JPH09189707A - Near field scanning optical microscope and scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily prevent mixing of the light used far an AFM (inter-atmomic force microscope)-dedicated optical system with the detection light of an NSOM (near field scanning optical microscope), etc., by easily securing a space for placing an objective lens required for the optical microscope for selecting a measuring area in a sample, coping with it. SOLUTION: A probe 3 is made to scan while it keeps a certain distance from a sample 15. For controlling them, the detection light of an NSOM from the probe 3 is used. Since the light of optical near field interaction from the probe 3 is used, the other light source is not required, and there is no spatial constraint on an objective lens caused by installation of the other optical system, and an objective lens 4 of high magnification can easily be used, and alignment of the sample 15 is easily performed. Both the change of relative distance between the emission position of the light emitted from the probe 3 and a detection optical system, or the change of emission direction of light can be applied for detecting the displacement of the probe 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning near-field optical microscope and a scanning probe microscope. More specifically, a probe close to an object to be observed (sample) is attached to the object to be observed (sample). When measuring the force acting between the microscope or the object to be observed (sample) and the probe, the optical characteristics of the object to be observed are detected by scanning relative to each other and detecting the light in the vicinity of the object to be observed. The present invention relates to a microscope suitable for application to a microscope.

[0002]

2. Description of the Related Art Compared with an optical microscope whose resolution is limited by the diffraction limit, a probe whose aperture is smaller than the wavelength of light or a probe whose tip has a similarly small radius of curvature is scanned relative to the sample. Scanning near-field optical microscope (hereinafter NSOM (Ne
(also referred to as ar-Field Scanning Optical Microscope)) is expected to be applied in the industrial and medical fields, since resolution up to the diameter of the probe tip (up to several tens of nm) can be obtained.

As a method of capturing the optical information of the NSOM, a type in which illumination light is incident from the back surface of the sample and an evanescent wave or the like generated on the surface side of the sample is captured by a probe, the illumination light is incident from the surface of the sample, and scattered light by the sample There are several types, such as a type that captures light with a probe with a minute aperture, a type that emits illumination light from a probe with a minute aperture and captures transmitted light and scattered light from the sample. The method of relatively scanning the probe while maintaining a constant distance is, for example, roughly divided into the following two.

One is a type in which illumination light is incident from the back surface of the sample as described above and an evanescent wave or the like generated on the surface side of the sample is taken in by a probe.
Umeda et al. "Second-order differential characteristics of evanescent damped waves"
(Proceedings of the 1st Research Symposium of Near Field Optics Research Group
1994) (Reference 1), the distance between the sample and the probe is measured from the attenuation curve of the detected evanescent wave, and a certain distance is maintained with respect to the sample accordingly. The other is “A COMBINED NEA” by van Hulst and others.
R FIELD OPTICAL AND FORCE MICROSCOPE ”(Scanning M
icroscopy Vol. 7, No. 3 (1993) 78th
9-792) (reference 2) and Japanese Patent Laid-Open No. 6-160719.
A method such as AFM (Atomic Force Microscope) as disclosed in Japanese Patent Publication (Reference 3) is used, and is a method of detecting the displacement of the probe caused by the force acting between the sample and the probe.

The former method using the attenuation curve of the evanescent wave does not require any other optical system because it directly uses the detection light of NSOM, but it is used for a sample whose refractive index is changing. If this is done, the parameters of this attenuation curve will also change, so while scanning relative to the sample,
Move the probe perpendicular to the sample at each point,
You have to measure the parameters at that location. On the other hand, the latter method using the AFM does not require such a thing, but additionally adds an optical system for measuring the displacement of the probe. Of the above methods, the AFM method is generally used at present because of problems such as measurement time.

[0006]

However, the generally used AFM method has the following problems. That is, since the scanning probe microscope generally has a narrow scanning range, it is difficult to find a portion to be observed in the sample. Therefore, it is also preferable to use a combination of an optical microscope, but in this case, since an optical system for measuring the displacement of the probe of the AFM exists around the probe, it is difficult to secure a space for placing the objective lens of the optical microscope. Will be. Further, since the light used by this optical system mixes with the detection light of NSOM, a mechanism for separating the light is required.

