Optical device and method for controlling the optical device

Abstract

To efficiently focus an objective lens regardless of the magnification of the objective lens.SOLUTION: The light sources 1 emit illumination light L1. The objective lens 5 condenses the illumination light L1 on the sample 90. The photodetectors 9 and 10 are provided at a front focus position and a rear focus position with respect to the sample 90, respectively, and detect reflection light L2 from the sample 90. The photodetector 8 detects the reflected beam L2 incident through the objective lens 5. The beam splitter 3 splits the reflection light L2 into the photodetectors 9 and 10 and the photodetector 8. The focus control unit 11 performs focusing control of the objective lens 5 with respect to the sample 90 based on the detection results of the photodetectors 9 and 10. The adjusting lens 7 is provided between the beam splitter 3 and the photodetectors 9 and 10. The lens controller 12 adjusts the optical distance between the beam splitter 3 and the photodetectors 9 and 10 to a value corresponding to the magnification of the objective lens 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical device and a method for controlling the optical device.

Background Art

[0002] In imaging devices using an optical system such as a camera or a microscope, focus detection for automatically focusing on a subject is widely performed. As such focus detection, front-pin and rear-pin type focus detection is known (Patent Document 1).

[0003] In the front-pin and rear-pin method, two photodetectors are respectively arranged at positions where the focus of the secondary light beam from the sample is in front of the light receiving surface and at a position deeper. Then, while changing the distance between the objective lens and the sample, the intensities of the secondary light beams detected by the two detectors are monitored, and the position of the objective lens when the two reach a predetermined balance is detected as the position where the focus of the objective lens is in focus on the sample.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above front-pin and rear-pin method, generally, the distance between two positions of the objective lens where the intensity of the light detected by each of the two photodetectors is maximum is called the pull-in range. It is known that this pull-in range is wide when the magnification of the objective lens is low and narrow when the magnification of the objective lens is high.

[0006] Therefore, when using a high-magnification objective lens, the range in which the objective lens can be moved between the front and back focus points to find the point of focus becomes smaller. As a result, detecting the point of focus of the objective lens becomes difficult. [Means for solving the problem]

[0007] The optical apparatus according to this disclosure comprises: a light source that emits illumination light; an objective lens that focuses the illumination light onto a sample; a first detection means provided at a front-pin position relative to the sample and detecting secondary rays generated when the sample is irradiated with the illumination light; a second detection means provided at a rear-pin position relative to the sample and detecting the secondary rays; a third detection means that detects the secondary rays incident through the objective lens; a separation means that separates the secondary rays into the first and second detection means and the third detection means; a focus control means that controls the focusing of the objective lens on the sample based on the detection results of the first and second detection means; and an optical distance adjustment means provided between the separation means and the first and second detection means, which can adjust the optical distance between the separation means and the first and second detection means to a value corresponding to the magnification of the objective lens.

[0008] The control method for an optical apparatus according to this disclosure comprises a light source that emits illumination light, an objective lens that focuses the illumination light onto a sample, a first detection means provided at a front-pin position relative to the sample and detecting secondary rays generated when the sample is irradiated with the illumination light, a second detection means provided at a rear-pin position relative to the sample and detecting the secondary rays, a third detection means that detects the secondary rays incident through the objective lens, and a separation means that separates the secondary rays into the first and second detection means and the third detection means, respectively. In this optical apparatus, the control method performs focusing control of the objective lens relative to the sample based on the detection results of the first and second detection means, and controls an optical distance adjustment means provided between the separation means and the first and second detection means to adjust the optical distance between the separation means and the first and second detection means to a value corresponding to the magnification of the objective lens. [Effects of the Invention]

[0009] According to this disclosure, the objective lens can be efficiently focused regardless of its magnification. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram schematically shows the configuration of the optical device according to Embodiment 1. [Figure 2] This diagram schematically shows the relationship between the position of the objective lens and the intensity of the reflected light detected by the photodetector. [Figure 3] This diagram schematically shows the path of light in an optical device when the magnification of the objective lens is high. [Figure 4] This diagram schematically shows the path of light in an optical device when the magnification of the objective lens is low. [Figure 5] This figure schematically shows the configuration of the optical device according to Embodiment 2. [Modes for carrying out the invention]

[0011] The specific configuration of this embodiment will be described below with reference to the drawings. The following description illustrates preferred embodiments of the present disclosure, and the scope of the present disclosure is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same components.

