Probe opening forming apparatus and near-field optical microscope using the same

Abstract: A probe opening forming apparatus (139) includes: light detecting means (140) for detecting a quantity of a light transmitted from a tip portion of the probe through a light of the source (116), which is on contact with the tip portion of the probe; storage means (142) for previously storing information about relation of the quantity of the light transmitted from the tip portion of the probe and the size of the opening; calculating means (144) for obtaining the value of the light quantity for obtaining an opening having a desirable size based on the information stored in the storage means (142); and pressing control means (126) for controlling the press of the tip portion of the probe against the light detecting means through the pressing means (114) such that a light quantity detected by the light detecting means (140) is equal to the light quantity calculated from the calculating means (144).

Description: BACKGROUND OF THE INVENTION In general, a microscope can observe a very fine portion without destruction in a non-contact with a sample and can further analyze a component of an observation object as well as a shape and a structure thereof by connecting a spectrum analyzer or the like, and has been applied to various fields. However, a general optical microscope cannot observe a smaller thing than a wavelength of a light and has a resolution thereof limited. On the other hand, in an electron microscope, the resolution can be enhanced greatly but it is very hard to carry out an operation in the air or in a solution. Thus, a high resolution microscope such as the electron microscope has not been always satisfactory particularly in the field in which a biological sample is to be treated. On the other hand, a near-field optical microscope based on a different principle from the general optical microscope or the electron microscope has recently been developed and an application thereof has been expected. The near-field optical microscope serves to detect a so-called evanescent light. More specifically, in Fig. 1, a near-field optical microscope 10 has a very small sample 12 to be measured which is put on a flat substrate 14. When an excited light 18 is incident from a light source 16 at such an angle that total reflection is carried out over the back face of the substrate 14, all propagated lights are reflected. However, a surface wave referred to as an evanescent light 20 is generated in the vicinity of the surfaces of the substrate 14 and the sample 12. The surface wave is locally present in a region at a distance within the wavelength of the light around the surface of an object. A probe 22 having a sharp end is inserted in the field of the evanescent light 20 to scatter the evanescent light 20. A part of a scattered light 21 enters the probe 22 and is guided to a detector 24, and data processing is carried out through a computer 26. Consequently, a distance between the tip portion of the probe 22 and the sample 12 can be grasped. Accordingly, a stage 30 is moved through the computer 26 and a stage controller 28 and a vertical distance between the tip portion of the probe 22 and the sample 12 is controlled such that the scattered light 21 has a constant intensity, and a surface of the sample 12 which is to be measured is scanned. Consequently, it is possible to accurately grasp the concavo-convex portions of the sample 12 in a non-contact with the sample 12. In addition, the tip of the probe 22 is only present in the field of the evanescent light 20 and does not come in contact with the object itself to be measured. Therefore, it is possible to observe a thing having a smaller value than the wavelength of the light without destruction in a non-contact with the sample 12. As shown in Fig. 2, the probe 22 includes a core 32 constituted by a dielectric having a light transmittance and a mask 34 constituted by a metal thin film bonded on the surface of the core 32 through evaporation or the like. An opening 36 is formed in the tip portion of the mask 34 and a tip portion 32a of the core 32 is appeared from the opening 36. As a method of forming the opening of the probe, for example, the tip of the core of an optical fiber is sharpened by a selective chemical etching method, a method of heating and stretching the tip or the like. In vacuum, a metal is heated and evaporated, and is bonded as a thin film to the surface of the sharpened probe, thereby forming a mask of a metal thin film or the like. Next, the mask of the tip portion is removed through etching method, focused ion beam (FIB) or the like, for example. Consequently, the opening 36 is formed. The probe 22 thus formed is attached to a head 31 of the near-field optical microscope 10 to carry out the near-field optical measurement described above. In order to enhance the resolution of the near-field optical microscope, it is necessary to form an opening having a desired size in the tip of the probe with high reproducibility. However, the mechanical dimension of the opening can be controlled but an optical characteristic such as a light transmittance cannot be controlled during formation by using the opening forming method described above. Consequently, the optical characteristic such as the light transmittance of the opening to which importance should be attached for performance has not been considered. For this reason, when the fabricated probe is actually attached to the near-field optical microscope