JP7444754B2 - Probe microscope and probe microscope optical axis adjustment method - Google Patents

Description

The present invention relates to a probe microscope and an optical axis adjustment method for a probe microscope.

A probe microscope scans a cantilever while bringing a probe close to the sample surface to observe the surface of the sample or measure the physical properties of the sample. A probe microscope irradiates the back of a cantilever with a laser and detects the reflected light with a photodetector to detect the displacement of the cantilever (optical lever method). An image of the cantilever taken by a camera is used to adjust the optical axis of the laser with respect to the cantilever. In the image taken by the camera, the laser beam image spreads widely and is affected by background light. Therefore, there is a problem in that it is difficult to specify the position of the laser, and it takes a long time to adjust the optical axis.

Japanese Patent Application Publication No. 9-145314 Japanese Patent Application Publication No. 2000-329772

An object of the present invention is to provide a probe microscope and a probe microscope optical axis adjustment method that can shorten the optical axis adjustment time.

(1) The probe microscope includes a cantilever, a first laser, an imaging device, an infinity optical system, a moving mechanism, a first rotating section, and a control section. The cantilever has a probe. The first laser emits a first laser beam that is incident on the cantilever. The imaging device captures images of the cantilever and the first laser beam. The infinite optical system is formed between the cantilever and the imaging device, and the first laser beam is incident thereon. The moving mechanism changes the relative position of the first laser beam and the cantilever. The first rotating section rotates the first laser to change a first incident angle of the first laser beam with respect to the infinite optical system. The control section controls the operation of the moving mechanism and the first rotating section. The control unit is configured to change the position of the first laser light image of the first laser light from the position of the first ghost light image of the first ghost light generated from the first laser light in the infinity optical system to an image taken by the imaging device. Obtained at. The control section drives at least one of the moving mechanism and the first rotation section so that the position of the first laser light image approaches a predetermined position of the cantilever.

(9) A method for adjusting the optical axis of a probe microscope uses the above-described probe microscope to carry out a first step and a second step. In the first step, the imaging device photographs the position of the first laser light image of the first laser light from the position of the first ghost light image of the first ghost light generated from the first laser light in the infinite optical system. Obtained in the image. In the second step, at least one of the moving mechanism and the first rotating section is driven so that the position of the first laser beam image approaches a predetermined position of the cantilever.

Since the first ghost light is generated in the infinite optical system, it is not affected by the focal length of the objective lens. Since the first ghost light image is clearly visible in the image taken by the imaging device, it is easy to specify the position of the first ghost light image. Since the first ghost light is generated from the first laser light, there is a close relationship between the relative positions of the two. By using the position of the first ghost light image, the position of the first laser light image can be easily obtained. Thereby, the optical axis adjustment time can be shortened.

(2) The storage unit stores a first relational expression expressing a first relative position between the first ghost light image and the first laser light image as a function of the first incident angle. The control unit obtains the first relative position by substituting the first incident angle into the first relational expression, and calculates the first laser light image from the position of the first ghost light image and the first relative position in the image captured by the imaging device. Get the position of.

(10) In the first step, the first incident angle is substituted into the first relational expression expressing the first relative position between the first ghost light image and the first laser light image as a function of the first incident angle, and the first Get relative position. In the first step, the position of the first laser light image is acquired from the position of the first ghost light image and the first relative position in the image photographed by the imaging device.

The first relative position is obtained by substituting the first angle of incidence into the first relational expression. The position of the first ghost light image is accurately specified based on the position of the first ghost light image and the first relative position. Thereby, the optical axis adjustment time can be shortened.

(3) The probe microscope further includes a second laser and a second rotating section. The second laser emits a second laser beam that is incident on the cantilever. The second rotating section rotates the second laser to change a second incident angle of the second laser beam with respect to the infinite optical system. The moving mechanism changes the relative positions of the first laser beam, the second laser beam, and the cantilever. The storage unit stores a second relative position between a second ghost light image of the second ghost light generated from the second laser light in the infinite optical system and a second laser light image of the second laser light, based on a second incident angle. A second relational expression expressed as a function is stored. The control unit acquires the relative ghost light positions of the first ghost light image and the second ghost light image from the image captured by the imaging device. The control unit obtains the first relative position by substituting the first incident angle into the first relational expression. The control unit obtains the second relative position by substituting the second angle of incidence into the second relational expression. The control unit obtains the relative laser light positions of the first laser light image and the second laser light image from the ghost light relative position, the first relative position, and the second relative position. The control section drives at least one of the moving mechanism, the first rotating section, and the second rotating section so that the relative position of the laser beam approaches a predetermined relative position.

(4) The first laser is a measurement laser that emits a measurement laser beam used on the displacement meter side of the cantilever. The second laser is an excitation laser that emits excitation laser light used to excite the cantilever.
Thereby, the first laser beam and the second laser beam are arranged at predetermined relative positions, and the sensitivity of the probe microscope is increased. Therefore, the accuracy of the probe microscope is improved.