[0012] Embodiment 1 An optical device according to Embodiment 1 will now be described. The optical device according to this embodiment is configured to have an optical system for imaging a sample, which is the object of the image capture. Figure 1 is a schematic diagram showing the configuration of the optical device according to Embodiment 1. The optical device 100 includes a light source 1, beam splitters 2 to 4, an objective lens 5, a lens 6, an adjustment lens 7, and photodetectors 8 to 10, a focus control unit 11, and a lens control unit 12.

[0013] Light source 1 is configured as a point light source and emits illumination light L1. Light source 1 may, for example, include a laser element and a slit provided in the path of the laser light emitted from the laser element, and the light that passes through the slit may be emitted as illumination light L1. In Figure 1 and the following figures showing the configuration of the optical device, the path of light in the optical device is indicated by an arrow line.

[0014] Illumination light L1 passes through beam splitter 2, adjustment lens 7, beam splitter 3, and objective lens 5 before irradiating the sample 90. The reflected light L2 generated by irradiating the sample 90 with illumination light L1 passes through objective lens 5 and enters beam splitter 3.

[0015] In the following, the reflected light L2 from sample 90 will also be referred to as secondary light produced when sample 90 is illuminated by illumination light L1. However, secondary light is not limited to reflected light. Secondary light may be various types of light produced when sample 90 is illuminated by illumination light L1, such as reflected light, transmitted light, scattered light, or fluorescence.

[0016] The objective lens 5 is configured to be drivable along the irradiation direction of the illumination light L1 to the sample 90 by the focus control unit 11 so that the focus FP1 is adjusted to the sample 90. Hereinafter, the irradiation direction of the illumination light L1 is also referred to as the Z direction. Also, let the focal length of the objective lens 5 be f1.

[0017] The beam splitter 3 separates the incident reflected light L2 toward the lens 6 of the detection optical system and the adjustment lens 7.

[0018] The reflected light L2 incident on the lens 6 is condensed by the lens 6 and then enters the photodetector 8. Here, let the focal length of the lens 6 be f3. The photodetector 8 is configured as, for example, a sensor in which light receiving elements are two-dimensionally arranged, such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and is configured to acquire the profile of the reflected light L2 required for the inspection of the sample 90 and the image of the sample 90. The photodetector 8 is provided at a position conjugate to the condensing position of the illumination light L1 to the sample 90 by the objective lens 5. Note that the photodetector 8 is also referred to as the third detection unit or the third detection means.

[0019] In this configuration, in order to improve the quality of the image of the sample 90 acquired by the photodetector 8, the optical system that irradiates the illumination light L1 from the light source 1 to the sample 90 and guides the reflected light L2 from the sample 90 to the photodetector 8 may be configured as a confocal optical system.

[0020] A part of the reflected light L2 incident on the adjustment lens 7 is reflected by the beam splitter 2 and then enters the beam splitter 4. The beam splitter 4 separates the incident reflected light L2 toward each of the photodetectors 9 and 10.

[0021] In this configuration, the focal point FP2 of the adjustment lens 7 coincides with the exit point of the illumination light L1 from the light source 1. Here, the focal length of the adjustment lens 7 is denoted as f2. Therefore, the focal point FP2 of the reflected light L2 separated by the beam splitter 4 is at a position conjugate to the exit point of the illumination light L1 from the light source 1. In the following, the focal length f2 of the adjustment lens 7 will also be referred to as the first focal length.

[0022] The photodetectors 9 and 10 and the focus control unit 11 constitute a front-pin, back-pin type focus control mechanism that drives the objective lens 5 in the Z direction so that the focus FP1 of the objective lens 5 is aligned with the sample 90. The photodetectors 9 and 10 are configured as light-receiving elements such as photodiodes and are configured to detect the intensity of incident reflected light L2. The photodetector 9 is also referred to as the second detection unit or second detection means, and the photodetector 10 is also referred to as the first detection unit or first detection means.