to carry out the measurement, the measurement cannot be carried out well in some cases. Consequently, it has been greatly desirable that a technique for forming an opening having a desired size in the tip of the probe with high reproducibility should be developed in consideration of the optical characteristic such as the light transmittance. However, there has not been a proper technique capable of solving the problem. A technique in which the transmittance is considered is described in the article by Pohl et al: "optical stethoscopy: image recording with resolution lambda/20", Appl. Phys. Lett., 44, pp 651-653 (1984). This article describes adjusting the size of an aperture of a tip for image recording with subwavelength resolution by monitoring the light flux transmitted with a photomultiplier while pressing the tip against a microscope slide. SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a probe opening forming apparatus for opening a mask of a tip portion of a probe with a desirable size, the probe being suitable for a near field optical measurement and comprising a core constituted by a material having a light transmittance and a mask formed on the core constituted by a material having a ductility and a light shielding property, the apparatus comprising: a light source for causing a light to be incident in the probe; light detecting means for detecting a quantity of light transmitted through the tip portion of the probe from the light source, which is in contact with the tip portion of the probe; pressing means for pressing the tip portion of the probe against the light detecting means in a direction of an optical axis; characterised by storage means for previously storing information about a relationship between the quantity of the light transmitted from the tip portion of the probe and the size of the opening; calculating means for obtaining the value of the quantity of light for obtaining an opening having a desirable size based on the information about the relationship between the quantity of the light transmitted from the tip portion of the probe and the size of the opening which is stored in the storage means; and pressing control means for controlling the press of the tip portion of the probe against the light detecting means in the direction of the optical axis through the pressing means such that a value of a light quantity detected by the light detecting means is equal to the value of the light quantity calculated from the calculating means. The core constituted by a material having a light transmittance is formed of an optical fiber material such as quartz, a semiconductor, CaF 2 , chalcogenide or the like. Moreover, the mask constituted by a material having a ductility and a light shielding property is formed of a metal thin film to be used for a mirror, for example, gold, aluminum, silver, chromium or titanium which is formed on the core through evaporation or the like. Furthermore, the mask formed in the tip portion of the probe is opened in the following manner. The mask formed in the tip portion of the probe has a ductility. Therefore, when the tip portion of the probe and the light detecting means are pressed in a direction of an optical axis, the mask is gradually stretched thinly so that an opening is formed. The tip portion of the core is appeared from the opening of the mask. Moreover, the light quantity value of the light transmitted from the tip portion of the probe is zero when the opening is not formed on the mask. When the opening is formed in the mask, the light quantity value is increased in proportion to the size of the opening. In the probe opening forming apparatus according to the present invention, a feeding means presses the tip portion of the probe and the light detecting means in the direction of the optical axis is suitably used for the pressing means such that the mask of the tip portion of the probe is gradually stretched thinly and opened without a breakage. In the probe opening forming apparatus according to the present invention, moreover, it is also suitable that a photodiode excellent in the responsiveness of an output value for a light receiving quantity should be used for the light detecting means. Here, the photodiode receives a light transmitted from the tip portion of the probe through a light receiving portion and outputs a current value proportional to the quantity of the received light. According to a second aspect of the present invention there is provided a near-field optical microscope comprising the probe opening forming apparatus, in which the microscope is arranged so that evanescent light incident on a surface to be measured in a sample is scattered through the tip portion of the probe having an opening formed thereon by the opening forming apparatus, and the scattered light is collected through the opening, or so that evanescent light leaking out of the opening is irradiated on the surface to be measured, and scattered light or reflected light is collected through the opening, thereby obtaining information about the surface to be measured in the sample; wherein the microscope comprises a substrate on which the sample is to be mounted, the substrate transmitting light from the opening of the probe to the light detecting means and being coplanar with a light receiving surface of the light detecting means; and a near field head, wherein the probe is attached to the near field head. Preferably, the substrate is divided into an area for carrying out a near field optical measurement