(5) The probe microscope further includes a lever support section that supports the cantilever. In the image taken by the imaging device, the position of the first ghost light image is adjusted so that the first ghost light image overlaps the lever support portion.
Since the surface of the lever support part is uniform, the visibility of the first ghost light image is improved by overlapping the first ghost light image with the lever support part.

(6) The probe microscope further includes a selection member that selects the first ghost light captured by the imaging device.
By using the position of the selected first ghost light image, the position of the first laser light image can be easily specified. Thereby, the optical axis adjustment time can be shortened.

(7) The control unit acquires the position of the first laser light image from the representative position of the plurality of first ghost light images in the image photographed by the imaging device.
By using the representative positions of the plurality of first ghost light images, the position of the first laser light image can be easily identified. Thereby, the optical axis adjustment time can be shortened.

(8) The probe microscope further includes an objective lens and an objective lens exchange mechanism. The objective lens focuses the first laser beam emitted from the infinite optical system. The objective lens exchange mechanism holds the objective lens in an exchangeable manner.
This makes it possible to use an objective lens with optimal magnification depending on the type of cantilever.

The control unit of the probe microscope acquires the position of the first laser light image from the position of the first ghost light image in the image taken by the imaging device. Thereby, the position of the first laser beam image can be easily acquired, so that the optical axis adjustment time can be shortened.

FIG. 1 is a schematic configuration diagram of a probe microscope according to an embodiment. An explanatory diagram of an objective lens exchange mechanism. FIG. 6 is an explanatory diagram of the behavior of the first laser light image due to movement of the first laser. FIG. 6 is an explanatory diagram of the behavior of the first laser light image due to rotation of the first laser. FIG. 3 is an explanatory diagram of the principle of generation of first ghost light. FIG. 6 is an explanatory diagram of the behavior of the first ghost light image due to rotation of the first laser. Image taken when the objective lens is out of focus. Image taken when the objective lens is in focus. FIG. 6 is an explanatory diagram of optical axis adjustment of the second laser.

Hereinafter, a probe microscope and a method for adjusting the optical axis of the probe microscope according to embodiments will be described with reference to the drawings.
(probe microscope)
FIG. 1 is a schematic configuration diagram of a probe microscope according to an embodiment. In this application, the Z direction, X direction, and Y direction of the orthogonal coordinate system are defined as follows. The Z direction is the direction in which the objective lens 18 and the cantilever 3 are separated. The +Z direction is a direction from the tip of the cantilever 3 toward the objective lens 18. For example, the Z direction is a vertical direction, and the +Z direction is vertically upward. The X direction and the Y direction are directions perpendicular to the Z direction. For example, the X direction and the Y direction are horizontal directions. The +X direction is the right direction when facing the page of FIG.

The probe microscope 1 includes a cantilever unit 5, a laser unit 10, an optical axis adjustment unit 20, a control section 35, and a storage section 36.
The cantilever unit 5 includes a cantilever 3, a probe 2, a lever support 4, and a photodetector 6.

The cantilever 3 is formed into an elongated flat plate shape. The normal direction of the cantilever 3 intersects the Z direction. The probe 2 is placed at the tip of the cantilever 3 in the −X direction. The probe 2 is arranged on the −Z direction surface of the cantilever 3 and tapers toward the −Z direction. The probe microscope 1 brings the probe 2 close to the surface of the sample S to observe the surface of the sample S or measure the physical properties of the sample S. The lever support part 4 is arranged at the base end of the cantilever 3 in the +X direction. The lever support portion 4 supports the cantilever 3 as a cantilever beam.

Photodetector 6 is arranged near cantilever unit 5. The photodetector 6 detects the first laser beam D1 reflected from the back surface (the surface in the +Z direction) of the cantilever 3. The probe microscope 1 detects the displacement of the cantilever 3 from the detection position of the first laser beam D1 by the photodetector 6. When operating in contact mode, the probe microscope 1 brings the probe 2 close to the surface of the sample S and scans the cantilever 3. The probe microscope 1 moves the sample S in the Z direction so that the displacement of the cantilever 3 detected by the photodetector 6 is constant. The probe microscope 1 performs surface observation or physical property measurement of the sample S based on the amount of movement of the sample S in the Z direction.

The laser unit 10 causes laser beams D1 and D2 to be incident on the cantilever 3. The laser unit 10 includes a first laser 11, a second laser 12, a dichroic cube 13, a polarizing beam splitter (hereinafter referred to as PBS) 15, a first rotating section 31, and a second laser. It has a moving part 32, an objective lens 18, an objective lens exchange mechanism 40, and a moving mechanism 30.

The first laser 11 is a measurement laser used, for example, on the displacement meter side of the tip of the cantilever 3. The first laser 11 emits, for example, a first laser beam D1 having a wavelength of 635 nm. The first laser beam D1 is incident on the tip of the cantilever 3 in the −X direction.

