JPH10232342A - Autofocusing device for microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an autofocusing device capable of executing autofocusing operation with high accuracy even when the depth of focus is made deep without largely influencing various kinds of specimens by the characteristic of a lens optical system. SOLUTION: In this device 1, specified voltage V is impressed on a focusing objective lens driving coil 25 based on the returned light of a laser beam irradiating the focusing reference area R2 of the specimen R, and a focusing objective lens 21 is focused on the area R2. When an actuator 50 integrally drives the coil 25, the lens 21 and an objective lens for observing a specimen 11, a driving control part 60 performs servo control so that the impressed voltage V on the coil 25 may coincide with reference voltage VO previously set, and the lens 11 is focused on the observing area R1 of the specimen R.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope autofocus apparatus for automatically focusing an objective lens when performing microscope observation.

[0002]

2. Description of the Related Art As a system for taking a photograph of a biological microscope, there is known a system equipped with an auto-focusing device using a CCD camera in order to automate a focusing operation of a photographing device attached to an optical microscope. The use of the auto-focusing device enables the photographing to be performed with higher precision and without blur than the focusing operation by visual observation. That is, when photographing a pathological specimen or the like with an optical microscope, a low-magnification (low-magnification) photograph for grasping the entire image of the specimen and a high-magnification (high-magnification) photograph for closely examining the lesion are taken. In many cases, focusing on a low-magnification photograph is difficult, and the photographed image is often blurred even if it is clearly visible when visually observed. The difficulty in focusing when using a low-magnification objective lens is due to the fact that the depth of focus of the optical system of the photographing device is shallower than the visual depth of focus.

[0003] In view of this point, the applicant of the present application has previously described Japanese Utility Model Application
In the specification of Japanese Patent No. 25478, there is proposed a microscope photographic device provided with an autofocus device for easily performing autofocus of the photographic device even when the magnification of the objective lens in the microscope is about 1 to 4 times. doing. This autofocus device is of a contrast detection type. An outline of the operation will be described with reference to FIG. In the autofocus device 200, an image of a subject 202 formed through a lens optical system 201 of an optical microscope and a photographing device is converted into an image by an image pickup device 20 such as a CCD camera.
3 can be taken in. While moving the stage of the optical microscope, a video signal is taken in at a certain timing, its high frequency component is detected, and the contrast of the video signal is calculated. The stage scans the lens optical system 201 between its far point side and its near point side. By this scanning, a contrast curve as shown by a curve C is obtained. It is determined that the position where the value P having the highest contrast is obtained is the focus point.

[0004]

However, in a system having such a contrast detection type autofocus device 200, the focus position cannot be detected unless the lens optical system 201 is scanned, and as shown in FIG. It is not suitable for focusing on a continuously moving work. Further, since an image signal captured through the lens optical system 201 is used, its performance largely depends on the characteristics of the lens optical system 201. In addition, as shown by the solid line LN1 in FIG. 9, when the contrast of the work is insufficient, an accurate autofocus operation cannot be expected. Further, as shown by solid lines LN2 and LN3 in FIG. 9, if the illuminance is too bright or too dark, an accurate autofocus operation cannot be expected. Further, as shown by the solid line LN4 in FIG.
When the depth of focus is deep, the contrast peak as a result of scanning is not steep, and the accuracy is low. Further, on a glossy surface such as a metal surface, as shown in FIG. 10, a malfunction may occur due to pseudo-resolution Q due to distortion of the lens optical system 201.

[0005] In view of the above, the object of the present invention is to provide:
A microscope that can perform autofocus operation with high accuracy on continuously moving workpieces and various specimens such as glossy surfaces without being greatly affected by the characteristics of the lens optical system, even when the depth of focus is deep. Realizing an auto-focusing device for use.

