JP4136911B2 - Infrared microscope and measuring position determination method thereof - Google Patents

Description

  The present invention relates to an infrared microscope that irradiates a sample with infrared light and performs spectroscopic analysis of the sample from the absorption spectrum of the reflected light or transmitted light. In particular, the prism is brought into contact with the sample, and the infrared light is transmitted through the prism. It has an ATR measurement mode based on ATR (Attenuated Total Reflectance), which measures the absorption spectrum of infrared light reflected on the sample surface by irradiating the sample surface with an incident angle greater than the total reflection critical angle. It relates to an infrared microscope.

  In the sample analysis method using total reflection absorption (ATR method), the sample is brought into contact with a prism (ATR prism) having a refractive index larger than that of the sample, and the infrared light is directed to the surface of the sample to exceed the total reflection critical angle. Irradiate at an incident angle of. After the infrared light is incident on the ATR prism, it is totally reflected at the boundary surface between the ATR prism and the sample. During this total reflection, the infrared light enters the sample side slightly beyond the boundary surface (a fraction of the wavelength of the measurement infrared light), and receives intrinsic absorption at the surface portion of the sample. Thus, the sample surface can be analyzed by measuring the absorption spectrum of the infrared light reflected on the sample surface.

  In the infrared microscope-ATR method, a method of measuring a total reflection spectrum by attaching a total reflection prism such as zinc selenide, diamond, germanium or the like to the tip of a reflection objective mirror and pressing a measurement sample on the prism is the mainstream.

  When zinc selenide or diamond is used as a prism, these transmit visible light, so the sample can be observed through the prism, but when using a prism that does not transmit visible light, such as germanium, the prism is moved. Or a sample is observed with a microscope using another observation lens (see Patent Document 1).

In addition, when a Cassegrain mirror is used as the reflecting objective mirror, the position of the prism with respect to the reflecting objective mirror is generally adjusted to a position where the amount of reflected light is maximum when the sample is not in contact with the prism. .
Japanese Patent Laid-Open No. 10-325792

In an ATR reflective objective mirror using a prism that does not transmit visible light, such as germanium, a difference occurs between the observed sample position and the sample measurement position where the prism comes into contact and is actually measured.
Further, when a Cassegrain mirror is used as a reflection objective mirror, due to the structure of the Cassegrain mirror, the deviation between the two can be reduced to some extent by adjustment with the amount of reflected light, but it is difficult to make them completely coincide with each other. Deviations of ˜100 μm or more occur.
For this reason, when trying to measure a sample smaller than this difference, measurement at another position is performed, and a useful result cannot be obtained.
In addition, the measured position cannot be accurately grasped.

A first object of the present invention is to provide a method capable of determining a sample measurement position that is actually measured by the ATR method.
A second object of the present invention is to provide an infrared microscope capable of eliminating a deviation between a sample observation position observed by a method other than the ATR method and a sample measurement position actually measured by a prism contacting with the ATR method. .

  The method of the present invention for achieving the first object detects a sample position to be actually measured by scanning and measuring a linear minute object. That is, in the method of the present invention, the prism is brought into contact with the sample on the sample stage, and infrared light is irradiated to the sample surface through the prism at an incident angle that is equal to or greater than the total reflection critical angle, and reflected by the sample surface. In the infrared microscope having the ATR measurement mode for measuring the absorption spectrum of the infrared light, the measurement position of the sample is determined by including the following first and second steps.

  The first step is an observation mode that does not use a prism. A sample stage is observed when a linear sample having a width smaller than the spatial resolution of the prism is observed and the sample stage is positioned so that the linear sample crosses the observation field center. The sample observation position coordinates are obtained from the coordinates of the sample stage and the coordinates of the sample stage when the sample stage is positioned so that the linear sample crosses the observation field center again.

  The second step is to measure the linear sample in the ATR measurement mode, scan the linear sample in the width direction, and detect the linear sample when the linear sample is detected. This is a step of obtaining the measurement position coordinates of the sample in the ATR measurement mode from the coordinates of the sample stage when the linear sample is detected by rotating the linear sample again in the width direction.

  Here, the spatial resolution of the prism means the size of the part actually measured. If a prism with a diameter of 100 μm is used as the contact surface with the sample, and the obtained vector is information from all of the sample portions in contact with the prism, the size in contact with the prism, that is, 100 μm is the spatial resolution. However, in the case of information from a specific part of the sample part in contact with the prism, the size of that part becomes the spatial resolution. This spatial resolution is determined by the shape of the prism, the size of the infrared light beam (aperture size), and the like.

  The infrared microscope of the present invention that achieves the second object is that a prism is brought into contact with a sample on a sample stage, and infrared light is irradiated toward the sample surface through the prism at an incident angle greater than the critical angle for total reflection. An infrared microscope having an ATR measurement mode for measuring an absorption spectrum of infrared light reflected from the sample surface, the sample observation position in the observation mode not via the prism, and the sample measurement in the ATR measurement mode. A storage unit that stores a shift amount from the position, and a stage that moves the sample stage by a shift amount stored in the storage unit so that the sample observation position and the sample measurement position coincide with each other in the ATR measurement mode. A movement control unit.