and an area for forming an opening on the probe, the area for forming an opening on the probe including the light detecting means of the probe forming apparatus. Preferably, in the present invention, a feeding means controls a distance between the tip portion of the probe and the surface to be measured in the sample in a direction of an optical axis is used for the pressing means. Preferably, in the present invention, the near-field optical microscope comprises an opening diameter checking mechanism is an opening diameter checking mechanism for checking a size of an opening in a tip portion of a probe having the opening formed thereon, the opening diameter checking mechanism includes a light source, a light detecting means, a pressing means, a storage means, and a comparing means. Here, the light source causes a light to be incident in the probe. The light detecting means detects a quantity of a light transmitted from the tip portion of the probe through a light of the light source, which is on contact with the tip portion of the probe. The pressing means presses the tip portion of the probe against the light detecting means in a direction of an optical axis. The storage means previously stores information about relation of the quantity of the light transmitted from the tip portion of the probe and the size of the opening. The comparing means applies a value of a light quantity detected by the light detecting means to the information about relation of the quantity of the light transmitted from the tip portion of the probe and the size of the opening which is stored in the storage means, thereby obtains the size of the opening in the tip portion of the probe. Preferably, in the present invention, the near-field optical microscope comprises an opening diameter regulating mechanism for changing a size of an opening in a tip portion of a probe having the opening formed thereon, the opening diameter regulating mechanism includes a light source, a light detecting means, a pressing means, a storage means, a setting means, a calculating means, and a pressing control means. Here, the light source causes a light to be incident on the probe. The light detecting means detects a quantity of a light transmitted from the tip portion of the probe through a light of the light source, which is on contact with the tip portion of the probe. The pressing means presses the tip portion of the probe against the light detecting means in a direction of an optical axis. The storage means previously stores information about relation of the quantity of the light transmitted from the tip portion of the probe and the size of the opening. The setting means sets a desirable size of the opening in the tip portion of the probe. The calculating means obtains the value of the light quantity for obtaining an opening having a size set by the setting means based on the information about the relation of the quantity of the light transmitted from the tip portion of the probe and the size of the opening which is stored in the storage means. The pressing control means controls the press of the tip portion of the probe against the light detecting means in the direction of the optical axis through the pressing means such that a value of a light quantity detected by the light detecting means is equal to the value of the light quantity calculated from the calculating means. In a probe opening forming apparatus according to the present invention and the near-field optical microscope using the probe opening forming apparatus, pressing control means for controlling the press of a tip portion of a probe with light detecting means in a direction of an optical axis through pressing means such that a value of a light quantity detected by the light detecting means for detecting a quantity of a light transmitted from the tip portion of the probe is equal to a value of a light quantity for obtaining an opening having a desirable size. Therefore, it is possible to easily form an opening having a desirable size in the tip portion of the probe. In the near-field optical microscope in accordance with the present invention, moreover, an opening diameter checking mechanism for checking the size of the opening in the probe having the opening formed thereon is provided. Consequently, the size of the opening of the probe can be checked easily. Furthermore, an opening diameter regulating mechanism for changing the size of the opening in the probe having the opening formed thereon is provided. Consequently, the size of the opening of the probe can be changed easily. BRIEF DESCRIPTION OF THE DRAWINGS Examples of the present invention will now be described in detail with reference to the accompanying drawings, in which: Fig. 1 is a view illustrating the schematic structure of a general near-field optical microscope; Fig. 2 is a view illustrating a probe; Fig. 3 is a view illustrating the schematic structure of a near-field optical microscope according to an embodiment of the present invention; Fig. 4 is a view illustrating a place in the near-field optical microscope shown in Fig. 3 where a probe opening forming apparatus is to be provided; Fig. 5 is a view illustrating the schematic structure of the probe opening forming apparatus of the near-field optical microscope shown in Fig. 3; Figs. 6A, 6B and 6C are views illustrating the action of the probe opening forming apparatus shown in Fig. 5; Fig. 7 is a view illustrating the schematic structure of an opening diameter checking mechanism of the near-field optical