The second laser 12 is, for example, an excitation laser used to excite the cantilever 3. The second laser 12 emits a second laser beam D2 having a wavelength of 785 nm, for example. The second laser beam D2 is incident on the base end of the cantilever 3 in the +X direction.
When operating in a dynamic mode, the probe microscope 1 moves the probe 2 close to the surface of the sample S and scans the cantilever 3 while vibrating the cantilever 3 at a resonant frequency. The probe microscope 1 moves the sample S in the Z direction so that the displacement amplitude of the cantilever 3 detected by the photodetector 6 is constant. The probe microscope 1 performs surface observation or physical property measurement of the sample S based on the amount of movement of the sample S in the Z direction. In the probe microscope 1, the cantilever may be excited by a piezo element instead of the second laser 12. Note that when the cantilever is excited with a laser, only the lever portion vibrates, so there is an advantage that a vibration state extremely close to an ideal vibration state can be achieved and highly accurate measurement can be performed. When a cantilever is excited by a piezo element, parts other than the lever part vibrate, which tends to cause noise, but there is an advantage that there is no need to adjust the excitation laser.

The dichroic cube 13 multiplexes the first laser beam D1 and the second laser beam D2 and makes them enter the PBS 15.
The PBS 15 separates the incident light into P polarized light and S polarized light. The spectral plane 16 of the PBS 15 reflects, for example, S-polarized light and transmits P-polarized light. The end surface 17 of the PBS 15 is subjected to antireflection treatment (AR coating). The laser beams D1 and D2 are S-polarized and enter the PBS 15. The laser beams D1 and D2 are reflected by the spectral plane 16 of the PBS 15 and are emitted from the PBS 15 in the −Z direction.
An optical element such as a quarter wavelength plate or a polarizing plate may be appropriately placed on the optical axis of the probe microscope 1.

The first rotating section 31 changes the first incident angle of the first laser beam D1 with respect to the PBS 15 by rotating the first laser 11.
The second rotating section 32 changes the second incident angle of the second laser beam D2 with respect to the PBS 15 by rotating the second laser 12.

The objective lens 18 focuses the laser beams D1 and D2 emitted from the PBS 15 toward the cantilever 3.
FIG. 2 is an explanatory diagram of the objective lens exchange mechanism. Since the optimal magnification of the objective lens 18 differs depending on the type of cantilever 3, it is desirable that the objective lens 18 be replaceable. The objective lens exchange mechanism 40 holds the objective lens 18 exchangeably with respect to the lens support part 41. The lens support portion 41 has a dovetail groove 42 . The dovetail groove 42 is a groove in which the width of the opening is smaller than the width of the bottom. The objective lens 18 has a tenon 48 that engages with the dovetail groove 42 . The objective lens 18 is positioned by engaging the tenon 48 of the objective lens 18 with the dovetail groove 42 of the lens support portion 41. The cap screw 45 fixes the objective lens 18 to the lens support portion 41 . The objective lens exchange mechanism is not limited to the example shown in FIG. 2, and may be a revolver equipped with a plurality of objective lenses 18 having different magnifications.

The moving mechanism 30 changes the relative positions of the laser beams D1 and D2 and the cantilever 3 by changing the relative positions of the laser unit 10 and the cantilever unit 5 shown in FIG. The moving mechanism 30 can move at least one of the laser unit 10 and the cantilever unit 5 in the X direction, the Y direction, and the Z direction.

The optical axis adjustment unit 20 is used to adjust the optical axes of the laser beams D1 and D2 with respect to the cantilever 3. The optical axis adjustment unit 20 includes an illumination device 21, a beam splitter 23, an imaging lens 28, and a camera (imaging device) 25.
The illumination device 21 emits illumination light 22 that illuminates the cantilever 3. Beam splitter 23 reflects illumination light 22 toward cantilever 3 . The beam splitter 23 transmits the scattered light R from the cantilever 3 toward the imaging lens 28 . The imaging lens 28 focuses the scattered light R from the cantilever 3 toward the camera 25.

Camera 25 has an image sensor 26. The camera 25 captures an image of the scattered light R from the cantilever 3. In addition to the image of the cantilever 3, the image taken by the camera 25 includes a first laser light image d1 of the first laser light D1 and a second laser light image d2 of the second laser light D2 that are formed near the cantilever 3. is displayed (see Figure 9).

An infinite optical system PL in which light travels in parallel is formed between the objective lens 18 and the imaging lens 28, which are arranged between the cantilever 3 and the camera 25. Laser beams D1 and D2 and illumination light 22 are incident on optical elements arranged in infinite optical system PL. In the embodiment, laser beams D1 and D2 are incident on the PBS 15, and illumination light 22 is incident on the beam splitter 23. The optical elements into which the laser beams D1 and D2 and the illumination light 22 are incident are not limited to these. The angle of incidence of the laser beams D1 and D2 on the PBS 15 corresponds to the angle of incidence of the laser beams D1 and D2 on the infinite optical system PL. The angle of incidence of the laser beams D1 and D2 on the PBS 15 corresponds to the angle of incidence of the laser beams D1 and D2 on the objective lens 18.

