction (vertically upward) to adjust the focus FP of the objective lens 11 to the object. This makes it possible to reduce vibrations similar to the first embodiment. As a result, not only can the time required to adjust the focus of the objective lens 11 to the object be shortened, but also the objective lens 11 can be aligned with high accuracy.

[0065] Although the autofocus device and microscope device according to the embodiment of the present invention have been described above, the present invention is not limited to the above embodiment and can be freely modified within the scope of the present invention. For example, in the above-mentioned embodiment, 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 shifted from the optical axis AX of the objective lens 11.

[0066] In the above embodiment, an example has been described in which the detection position DP is set at a position that is a reference distance d away from the focal plane PL in the forward direction. However, the detection position DP may be set at a position that is a reference distance d away from the focal plane PL in the direction opposite to the forward direction. In a case where such a setting is made, for example, the initial position of the objective lens 11 may be set at a position close to the well plate WP, and whether or not an object is placed at the detection position DP may be detected while moving the objective lens 11 away from the well plate WP. [Explanation of symbols]

[0067] 1. Microscope equipment 11 Objective lens 12. Microscope 20 Autofocus Device 21 Laser 25 Actuator 27 Cylindrical Lens 28 4-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

1. A drive unit that moves the objective lens in the direction of the optical axis; 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:

2. 2. 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.

3. 3. 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.

4. 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:

5. 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:

6. The autofocus device according to claim 1 , further comprising a light source unit that emits light that is condensed at a focal point of the objective lens.

7. The autofocus device according to claim 1 , wherein the detection unit includes a triangulation type displacement sensor.

8. 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