[0006]

In order to solve the above-mentioned problems, an autofocus apparatus for a microscope according to the present invention comprises:
A focusing objective lens movable in an optical axis direction parallel to an optical axis of a microscope sample observation objective lens, and a laser light source for irradiating a laser beam to a focusing reference area of the specimen via the focusing objective lens A light receiving unit for detecting return light from the focusing reference area; an error detecting unit for detecting a focus position error of the focusing objective lens based on a detection result at the light receiving unit; A focusing objective lens driving coil for driving the focusing objective lens in the optical axis direction based on a detection result of the detection unit to focus the focusing objective lens on the focusing reference area; A lens driving mechanism for driving the specimen observation objective lens in the optical axis direction integrally with the objective lens drive coil and the focusing objective lens to focus the specimen observation objective lens on the observation area of the specimen; For the specimen observation by the lens driving mechanism. When an object lens is focused on the observation area, the voltage applied to the focusing objective lens driving coil for focusing the focusing objective lens on the focusing reference area is a reference voltage set in advance. Drive control means for controlling the drive of the objective lens for specimen observation by the lens drive mechanism so as to match the voltage.

In the autofocus apparatus for a microscope according to the present invention, the focusing objective lens is driven when the focusing objective lens is focused on the focusing reference area of the specimen based on the return light from the specimen at the light receiving section. By performing servo control so that the voltage applied to the coil becomes a preset reference voltage, the objective lens for specimen observation is focused on the observation region of the specimen. Therefore, since the focus position of the objective lens for specimen observation is searched by the shape of the image formed at the light receiving unit, etc., when the contrast of the specimen is insufficient, when the illuminance is too bright or too dark, the depth of focus is reduced. When it is deep, even on a glossy surface such as a metal surface, the specimen observation objective lens can be focused on the specimen with high accuracy without being affected by distortion of the optical system. Also, unlike a contrast detection type autofocus device, it is not necessary to scan the optical system in the optical axis direction over time, so focusing on a continuously moving workpiece is possible if the timing is adjusted. is there.

In the present invention, the reference voltage is set as a value when the observation region and the focus reference region are located at different positions in the optical axis direction, or when the observation region and the focus reference region are set to different values. Any of the cases where the value is set as a value when the region and the region are located at the same position in the optical axis direction may be used.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

(Overall Configuration) FIG. 1 is a block diagram showing the overall configuration of an autofocus apparatus for a microscope according to the present invention.

The microscope autofocus apparatus 1 shown in FIG. 1 includes a microscope 10 having a specimen observation objective lens 11 having an optical axis L1 and an optical axis L2 parallel to the optical axis L1 near the specimen observation objective lens 11. Focusing device 20 having a focusing objective lens 21 provided with a microscope 10 and a focusing device 2
0 and a frame 30 integrally mounted with the
The lens driving device 40 moves the specimen observation objective lens 11 up and down along the directions of the optical axes L1 and L2 integrally with the focusing objective lens 21 and the like via the reference numeral 0. The lens driving device 40 includes a stepping motor 50 (objective lens driving mechanism) that drives the frame 30 up and down.
And a drive control unit 60 for controlling the stepping motor 50 to focus the specimen observation objective lens 21 on the specimen.

The microscope 10 is the same as the conventional one except that it is mounted on a frame 30. A sample observation objective lens 11 faces a stage 12 on which a sample is mounted.

(Structure of Focusing Apparatus) The focusing apparatus 20 is of a magnetic drive type, basically like a focusing mechanism of an optical pickup for reproducing a compact disk or the like. 21, a laser light source unit 22 for irradiating the sample with laser light via the focusing objective lens 21, and a light receiving unit 23 for detecting return light from the sample
And an error detecting section 24 for detecting a focus position error of the focusing objective lens 21 based on the detection result of the light receiving section 23.
And a focusing objective lens driving coil 25 for driving the focusing objective lens 21 in the direction of the optical axis L2 based on the detection result of the error detection unit 24 to focus the focusing objective lens 21 on the sample. Is configured. The error detection unit 24 is configured as a part of a focusing control unit 26 that applies a predetermined voltage to the focusing objective lens driving coil 25 based on the detection result. From the focus control unit 26 to the lens driving device 40
The reference voltage V0 to be set in advance before observing the specimen and the voltage applied to focus the objective lens driving coil 25 for focusing when observing the specimen are applied to the drive control unit 60 of FIG. V is input, and based on the input result, the drive control unit 60 controls the optical axis L1 of the specimen observation objective lens 21 by the stepping motor 50.
Control the drive in the direction.