The control section 35 controls the operation of each section of the probe microscope 1. The probe microscope 1 includes a CPU (Central Processing Unit), a memory, an auxiliary storage device, and the like. The CPU functions as the control unit 35 by executing programs stored in the memory and auxiliary storage device. As will be described later, the control unit 35 analyzes the image taken by the camera 25 and acquires the positions of the laser light images d1 and d2. The control unit 35 controls the operations of the moving mechanism 30, the first rotating unit 31, and the second rotating unit 32 so that the laser light images d1 and d2 approach predetermined positions.
The storage unit 36 stores a first relational expression and a second relational expression, which will be described later.

(Laser light image and ghost light image)
The behavior of the first laser light image d1 due to the movement and rotation of the first laser 11 will be explained.
FIG. 3 is an explanatory diagram of the behavior of the first laser light image due to movement of the first laser. FIG. 4 is an explanatory diagram of the behavior of the first laser light image due to rotation of the first laser. In FIGS. 3 and 4, some of the constituent members of the probe microscope 1 are omitted for easy understanding. The behavior of the second laser light image d2 due to the movement and rotation of the second laser 12 is also similar to that of the first laser light image d1.

FIG. 3 shows a case where the first laser 11 is moved. Before and after the movement of the first laser 11, the first incident angle of the first laser beam D1 with respect to the PBS 15 does not change. The first laser beam D1m after the movement of the first laser 11 enters the PBS 15 and the objective lens 18 in parallel with the first laser beam D1 before movement. The first laser beams D1 and D1m before and after the movement of the first laser 11 are focused at the same position by the objective lens 18. The first laser light images d1 and d1m before and after the movement of the first laser 11 are at the same position. In this way, even if the first laser 11 moves, the first laser light image d1 does not move.

FIG. 4 shows a case where the first laser 11 is rotated. Before and after the rotation of the first laser 11, the first incident angle θ1 of the first laser beam D1 with respect to the PBS 15 changes. The first laser beam D1r after the first laser 11 is rotated enters the objective lens 18 at a different angle from the first laser beam D1 before the rotation. The first laser beams D1 and D1r before and after the rotation of the first laser 11 are focused at different positions by the objective lens 18. In the example of FIG. 4, on the back surface of the cantilever 3, the first laser light image d1r of the first laser 11 after rotation moves in the +X direction with respect to the first laser light image d1 before rotation. In the captured image of the camera 25, the first laser light image d1r after the first laser 11 is rotated moves in the −X direction with respect to the first laser light image d1 before the rotation. In this way, when the first laser 11 rotates, the first laser light image d1 moves. The position of the first laser light image d1 is a function of the rotation angle (and rotation direction) of the first laser 11. The rotation angle of the first laser 11 corresponds to the first incident angle θ1 of the first laser beam D1 with respect to the PBS 15. The first incident angle θ1 of the first laser beam D1 with respect to the PBS 15 corresponds to the first incident angle of the first laser beam D1 with respect to the objective lens 18.

The first ghost light G1 generated from the first laser light D1 will be explained.
FIG. 5 is an explanatory diagram of the principle of generation of the first ghost light. In FIG. 5, some of the constituent members of the probe microscope 1 are omitted for easy understanding. The second ghost light G2 generated from the second laser light D2 is also similar to the first ghost light G1.

As described above, the first laser beam D1 is S-polarized and enters the PBS 15. The first laser beam D1 is reflected by the spectral plane 16 and exits from the PBS 15.
However, not all of the first laser light D1 is S-polarized light, and the first laser light D1 includes P-polarized light. The spectral plane 16 of the PBS 15 does not reflect all of the S-polarized light and transmit all of the P-polarized light, but rather transmits part of the S-polarized light and reflects part of the P-polarized light. Although the end face 17 of the PBS 15 is subjected to anti-reflection treatment, the end face 17 of the PBS 15 reflects a part of the laser beam.

A part of the first laser beam D1 that is incident on the PBS 15 and reflected by the spectral plane 16 is reflected by the end surface 17a of the PBS 15, and a first ghost beam G1a is generated. The first ghost light G1a passes through the spectral plane 16 and is emitted from the PBS 15 toward the camera 25.
A part of the first laser light D1 that has entered the PBS 15 is transmitted through the spectral plane 16, and a first ghost light G1b is generated. The first ghost light G1a is reflected by the end surface 17b and the spectral surface 16, and is emitted from the PBS 15 toward the camera 25.

In this way, the first ghost light G1 is generated due to unplanned reflection and transmission of the first laser light D1 that has entered the PBS 15. In addition to the first ghost lights G1a and G1b described above, various kinds of first ghost lights G1 are generated. Since it is mainly P-polarized light that passes through the PBS 15, the first ghost light G1 is often P-polarized light.