[0023] The photodetectors 9 and 10 are positioned at different optical distances from the beam splitter 4. In this example, the optical distance between photodetector 9 and beam splitter 4 is greater than the optical distance between photodetector 10 and beam splitter 4. Therefore, photodetector 9 is positioned further away from the focal point FP2 of the reflected light L2 (back-pin position), and photodetector 10 is positioned closer to the focal point FP2 of the reflected light L2 (front-pin position).

[0024] The photodetectors 9 and 10 each output detection signals DET1 and DET2, which indicate the intensity of the received reflected light L2, to the focus control unit 11.

[0025] The focus control unit 11 is configured as a drive mechanism capable of adjusting the position of the objective lens 5 in the Z direction so that the focal point FP1 of the objective lens 5 is aligned with the sample 90, based on the detection signals DET1 and DET2. This allows the focus control unit 11 to drive the objective lens 5 to a position where the focal point FP1 is aligned with the sample 90. The focus control unit 11 can utilize various drive mechanisms, such as those having drive components like motors.

[0026] The adjustment lens 7 and the lens control unit 12 are configured as optical distance adjustment means capable of adjusting the optical distance between them and the photodetectors 9 and 10 according to the control signal CON2 which indicates the magnification of the objective lens 5.

[0027] The adjustment lens 7 is configured as a variable-focus lens that allows adjustment of the focal length f2 on the output side of the reflected light L2, i.e., on the beam splitter 2 side. The adjustment lens 7 may be configured as a zoom lens composed of multiple lenses. Alternatively, the adjustment lens 7 may be configured as a single lens with a variable focal length.

[0028] The lens control unit 12 receives a control signal CON2 indicating the magnification of the objective lens 5, and controls the focal length f2 of the adjustment lens 7 by the control signal CON1 according to the magnification of the objective lens 5.

[0029] Furthermore, the adjustment lens 7 is not limited to a single lens. For example, the lens control unit 12 may be configured to select a lens corresponding to the objective lens 5 from a plurality of lenses with different focal lengths as the adjustment lens 7, and to place the selected lens between the beam splitter 3 and the photodetectors 9 and 10.

[0030] Next, the front-pin / rear-pin focusing control method will be described. As described above, the optical device 100 is configured such that the focal point FP2 of the reflected light L2 is rear-pinned with respect to the photodetector 9 and front-pinned with respect to the photodetector 10. In the front-pin / rear-pin focusing control method, the amount of light detected by the photodetectors 9 and 10 changes as the position of the objective lens 5 in the Z direction relative to the sample 90 is displaced.

[0031] Figure 2 schematically shows the relationship between the position of the objective lens 5 in the Z direction and the intensity of reflected light detected by photodetectors 9 and 10. Since the focal point FP2 of the reflected light L2 relative to photodetectors 9 and 10 is different, as shown in Figure 2, if the position of the objective lens 5 in the Z direction is taken as the horizontal axis, the peak of the detection signal DET1, which indicates the intensity of reflected light L2 detected by photodetector 9, and the peak of the detection signal DET2, which indicates the intensity of reflected light L2 detected by photodetector 10, are at different positions. In front-pin / rear-pin focusing control, the distance between the peak of detection signal DET1 and the peak of detection signal DET2 is generally called the pull-in range D.

[0032] When the photodetectors 9 and 10 are positioned appropriately, the position where the intensity of the detection signal DET1 and the intensity of the detection signal DET2 are balanced corresponds to the state in which the objective lens 5 is in focus FP1 relative to the sample 90. Therefore, by monitoring the detection signals DET1 and DET2, the focus control unit 11 can drive the objective lens 5 to the position in which the FP1 is in focus relative to the sample 90.

[0033] In this case, the focus control unit 11 may detect the position where the error signal E, based on the difference between the detection signals DET1 and DET2, becomes 0, as the position where the focus FP1 of the objective lens 5 is in focus with respect to the sample 90 (sometimes called the just-focus position). The error signal E may be defined, for example, by the following formula. E = (DET1 - DET2) / (DET1 + DET2)

[0034] Next, we will explain the effect of the magnification of the objective lens 5 on the front-focus / back-focus control. In a typical optical system, there is no configuration to change the focal length of the adjustment lens 7, as in the optical device 100. Therefore, when the magnification of the objective lens 5 is changed, the retraction range D described above changes. When the magnification of the objective lens 5 is high (for example, 100x), the retraction range D becomes narrower compared to when the magnification of the objective lens 5 is low (for example, 10x). This will be explained in detail below.

