JP3217097B2 - High resolution microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-resolution microscope and, more particularly, to a microscope which can be viewed at a high resolution by detecting a sample from a direction substantially perpendicular to a sample illumination direction.

[0002]

2. Description of the Related Art A commonly used bright-field microscope is:
There is a limit to the spatial frequency of the sample incident on the objective lens,
Since it works as a low frequency filter, high spatial frequency components cannot be observed. For this reason, a dark field microscope for capturing and observing a high-frequency spatial frequency component is known.
In this microscope, the illumination system is configured as shown in FIG. 9, and the sample is illuminated obliquely downward from a dark field condenser so that the directly transmitted light does not enter the objective lens of the microscope. The high-frequency component of the diffracted light is made incident on the objective lens, and the spatial high-frequency component of the sample is taken in as a bandpass filter to observe the high-frequency component.

[0003]

However, in some optical microscopes such as the above-mentioned dark-field microscope, the angle of oblique incidence is limited by the physical structure of the dark-field condenser. There is a limit to the high frequency component of light.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a high-resolution microscope capable of obtaining a higher resolution than the resolution determined by an objective lens.

[0005]

According to the present invention, there is provided a high-resolution microscope for detecting an object having a resolution smaller than the resolution of an objective lens. Are arranged relatively movably, and a ring-shaped detector that detects the intensity of the evanescent wave that spreads concentrically around the small aperture is placed, and relatively scans the small aperture plate along the sample surface. It is characterized in that the total intensity of the evanescent wave is detected to determine the transmittance distribution of the sample.

Another high-resolution microscope according to the present invention is a microscope for detecting an object having a resolution smaller than the resolution of an objective lens. A movable detector, a detector that detects the total intensity of the evanescent wave that travels in one direction perpendicular to the micro slit, is arranged in parallel with the micro slit, and the micro slit plate is relatively rotated and scanned along the sample surface. While detecting the total intensity of the evanescent wave, the transmittance distribution of the sample is obtained from the detected total intensity of the evanescent wave.

[0007]

[0008]

[0009]

According to the present invention, the spatial frequency which can be taken into the objective lens can be increased by detecting from a direction substantially perpendicular to the specimen illumination direction by using a dark-field microscope utilizing oblique incidence. Therefore, an object smaller than the resolution of the objective lens can be detected. Among them, those utilizing evanescent waves are particularly suitable for obtaining a high-resolution image of a minute object because they utilize a plane perpendicular to the wave irradiation direction.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and embodiments of the present invention will be described below with reference to the drawings. First, the basic principle of the present invention will be described. Considering the optical resolution of the sample, as shown schematically in FIG. 3, when a sample S having a periodic structure is present, its illumination light L is composed of a straight light (zero-order light) 1 and a first-order diffracted light 2. , 2 '. Depending on only the straight light 1, the sample S
The periodic structure cannot be recognized, but the presence of the periodic structure can be known by detecting the presence of any of the first-order diffracted lights 2, 2 '. By the way, the shorter the period of the sample S, the larger the diffraction angle θ of the first-order diffracted lights 2, 2 ′. Depending on the ordinary objective lens, light having a diffraction angle θ close to 90 ° cannot be taken in as imaging light, so that the above-mentioned resolution d = λ / 2NA is determined.

Therefore, in the present invention, 90 °
Is positively taken in so as to detect the presence of a structure smaller than the resolution d = λ / 2NA of the objective lens in the sample S. For example, as shown in an optical path diagram in FIG. 1, the illumination light L is condensed by a condenser lens 4 along the sample surface near the observation point of the sample S arranged on the stage 3. When the light is condensed in this way, as shown in FIG. 2, near the observation point of the sample S, the wavefront of the illumination light L becomes a plane substantially perpendicular to the sample surface, advances along the vicinity of the sample S surface, and Due to the spatial frequency of a minute object smaller than the resolution of the objective lens 6, 90 ° with respect to the incident light L
, And the diffracted light 5 is divided into an objective lens 6,
Observed through the eyepiece 7. Therefore, it is known that a structure smaller than the resolution exists in a minute area of the sample S determined by the resolution of the objective lens 6. Note that, instead of observing with the eye using the eyepiece 7, detection may be performed by arranging a two-dimensional detector on the image plane or by scanning the image plane using a one-dimensional detector. it can.