microscope shown in Fig. 3; Figs. 8A and 8B are views illustrating the action of the opening diameter checking mechanism shown in Fig. 7; Fig. 9 is a view illustrating the schematic structure of an opening diameter regulating mechanism of the near-field optical microscope shown in Fig. 3; Figs. 10A and 10B are views illustrating the action of the opening diameter regulating mechanism shown in Fig. 9; Figs. 11A and 11B are views illustrating a spectroscope to be suitably used in the near-field optical microscope; Fig. 12 is a view illustrating a variant of the spectroscope to be suitably used in the near-field optical microscope, Fig. 13 is a view illustrating a state in which an end face of a fiber is observed through an observing mechanism to be suitably used in the near-field optical microscope; Fig. 14 is a view illustrating a state in which a sample is simply observed through the observing mechanism shown in Fig. 13 and measured; Fig. 15 is a view illustrating a variant of the observing mechanism shown in Fig. 14; Fig. 16 is a view illustrating a mechanism for displaying an optical path or the like which is to be suitably used in the near-field optical microscope; Fig. 17 is a view illustrating a gas discharge switching mechanism to be suitably used in the near-field optical microscope; Fig. 18 is a view illustrating the schematic structure of an infrared near-field optical microscope to be suitably used in the near-field optical microscope; Fig. 19 is a view illustrating a light collecting mechanism to be suitably used in the infrared near-field optical microscope or the like; Fig. 20 is a view illustrating a mechanism for automatically setting a resonance frequency which is to be suitably used in the near-field optical microscope; Fig. 21 is a view illustrating a mechanism for controlling a distance between a probe and a sample which is to be suitably used in the near-field optical microscope; Fig. 22 is a view illustrating a mechanism for monitoring a near-field mapping spectrum analysis which is to be suitably used in the near-field optical microscope; and, Fig. 23 is a view illustrating a mechanism for measuring a near-field where electric field is applied using a flat probe which is to be suitably used in the near-field optical microscope. DETAILED DESCRIPTION Fig. 3 shows the schematic structure of a near-field optical microscope according to an embodiment of the present invention. Portions corresponding to those in Fig. 1 have the reference numeral 100 added thereto and description will be omitted. In the near-field optical microscope shown in Fig. 3, a sample 112 is provided on a substrate 114 and an excited light 118 is incident on a surface to be measured in the sample 112 so that an evanescent light 120 is generated on the surface to be measured in the sample 112. When the tip portion of a probe 122 is inserted into the field of the evanescent light 120, the field of the evanescent light 120 is scattered by the tip portion of the fiber probe 122. A part of the scattered light 121 enters the probe 122 through an opening and is split into a Rayleigh light, a fluorescence and a photoluminescence light through a spectroscope 138 which are then detected by a detector 124. Then, a data processing is carried out through a computer 126 so that a distance between the tip of the probe and the surface to be measured can be grasped through the Rayleigh light. Accordingly, when the surface to be measured in the sample 112 is scanned while controlling a vertical distance between the tip portion of the probe 122 and the surface to be measured in the sample 112 such that the intensity of the Rayleigh light detected by the detector 124 becomes constant through a stage controller 128 and an XYZ stage 130, it is possible to accurately grasp the concavo-convex portions of the sample 112 in a non-contact with the sample 112. In addition, it is possible to simultaneously obtain component information on each measuring point of the surface to be measured in the sample 112 through the spectrum. While the probe 122 is usually attached to a head of the near-field optical microscope 131, it is an article for consumption. Therefore, it is necessary to remove the probe 122 from the head 131 to be exchanged. However, the quality of the opening influences the resolution of the near-field optical microscope or the like. For example, when the probe such as an article on the market which has already been fabricated is exchanged and is attached to the head of the near-field optical microscope to carry out a measurement, the measurement cannot be carried out with a satisfactory brightness and the same precision in some cases. The details of the cause have not been clear. According to the present inventors, however, even if the mechanical dimension of the probe opening has high precision, the light transmission efficiency of the opening is sometimes varied if the probe is used for an actual measurement. A reason is that the light transmission efficiency of the opening is changed if the probe is exchanged. Moreover, the stage has a slight inclination depending on individual microscopes in many cases. In the probe of a manufactured article, a stage surface is not parallel with a probe opening surface but is shifted therefrom in some cases. Consequently, the evanescent light cannot be uniformly irradiated on the surface to be measured in the sample from the probe opening or a light scattered from the field of the evanescent light cannot be uniformly collected from