(Configuration of Control System) The configuration of the control system in the microscope autofocus apparatus 1 thus configured can be represented as a circuit block diagram shown in FIG. That is, the drive control unit 60 of the lens driving device 40 includes a switching regulator 601 as a power supply unit,
A driver 602 for the stepping motor and a stepping motor drive circuit 603 are configured. In the present embodiment, an output from the focus control unit 26 of the focusing device 20 (applied to the focusing objective lens driving coil 25 The voltage V) is input to the servo circuit 604 together with a reference voltage V0 (initial position voltage) described later.

(Configuration of Light Receiving Unit) As can be seen from FIG.
In the focusing device 20, similarly to the optical pickup, the laser light emitted from the laser light source unit 22 is applied to the sample on the stage 12 via a polarizing beam splitter (not shown) or a focusing objective lens 21. The return light therefrom again reaches the light receiving section 23 through the focusing objective lens 21. Here, the light receiving unit 23 has four light receiving elements as in the focusing mechanism using the astigmatism method. That is,
As shown in FIG. 3A, a photodetector 230 including four photodiodes 23A to 23D is used for the light receiving section 23, and FIG. An example of the change is shown. In a state where there is no focusing error, that is, in a focusing position, a perfect circular light spot Pb is formed on the photodetector 230, and outputs A to D from the photodiodes 23A to 23D are equal. On the other hand, when the specimen is on the far point side with respect to the focus position (meridional focus position), an elliptical light spot Pa having a long axis in the horizontal axis direction is formed on the photodetector 230. Is done. In this case, the photodiodes 23A,
Compared to the outputs A and C from 3C, the photodiode 23
Outputs B and D of B and 23D are high. Conversely, when the specimen is on the near point side with respect to the in-focus position (sagittal in-focus position), an elliptical light spot Pc whose longitudinal axis is the long axis is formed on the photodetector 230. Is done. In this case, the outputs A and C of the photodiodes 23A and 23C are larger than the outputs B and D of the photodiodes 23B and 23D. Accordingly, the focusing position error signal [(A + C)-(B + D)] of the focusing objective lens 21 is obtained based on such a change in the amount of light received by each of the photodiodes 23A to 23D. Since it changes as shown in B), its zero cross point corresponds to the in-focus position.

(Observation Object / Specimen) In the microscope autofocus apparatus 1 configured as described above, as shown in FIG. 4A, the specimen observation objective lens 11 of the microscope and the focusing objective of the focusing apparatus 20 are used. The lens 21 is the same specimen R
Are focused on different regions R1 and R2, respectively. In the specification of the present application, of the two regions R1 and R2, a region where the specimen observation objective lens 11 is focused is referred to as an observation region R1,
A region where the focusing objective lens 21 is focused is defined as a focusing reference region R.
Two. That is, the observation region R1 is a region where the observation is actually performed via the microscope 10, and the focusing reference region R2 is the sample observation objective lens 1 as described later.
This is a reference area for setting the lens position when focusing on the observation area R1. Therefore, the observation region R1 and the focus reference region R2 are either at the same height position in the directions of the optical axes L1 and L2, or at different height positions in the directions of the optical axes L1 and L2. However, the application of the microscope autofocus device 1 of the present embodiment is shown in FIG.
As shown in (B), (C), and (D), any sample R
In this case, the observation region R1 and the focus reference region R2 also have the optical axis L
1. It is assumed that the relative positions in the directions of L1 and L2 match.