Meanwhile, a light wave traveling in a direction perpendicular to the observation direction can be formed by an evanescent wave generated by total reflection and traveling along the vicinity of the sample surface. This evanescent wave will be described. As schematically shown in FIG. 4, when the refractive index of the medium in the upper part of the figure is relatively small and the refractive index of the medium in the lower part is large, When the light L is incident from the medium at an incident angle equal to or greater than the critical angle, the incident light L is totally reflected. At this time, in the upper medium near the interface P, as shown in FIG. An evanescent wave (surface wave) is generated which attenuates and travels in the direction of the incident light L along the interface P. This wave
An inhomogeneous wave having an equal-amplitude surface and an equal-phase surface different from each other, and a surface wave propagating in one direction.
It is analyzed as an nneck surface wave, and the experimental results of long wave radio wave propagation are almost explained by theory. Then, the wavelength of the evanescent wave is shorter than the wavelength of the incident light L.

In order to form illumination light traveling along the vicinity of the sample surface by such a total reflection evanescent wave, a prism 8 for attaching the sample S to the total reflection surface is provided as shown in an optical path diagram in FIG. The incident light L is made incident on the incident surface, the incident light L is totally reflected by the surface of the sample S mounted on the total reflection surface of the prism 8, and an evanescent wave traveling along the vicinity of the sample surface near the surface of the sample S is formed. generate.
This wave travels along the vicinity of the surface of the sample S, and is diffracted at an angle close to 90 ° with respect to the traveling direction of the evanescent wave by the spatial frequency of a minute object smaller than the resolution of the objective lens 6 near the sample. Observed through the objective lens 6 and the eyepiece 7. Therefore, it is known that a structure smaller than the resolution exists in a minute area of the sample S determined by the resolution of the objective lens 6. In this case,
Since the wavelength of the evanescent wave is shorter than the wavelength of the incident light L, the resolution is improved as compared with the case of FIG. Also in this case, instead of the eyepiece 7, detection can be performed by arranging a two-dimensional detector on the image plane, or by scanning the image plane using a one-dimensional detector.

By the way, an evanescent wave can be generated even from a minute aperture having a wavelength or less. First, an evanescent wave caused by the minute aperture will be described. FIG.
As shown in FIG. 7A, when the aperture is large compared to the wavelength, as shown in FIG. Pass through the aperture A as a substantially plane wave,
When becomes smaller, it comes out as a fan-shaped wave, and when it becomes about the wavelength, it comes out almost as a spherical wave. On the other hand, in the case of FIG. 2B in which the diameter of the aperture A is equal to or less than the wavelength, when a scalar light wave enters the aperture A, the diffraction field from the aperture A is represented by the Rayleigh-Sommerfeld diffraction formula. The evanescent wave is given as a convolution of the light field on the aperture A and the spherical wave weighted with the tendency factor, and attenuates exponentially in the direction perpendicular to the aperture A as shown in the figure. The traveling direction of this evanescent wave is different from the total reflection evanescent wave, and is a traveling wave that is axially symmetric with respect to the opening as a central axis, and is a wave whose concentric phase surface spreads concentrically.

A high-resolution microscope can be constructed by using the evanescent wave generated by the minute aperture. FIG.
(A) is a perspective view of the microscope, and (b) shows an optical path diagram. As shown in the figure, the sample S is placed on a transparent stage 3 and a small aperture plate 9 having a small aperture A having a wavelength equal to or less than the wavelength as shown in FIG. I have. A ring-shaped detector 10 is integrally mounted around the micro-aperture plate 9 and detects the entire intensity of the evanescent wave W concentrically spreading from the micro-aperture A. The detector 10 is provided with an xy scanner 11 so that the micro aperture plate 9 and the detector 10 can be xy scanned along the surface of the sample S integrally. Scans over the sample S. In such an arrangement, when the laser beam L is condensed on the sample S from below the transparent stage 3 by the condenser lens 4, a part of the light that has passed through the sample S corresponding to the position of the minute aperture A is changed in the illumination direction. Becomes an evanescent wave W traveling at a right angle, reaches the detector 10, and detects its full intensity. This intensity is the same as the sample S at the position of the minute opening A.
Is proportional to the transmittance of the sample A, so that the small aperture A
Is two-dimensionally scanned, the transmittance distribution of the sample S can be detected with the resolution of the minute aperture A, that is, with a resolution equal to or less than the wavelength.