The present invention has been made in view of the above points, and it is an object of the present invention to provide the improved scanning near-field optical microscope and scanning probe microscope by improving the disadvantages described above. .

[0008]

According to the present invention, means for irradiating an object to be observed with light and means for detecting the intensity of the optical near field of the object to be observed are provided to cause an optical near field interaction. Is a scanning near-field optical microscope that measures the optical characteristics of the object to be observed by scanning the probe relative to the object to be observed while maintaining a constant distance, A scanning near-field optical microscope is provided, which is characterized in that the relative distance between the probe and the object to be observed is controlled by using the optical signal generated by the action. A scanning probe microscope that controls the relative distance between the sample and the probe by detecting the displacement of the probe or the change in the resonance frequency of the probe caused by the force acting between the sample and the probe, A scanning probe microscope is provided, characterized in that the means for detecting the change of a light emitting point provided on the probe is used.

In the present invention, attention is paid to the following points when the probe is brought close to the sample to be observed and is relatively scanned to control the distance between the probe and the sample. Generally, in the case of the AFM method, it is difficult to find a portion to be observed in the sample due to a narrow scanning range. Therefore, when an optical microscope is used in combination, a dedicated optical system for measuring the displacement of the AFM probe is used. Since it exists around the probe, it is difficult to secure a space for placing the objective lens of the optical microscope, and the light used by the optical system mixes with the detection light of NSOM. However, the reason that the probe in the vicinity of the sample is bent by the interatomic force is that the portion of the probe tip portion that causes the optical near-field interaction is attracted to the sample and its position is displaced. Also,
The emission direction of the emitted light from the probe also tilts when the probe bends. Therefore, by measuring these, the distance between the probe and the sample can be controlled.

Whichever is used, since light of optical near-field interaction by the probe can be used, no other dedicated light source is required. Therefore, an optical system dedicated to control the relative distance between the external probe and the sample (for example, the detection system light source 1 of the comparative example FIG. 7) is used.
6, the condensing lens 17, the optical position detecting element 18, etc.), there are no disadvantages, in particular, there are no spatial restrictions on the objective lens, and as a result, a space for arranging the objective lens can be easily secured. As a result, it is possible to use a high-magnification objective lens when using a combination of optical microscopes, and therefore it is also possible to provide an apparatus configuration that facilitates the alignment of the sample. In this case, the portion of the probe that causes the optical near-field interaction is near the sample, and the best position of the objective lens for measuring the light emitted from the probe and the best position for optical microscope observation are used. It is possible to easily adjust the position of the objective lens at the same position in terms of performance. As a result, an improved device configuration can be achieved in which the optical system for measuring the displacement of the probe of the AFM and the detection optical system of the NSOM can be used in common while avoiding the disadvantages described above.

In the present invention, an objective lens is used to measure these changes, for example, to measure the displacement of the portion of the probe tip that causes optical near-field interaction, and when that portion is at the focal position. Using a total reflection prism, it is possible to change the light emitted from the objective lens into a parallel light beam, a divergent light beam, and a converging light beam when the lens moves from the focus position toward the lens direction and away from the focus position. By measuring the displacement of the probe,
Realized (eg, FIG. 2). Further, when the direction of the emitted light from the probe changes, the amount of change in the emitted light direction due to the bending of the probe can be measured by detecting the emitted light from the objective lens with a split detector utilizing the fact that the optical axis shifts. For example, FIG. 3B.

Using the above principle, a probe microscope of another type, for example, an AFM, attaches a fluorescent dye to the probe to emit light by epi-illumination, and a detection system filters to detect only the fluorescent light. This makes it possible to adopt a device configuration that eliminates the same restrictions around the probe. The above method can be performed in a mode in which the distance between the probe and the sample is directly detected by the displacement of the probe, but the vibration response changes when the probe is scanned while being excited in the direction perpendicular to the sample, It can also be applied as a detection system when a so-called tapping mode is used.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of the present invention, and exemplify a configuration in which the total reflection characteristic is used for detecting the displacement of the probe. In this example, as shown in FIGS. 1 and 2, a probe 1, an objective lens 4 for detecting light, a light splitting mirror 5 for splitting light, a triangular prism 7, and reference numerals 8, 9,
The photodetectors A, B, and C shown with 10 are provided, and an imaging lens 13 and an image pickup device 14 are provided.