The first ghost light G1 generated by the infinite optical system PL is focused toward the camera 25 by the imaging lens 28. In addition to the cantilever 3 and the first laser light image d1 described above, the first ghost light image g1 of the first ghost light G1 is reflected in the image taken by the camera 25. Since the first ghost light G1 is generated from the first laser light D1, there is a close relationship between the relative positions of the first ghost light image g1 and the first laser light image d1. As will be described later, the control unit 35 acquires the position of the first laser light image d1 based on the position of the first ghost light image g1.

As described above, a plurality of first ghost lights G1 are generated from the first laser light D1. A plurality of first ghost light images g1 may be used to obtain the position of the first laser light image d1, or any one of the first ghost light images g1 may be used. In the former case, the position of the first laser light image d1 is acquired based on the representative positions of the plurality of first ghost light images g1. For example, the representative position is the center of gravity position. In the latter case, the first ghost light image g1 to be used is selected. A selection member 24 for the first ghost light G1 is arranged between the PBS 15 and the camera 25. The sorting member 24 sorts out the first ghost light G1 photographed by the camera 25. The plurality of first ghost lights G1 have different polarization directions, light intensities, and the like. The sorting member 24 is a polarizing plate, an ND filter, or the like. When the sorting member 24 is a polarizing plate, the first ghost light G1a in a specific polarization direction passes through the sorting member 24 and is photographed by the camera 25. The ND filter reduces the light intensity of all wavelengths of light. When the selection member 24 is an ND filter, the first ghost light G1a having a high light intensity passes through the selection member 24 and is photographed by the camera 25.

The behavior of the first ghost light image g1 due to the movement and rotation of the first laser 11 will be explained. The behavior of the second ghost light image g2 due to the movement and rotation of the second laser 12 is also similar to that of the first ghost light image g1.
The behavior of the first ghost light image g1 when the first laser 11 is moved is similar to the behavior of the first laser light image d1. The first ghost light G1 after the first laser 11 has moved is incident on the imaging lens 28 in parallel with the first ghost light G1 before the movement. The first ghost light G1 before and after the movement of the first laser 11 is focused at the same position by the imaging lens 28. Even if the first laser 11 moves, the first ghost light image g1 does not move.

FIG. 6 is an explanatory diagram of the behavior of the first ghost light image due to rotation of the first laser. In FIG. 6, illustration of some of the constituent members of the probe microscope 1 is omitted for easy understanding. Before and after the rotation of the first laser 11, the first incident angle θ1 of the first laser beam D1 with respect to the PBS 15 changes. Before and after the first laser 11 rotates, the incident angle of the first laser 11 with respect to the spectral plane 16 and end face 17 of the PBS 15 also changes. For example, the first laser 11 is reflected by the end face 17 of the PBS 15, and the first ghost light G1 is generated. The first ghost light G1r after the first laser 11 is rotated enters the imaging lens 28 at a different angle from the first ghost light G1 before the rotation. The first ghost lights G1 and G1r before and after the rotation of the first laser 11 are focused at different positions by the imaging lens 28. In the example of FIG. 6, in the image taken by the camera 25, the first ghost light image g1r after rotation of the first laser 11 moves in the +X direction with respect to the first ghost light image g1 before rotation. In this way, when the first laser 11 rotates, the first ghost optical image g1 moves. The position of the first ghost light image g1 is a function of the rotation angle (and rotation direction) of the first laser 11. The rotation angle of the first laser 11 corresponds to the first incident angle θ1 of the first laser beam D1 with respect to the PBS 15.

As described above, in the photographed image of the camera 25, the first laser light image d1r of the first laser 11 after rotation moves in the −X direction with respect to the first laser light image d1 before rotation. Conversely, the first ghost light image g1r after rotation of the first laser 11 moves in the +X direction with respect to the first ghost light image g1 before rotation. Before and after the movement of the first laser 11, the first laser light image d1 and the first ghost light image g1 move in mutually opposite directions.

As mentioned above, the position of the first laser light image d1 is a function of the first incident angle θ1 of the first laser light D1 with respect to the PBS 15. The position of the first ghost light image g1 is also a function of the first incident angle θ1. The first relative position between the first ghost light image g1 and the first laser light image d1 is obtained by the difference between the two. The first relative position (distance and direction) L1 is expressed by a first relational expression L1 (θ1) as a function of the first incident angle θ1. The same applies to the second laser 12. The second relative position (distance and direction) L2 between the second ghost light image g2 and the second laser light image d2 is determined by the second relational expression L2 ( θ2). The first relational expression L1 (θ1) and the second relational expression L2 (θ2) are obtained in advance through experiments, simulations, etc. before the probe microscope 1 is shipped. The first relational expression L1 (θ1) and the second relational expression L2 (θ2) are stored in the storage unit 36.

(Optical axis adjustment of probe microscope)
Optical axis adjustment of the probe microscope will be explained.
In the probe microscope 1, various types of cantilevers 3 and objective lenses 18 are used depending on the type of sample S, etc. Each time the cantilever 3 and objective lens 18 are replaced, the optical axis of the probe microscope is adjusted.