[0035] The retraction range D is determined by the optical distance L between the focal point FP2 of the reflected light L2 incident on the photodetectors 9 and 10 and the photodetectors 9 and 10, the focal length f1 of the objective lens 5, and the focal length f2 of the adjustment lens 7 on the light source 1 side. In the following, the focal length f1 of the objective lens 5 will also be referred to as the second focal length.

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[0036] In a typical optical system, a fixed-focus relay lens is placed in the position of the adjustment lens 7. That is, when the magnification of the objective lens 5 is changed while the focal length f2 is fixed, only the focal length f1 of the objective lens 5 changes. Therefore, the value of α changes, and the retraction range D fluctuates.

[0037] When the magnification of objective lens 5 is low, i.e., when the focal length f1 is long, α becomes small. As a result, the retraction range D becomes large. On the other hand, when the magnification of objective lens 5 is high, i.e., when the focal length f1 is short, α becomes large. As a result, the retraction range D becomes small. In other words, in a front-pin / rear-pin focus detection mechanism in a typical optical device, the higher the magnification of objective lens 5, the narrower the retraction range D between the front and rear pins becomes.

[0038] Therefore, while ensuring the effectiveness of the front-pin / rear-pin focus control system, the range in which the objective lens 5 can be moved in the Z direction between the front-pin and rear-pin positions becomes smaller, requiring high precision to align the objective lens 5 to the just-focus position. As a result, when the magnification of the objective lens 5 is high, problems may arise such as the focus control taking a long time and the accuracy of the focus degrading.

[0039] To overcome the difficulty in controlling focus due to the magnification of the objective lens 5 as described above, the optical device 100 according to this embodiment is configured to prevent or suppress fluctuations in the retraction range D due to changes in the magnification of the objective lens 5 by suitably controlling the focal length f2 of the adjustment lens 7.

[0040] The control of the focal length f2 of the adjustment lens 7 of the optical device 100 will now be described. The lens control unit 12 instructs the adjustment lens 7 by control signal CON1 to set a focal length f2 that allows the value of α to be set to a desired value when the magnification of the objective lens 5 indicated by control signal CON2 is applied. This makes it possible to set the focal length f2 of the adjustment lens 7 to a desired focal length corresponding to the magnification of the objective lens 5 indicated by control signal CON2.

[0041] Figure 3 schematically shows the path of light in an optical device when the objective lens magnification is high. Figure 4 schematically shows the path of light in an optical device when the objective lens magnification is low. In Figure 3, the focal length of the high-magnification objective lens 5 is f1 A The focal length of adjustment lens 7 is set to f2 A In Figure 4, the focal length of the low-magnification objective lens 5 is set to f1 B The focal length of adjustment lens 7 is set to f2 B The focal length of adjustment lens 7 is f2 A and the focal length of the adjustment lens 7 detachment 2 B All of these points coincide with the emission point of illumination light L1 from light source 1.

[0042] In Figures 3 and 4, the position of the adjustment lens 7 is shown differently for illustrative purposes; however, this does not necessarily mean that the position of the adjustment lens 7 is actually different. Of course, if the adjustment lens 7 is configured as a variable-focus lens, such as a zoom lens, which can change the focus without changing its position or shape, then the position of the adjustment lens 7 does not need to change even when the magnification of the objective lens 5 is changed.

[0043] When the magnification of the objective lens 5 is high, as shown in Figure 3, the lens control unit 12 adjusts the focal length f2 A The adjustment lens 7 is controlled so that the focal length is shortened. Also, when the magnification of the objective lens 5 is low, the lens control unit 12 controls the focal length as shown in Figure 4. f2 B The adjustment lens 7 is controlled to increase its length.

[0044] In this case, it is desirable for the lens control unit 12 to instruct the adjustment lens 7 to set a focal length f2 so that α remains constant regardless of the magnification of the objective lens 5, that is, so that the ratio of the focal length f1 of the objective lens to the focal length f2 of the adjustment lens 7 remains constant. This makes it possible to maintain a constant retraction range D.