the surface to be measured in the sample. The present invention has a first feature that a near-field optical microscope comprises a probe opening forming apparatus capable of forming an opening having a desirable size in the tip portion of a probe in which the opening is not formed. In the present embodiment, therefore, an opening forming apparatus 139 shown in enlarged views of Figs. 4 to 5 is provided. As shown in Fig. 4, the substrate 114 of the XYZ stage 130 to be actually used for a near-field optical measurement is divided into an area A1 for carrying out a usual near-field optical measurement and an area A2 for opening formation or the like. The area A2 is provided with a PIN photodiode (light detecting means) 140 of the probe opening forming apparatus 139 such that a light receiving surface 146 thereof is on the level with the surface of the substrate 114. Moreover, the probe opening forming apparatus 139 comprises a light source 116 shown in Fig. 5, the XYZ stage (pressing means) 130, an HDD (storage means) 142 of the computer 126, and a CPU (calculating means, pressing control means) 144 of the computer 126. Moreover, one of ends of the probe in which an opening is not formed is fixed to a head of the near-field optical microscope. The light source 116 to be used in the near-field optical microscope is also used as a light source for the probe opening forming apparatus 139. The excited light (light) 118 is incident in the probe 122 from the light source 116. Moreover, the PIN photodiode (light detecting means) 140 has an excellent characteristic that the quantity of the transmitted light can be measured efficiently. During the formation of the opening, the PIN photodiode 140 comes in contact with the tip portion of the probe 122 to detect the quantity of the light transmitted from the tip portion of the excited light 118. Furthermore, a mechanism for driving the XYZ stage 130 to be used in the near-field optical microscope in a Z-axis direction is also used as the pressing means of the opening forming apparatus 139. When the light receiving surface 146 of the photodiode 140 is gradually pressed against the tip portion of the probe through the XYZ stage 130, the mask 134 of the tip portion of the probe is gradually stretched thinly so that the core 132 is appeared from the mask opening. Thus, the opening is formed. The HDD 142 of the computer 126 which is used in the near-field optical microscope is also used as the storage means of the opening forming apparatus. The HDD 142 prestores information about relation of the quantity of the light transmitted from the tip portion of the probe 122 and the size of the opening. The CPU 144 of the computer 126 which is used in the near-field optical microscope is also used as the calculating means of the opening forming apparatus. The CPU 144 calculates the value of the light quantity for obtaining an opening having a desirable size from the information about the relation of the quantity of the light transmitted from the tip portion of the probe 122 and the size of the opening which is stored in the HDD 142. The CPU 144 of the computer 126 which is used in the near-field optical microscope is also used as the pressing control means of the opening forming apparatus. The CPU 144 controls the pressing of the photodiode against the tip portion of the probe in a direction of an optical axis through the XYZ stage 130 such that the value of the light quantity detected by the photodiode 140 is equal to a value of a light quantity calculated by the CPU 144. More specifically, the light receiving surface 146 of the photodiode 140 is caused to contact in the tip portion of the probe 122 in which the opening is not formed as shown in Fig. 6A. As shown in Fig. 6B, the quantity of the light transmitted from the tip portion of the probe through the excited light 118 is detected and the value of the light quantity is monitored by the computer 126 to move the substrate 114 upward through the XYZ stage 130. Consequently, the light receiving surface 146 of the photodiode 140 is gradually pressed against the tip portion of the probe 122 upward in the drawing. Through the gradual pressing, the mask 134 in the tip portion of the probe is gradually stretched thinly because it has a ductility. Consequently, an opening is gradually formed so that a tip portion 132a of a core 132 is appeared from the opening. When the tip portion 132a of the core 132 is appeared, the value of the light quantity detected by the photodiode 140 which is zero is increased in proportion to an opening diameter. Consequently, the computer 126 gradually presses the photodiode 140 against the tip portion of the probe 122 until a value of a transmitted light quantity to obtain a desirable opening diameter is set through a mechanism for moving the XYZ stage 130 in the Z-axis direction. Thus, the opening 136 having a desirable opening diameter d is formed on the mask 134 in the tip portion of the probe 122 as shown in Fig. 6C. Therefore, the opening can be formed through the PIN photodiode 140 capable of efficiently measuring the quantity of a transmitted light while monitoring the value of a transmitted light quantity measured efficiently. Consequently, also in the case in which the probe is exchanged, it is possible to form an opening having an desired size with high reproducibility. For example, a round opening can be formed or the protrusion of a core portion can be reduced easily. Moreover, the opening is formed in a state in which a sample stage