Optical axis adjustment of the first laser beam D1 will be explained. As described above, the first laser 11 is a measurement laser used, for example, on the displacement meter side of the tip of the cantilever 3. When the first laser beam D1 is focused on the tip of the cantilever 3, the amount of light received by the photodetector 6 increases, and the sensitivity to the displacement of the cantilever 3 increases. The optical axis of the first laser beam D1 is adjusted so that the first laser beam D1 is focused on the tip of the cantilever 3. The optical axis adjustment is performed by driving at least one of the moving mechanism 30, the first rotating section, and the second rotating section based on the captured image of the camera 25. Optical axis adjustment may be performed automatically by the control unit 35 or manually by an operator.

FIG. 7 shows an image taken when the objective lens is out of focus. That is, in the example of FIG. 7, the cantilever 3 is spaced apart from the focal length of the objective lens 18. As described above, the cantilever 3, the first laser light image d1, and the first ghost light image g1 are reflected in the image taken by the camera 25. Since the objective lens is out of focus, the outline of the cantilever 3 is blurred, and the first laser light image d1 is greatly spread. The surface of the sample S is reflected on the outside of the cantilever 3. The surface of the sample S is diverse, and the first laser beam image d1 is buried in background light and becomes difficult to see. Particularly when the surface of the sample S is dark, the scattered light becomes weak, making it difficult to specify the position of the first laser beam image d1. Therefore, it is difficult to adjust the optical axis so that the first laser light image d1 is placed at the tip of the cantilever 3.

In the image taken by the camera 25, the first ghost light image g1 is clearly visible. This is because the first ghost light image g1 is generated in the infinite optical system PL and is therefore not affected by the focal length of the objective lens 18. The control unit 35 acquires the position of the first laser light image d1 from the position of the first ghost light image g1 in the image captured by the camera 25 (first step). The control unit 35 reads the first relational expression L1 (θ1) from the storage unit 36, substitutes the first incident angle θ1, and determines the first relative position L1 between the first ghost light image g1 and the first laser light image d1. get. The control unit 35 adds the first relative position L1 to the position of the first ghost light image g1 to obtain the position of the first laser light image d1.

FIG. 8 is a captured image when the objective lens is in focus. That is, in the example of FIG. 8, the cantilever 3 is close to the focal length of the objective lens 18. The control unit 35 drives at least one of the moving mechanism 30 and the first rotating unit 31 so that the position of the first laser light image d1 approaches the tip (predetermined position) of the cantilever (second step). . The control unit 35 drives the moving mechanism 30 to adjust the relative position of the laser unit 10 and the cantilever unit 5 in the Z direction. As a result, the cantilever 3 approaches the focal length of the objective lens 18, and the objective lens 18 is brought into focus. The control unit 35 drives at least one of the moving mechanism 30 and the first rotating unit 31 to adjust the relative position of the first laser light image d1 with respect to the cantilever 3 in the XY directions. As a result, the first laser light image d1 is placed at the tip of the cantilever 3, and the optical axis adjustment of the first laser light D1 is completed.

As described above, in the image taken by the camera 25, the surface of the sample S is shown on the outside of the lever support section 4. Since the surface of the sample S is diverse, when the first ghost light image g1 overlaps with the sample S, the visibility of the first ghost light image g1 decreases. In the image taken by the camera 25, the position of the first ghost light image g1 is adjusted so that the first ghost light image g1 overlaps with the lever support part 4 of the cantilever 3. The surface of the lever support portion 4 is uniform. By overlapping the first ghost light image g1 with the lever support portion 4, the visibility of the first ghost light image g1 is improved. The position of the first ghost light image g1 can be adjusted by tilting the PBS 15 and moving the first ghost light image g1 more than the first laser light image d1. The position of the first ghost light image g1 can also be adjusted by using both the tilting of the camera 25 and the rotation of the first laser 11. In the latter case, the device configuration of the probe microscope 1 is simplified.

Optical axis adjustment of the second laser beam D2 will be explained. As described above, the second laser 12 is an excitation laser used to excite the cantilever 3, for example. The second laser 12 is modulated near the resonant frequency of the cantilever 3. When the second laser beam D2 is focused at a predetermined position on the base end of the cantilever 3, the amplitude of the cantilever 3 increases, and the sensitivity of the photodetector 6 increases. The cantilever 3 has different sizes and lengths depending on the resonance frequency. In order to vibrate each cantilever 3, there is an optimal irradiation position of the second laser beam D2. The optical axis of the second laser beam D2 is adjusted so that the second laser beam D2 is focused at a predetermined position on the base end of the cantilever 3.