[0045] Furthermore, even if the lens control unit 12 cannot maintain α at a constant set value depending on the magnification of the objective lens 5, it is desirable to instruct the adjustment lens 7 to set a focal length f2 such that the value is within a predetermined range that approximates the set value as closely as possible, that is, so that the ratio of the focal length f1 of the objective lens to the focal length f2 of the adjustment lens 7 is within a predetermined range. This makes it possible to set the retraction range D to a value greater than the predetermined value.

[0046] Furthermore, the photodetector 8 used to image the sample 90 receives reflected light L2 from the sample 90 without passing through the adjustment lens 7. Therefore, an image of the sample 90 can be acquired regardless of the change in the magnification of the objective lens 5.

[0047] Therefore, with this configuration, even when the magnification of the objective lens is changed, the retraction range D can be kept constant or within a desired range by suitably changing the focal length of the adjustment lens 7. As a result, the focus FP1 of the objective lens 5 can be efficiently aligned with the sample 90, regardless of the magnification of the objective lens 5.

[0048] Embodiment 2 The optical device according to Embodiment 2 will now be described. The optical device according to this embodiment is configured to further include a magnification changing mechanism for the objective lens.

[0049] Figure 5 is a schematic diagram showing the configuration of the optical device 200 according to Embodiment 2. Compared to the optical device 100 according to Embodiment 1, the optical device 200 further includes a magnification changing unit 13. The magnification changing unit 13 switches the magnification of the objective lens 5 according to a control signal CON2 that indicates the magnification of the objective lens 5, which is provided by a user or the like.

[0050] If the magnification can be changed using the same lens, such as when the objective lens 5 is configured as a variable magnification lens, the magnification of the objective lens 5 may be switched by applying a control signal CON3 to the objective lens 5, as shown in Figure 5.

[0051] Furthermore, the magnification changing unit 13 may be configured to use an objective lens selected from a plurality of objective lenses with different magnifications according to the control signal CON2 as the objective lens 5. For example, the magnification changing unit 13 may have a mechanism that selects the objective lens to be used as the objective lens 5 from a plurality of objective lenses attached to the revolver by driving the revolver.

[0052] As described above, with this configuration, the magnification of the objective lens 5 is automatically changed in response to the control signal CON2, and the focal length of the adjustment lens 7 is suitably changed, thereby maintaining a constant retraction range D or keeping it within a desired range. As a result, similar to Embodiment 1, the focus FP1 of the objective lens 5 can be efficiently aligned with the sample 90, regardless of the magnification of the objective lens 5.

[0053] Other embodiments Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0054] The above-described configuration of the optical device is merely illustrative, and other configurations are possible as long as illumination light L1 emitted from the light source 1 irradiates the sample 90 and secondary rays from the sample 90 can be detected by photodetectors 8-10. For example, although the optical device according to the above embodiment was described as having a refractive optical system, the optical device may be configured to have a refractive reflective optical system or a reflective optical system, and to have means for adjusting the focal length of secondary rays, similar to the adjustment lens 7, as needed.

[0055] Furthermore, although the focus control unit 11 has been described as driving the objective lens 5 to a position where the focus FP1 is aligned with the sample 90, it is not limited to this. The focus control unit 11 only needs to change the relative position between the sample 90 and the objective lens 5, and may also drive a stage or the like that holds the sample 90.

[0056] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0057] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments rather than with only one specific embodiment. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps shown in any of the drawings may be changed as appropriate. [Explanation of Symbols]

[0058] 1 light source 2-4 Beam Splitter 5. Objective lens 6 lenses 7 Adjustment lenses 8-10 Photodetectors 11 Focus Control Unit 12 Lens control unit 13. Magnification Change Section 90 samples 100, 200 optical equipment CON1~CON3 Control Signals DET1, DET2 detection signals L1 illumination light L2 reflected light

Claims

1. A light source that emits illumination light, An objective lens that focuses the illumination light onto the sample, A first detection means is provided at a front pin position relative to the sample and detects secondary rays generated when the sample is irradiated with the illumination light, A second detection means is provided at a rear-pin position relative to the sample and detects the secondary light ray, A third detection means for detecting the secondary light rays incident through the objective lens, The secondary light beam is separated into the first and second detection means and the third detection means, and the separation means is provided to separate it. A focus control means that controls the focusing of the objective lens on the sample based on the detection results of the first and second detection means, The separation means and the first and second detection means are provided and have a variable focus lens on the first and second detection means side that can adjust the first focal length, and by controlling the first focal length of the variable focus lens to a value corresponding to the magnification of the objective lens, the optical distance between the separation means and the first and second detection means can be adjusted to a value corresponding to the magnification of the objective lens. optical equipment.