The photodetector (A) 8, the photodetector (B) 9, and the photodetector (C) 10 are connected to a signal processing system, and the optical branch mirror 5 is connected to the photodetector (C) 10.
The detection light reflected by and also reflected by the triangular prism 7 is made incident. On the other hand, the two photo detectors of the photo detector (A) 8 and the photo detector (B) 9 are arranged as a pair as shown in FIG. And is used for detecting and controlling the position of the tip 2 of the probe 1.

Further, the imaging lens 13 and the image pickup device 14 are
It is provided as a component of an optical microscope for optically observing the sample 15. The optical image transmitted through the mirror 5 is formed as an enlarged image on the image pickup device 14 through the image forming lens 13, the output of the image pickup device 14 is given to the monitor for optical microscope observation, and the optical microscope image is measured of the sample 15. This is used for positioning the measurement site of the sample 15 when selecting a region.

As the probe 1, a probe having a cantilever (cantilever) which is easily bent by a weak force and whose tip is provided with a fluorescent dye is used as the probe 1.
In this example, the probe tip 2 coated with the fluorescent dye is used as described above, but it is of course possible to use a probe tip having fine fluorescent beads attached to the tip of the probe. Also, not limited to the above,
A configuration in which a light emitting point is provided on the probe by some means can be adopted.

In this example, as the NSOM, as shown in the figure, light of the excitation wavelength of the fluorescent dye is made incident from the back surface of the sample 15 at an angle of total reflection or more, and an evanescent wave generated according to the material and shape of the sample 15 is used. It is detected that the light emission intensity of the tip portion 2 of the minute probe 1 changes depending on the intensity of the signal, and an image is obtained by signal processing. Since the intensity of the evanescent wave rapidly decreases exponentially as it goes away in the direction perpendicular to the sample, the evanescent wave cannot be detected by the optical system without the probe 1, and the tip of the probe 1 close to the sample cannot be detected. Since only the portion 2 receives the intensity, the electric field on the sample can obtain a resolution as large as the size of the tip of the probe 1. In addition, here, the light source,
The means for irradiating the sample 15 with light from the light source is not shown.

As the AFM, when the sample 15 and the probe tip 2 come close to each other, a near-field force such as a van der Waals force works and the probe 1 bends. The shape of the sample 15 can be measured by scanning while changing the relative distance between the sample 15 and the probe tip 2 so that the bending becomes a certain amount and plotting the changed relative distance.

As a method of keeping the relative distance between the probe tip 2 and the sample 15 constant, the objective lens 4 focused on the fluorescent portion (the probe tip coated with a fluorescent dye) that shines at the probe tip is used. In the case of a general NSOM, the fluorescent portion emitted from the tip of the probe viewed from the objective lens 4 is considered to be a point light source having no size because it is below the diffraction limit. The light emitted from the objective lens 4 by this point light source is totally reflected by the triangular prism 7, which is set so as to be reflected at the critical angle when the light emitting point is at the in-focus position (FIG. 1). . In this example, such objective lens 4 also
It is also used for optically observing the sample 15 by projecting a magnified image on the image sensor 14 by the imaging lens 13, and, as will be described later, the optical system for measuring the displacement of the probe of the AFM and the NSOM. The detection optical system is common.