surface to be actually used is provided on the level with the light receiving surface of the photodiode 140. Therefore, even if the stage surface is inclined, an opening surface parallel with the stage surface can be formed. In addition, the measurement is carried out in a state in which the probe having the opening thus formed thereon is attached to the head of the near-field optical microscope. Therefore, the measurement can be carried out accurately. Furthermore, the function of each component of the opening forming apparatus is implemented by using each component of the near-field optical microscope. As compared with the case in which they are provided separately, therefore, a structure can be simplified and the size of the apparatus can be reduced. Thus, the probe attached to the head of the near-field optical microscope can be used continuously until it is exchanged in the normal near-field optical measuring area A1 of the stage 130. In some cases, moreover, the opening diameter is changed during the use of the opening formed as described above. However, it has conventionally been supposed that the probe is removed from the microscope to carry out a check. However, simple checking means has not been present. Moreover, after the probe is attached, it is necessary to regulate an optical axis with an optical system for controlling the vibration and amplitude of the probe and the like, which is complicated. The present invention has a second feature that the near-field optical microscope is provided with an opening diameter checking mechanism capable of checking the size of the opening in the tip portion of the probe which is formed by the probe opening forming apparatus, thereby carrying out the check with the probe attached to the head of the near-field optical microscope. In the present embodiment, therefore, an opening diameter checking mechanism 147 shown in the enlarged view of Fig. 7 is provided. In Fig. 7, the opening diameter checking mechanism 147 includes the light source 116, the HDD (storage means) 142, the photodiode (light detecting means) 140 and the CPU (comparing means) 144. The XYZ stage 130 causes the light receiving surface 146 of the photodiode 140 to contact in the tip portion of the probe. The CPU (comparing means) 144 applies the value of the light quantity detected by the photodiode 140 to the information about the relation of the quantity of the light transmitted from the tip portion of the probe and the size of the opening which is stored in the HDD 142, thereby calculating the size of the opening formed in the tip portion of the probe. As a result, the probe 122 is positioned above the area A1 of the XYZ stage 130 during the normal near-field optical measurement, while the probe 122 having the opening 136 formed through the opening forming apparatus 139 is moved to the area A2 of the XYZ stage 130 as shown in Fig. 8A during the check of the opening diameter. It is possible to easily detect that the opening having a predetermined diameter is formed or not by causing the light receiving surface of the photodiode to contact in the tip portion of the probe through the XYZ stage 130 with the probe 122 attached as shown in Fig. 8B. In other words, the value of the light quantity of the light transmitted from the opening through the excited light has a proportional relationship with the size of the opening. Therefore, the quantity of the light transmitted from the tip portion of the probe is detected by the photodiode 140 with the light receiving surface 146 of the photodiode 140 contacting on the tip potion of the probe. The CPU 144 applies the value of the light quantity thus detected to the information about the relation of the quantity of the light transmitted from the tip portion of the probe and the size of the opening which is stored in the HDD 142, thereby calculating the size of the opening formed in the tip portion of the probe. Furthermore, the function of each component of the opening diameter checking mechanism is implemented by using each component of the near-field optical microscope (opening forming apparatus). As compared with the case in which they are provided separately, therefore, the structure can be simplified and the size of the apparatus can be reduced. When the opening diameter is sufficient after the checking, the probe is returned to the area A1 of the XYZ stage 130 to carry out a normal near-field optical measurement. On the other hand, in some cases, the opening diameter of the opening formed as described above is changed or is to be changed after the formation. However, conventionally, it is necessary to exchange the probe. After the probe is attached, it is necessary to regulate the optical axis with the optical system for controlling the vibration and amplitude of the probe, which is complicated. The present invention has a third feature that the near-field optical microscope is provided with an opening diameter regulating mechanism capable of changing the size of the opening of the probe which is formed by the probe opening forming apparatus, thereby changing the size of the probe attached to the head of the near-field optical microscope. In the present embodiment, therefore, an opening diameter regulating mechanism 149 shown in the enlarged view of Fig. 9 is provided. The opening diameter regulating mechanism 149 includes the light source 116, the photodiode (light detecting means) 140, the CPU (calculating means, press controlling means) 142, and an input device (setting means) 151. The