FIG. 9 is an explanatory diagram of optical axis adjustment of the second laser. In addition to the cantilever 3, the first laser light image d1, and the first ghost light image g1, a second laser light image d2 and a second ghost light image g2 are captured in the image taken by the camera 25. As described above, the wavelength of the first laser beam D1 and the wavelength of the second laser beam D2 are different. In this case, the first laser light image d1 and the first ghost light image g1 are distinguished from the second laser light image d2 and the second ghost light image g2 due to the difference in light color. The optical axis adjustment of the second laser beam D2 can be performed in the same way as the optical axis adjustment of the first laser beam D1. The control unit 35 reads out the second relational expression L2 (θ2) from the storage unit, substitutes the second incident angle θ2, and calculates the second relative position L2 between the second ghost light image g2 and the second laser light image d2. get. The control unit 35 adds the second relative position L2 to the position of the second ghost light image g2 to obtain the position of the second laser light image d2. The control unit 35 drives at least one of the moving mechanism 30 and the second rotating unit 32 so that the position of the second laser light image d2 approaches the base end (predetermined position) of the cantilever 3.

The probe microscope 1 excites the cantilever 3 and performs measurements. Therefore, the relationship between the incident position of the first laser beam D1 and the incident position of the second laser beam with respect to the cantilever 3 is important. The control unit 35 acquires the laser beam relative position Ld between the first laser beam image d1 and the second laser beam image d2 as follows. The control unit 35 analyzes the captured image of the camera 25 and obtains the ghost light relative position Lg between the first ghost light image g1 and the second ghost light image g2. Since the first ghost light image g1 and the second ghost light image g2 are clearly visible in the photographed image of the camera 25, the ghost light relative position Lg is accurately acquired. The control unit 35 obtains the first relative position L1 between the first ghost light image g1 and the first laser light image d1 by substituting the first incident angle θ1 into the first relational expression L1 (θ1). The control unit 35 obtains a second relative position L2 between the second ghost light image g2 and the second laser light image d2 by substituting the second incident angle θ2 into the second relational expression L2 (θ2). The control unit 35 obtains the laser beam relative position Ld using the following equation (1).
Ld=L1-L2-Lg... (1)

The control unit 35 controls the moving mechanism 30, the first rotating unit 31, and the At least one of the two rotating parts 32 is driven. With the above steps, the optical axis adjustment of the second laser beam D2 is completed.

As detailed above, the probe microscope 1 of the embodiment includes the cantilever 3, the first laser 11, the camera 25, the infinite optical system PL, the moving mechanism 30, the first rotating section 31, It has a control section 35. The cantilever 3 has a probe 2. The first laser 11 emits a first laser beam D1 that is incident on the cantilever 3. The camera 25 takes images of the cantilever 3 and the first laser beam D1. The infinite optical system PL is formed between the cantilever 3 and the camera 25, and the first laser beam D1 is incident thereon. The moving mechanism 30 changes the relative position between the first laser beam D1 and the cantilever 3. The first rotating section 31 rotates the first laser 11 to change the first incident angle θ1 of the first laser beam D1 with respect to the infinite optical system PL. The control unit 35 controls the operation of the moving mechanism 30 and the first rotating unit 31. The control unit 35 changes the position of the first laser light image d1 of the first laser light D1 from the position of the first ghost light image g1 of the first ghost light G1 generated from the first laser light D1 in the infinite optical system PL. is acquired in the image taken by the camera 25. The control unit 35 drives at least one of the moving mechanism 30 and the first rotating unit 31 so that the position of the first laser beam image d1 approaches a predetermined position of the cantilever 3.

In the method for adjusting the optical axis of the probe microscope 1 according to the embodiment, the probe microscope 1 is used to carry out a first step and a second step. In the first step, from the position of the first ghost light image g1 of the first ghost light G1 generated from the first laser light D1 in the infinite optical system PL, to the position of the first laser light image d1 of the first laser light D1. is acquired in the image taken by the camera 25. In the second step, at least one of the moving mechanism and the first rotating section is driven so that the position of the first laser beam image d1 approaches a predetermined position of the cantilever.

Since the first ghost light G1 is generated in the infinite optical system PL, it is not affected by the focal length of the objective lens 18. Since the first ghost light image g1 is clearly visible in the image taken by the camera 25, it is easy to specify the position of the first ghost light image g1. Since the first ghost light G1 is generated from the first laser light D1, there is a close relationship between the relative positions of the two. By using the position of the first ghost light image g1, the position of the first laser light image d1 can be easily obtained. Thereby, the optical axis adjustment time can be shortened.

Although one embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and modifications, combinations, and deletions of the configuration within the scope of the gist of the present invention. etc. are also included.
In the embodiment, the position of the first laser light image d1 was acquired based on the position of the first ghost light image g1. On the other hand, the position of the first laser light image d1 may be acquired based on the position of the first ghost light image g1 and the position of the outline of the cantilever 3.
Further, although FIG. 1 shows an example in which two laser beams are incident on the cantilever 3, three or more laser beams may be incident on the cantilever 3. When three or more laser beams are used, any laser beam may be treated as the "first laser beam", as long as such treatment is possible due to the configuration of the optical system, etc. Any laser light other than the laser light treated as "laser light" may be handled as "second laser light".