Hereinafter, the sample 15 and the probe 1 in this example
The relative scanning with respect to and the control of the relative distance at that time will be further described with reference to FIG. Regarding scanning, basically, light of the above-mentioned excitation wavelength is made incident from the back surface of the sample 15 so as to be totally reflected on the sample surface, and as described above, the fluorescent dye of the probe 1 is selected according to the sample 15 of the observation object. This can be done by performing relative scanning with respect to the sample 15 while causing the tip end portion 2 marked with light emission to thereby obtain the optical information of NSOM to be an image in the signal processing system with the above-mentioned resolution. be able to. Then, in controlling the distance between the probe 1 and the sample 15 during the scanning, the displacement of the tip portion 2 of the probe 1 due to the bending of the probe 1 as described above, that is, in this case, the tip position of the probe 1 By utilizing the light generated by the fluorescent part that emits light and detecting and measuring the change of the site on the probe by using this, another light source (exclusively for measuring the displacement of the probe is used. The distance between the probe 1 and the sample 15 can be controlled without the need for a light source in an optical system, etc.

In practice, in order to measure such a variation, the objective lens 4 focused on the fluorescent portion shining at the probe tip 2 as described above is used, and the tip of the probe 1 concerned is used. The objective lens 4 is used to measure the displacement of a part, for example when the part is at the focus position,
A total reflection prism is used to change the light emitted from the objective lens 4 into a parallel light beam, a divergent light, and a focused light when approaching the lens 4 from the focus position and distant from the focus position. The displacement angle of the probe 1 may be measured by detecting the divergence angle thereof by using the triangular prism 7, the photodetector (A) 8 and the photodetector (B) as an example of specific means. 9 is provided to detect the position of the fluorescent portion of the probe tip 2 that emits light (FIGS. 1 and 2).

In the state of FIG. 1, the fluorescent portion of the tip portion 2 of the probe 1 is at the in-focus position, and the light emitted from the objective lens 4 by the tip fluorescent portion is a parallel light beam as shown in the figure. . In such a state, this passes through the system of the objective lens 4 → the mirror 5 → the triangular prism 7, and the triangular prism 7
It is incident on the photodetector (C) 10 as light information to be reflected and taken in by. From such a state, as shown in FIG. 2, for example, when the sample 15 has a convex shape and the sample 15 and the probe 1 come close to each other as the scanning is performed, and the bending of the probe 1 increases, the tip of the probe 1 becomes the objective lens 4. Is slightly shifted from the in-focus position of (1) in the direction in which the distance between the objective lens 4 and the objective lens 4 becomes smaller, and therefore the light beam incident on the lower side of the triangular prism 7 in the drawing is as shown by the solid line in the figure. The light is reflected at an angle smaller than the critical angle, part of which passes through the triangular prism 7, and is detected by one of the photodetectors (A) 8 provided on the back surface of the triangular prism 7 (in FIG. 2, solid line state and broken line state). reference). On the other hand, at this time, in the figure, the light beam incident on the upper side of the triangular prism 7 is incident at an angle larger than the critical angle, so that it is totally reflected and is not detected by the other photodetector (B) 9 on the rear surface of the triangular prism 7 ( (Fig. 2).

On the contrary, when the sample 15 is dented and the probe 1 is pulled downward (in the lower direction in the figure, the direction in which the distance to the objective lens 4 increases), the above-mentioned Opposite state, one photo detector (A)
8 is not detected, the other photodetector (B)
Detection is made at 9. In this principle, the sensitivity is determined by the NA of the objective lens 4 used, and the larger the NA, the higher the sensitivity.

The position of the fluorescent portion of the probe tip 2 which emits light can be detected from these information. Also in such detection, the system of the objective lens 4 → the mirror 5 → the triangular prism 7 is commonly used, and the position is detected in this way, and based on this, the fluorescing of the probe tip is emitted. It is controlled by an adjusting device (not shown) so as to keep the distance between the light portion and the sample 15 constant. N
The SOM signal can be obtained by summing the signals detected by the photodetector (A) 8, the photodetector (B) 9, and the photodetector (C) 10, but if the probe position is sufficiently controlled, the photodetector is detected. (C) Only the 10 signal is sufficient.