(Operation) An operation performed by the microscope autofocus apparatus 1 having the above-described configuration will be described with reference to FIGS. In this apparatus, first, a reference voltage V0 for a specimen R to be observed is set. In setting the reference voltage V0, the sample R is placed in the stage 1
After the mounting, the drive signal is input to the stepping motor 50 directly from the outside or via the drive control unit 60, and the specimen observation objective lens 11 is moved up and down together with the frame 30 as shown in FIG. As shown in (1), the specimen observation objective lens 11 is visually focused on the observation region R1 on the sample specimen R. In this state, on the side of the focusing device 20, laser light is emitted from the laser light source unit 22 to the focusing reference region R22 of the sample R through the focusing objective lens 21. The return light at this time reaches the light receiving unit 23 through the focusing objective lens 21, but as described with reference to FIG. 3, the light receiving unit 2 depends on the image forming shape at this time.
3 are different. Therefore, if the voltage V is applied to the focusing objective lens driving coil 25 based on this output, the focusing objective lens 21 can be focused on the focusing reference region R1 of the sample R. At this time, the voltage V applied to the focusing objective lens driving coil 25 is:
Thereafter, when observing the same type of sample R, the reference voltage V0 is input to the drive control unit 60. Note that the height position of the focusing device 20 on the frame 30 is determined when the focusing objective lens 21 is positioned substantially at the center of the height of the focusing objective lens drive coil 25. 21 is adjusted so as to focus on the focus reference region R2 of the sample R, and the movable range of the focus position is widened.

The operation when a new sample R is observed under a microscope will be described below. First, if the height position of the observation region R1 and the reference region R2 for focusing are the same between the sample this time and the sample sample R and the thickness dimension is the same,
As shown in FIG. 4B, the specimen R is placed on the stage 12, and the specimen observation objective lens 11 is in focus with respect to the observation region R1.

On the other hand, as shown in FIG.
It is assumed that the relative position of the observation region R1 and the reference region R2 for focusing is the same between the current sample R and the sample sample, but the thickness of the sample R is thinner than the sample sample. In this case, only by placing the sample R on the stage 12, the focus reference region R2 is located at a point far from the focusing objective lens 21, and the observation region R1 is located at the sample observation objective lens 11
Far away from However, on the side of the focusing device 20, a predetermined voltage V is applied to the focusing objective lens driving coil 25 based on the detection result of the light receiving unit 23, and the focusing objective lens 21 is turned on as shown in FIG. As shown by the dotted line in FIG. In this state, the observation region R1 of the specimen observation objective lens 11 remains at the far point. However, in the present embodiment, the polarity of the voltage V applied to the focusing objective lens drive coil 25 in the lens driving device 40 ( Based on ±), the drive control unit 60 outputs a drive signal to the stepping motor 50, and moves the sample observation objective lens 21 in a direction to approach the sample R. At this time, since the focusing objective lens 21 also moves in the direction approaching the specimen R, the voltage V applied to the focusing objective drive coil 25 is
Changes. Then, the drive control unit 60 drives the stepping motor 50 while feeding back the result of comparing the previously set reference voltage V0 with the current applied voltage V to the focusing objective drive coil 25, and the two values match. At this point, the driving of the stepping motor 50 is stopped. As a result of such servo control, the specimen observation objective lens 11 is focused on the observation region R1.

On the contrary, as shown in FIG.
It is assumed that the relative position of the observation region R1 and the focusing reference region R2 is the same between the current sample R and the sample sample, but the thickness dimension of the current sample R is larger than the sample sample. In this case, only by placing the sample R on the stage 12, the focusing reference region R2 is located at a point near the focusing objective lens 21, and the observation region R1 is located at the sample observation objective lens 11.
Is near to. However, on the side of the focusing device 20, a predetermined voltage V is applied to the focusing objective lens driving coil 25 based on the detection result of the light receiving unit 23, and the focusing objective lens 21 is turned on as shown in FIG. As shown by the dotted line in FIG. In this state, the observation region R1 of the specimen observation objective lens 11 remains at the near point, but in the present embodiment, the polarity of the voltage V applied to the focusing objective lens drive coil 25 in the lens driving device 40 ( Based on ±), the drive control unit 60 outputs a drive signal to the stepping motor 50, and moves the specimen observation objective lens 21 in a direction away from the specimen R. At this time, since the focusing objective lens 21 also moves in a direction away from the sample R, the voltage V applied to the focusing objective drive coil 25 changes. Therefore, the drive control unit 60 compares the previously set reference voltage V0 with the current focusing objective drive coil 2.
The stepping motor 50 is driven while feeding back the result of comparison with the voltage V applied to the step 5, and when the values match, the driving of the stepping motor 50 is stopped.
As a result of such servo control, the objective lens for specimen observation 1
1 focuses on the observation region R1.