The high-resolution microscope shown in FIG. 7 can be developed to observe a high-resolution image according to the principle of computer tomography (CT). FIGS. 8A and 8B show a perspective view and an optical path diagram of the microscope. As in the case of FIG.
Is placed on a transparent stage 3. In this case, a micro slit plate 9 'having a micro slit A' having a width equal to or less than the wavelength is arranged on the sample S instead of a micro aperture plate having a minute aperture equal to or less than the wavelength. A single detector 10 'such as a photomultiplier tube is integrally attached to the minute slit plate 9' in parallel with the slit A '. Then, the total intensity of the evanescent wave W traveling in one direction is detected. The stage 3 is provided with an x-.theta. Scanner 11 'so as to scan the sample S along the surface by x-.theta., Whereby the minute slit A' relatively scans the sample S. Will do. In such an arrangement, when the laser light L is condensed on the sample S from below the transparent stage 3 by the condenser lens 4 ′ formed of a cylindrical lens, one of the light passing through the sample S corresponding to the position of the minute slit A ′ is obtained. The part becomes an evanescent wave W which travels at right angles to the illumination direction and the slit direction, reaches the detector 10 'and detects its full intensity. This intensity is set to I (θ, x) corresponding to the slit position (θ, x), the integral in the slit direction is set to ∫ds, and the transmittance distribution of the sample S is set to f
If (x, y), there is a relationship of I (θ, x) = ∫f (x, y) ds. Therefore, the parameter (θ, x) is changed, the corresponding I (θ, x) is detected, and the transmittance distribution f (x, x) of the sample S is obtained from the obtained I (θ, x).
y) can be obtained by calculating at a high resolution below the wavelength. (Calculating f (x, y) from I (θ, x)
This is a problem referred to as an "image reproduction method from projection" and has been put to practical use (for example, "Image Processing Handbook", pages 526 to 531, edited by the Image Processing Handbook Editing Committee (June 8, 1987) Published by Shokodo Co., Ltd.)).

Although the high-resolution microscope of the present invention has been described in several embodiments, the present invention is not limited to these embodiments, and various modifications are possible.

[0018]

As is clear from the above description, according to the high-resolution microscope of the present invention, any object can detect an object smaller than the resolution of the objective lens by detecting the object from a direction substantially perpendicular to the sample illumination direction. Detectable. Among them, those utilizing evanescent waves, in particular, have higher resolution because the wavelength is shorter than the wavelength of ordinary light.

[Brief description of the drawings]

FIG. 1 is an optical path diagram of a high-resolution microscope according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a state of illumination light near an observation point of a sample in FIG.

FIG. 3 is a schematic diagram for explaining an optical resolution of a sample.

FIG. 4 is a diagram schematically illustrating an evanescent wave generated by total reflection.

FIG. 5 is an optical path diagram of a high-resolution microscope according to a second embodiment.

FIG. 6 is a diagram schematically showing that an evanescent wave is generated by reducing the aperture diameter.

FIG. 7 is a perspective view and an optical path diagram of a high-resolution microscope according to a third embodiment.

FIG. 8 is a perspective view and an optical path diagram of a high-resolution microscope according to a fourth embodiment.

FIG. 9 is a diagram showing a configuration of an illumination system of a conventional dark field microscope.

[Explanation of symbols]

 S ... Sample L ... Incident light A ... Aperture P ... Interface A '... Slit W ... Evanescent wave 1 ... Straight light (0th-order light) 2,2' ... First-order diffracted light 3 ... Stage 4, 4 '... Condenser lens 5 ... Diffracted light 6 Objective lens 7 Eyepiece 8 Prism 9 Micro aperture plate 9 'Micro slit plate 10, 10' Detector 11 xy scanner 11 'x-theta scanner

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-85446 (JP, A) JP-A-53-24637 (JP, U) JP-B-39-26805 (JP, B1) JP-B-48 21621 (JP, Y1) APPLIED OPTICS, 1 AUGUST 1981, Vol. 20, No. 15, p. 2656-2664 (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 21/00

Claims (2)

(57) [Claims] 1. A microscope for detecting an object having a resolution smaller than the resolution of an objective lens, wherein a micro-aperture plate having a micro-aperture of a wavelength or less is relatively movably disposed on a sample, and concentrically around the micro-aperture. A ring-shaped detector that detects the intensity of the evanescent wave that spreads over the surface of the sample and detects the total intensity of the evanescent wave while relatively scanning the small aperture plate along the sample surface to determine the transmittance distribution of the sample A high-resolution microscope characterized by the following. 2. A microscope for detecting an object smaller than the resolution of an objective lens, wherein a micro-slit plate having a micro-slit having a width equal to or less than a wavelength is relatively movably disposed on a sample, and is orthogonal to the micro-slit. A detector that detects the total intensity of the evanescent wave going to one side is arranged in parallel with the minute slit, and the total intensity of the evanescent wave is detected while relatively rotating and moving scanning the minute slit plate along the sample surface, A high-resolution microscope, wherein a transmittance distribution of a sample is obtained from the total intensity of the detected evanescent waves.