In this way, the relative distance between the probe 1 and the sample 15 can be controlled, and the optical information used in the distance control is not limited to that used in the optical system dedicated to the AFM. This can be done by using the light emitted by the fluorescent part of the probe tip 2 used for the measurement of NSOM. Therefore, needless to say that a dedicated light source is not required separately, by adopting such a configuration, it is possible to satisfactorily solve the problems existing in the generally used AFM method, and to perform probe position control. Therefore, there is no disadvantage caused by installing an external optical system. In particular, when using an objective lens, it is possible to remove the spatial restrictions on the lens and to avoid the difficulty of introducing a high-magnification objective lens to that extent. Even when using an optical microscope in combination, the NSOM can be used during scanning. It is possible to easily use a lens for condensing the detection light of 1) and a lens used for observing the surface of the sample 15 with an optical microscope, and to select the measurement region of the sample 15 as in this example, It is possible to realize a device configuration in which the above-mentioned objective lens 4 is shared.

In this example, the objective lens 4 is used both for the position detection of the probe 1 and the detection optical system of the NSOM as described above, and the objective lens-imaging lens 13-
It is also used for alignment of the sample 15 by the system of the image pickup device 14. As mentioned above, it is desirable that the NSOM observation area is small and the observation optical system has a high NA. However, according to this method, it is possible to alleviate the space constraint of placing the objective lens of the optical microscope for searching the portion to be observed in the sample 15, and it is generally possible to easily use a high NA with a short working distance. In addition to facilitating the alignment of the sample 15 when selecting the measurement region, this is the same as the above-described case when the probe 1 close to the sample 15 is relatively scanned with respect to the sample 15. This also leads to higher sensitivity in detecting the position of the probe 1, which leads to an even more advantageous direction. If high sensitivity can be obtained in accordance with the large NA of the objective lens used, the more effective distance control of the both can be achieved.

At this time, even if the objective lens 4 with a high NA is used, the probe tip 2 and the surface of the sample 15 are close to each other within the depth of focus of the objective lens 4, so that the measurement region is observed with an optical microscope to measure the measurement site. After positioning to the scanning area, AFM / NSOM measurement can be performed as it is, and vice versa. In the above, the case where the displacement of the probe caused by the force acting between the sample to be observed and the probe is detected and the distance is controlled is not limited to this, but the change of the resonance frequency of the probe is detected. Therefore, it can be applied even when controlling the relative distance between the two.

Next, another embodiment will be described with reference to FIGS.
This will be described below. This embodiment (second embodiment) uses the fact that the direction of emission of the NSOM detection light from the probe changes when the probe is bent due to atomic force or the like.

The basic structure of this embodiment can be the same as that of the above-described embodiment, and the same components are designated by the same reference numerals. In this example, a probe 3 as shown in FIGS. 3 and 4 is used as a probe, and a photodetector is provided with an optical branching mirror 5 as shown in FIG.
A photodetector (D) 11 and a photodetector (E) 12 facing each other are used. The objective lens 4 is an imaging lens 13
Other constituent elements may be the same as those in the above-described example, such as being used for optically observing the sample 15 by projecting a magnified image on the image pickup device 14.

In order to explain the main parts and characteristics of this embodiment, the probe 3 is provided with a needle-like projection 3a on a cantilever (cantilever) which is easily bent by a weak force. The material 3b made of fiber-like material such as glass corresponding to the opening is used (FIG. 4).
(A), (b)).

Also in this example, as the NSOM, light is incident from the back surface of the sample 15 at an angle of total reflection or more, and the minute opening portion of the probe 3 is small due to the intensity of the evanescent wave generated depending on the material and shape of the sample 15. A change in the intensity of light emitted from is detected, and signal processing is performed to form an image.
Therefore, also here, the sample 15 should be totally reflected on the sample surface.
It is possible that light is incident from the back surface and the evanescent wave generated on the surface of the sample is scanned relative to the sample 15 while being converted into propagating light by the probe 3 having a minute opening. This propagating light is collected by the objective lens 4, detected by the photodetector, and imaged as a scanning near-field optical microscope image by the signal processing system.

In this example, as a method for keeping the relative distance between the probe 3 and the sample 15 constant, the detection light emitted from the minute opening portion of the probe 3 tilts due to the bending of the cantilever, and the detection light is detected. The fact that the light emitted from the objective lens 4 is shifted is detected by the two photodetectors (D) 11 and (E) 12 (in FIG. 3B, broken line state and solid line). See state).

