JP2005207935A - Near-field optical microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a near-field optical microscope having high temporal/spatial resolving powers. <P>SOLUTION: The near-field optical microscope is constituted, so that a sample 40 which serves as a measuring object is arranged on one side of a transparent substrate 10 which serves as a sample stage, having a non-linear optical thin film 101 changed in light transmissivity, corresponding to the intensity of the incident light and the near-field light emitted, by irradiating the transparent substrate with a light spot from the other side thereof being used to measure the characteristics of the sample, from one side of the transparent substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a microscope using near-field optics.

  There is a laser scanning confocal microscope as a type of microscope used for observing a sample having a fine structure such as a biological cell or a polymer. A high-speed scanning of about 300 frames / second has been realized by means such as using a Nipkow disk for laser scanning. Such a laser scanning confocal microscope achieves higher spatial resolution than a general optical microscope by devising an optical system. However, as long as propagating light is used, there is a resolution limit called a diffraction limit. The spatial resolution when using visible light is limited to about 0.2 μm.

  On the other hand, a scanning near-field optical microscope (SNOM) can be cited as one that realizes a resolution exceeding the diffraction limit with a microscope using light. The SNOM can etch a tip of an optical fiber or the like to form a minute opening at the tip of the optical fiber, and scan the sample with near-field light generated therefrom to obtain an image. Thereby, an image having a structure smaller than the diffraction limit of light can be obtained. However, in SNOM, since the image is acquired by physically scanning the probe, there is a problem that the time resolution is low.

  As another example of a method for measuring a sample using a near-field light source, there is a method disclosed in Jurgen Boytan et al. This is a measurement technique in which a near-field light source is arranged in an array in a form of being incorporated into a flat substrate, and a biological sample is directly arranged thereon. However, in this method, there is a problem that the analysis information of the biological object cannot be acquired as spatially continuous information because the light source exists at a place where it jumps.

  In view of the above, an object of the present invention is to provide a microscope using near-field optics that solves the problems of the prior art and has high temporal and spatial resolution.

  In the near-field optical microscope according to the present invention, a sample to be measured is arranged on one side of a transparent substrate having a thin film whose light transmittance changes according to the light intensity of incident light, and from the other side of the transparent substrate. The characteristic of the sample is measured from one side of the transparent substrate using near-field light generated by irradiating a light spot. In the near-field optical microscope of the present invention, a sample placed on a transparent substrate serving as a sample stage is scanned with a light spot from below the sample stage, instead of scanning the sample with an optical fiber probe or the like as in the prior art. taking measurement. The transparent substrate is provided with a thin film whose light transmittance changes according to the light intensity of incident light, and light passes through the thin film only in the portion irradiated with the scanning light spot, and the sample is photoexcited. At this time, an optical opening is generated in the portion irradiated with the light spot. However, since the size of the opening is smaller than the light spot, the light emitted from the opening becomes near-field light. Thereby, high spatial resolution can be obtained without being limited by the diffraction limit of light. In addition, since the opening is formed at the place where the light spot is irradiated, the sample response at an arbitrary position can be measured by adjusting the light spot position.

The sample characteristics may include fluorescence response, absorption.

  The light transmittance of the thin film may be increased by light locally irradiated by the light spot or heat generated by irradiation.

  The measurement of the characteristics of the sample may be performed while scanning the light spot.

  The light source that causes the light transmittance change of the thin film and the light source for measuring the characteristics of the sample may be the same.

  A light source for causing a change in light transmittance of the thin film and a light source for measuring the characteristics of the sample may be provided separately. In this way, the wavelength selectivity of light for measurement can be improved.

  Preferably, the thin film is sandwiched between dielectric thin films. In this way, the process of changing the light transmittance of the thin film can be stabilized.

  Suitably, the said transparent substrate has a transparent thin film arrange | positioned between the said thin film and the said sample. If such a transparent thin film is made into an appropriate film thickness, the sample can be prevented from being damaged by the heat generated by the light spot.

  Preferably, the transparent substrate has an adhesive layer that adheres to the sample. If it does in this way, it will become easy to fix a sample to a transparent substrate, and stable analysis will become possible.

  According to the present invention, in the optical measurement and analysis such as the fluorescence response and light absorption of the sample, the plane can be scanned with near-field light. Therefore, the conventional optical measurement is limited due to the diffraction limit. It is possible to dramatically improve the spatial resolution. Further, since a method of scanning only light rays without using a probe such as an optical fiber as a conventional scanning method is adopted, the scanning speed can be improved and the time resolution can be improved.

  FIG. 1 is a diagram showing an example of the configuration of the near-field optical microscope of the present invention. The near-field optical microscope includes a sample stage 10, a light spot scanning mechanism 20, an imaging device 30, and a lens 50. A sample 40 to be measured is placed on the sample stage 10.

