Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2001-11-07
2004-03-23
Porta, David (Department: 2881)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S216000, C250S306000, C073S105000
Reexamination Certificate
active
06710331
ABSTRACT:
RELATED APPLICATIONS
This application claims the priority of Japanese Patent Application No. 2000-345372 filed on Nov. 13, 2000, which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a near-field microscope.
More particularly, the present invention relates to an improvement of a near-field microscope having a mechanism for eliminating an effect of noise from a measurement result.
BACKGROUND OF THE INVENTION
A general optical microscope can not observe an object which is smaller than a light wavelength, and its resolution is limited. On the other hand, although an electronic microscope or the like can improve resolution remarkably, operation in air or solution is very difficult. Thus, a high resolution microscope such as electronic microscope has not always been satisfactory in the field handling physiological specimens in particular.
In contrast, in recent years, there has been developed a near-field microscope based on a principle which is different from that of a general optical microscope or electronic microscope, and its application is expected. This near-field microscope detects a so called near-field light. That is, the near-field microscope observes a measurement sample based on the following principle.
When light is emitted to a measurement sample, a surface wave called a near-field light is generated in the vicinity of a measurement surface. This surface wave is localized with a distance in a region within a light wavelength on a object surface.
A probe with its sharp tip is inserted into a field of near-field light, near-field light is scattered, and its scattered light intensity is measured, whereby a spectrum in a minutely small region within a light wavelength can be obtained. Alternatively, when a probe is oscillated at its resonance frequency, and the probe and the surface of a measurement object are approached, a distance between the surface of the measurement object and probe can be controlled by using the fact that its amplitude decreases.
Therefore, a probe is scanned while the amplitude of the probe is constant, whereby the tip end position of the probe properly reflects irregularities of the measurement object. Moreover, the probe tip end merely exists in a field of near-field light, and does not come into contact with the measurement object. Thus, an object which is smaller than a value of light wavelength can be observed in a non-contact and non-destructive manner relevant to a sample.
However, minutely small irregularities are provided on the surface of a measurement object. Due to an effect of the irregularities, even in a near-field microscope, the measurement result includes a noise that mainly has a background consisting of reflection light or the like from a sample.
In addition, a near-field technique capable of achieving spatial resolution exceeding a wavelength limit has been mainly used to observe a more precise measurement sample image within a range that is smaller than light wavelength. Thus, visible light laser has been mainly used.
In addition, although there has existed a microscope using an infrared light with its monochromatic wavelength because its object is to sample an image when a measurement object is observed in spatial resolution exceeding a wavelength limit, an apparatus capable of spectrum measurement due to an infrared light has not existed. However, because of its long wavelength, an infrared light is very useful if application exceeding a wavelength limit by a near-field is possible.
In addition, if a near-field spectrum can be sampled by using an infrared light, spectrum measurement within a range smaller than light wavelength is possible, and a measurement sample can be analyzed in more detail.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the foregoing problem. It is an object of the present invention to provide a near-field microscope capable of eliminating an effect of noise from a measurement result and to provide an infrared near-field microscope using an infrared light source as a light source, thereby enabling near-field infrared spectrum measurement within a range that is smaller than light wavelength using a near-field technique.
In order to achieve the foregoing object, according to one aspect of the present invention, there is provided a near-field microscope comprising: a probe for scattering a near-field light; light emitting means including a light source for emitting light to a sample or the probe; and light sampling means for sampling and detecting a light that includes information of the sample scattered by said probe, said microscope comprising: control means for spacing the sample or probe from a field of a near-field light generated by the light emission or disposing the sample or probe at a position that is shallow in a field of near-field light, thereby detecting a noise by the light sampling means; inserting the sample or probe deeply into a field of near-field light generated by the light emission, thereby detecting light intensity by the light sampling means; and computing means for computing a measurement result obtained by subtracting a noise from the light intensity.
Preferably, in a near-field microscope of the invention, there are provided: spectroscopic means for spectrographically dispersing light emitted to a sample or probe by the light emitting means or light containing information on a sample scattered by said probe into light within a specific wavelength range; and analysis means for storing and analyzing measurement data for each wavelength sampled by the light sampling means, whereby a near-field spectrum on a sample can be sampled.
Preferably, in a near-field microscope of the invention, an interferometer is used for the spectroscopic means, the interferometer includes a movement mirror that carries out reciprocal movement, the control means controls so that the sample or probe is deeply inserted into a field of a near-field light in a forward passage of said movement mirror, light intensity is detected by the light sampling means, said sample or probe is spaced from a field of a near-field light in a backward passage of the movement mirror and is disposed at a position that is shallow in a field of near-field light, and a noise is detected by said light sampling means.
Preferably, in a near-field microscope of the invention, light emitted by light emitting means is infrared light.
Preferably, in a near-field microscope of the invention, a light source contained in light emitting means is a high temperature heating element.
Preferably, in a near-field microscope of the invention, a light source for emitting light to a sample or probe is a wavelength variable laser.
Preferably, in a near-field microscope of the invention, the spectroscopic means is composed of any of a wavelength variable filter, a band pass filter having an arbitrary wavelength width, a Fourier transform type spectroscopic device or a dispersion type spectroscopic device.
Preferably, in a near-field microscope of the invention, the light emitting means carries out illumination by means of reflecting illumination that emits light directly to a sample or the probe, thereby generating a near-field light and/or by means of total reflecting illumination that brings a prism of a medium with its high refraction index into contact with a sample and reflects the light totally at a boundary of the sample and prism, thereby generating a near-field light on a sample surface.
Preferably, in a near-field microscope of the invention, the light emitting means can be selected by switching it to illumination of either one of the reflecting illumination and the total reflecting illumination.
Preferably, in a near-field microscope of the invention, the light emitting means is composed of at least a light source and a Cassegrainian mirror.
Preferably, in a near-field microscope of the invention, the shape of a medium with its high refraction index of the total reflecting prism for use in total reflecting illumination is a hemispheric or analogous shape, and a f
Kimura Shigeyuki
Narita Yoshihito
Jasco Corporation
Meyer David C
Porta David
Snider Ronald R.
Snider & Associates
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