These points will be further described with reference to FIG. FIG. 7 is an example shown in comparison with the case of FIG. 3, which is a comparative example in which the probe 3 is used and the relative distance between the probe and the object to be observed is to be controlled by the AFM (for example, in Reference 3 above). It can be used). Figure 7
In the case of the above configuration, as shown in the figure, the detection light source 16, the condenser lens 17, and the optical position detection element 18 are provided between the probe 3 having a minute opening at the tip and the objective lens 4 '.

During scanning, the NSOM detection light is collected by the objective lens 4'and detected by the photodetector 10. Here, the scanning is performed while keeping the distance between the sample 15 and the probe 3 constant, and the principle of the AFM described below is used for this. That is, when the sample 15 has irregularities, and the tip of the probe 3 approaches the sample 15, the probe 3 causes the probe 3 to move due to the atomic force.
It is attracted to 5 and bends. In FIG. 7, the deflection angle is detected by the optical position detection element 18 as a change in the reflection angle of the light applied to the back surface of the probe 3 from the detection light source 16 through the condenser lens 17, but the probe 3 and the sample 1
It is considered that keeping the distance between 5 constant is equivalent to keeping the bending angle constant, and the distance between the sample 15 and the probe 3 is adjusted by the output of the optical position detecting element 18.

As a method for keeping the distance between the probe 3 and the sample 15 constant, this method is highly accurate, but in the one shown in FIG. 7, the optical system for detecting the displacement (deflection angle) of the probe is used. Can be pointed out to have the following drawbacks because it is separate from the optical near field detection optical system, especially the objective lens 4 '. Generally, in NSOM, it is difficult to locate the observation site of the sample because the observation target is small. Therefore, an optical microscope image is taken by the image sensor 1 using the objective lens 4 '.
Positioning is performed while observing in No. 4, but in this case, for the purpose, it is desirable to adopt a higher magnification objective lens as described above.

However, in general, the higher the magnification of the objective lens, the smaller the distance between the lens and the sample, that is, the so-called working distance, tends to be smaller. Therefore, in the case of the configuration of FIG. 7, considering the space in which the optical systems 16 to 18 for detecting the displacement (deflection angle) of the probe are installed, as shown in the figure, the objective lens 4 ′ is a high-magnification objective lens. Cannot be used, and a relatively low magnification objective lens 4'cannot be used and must be used. Moreover, with the low-magnification objective lens 4 ', since the NA, which is the angle of capturing light from the object, is small, the light from the probe 3 may not be sufficiently condensed.

More specifically, as another problem, the light source 16 for the detection system, which is actually used in the optical system for detecting the displacement (deflection angle) of the probe 3, is not limited to the probe 3 and the sample 15. Since it is often partially irradiated, it may become noise when the optical signal due to the optical near-field interaction generated by the probe 3 is taken in as a scanning near-field optical microscope image. There is also a drawback that some kind of filter is required.

On the other hand, in the case of the configuration according to this example,
As a method of controlling the distance between the probe 3 and the sample 15, it is necessary to use the optical signal itself due to the generated optical near field interaction and the change in the emitting direction under the following consideration. Basically. That is, the probe 3 is bent by the interatomic force, and the emission direction of the emitted light from the probe 3 is inclined. Therefore, the distance between the probe 3 and the sample 15 can be controlled by measuring the inclination. That is, as shown in FIG. 3, in this example, when the detection light emitted from the probe 3 tilts in its direction due to the bending of the cantilever, the light emitted from the objective lens 4 for light detection is shifted. (Fig. 3 (b)), photo detector (D)
11 and the photodetector (E) 12 detects the amount of deviation from the difference in the amount of light detected by the two photodetectors, and NS from the total amount of light.
Obtain the OM image signal. Thus, the position of the tip of the probe 3 is detected from these pieces of information, and the first
Similar to the embodiment, control is performed by an adjusting device (not shown) so as to keep the distance between the tip of the probe 3 and the sample 15 constant. Since the light of the optical near-field interaction by the probe 3 is used, no other light source is required as in the above embodiment.