  The sample stage 10 includes a nonlinear optical thin film 101 whose complex refractive index changes nonlinearly according to the intensity of incident light, and thereby the light transmittance changes. The nonlinear optical thin film 101 can be formed of a known nonlinear optical thin film material such as antimony or silver oxide. A material whose light transmittance is changed by heat generated by light irradiation may be used. The sample stage 10 preferably further includes transparent dielectric thin films 102 and 103 that sandwich the nonlinear optical thin film 101. The dielectric thin film 102 is formed thinner than the range where the near-field light can reach, and the distance between the nonlinear optical thin film 101 and the sample 40 is kept constant. The dielectric thin film 102 is preferably selected to have a thickness such that the sample 40 is not damaged by the heat generated by the light spot. An adhesive layer having adhesiveness to the sample 40 may be provided on the upper surface of the sample stage 10 so that the sample 40 can be easily fixed.

  The light spot scanning mechanism 20 includes two elements, an optical system portion and a scanning mechanism portion. The optical system portion includes a laser light source and an optical system for forming a light spot for condensing the laser light from the light source and irradiating it on the thin film 101. The scanning mechanism portion includes a mirror for scanning the thin film 101 by moving the position of the light spot in the XY direction on the surface of the thin film 101, and a drive portion of the mirror. In another embodiment, the light spot may be fixed, and scanning may be performed by moving the sample stage 10 in the XY direction.

  The imaging device 30 is located on the opposite side of the scanning mechanism 20 via the sample stage 10. The lens 50 is disposed between the sample stage 10 and the imaging device 30. As the sample 40, a sample having a fine structure is suitable, and for example, a cell isolated from a living tissue or a cultured cell can be considered.

  FIG. 2 is a diagram for explaining the principle of generating near-field light by irradiating a light spot. The same reference numerals as in FIG. 1 indicate similar elements. The light spot scanning mechanism 20 scans the light spot on the nonlinear optical thin film 101. The intensity distribution of the spot light by the laser light has a Gaussian distribution. Therefore, the region of the light intensity exceeding the threshold value for forming the optical aperture on the nonlinear optical thin film 101 is smaller than the size of the spot light as shown in FIG. Therefore, the spot light focused to the diffraction limit size forms an opening having a size smaller than the diffraction limit on the nonlinear optical thin film 101. By this opening, near-field light is generated from the area irradiated with the spot light. Therefore, by scanning the light spot on the nonlinear optical thin film 101 by the light spot scanning mechanism 20, the plane can be scanned with near-field light. In another embodiment, a light source that generates a light spot for forming the optical aperture and a light source that generates light for generating near-field light through the aperture are separately provided and used for measurement. You may make it improve the wavelength selectivity of light.

  FIG. 3 is a diagram for explaining the operation of the near-field optical microscope according to the present invention. The same reference numerals as in FIG. 1 indicate similar elements. As described above, by irradiating the nonlinear optical thin film 101 with the spot light by the light spot scanning mechanism 20, an optical opening is formed in the nonlinear optical thin film 101. Since the opening is smaller than the diffraction limit of light, near-field light is generated by spot irradiation light. By exciting the sample 40 with this near-field light, the light emitted from a very local region below the diffraction limit is condensed as a fluorescence response signal by the lens 50 and measured by the imaging device 30. By analyzing this measurement result, it is possible to acquire fluorescence response and light absorption data from a very local region in the region below the diffraction limit. By combining the data obtained by the imaging device 30 and the X and Y coordinate values of the position irradiated with the spot light by the light spot scanning mechanism 20 at that time, the fluorescence response of the sample 40 is converted into a two-dimensional fluorescence. It can be reconstructed as a response distribution image.

It is a figure which shows an example of a structure of the near-field optical microscope of this invention. It is a figure for demonstrating the principle which irradiates a light spot and generates near-field light. It is a figure explaining operation | movement of the near-field optical microscope by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sample stage 20 Optical spot scanning mechanism 30 Imaging apparatus 40 Sample 101 Nonlinear optical thin film 102, 102 Dielectric thin film

Claims (9)

  Proximity generated by placing a sample to be measured on one side of a transparent substrate having a thin film whose light transmittance changes according to the light intensity of incident light and irradiating a light spot from the other side of the transparent substrate A near-field optical microscope configured to measure the characteristics of the sample from one side of the transparent substrate using field light.   The near-field optical microscope according to claim 1, wherein the characteristics of the sample include fluorescence response and absorption.   3. The near-field optical microscope according to claim 1, wherein the light transmittance of the thin film is increased by light locally irradiated by a light spot or heat generated by irradiation. microscope.   4. The near-field optical microscope according to claim 1, wherein the measurement of the characteristics of the sample is performed while scanning the light spot.   5. The near-field optical microscope according to claim 1, wherein a light source for causing a change in light transmittance of the thin film and a light source for measuring characteristics of the sample are the same. The feature near-field optical microscope.   5. The near-field optical microscope according to claim 1, wherein a light source for causing a change in light transmittance of the thin film and a light source for measuring characteristics of the sample are separated. The feature near-field optical microscope.   The near-field optical microscope according to claim 1, wherein the thin film is sandwiched between dielectric thin films.   8. The near-field optical microscope according to claim 1, wherein the transparent substrate has a transparent thin film disposed between the thin film and the sample. 9.   9. The near-field optical microscope according to claim 1, wherein the transparent substrate has an adhesive layer that adheres to the sample.

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