D1...first laser light, d1...first laser light image, D2...second laser light, d2...second laser light image, G1...first ghost light, g1...first ghost light image, G2...second ghost Light, g2...Second ghost light image, Ld...Laser beam relative position, Lg...Ghost light relative position, L1...First relative position, L1(θ1)...First relational expression, L2...Second relative position, L2( θ2)... Second relational expression, PL... Infinity optical system, θ1... First incident angle, θ2... Second incident angle, 1... Probe microscope, 2... Probe, 3... Cantilever, 4... Lever support part, 11... First laser, 12... Second laser, 18... Objective lens, 24... Sorting member, 25... Camera (imaging device), 30... Moving mechanism, 31... First rotating section, 32... Second rotating section, 35 ...control section, 36...storage section, 40...objective lens exchange mechanism.

Claims (10)

a cantilever having a probe;
a first laser that emits a first laser beam that is incident on the cantilever;
an imaging device that captures images of the cantilever and the first laser beam;
an infinity optical system formed between the cantilever and the imaging device, into which the first laser beam is incident;
a moving mechanism that changes the relative position of the first laser beam and the cantilever;
a first rotating part that rotates the first laser to change a first incident angle of the first laser beam with respect to the infinite optical system;
a control unit that controls operations of the moving mechanism and the first rotating unit;
The control unit includes:
An image taken by the imaging device of the position of the first laser light image of the first laser light from the position of the first ghost light image of the first ghost light generated from the first laser light in the infinity optical system. obtained in
driving at least one of the moving mechanism and the first rotating section so that the position of the first laser light image approaches a predetermined position of the cantilever;
probe microscope. further comprising a storage unit that stores a first relational expression expressing a first relative position between the first ghost light image and the first laser light image as a function of the first incident angle;
The control unit obtains the first relative position by substituting the first incident angle into the first relational expression, and calculates the position of the first ghost light image in the image captured by the imaging device and the first relative position. obtaining the position of the first laser light image from the position;
The probe microscope according to claim 1. a second laser that emits a second laser beam that is incident on the cantilever;
further comprising a second rotating part that rotates the second laser to change a second incident angle of the second laser beam with respect to the infinite optical system,
The moving mechanism changes the relative positions of the first laser beam and the second laser beam and the cantilever,
The storage unit stores a second relative position between a second ghost light image of a second ghost light generated from the second laser light in the infinite optical system and a second laser light image of the second laser light, storing a second relational expression expressed as a function of the second incident angle;
The control unit includes:
obtaining ghost light relative positions of the first ghost light image and the second ghost light image from an image taken by the imaging device;
Substituting the first incident angle into the first relational expression to obtain the first relative position;
Substituting the second angle of incidence into the second relational expression to obtain the second relative position;
Obtaining the relative laser light positions of the first laser light image and the second laser light image from the ghost light relative position, the first relative position, and the second relative position,
driving at least one of the moving mechanism, the first rotating section, and the second rotating section so that the relative position of the laser beam approaches a predetermined relative position;
The probe microscope according to claim 2. The first laser is a measurement laser that emits a measurement laser beam used on the displacement meter side of the cantilever,
The second laser is an excitation laser that emits excitation laser light used to excite the cantilever.
The probe microscope according to claim 3. further comprising a lever support part that supports the cantilever,
In the image taken by the imaging device, the position of the first ghost light image is adjusted so that the first ghost light image overlaps the lever support part.
The probe microscope according to any one of claims 1 to 4. further comprising a sorting member that sorts the first ghost light captured by the imaging device;
The probe microscope according to any one of claims 1 to 5. The control unit acquires the position of the first laser light image from a representative position of the plurality of first ghost light images in the image captured by the imaging device.
The probe microscope according to any one of claims 1 to 5. an objective lens that focuses the first laser beam emitted from the infinity optical system;
further comprising an objective lens exchange mechanism that exchangeably holds the objective lens;
A probe microscope according to any one of claims 1 to 7. a cantilever having a probe;
a first laser that emits a first laser beam that is incident on the cantilever;
an imaging device that captures images of the cantilever and the first laser beam;
an infinity optical system formed between the cantilever and the imaging device, into which the first laser beam is incident;
a moving mechanism that changes the relative position of the first laser beam and the cantilever;
a first rotating part that rotates the first laser to change a first incident angle of the first laser beam with respect to the infinite optical system;
Using a probe microscope with
An image taken by the imaging device of the position of the first laser light image of the first laser light from the position of the first ghost light image of the first ghost light generated from the first laser light in the infinity optical system. A first step of obtaining the
a second step of driving at least one of the moving mechanism and the first rotating section so that the position of the first laser light image approaches a predetermined position of the cantilever;
How to adjust the optical axis of a probe microscope. In the first step, the first incident angle is substituted into a first relational expression expressing a first relative position between the first ghost light image and the first laser light image as a function of the first incident angle. obtaining the first relative position, and obtaining the position of the first laser light image from the position of the first ghost light image and the first relative position in the image captured by the imaging device;
The optical axis adjustment method for a probe microscope according to claim 9.

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