2. The variable focus lens is configured as a single lens with a variable focal length. The optical apparatus according to claim 1.

3. The aforementioned variable-focus lens is configured as a zoom lens consisting of a combination of multiple lenses. The optical apparatus according to claim 1.

4. The optical distance adjustment means controls the first focal length such that the retraction range between the front and rear focus points due to a change in the magnification of the objective lens becomes larger than a predetermined value, or such that the retraction range remains constant regardless of the change in the magnification of the objective lens. The optical apparatus according to claim 2 or 3.

5. The optical distance adjustment means controls the first focal length such that the ratio of the first focal length to the second focal length of the objective lens is within a predetermined range, or remains constant regardless of changes in the magnification of the objective lens. The optical apparatus according to claim 4.

6. A light source that emits illumination light, An objective lens that focuses the illumination light onto the sample, A first detection means is provided at a front pin position relative to the sample and detects secondary rays generated when the sample is irradiated with the illumination light, A second detection means is provided at a rear-pin position relative to the sample and detects the secondary light ray, A third detection means for detecting the secondary light rays incident through the objective lens, The secondary light beam is separated into the first and second detection means and the third detection means, and the separation means is provided to separate it. A focus control means that controls the focusing of the objective lens on the sample based on the detection results of the first and second detection means, The system includes optical distance adjustment means provided between the separation means and the first and second detection means, which can adjust the optical distance between the separation means and the first and second detection means to a value corresponding to the magnification of the objective lens, The optical distance adjustment means has a plurality of lenses with different focal lengths, and a lens with a focal length corresponding to the magnification of the objective lens selected from the plurality of lenses is placed between the separation means and the first and second detection means. optical equipment.

7. The optical system, which includes at least the light source and the third detection means, constitutes a confocal optical system. The optical apparatus according to any one of claims 1 to 3 and 6.

8. The third detection means is provided at a position conjugate to the focusing position of the illumination light onto the sample by the objective lens, The optical apparatus according to any one of claims 1 to 3 and 6.

9. The system further includes a magnification changing means capable of changing the magnification of the objective lens according to information specifying the magnification of the objective lens, The optical distance adjustment means controls the optical distance between the separation means and the first and second detection means so that it becomes a value corresponding to the magnification of the objective lens specified by the information. The optical apparatus according to any one of claims 1 to 3 and 6.

10. An optical apparatus comprising: a light source that emits illumination light; an objective lens that focuses the illumination light onto a sample; a first detection means provided at a front-pin position relative to the sample and detecting secondary rays generated when the sample is irradiated with the illumination light; a second detection means provided at a rear-pin position relative to the sample and detecting the secondary rays; a third detection means that detects the secondary rays incident through the objective lens; and a separation means that separates the secondary rays into the first and second detection means and the third detection means, Based on the detection results from the first and second detection means, the focus adjustment control of the objective lens for the sample is performed. The optical distance adjustment means provided between the separation means and the first and second detection means controls the first focal length of the variable focus lens on the first and second detection means side to a value corresponding to the magnification of the objective lens, thereby adjusting the optical distance between the separation means and the first and second detection means to a value corresponding to the magnification of the objective lens. A method for controlling optical devices.

11. An optical apparatus comprising: a light source that emits illumination light; an objective lens that focuses the illumination light onto a sample; a first detection means provided at a front-pin position relative to the sample and detecting secondary rays generated when the sample is irradiated with the illumination light; a second detection means provided at a rear-pin position relative to the sample and detecting the secondary rays; a third detection means that detects the secondary rays incident through the objective lens; and a separation means that separates the secondary rays into the first and second detection means and the third detection means, Based on the detection results from the first and second detection means, the focus adjustment control of the objective lens for the sample is performed. By arranging a lens with a focal length corresponding to the magnification of the objective lens, selected from a plurality of lenses with different focal lengths provided by the optical distance adjustment means between the separation means and the first and second detection means, the optical distance between the separation means and the first and second detection means is adjusted to a value corresponding to the magnification of the objective lens. A method for controlling optical devices.

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