input device 151 can set the desirable size of the opening in the tip portion of the probe to the computer 126. The CPU (comparing means) 144 applies the opening diameter set by the input device 151 to the information about the relation of the quantity of the light transmitted from the tip portion of the probe and the size of the opening which is stored in the HDD 142, thereby calculating the valve of the light transmitted from the tip portion of the probe in order to obtain the desirable opening diameter. The CPU 144 controls the pressing of the light receiving surface 146 of the photodiode 140 against the tip portion of the probe through the movement (upward movement) of the XYZ stage 130 in the Z-axis direction such that the value of the transmitted light quantity which is detected by the photodiode 140 is equal to the value of a light quantity which is calculated by the CPU 142. As a result, the probe is positioned above the area A1 of the XYZ stage during the normal near-field optical measurement, while the probe 122 having the opening 136 formed through the opening forming apparatus 139 is moved to the area A2 of the substrate 114 in the XYZ stage 130 as shown in Fig. 10A during the change. As shown in Fig. 10B, the light receiving surface of the photodiode 140 is caused to contact in the tip portion of the probe, thereby inputting the desirable size of the opening through the input device 151. Then, the CPU 144 calculates the value of the light quantity for obtaining the size of the opening input by the input device 151 through application to the information about a detected quantity which is stored in the HDD 142. In a state in which the light receiving surface 146 of the photodiode 140 contacts in the tip portion of the probe, the CPU 144 controls the pressing of the light receiving surface of the photodiode against the tip portion of the probe through the movement in the Z-axis direction of XYZ stage 130 while detecting the quantity of the light transmitted from the tip portion of the probe through the photodiode 140 such that the value of the transmitted light quantity which is detected by the photodiode 140 is equal to the value of the light quantity which is calculated by the CPU 142. Thus, the change to an opening diameter d of the probe opening can easily be carried out. After the opening diameter is changed, the probe is returned to the area A1 of the XYZ stage to carry out the normal near-field optical measurement. In the present embodiment, thus, it is possible to easily desirably change the size of the opening by pressing the light receiving surface of the photodiode against the tip portion of the probe 122 with the probe 122 attached. Furthermore, the function of each component of the opening diameter regulating mechanism is implemented by using each component of the near-field optical microscope (the opening forming apparatus, the opening diameter checking mechanism). As compared with the case in which they are provided separately, therefore, the structure can be simplified and the size of the apparatus can be reduced. As described above, the near-field optical microscope 110 according to the present embodiment comprises the opening forming apparatus 139 for forming an opening while actually monitoring the transmittance characteristics of the opening. Therefore, it is possible to form an opening having an intended size with high reproducibility. In addition, the sample stage surface to be actually used is provided on the level with the light receiving surface of the photodiode 140 to form the opening. Therefore, it is possible to form an opening surface parallel with the stage surface. The near-field optical measurement is used continuously until the probe is exchanged. Therefore, it is possible to accurately carry out the near-field optical measurement above the area A1. In the present embodiment, moreover, the opening diameter checking mechanism 147 is provided. Therefore, it is possible to easily check the opening of the probe having the opening formed thereon through the movement of the probe to the area A2 on the level with the area A1 in the stage without removing the probe from the microscope. In the present embodiment, furthermore, the opening diameter regulating mechanism 149 is provided. Therefore, it is possible to desirably change the size of the opening easily through the movement of the probe to the area A2 on the level with the area A1 without removing the probe from the microscope. The near-field optical microscope according to the preset invention is not restricted to have the above-mentioned structure but various changes can be made without departing from the scope of the invention. With the above-mentioned structure, for example, the probe opening forming apparatus according to the present invention is incorporated in the near-field optical microscope. The probe opening forming apparatus according to the present invention can also be used independently. With the above-mentioned structure, moreover, the position in the Z-axis direction of the probe is fixed and the light detecting means is moved (upward) in the Z-axis direction is pressed against the tip portion of the probe. It is also preferable that the position in the Z-axis direction of the light detecting means should be fixed, the probe should be moved (downward) in the Z-axis direction through a mechanism for feeding a fine movement in the Z-axis direction or the like, thereby pressing the tip portion of the probe against the light detecting means.