That is, in comparison with FIG. 7, there is no spatial restriction on the objective lens (4 ') by installing the external optical systems 16 to 18 as shown in FIG. Also in the example, as shown in FIG. 3, a high-magnification objective lens 4 can be used, and the alignment of the sample 15 is facilitated. Since the portion of the probe 3 that causes the optical near-field interaction is close to the sample 15, observation of the measurement region with an optical microscope and AFM /
Switching of NSOM measurement becomes easy.

Further, the following points are also advantageous in this embodiment. That is, as described above, the amount of deviation can be detected by the photodetector (D) 11 and the photodetector (E) 12 of FIG. 3, but at this time, when generally detecting the amount of deviation, disturbance or fluctuation of the signal amount Considering this, it is possible to apply a means for normalizing the difference in light amount in the total light amount. As a result,
The sensitivity does not change even if the magnification of the objective lens 4 is changed.
Further, there is a characteristic that even if the position of the sample 15 is slightly deviated from the focus position of the objective lens 4 and the light flux to the photodetector (D) 11 and the photodetector (E) 12 diverges or converges, no influence occurs.

In the illustrated example, it is assumed that the scanning moves on the sample 15 side, but the mirror 5 for branching the detection light is placed at a position optically coherent with the pupil of the objective lens 4, and the probe 3 is placed. It is also possible to support the probe scanning method if it is synchronized with the scanning. Also, in the case of the first embodiment, the configuration according to the present embodiment may be applied, in which the probe displacement is detected by using the change in the direction of the light emitted from the fluorescent portion at the probe tip. It is also possible to implement it to obtain the above effect.

FIG. 5 and FIG. 6 show still another embodiment. This embodiment (third embodiment) corresponds to a modification of the second embodiment. In this example, the NSOM is
The light from the NSOM light source 19 is collimated by the collimator lens 20, the light condensed by the objective lens 4 is emitted from the minute aperture of the probe 3 to the sample 15 surface, and the light returning from the sample 15 surface is again probed by the probe 3. This is an example of using a so-called reflective type to capture. Therefore, as shown in FIGS. 5 and 6, in addition to the constituent elements shown in FIG. 3, there are further provided an optical branching mirror 6, an NSOM light source 19, and a collimator lens 20, and other constituent parts are the same as those of the second embodiment. It is the same.

Therefore, here, the light source, the means for irradiating the sample 15, which is the object to be observed, with light, and the means for detecting the intensity of the optical near field of the sample 15 are the light sources 19 for NSOM.
And the like. The light source is constituted by the NSOM light source 19, and the irradiation means is constituted by including a system of collimator lens 20-light splitting mirror 6-light splitting mirror 5-objective lens 4-probe 3. Also,
The detection means includes a system of probe 3-objective lens 4-light splitting mirror 5-light splitting mirror 6-photodetector (D) 11 and photodetector (E) 12.

In addition, this embodiment, like the second embodiment,
The fact that the emission direction of the NSOM detection light from the probe 3 changes is used for the AFM, and the content of the control of the relative distance between the probe 3 and the sample 15 by this is the same as that of the second embodiment. is there. The same effects as the above can be obtained also in this example, and the present invention can be implemented in such a mode.

The contents described above can be grasped as the following inventions. [1] A light source, means for irradiating the object to be observed with light, and means for detecting the intensity of the optical near field of the object to be observed, and a probe for causing optical near field interaction are covered. In a so-called scanning near-field optical microscope, in which an optical property of an object to be observed is measured by relatively scanning the object to be observed while maintaining a constant distance, an optical signal generated by the optical near-field interaction generated by the probe is used. The scanning near-field optical microscope is characterized in that the relative distance between the probe and the object to be observed is controlled thereby.