(Effect of this embodiment) As described above, this embodiment utilizes the fact that the relative positions in the directions of the optical axes L1 and L2 in the specimen R are the same in the observation region R1 and the focusing reference region R2. Then, the lens position necessary for focusing the specimen observation objective lens 11 on the observation region R1 is determined by the focusing objective lens driving required for focusing the focusing objective lens 21 on the focusing reference region R2. It is determined from the result of comparison between the voltage V applied to the coil 25 and the reference voltage V0. That is,
When the focusing objective lens 21 is focused on the focusing reference region R2 of the specimen R, the voltage V applied to the focusing objective lens driving coil 25 is equal to the reference voltage V0.
The specimen observation objective lens 11 is servo-driven in the direction of the optical axis L1 to perform the focusing operation. Therefore, since the focus position of the objective lens 11 for observing the specimen is searched for based on the shape of the image formed by the light receiving unit 23, when the contrast of the specimen R is insufficient, when the illuminance is too bright or too dark, When the depth of focus is deep, the specimen observation objective lens 11 can be focused with high accuracy even on a glossy surface such as a metal surface. Therefore, it is easy to accurately focus on the metal surface in the Vickers hardness tester. When observing a pathological specimen on the slide with a low-magnification biological microscope, the slide is moved to the focus reference region R2.
It is also easy to accurately focus on a pathological specimen.

Unlike a contrast detection type autofocus device, it is not necessary to scan the optical system in the direction of the optical axis over time, so that focusing on a continuously moving work can be performed as long as the timing is adjusted. It is possible.

Further, since it is only necessary to add a small device such as an optical pickup as the focusing device 20, it is easy to incorporate the focusing device 20 into the microscope 10.

(Structural Example of Lens Driving Apparatus) A structural example of a lens driving apparatus in the microscope autofocus apparatus of the present embodiment will be described. The drive control unit 60 and the focus control unit 26
It can be realized as a function of a microcomputer that operates based on a program stored in a ROM or the like, and can be configured as hardware using various control circuits (electronic circuits) as shown in FIG. Can also.

In FIG. 5, outputs A to D corresponding to the amounts of light received from the respective photodiodes 23A to 23D of the light receiving section 23 are respectively applied to a differential amplifier 101 by a signal Vref.
And the operational amplifiers 102 and 103 output the focus position error signal [(A + B) − (C + D)] and the added value (A) based on the outputs A to D extracted by the differential amplifier.
+ B + C + D).

Here, the focus position error signal [(A + B)-
(C + D)] draws an S-shaped curve H as shown in FIG. The position corresponding to the zero cross point Z of the curve H is the focusing position of the focusing objective lens 21. Therefore, on the side of the focusing device 20, the drive control unit 60 performs the servo control in a range corresponding to the region T.

In order to perform such servo control, FIG.
Of the calculation results obtained by the operational amplifiers 102 and 103 shown in (1), the focus position error signal [(A + B)-(C + D)]
Is subjected to phase compensation, gain, and level adjustment in the amplifiers 106 and 107 via the buffer 104 and the differentiating circuit 105. Thereafter, the output of the operational amplifier 107 and the inverted output of the operational amplifier 108
09 and the drive amplifier 1 via the analog switch 110.
11 is applied to the objective lens drive coil 25 with the coil drive signal output therefrom, whereby the focusing operation of the focusing objective lens 21 is performed. Here, the voltage V applied to the objective lens driving coil 25 is a driving voltage −F that causes the focusing objective lens 21 to approach the specimen R or a driving voltage + F that causes the focusing objective lens 21 to move away from the specimen R.