Claims: A probe opening forming apparatus (139) for opening a mask of a tip portion (132a) of a probe (122) with a desirable size, the probe (122) being suitable for a near field optical measurement and comprising a core (132) constituted by a material having a light transmittance and a mask (134) formed on the core constituted by a material having a ductility and a light shielding property, the apparatus comprising: a light source (116) for causing a light to be incident in the probe; light detecting means (140) for detecting a quantity of light transmitted through the tip portion of the probe from the light source, when the light detecting means is in contact with the tip portion of the probe; pressing means (130) for pressing the tip portion of the probe against the light detecting means in a direction of an optical axis; characterised by storage means (142) for previously storing information about a relationship between the quantity of the light transmitted from the tip portion of the probe and the size of the opening (136); calculating means (144) for obtaining the value of the quantity of light for obtaining an opening having a desirable size based on the information about the relationship between the quantity of the light transmitted from the tip portion of the probe and the size of the opening which is stored in the storage means; and pressing control means (144) for controlling the press of the tip portion of the probe against the light detecting means in the direction of the optical axis through the pressing means such that a value of a light quantity detected by the light detecting means is equal to the value of the light quantity calculated from the calculating means. An apparatus according to claim 1, wherein the light detecting means (140) comprises a photodiode for receiving a light transmitted from the tip portion of the probe through a light receiving portion and for outputting a current value proportional to the quantity of the received light. A near-field optical microscope (110) comprising the probe opening forming apparatus (139) according to any preceding claim, in which the microscope is arranged so that evanescent light incident on a surface to be measured in a sample (112) is scattered through the tip portion (132a) of the probe (122) having an opening (136) ormed thereon by the opening forming apparatus, and the scattered light is collected through the opening (136), or so that evanescent light leaking out of the opening (136) is irradiated on the surface to be measured, and scattered light or reflected light is collected through the opening, thereby obtaining information about the surface to be measured in the sample; wherein the microscope comprises a substrate (114) on which the sample (112) is to be mounted, the substrate transmitting light from the opening of the probe to the light detecting means and a surface of the substrate being coplanar with a light receiving surface (146) of the light detecting means; and a near field head, wherein the probe is attached to the near field head. An optical microscope according to claim 3, wherein the substrate (114) is divided into an area (A1) for carrying out a near field optical measurement and an area (A2) for forming an opening on the probe, the area (A2) for forming an opening on the probe including the light detecting means (140) of the probe forming apparatus. An optical microscope according to claim 3 or 4, comprising an opening diameter checking mechanism (147) for checking a size of an opening in a tip portion of a probe (122) having the opening (136) formed thereon, the opening diameter checking mechanism including comparing means (144) for applying a value of a light quantity detected by the light detecting means (140) to the information about the relation of the quantity of the light transmitted from the tip portion of the probe (122) and the size of the opening which is stored in the storage means (142), thereby obtaining the size of the opening (136) in the tip portion of the probe (122). An optical microscope according to claim 3 or 4, comprising an opening diameter regulating mechanism (149) for changing a size of an opening (136) in a tip portion of a probe (122) having the opening formed thereon, the opening diameter regulating mechanism including setting means (151) for setting a desirable size of the opening in the tip portion of the probe.

Inventors: INOUE TSUTOMU, MONONOBE SYUJI, NARITA YOSHIHITO, OHTSU MOTOICHI, SAIKI TOSHIHARU, TERUYAMA SUSUMU, INOUE, TSUTOMU, MONONOBE, SYUJI, NARITA, YOSHIHITO, OHTSU, MOTOICHI, SAIKI, TOSHIHARU, TERUYAMA, SUSUMU, Mononobe, Syuji, c/o Kanagawa Academy of Science, Ohtsu, Motoichi, c/o Kanagawa Academy of Science, Saiki, Toshiharu, c/o Kanagawa Academy of Science
Applicants: JAPAN SCIENCE & TECH CORP, JASCO CORP, KANAGAWA KAGAKU GIJUTSU AKAD, JAPAN SCIENCE AND TECHNOLOGY CORPORATION, JASCO CORPORATION, KANAGAWA ACADEMY OF SCIENCE AND TECHNOLOGY
Application year: 2001
Main classification: G02B21
IPC codes: G01N21, G01B11, G01Q70, G01Q10, G01Q60