[2] The displacement of the probe is detected by the change in the relative distance between the detection position and the emission position of the optical signal for constructing the scanning near-field optical microscope image emitted from the probe. The scanning near-field optical microscope according to the above item [1]. [3] The scanning near-field optical microscope according to the above-mentioned additional item [1], wherein the displacement of the probe is detected by a change in the emission direction of the optical signal for constructing the scanning near-field optical microscope image. [4] A lens for condensing an optical signal for constructing a scanning near-field optical microscope image and a lens for observing an object surface to be observed with an optical microscope can be used in common. 2] or the scanning near-field optical microscope according to the additional item [3]. [5] The distance between the portion of the probe that emits the optical signal for constructing the scanning near-field optical microscope image and the surface of the observed object is less than or equal to the depth of focus of the lens that collects the optical signal. The scanning near-field optical microscope according to the above item [4].

[6] In the scanning probe microscope, which controls the relative distance between the probe and the probe by detecting the displacement of the probe or the change of the resonance frequency of the probe caused by the force acting between the sample and the probe, A scanning probe microscope characterized in that a change in a light emitting point provided on a probe is used as a means for detecting a displacement. [7] The scanning probe microscope according to the above-mentioned additional item [6], wherein the change of the light emitting point is caused by the change of the relative distance between the light emitting point and the detection optical system. [8] The scanning probe microscope according to the above-mentioned additional item [6], wherein the change in the light emitting point is caused by a change in the direction of light emitted from the light emitting point.

[0048]

According to the present invention, the optical characteristic of the measurement region is measured by relatively scanning the probe in the vicinity of the sample to be observed and detecting the light in the vicinity of the sample, and the sample and the probe. It is possible to realize a suitable microscope when measuring the force acting between the two. It is possible to avoid the problem that it is difficult to secure the space for placing the objective lens of the optical microscope for searching the part to be observed in the sample, and the light used for the probe displacement detection optical system dedicated to the AFM is NSOM. Therefore, it is possible to eliminate disadvantages such as the need for a mechanism for separating the detection light and the detection light. Also, other types of probe microscopes, such as AF
If a light emitting point is provided on the probe at M by some means, an apparatus configuration having an advantage of excluding the probe displacement detection optical system around the probe can be taken. In addition, the distance between the probe and the sample can be directly detected by the displacement of the probe, and it is possible to change the vibration response when the probe is scanned while being excited in the direction perpendicular to the sample. It can also be applied as a detection system when using a so-called tapping mode.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration (first embodiment) of an example of the present invention.

FIG. 2 is a diagram for explaining an example of a usage mode in the same example.

FIG. 3 is a diagram showing another example (second embodiment) of the present invention.

4A and 4B are a perspective view and a sectional equivalent view showing a configuration of a probe in the same example.

FIG. 5 is a diagram showing a configuration (third embodiment) of still another embodiment of the present invention.

FIG. 6 is a diagram provided for explaining an example of a usage mode in the same example.

FIG. 7 is a configuration diagram of a comparative example shown in comparison with the configuration according to the present invention.

[Explanation of symbols]

 1 Probe 2 Fluorescent dye-coated probe tip 3 Probe 4 Objective lens 5 Optical branching mirror 6 Optical branching mirror 7 Triangular prism 8 Photodetector A 9 Photodetector B 10 Photodetector C 11 Photodetector D 12 Photodetector E 13 Binding Image lens 14 Image sensor 15 Sample 16 Light source for detection system 17 Condenser lens 18 Optical position detection element 19 Light source for NSOM 20 Collimator lens

Claims (2)

[Claims] 1. A probe for causing optical near-field interaction is provided with the object to be observed, comprising means for irradiating the object to be observed with light and means for detecting the intensity of the optical near-field of the object to be observed. A scanning near-field optical microscope for measuring the optical characteristics of the object to be observed while relatively scanning while maintaining a constant distance, by using an optical signal generated by the optical near-field interaction generated by the probe. A scanning near-field optical microscope, wherein the relative distance between the probe and the object to be observed is controlled. 2. A scanning probe microscope which controls the relative distance between the sample and the probe by detecting the displacement of the probe or the change in the resonance frequency of the probe caused by the force acting between the sample and the probe. A scanning probe microscope characterized in that a change of a light emitting point provided on the probe is used as a detecting means.