On the other hand, the addition value (A + B + C + D) obtained by the operational amplifier 103 is
Are input to the comparator 122 together with the comparison potential, and the comparator output 120 is input to the flip-flop 141. Also, the focus position error signal [(A + B)-(C + D)] obtained by the operational amplifier 102 is
Through an operational amplifier 131, the comparator 132 is input together with a comparison potential to a comparator 132. The comparator output 130 is input to a flip-flop 141 to detect the zero-cross point Z and drive the objective lens 21 for focusing. Is achieved.

That is, along the curve H shown in FIG. 6A, the added value (A + B + C + D) and the focus position error signal [(A + B)-(C + D)] are respectively shown in FIG.
It changes as shown in (B) and (C). FIG. 6 (B),
(C) shows the change of the added value (A + B + C + D) and the focus position error signal [(A + B)-(C + D)], and the outputs of the comparators 120 and 130 and the flop-flop 141 of these signals, respectively. Is shown. First, the flop-flop 141 is reset until the level of the added value (A + B + C + D) rises and the comparator output 120 falls from "H" to "L" of the binary signal (region a). As a result, as shown in FIG. 5, a sawtooth wave 142 is generated, and the sawtooth wave 142 is generated.
Are adjusted in gain and level by operational amplifiers 143 and 144. Also, the analog switch 146 is turned on via the NOT circuit 145, and the focusing objective lens driving coil 2 is turned on.
5 is driven to start the operation of focus position detection.

Thereafter, as shown in FIGS. 6B and 6C,
After the comparator output 120 of the added value (A + B + C + D) falls to “L”, the focus position error signal [(A +
B)-(C + D)] until the comparator output falls to “L” (region b), and the focus position error signal [(A
+ B)-(C + D)] passes through the zero cross point Z, so that the focusing position of the focusing objective lens 21 is determined.

The focus position error signal [(A + B)-
When the output 130 of the (C + D)] falls to "L" and triggers the flip-flop 141, and its output 140 rises to "H" (region c), the analog switch 146 is switched. Objective lens for focus 2
The servo drive to the in-focus position 1 is performed.

When the focusing operation of the focusing objective lens 21 is performed, the voltage V (−F, + F) applied to the focusing objective lens drive coil 25 is controlled by the drive control unit 60.
(Servo circuit 604 shown in FIG. 2) is input to differential amplifier 161 and compared with reference voltage V0. Based on the result of the comparison, the voltage-frequency conversion circuit 162 converts the frequency of the driving voltage V (+ F, -F), and outputs the driving pulse 163 of the stepping motor 50 to the stepping motor driving circuit 603 (see FIG. 2). As a result, the stepping motor 50 is driven. As a result of such servo control,
The position of the specimen observation objective lens 11 is set so that the voltage V applied to the focusing objective lens drive coil 25 becomes equal to the reference voltage V0. At this lens position, the specimen observation objective lens 11 is placed in the observation area. An in-focus state is established for R2.

When driving the focusing objective lens drive coil 25 by the drive amplifier 111 shown in FIG. 5, if a 180 ° phase shift occurs in the drive signal in the amplifier 111, oscillation occurs and servo control is not performed. Become stable. Therefore, as shown in FIG. 6D, the phase is advanced by 90 ° by the differentiating circuit 170, and the servo control is stabilized by performing fine correction of the phase.

[0034]

As described above, in the microscope autofocus apparatus according to the present invention, the focusing objective lens is focused on the focusing reference area of the specimen based on the return light from the specimen at the light receiving section. The sample observation objective lens is focused on the observation region of the sample by performing servo control so that the voltage applied to the focusing objective lens drive coil for the focusing becomes a preset reference voltage. Therefore, according to the present invention, since the focal position is searched for by the image forming shape at the light receiving unit, etc., if the contrast of the specimen is insufficient, the illuminance is too bright or too dark, if the depth of focus is deep, Further, even on a glossy surface such as a metal surface, the specimen observation objective lens can be focused on the observation region of the specimen with high accuracy without being affected by distortion of the optical system. Unlike a contrast detection type autofocus device, it is not necessary to scan the optical system in the optical axis direction over time, so focusing on a continuously moving workpiece is possible if the timing is adjusted. It is.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a microscope autofocus apparatus to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a control system of the autofocus apparatus shown in FIG.

3A is an explanatory diagram showing a change in an image forming shape on a photodetector used in a light receiving unit of the autofocus device shown in FIG. 1, and FIG. 3B is a diagram obtained from an output of the photodetector. FIG. 5 is an explanatory diagram of a focused position error signal.

FIGS. 4A to 4D are explanatory diagrams showing the operation principle of the autofocus device shown in FIG. 1;

FIG. 5 is a configuration example of a focusing control unit and a drive control unit of the autofocus device shown in FIG. 1;

FIGS. 6A to 6C are explanatory diagrams showing operations of a focus control unit and a drive control unit shown in FIG. 5, respectively.
FIG. 6D is a circuit diagram of a servo amplifier used in the focus control unit and the drive control unit shown in FIG.

FIG. 7 is an explanatory diagram showing a first problem in a conventional autofocus device.

FIG. 8 is an explanatory diagram showing a second problem in the conventional autofocus device.

FIG. 9 is an explanatory diagram showing a third problem in the conventional autofocus device.

FIG. 10 is an explanatory diagram showing a fourth problem in the conventional autofocus device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Autofocus apparatus for microscopes 11 Objective lens for sample observation 10 Microscope 12 Stage 20 Focusing device 21 Objective lens for focusing 22 Laser light source unit 23 Light receiving units 23A to 23D Photodiode 24 Error detecting unit 25 Objective lens driving coil for focusing 26 Focusing control unit 30 Frame 40 Lens driving device 50 Stepping motor (Objective lens driving mechanism) 60 Drive control unit 230 Photodetectors A to D Output of photodiodes L1 Optical axis of specimen observation objective lens L2 Light of focusing objective lens Axis Pa Light spot at meridional focus position Pb Light spot at focus state Pc Light spot at sagittal focus position R Sample R1 Sample observation region R2 Focus reference region V Applied voltage to focus objective lens drive coil V0 Reference voltage

Claims (3)

[Claims] 1. A focusing objective lens movable in an optical axis direction parallel to an optical axis of a sample observation objective lens of a microscope, and a laser beam is transmitted through the focusing objective lens to a focus reference area of the specimen. A laser light source unit for irradiating the object, a light receiving unit for detecting return light from the focus reference area, and an error detection for detecting a focus position error of the focusing objective lens based on a detection result of the light receiving unit. And a focusing objective lens driving coil that drives the focusing objective lens in the optical axis direction based on the detection result of the error detection unit to focus the focusing objective lens on the focusing reference area. And driving the specimen observation objective lens in the optical axis direction integrally with the focusing objective lens drive coil and the focusing objective lens to focus the specimen observation objective lens on the observation region of the specimen. Lens drive mechanism and the lens drive mechanism The voltage applied to the focusing objective lens driving coil for focusing the focusing objective lens on the focusing reference region when the objective observation objective lens is focused on the observation region is set in advance. And a drive control means for controlling the drive of the objective lens for specimen observation by the lens drive mechanism so as to match the reference voltage. 2. The auto microscope according to claim 1, wherein the reference voltage is set as a value when the observation region and the focusing reference region are located at different positions in the optical axis direction. Focus device. 3. The microscope according to claim 1, wherein the reference voltage is set as a value when the observation region and the focus reference region are located at positions where they coincide with each other in the optical axis direction. Autofocus device.