  In other words, the sample stage is automatically moved so that the observed and set position is at the measurement position by feeding back to the infrared microscope the deviation between the observed sample position and the actual sample position where the prism comes into contact. .

The deviation between the observed sample position and the sample position where the prism comes into contact and is actually measured is obtained in advance. For example, when the center of the observation position is the origin (0, 0) and the sample position actually measured by contact with the prism is (XY), the X and Y values are stored in the infrared microscope. . When the infrared microscope is switched from the observation mode to the ATR measurement mode, or when an instruction to operate the correction function is given to the infrared microscope, the sample stage moves by the values of X and Y stored in advance. The center of the observation position coincides with the measurement position.
The displacement amount stored in the storage unit may be obtained by any method, but one method is to use the difference between the observation position coordinates and the measurement position coordinates in the method of the present invention.

  According to the method of the present invention, since the measurement position can be accurately grasped by clarifying the actual measurement position in the ATR measurement mode, the reliability of the measurement result is improved and the measurement has been performed so far. Measurement of a material or region smaller than the amount of deviation between the observation position and the measurement position, which has been difficult, can be easily performed.

  According to the infrared microscope of the present invention, since the observation position and the measurement position coincide with each other, the position accuracy of the infrared microscope-ATR measurement is improved. It becomes easy and easy to do.

FIG. 1 shows the entire optical system of an infrared microscope according to one embodiment. However, the ATR prism is not shown here and will be described later with reference to FIG.
Reference numeral 2 denotes a transmission / reflection switching mirror for switching the measurement mode when performing infrared measurement between the transmission mode and the reflection mode. FTIR (Fourier transform infrared spectrophotometer) not shown in the transmission / reflection switching mirror 2 Infrared light is guided from the interferometer. In order to guide the infrared light from the switching mirror 2 onto the optical axis of the reflection objective mirror 10 composed of a Cassegrain mirror for the infrared reflection spectroscopic measurement mode, a plane mirror 4, a spherical mirror 6 and a half mirror 8 are provided. A sample stage 12 is provided below the reflective objective mirror 10 so that the focal point of the reflective objective mirror 10 is at a position 14 on the sample.
The sample stage 12 is moved in the X and Y directions in the horizontal plane by the stage movement control unit 50.

  A plane mirror 28, a spherical mirror 30, a pinhole 31, a plane mirror 32, and a condenser mirror 34 are provided in the lower part of the microscope in order to transmit infrared light from the switching mirror 2 from the lower surface of the sample for the infrared transmission spectroscopic measurement mode. Yes.

  The reflected infrared light by the infrared light irradiated on the sample by the reflection objective 10 or the infrared light transmitted through the sample is condensed again by the reflection objective 10. In order to guide the infrared light collected by the reflective objective mirror 10 to the MCT detector 26 of the infrared detector, the variable aperture 16, the plane mirrors 20 and 22, and the off-axis ellipsoidal mirror 24 are provided above the reflective objective mirror 10. Is provided.

  In order to irradiate the sample with visible light in the visible reflection observation mode, a halogen lamp 36, a lens system 38, and a half mirror 40 for introducing reflected illumination light are provided on the upper part, from the half mirror 40 to the plane mirror 18 and the reflection objective mirror 10. After that, visible light enters the sample. In order to transmit visible light to the sample in the visible transmission observation mode, a halogen lamp 42 and a transmission illumination light introduction plane mirror 43 are provided in the lower part, and visible light passes through the sample from the plane mirror 43 through the plane mirror 32 and the condenser mirror 34. To do.

  The sample stage 12 and the reflective objective mirror 10 are shown in FIG. An ATR prism 60 is disposed on a sample 54 placed on the sample stage 12. The ATR prism 60 has a spherical contact surface on the sample side and is held by a prism holder 62. The diameter of the ATR prism 60 is about 2 to 5 mm. The prism holder 62 is slidable in the horizontal direction, and the visible observation mode in which the ATR prism 60 is removed from the sample 54 or the normal infrared measurement mode (a) in which no prism is used, and the ATR prism 60 on the sample 54. It is possible to switch to the contacted ATR measurement mode (b).

Returning to FIG. 1, reference numeral 52 denotes a storage unit that stores a deviation amount between the sample observation position in the observation mode not via the prism 60 and the sample measurement position in the ATR measurement mode. In the ATR measurement mode, the stage movement control unit 50 moves the sample stage 12 so as to move the sample stage 12 by the amount of deviation stored in the storage unit 52 so that the sample observation position and the sample measurement position coincide with each other. Control.

Next, the operation of this embodiment will be described with reference to FIG.
In normal infrared microscope measurement (transmission, regular reflection), the measurement object is moved to the center of the microscope field, and the aperture 16 is opened, closed, and rotated in accordance with the size of the measurement object. As a result, only the light that has been transmitted or reflected through the measurement object in the aperture opening reaches the detector 26, and the other light is shielded, so that the spectrum of the measurement object is obtained. Even if there is a deviation between the aperture center of the aperture 16 and the center of the observation field, the state of the aperture 16 can be confirmed in the observation, and the position of the measurement target can be adjusted accordingly.

  On the other hand, in the infrared microscope-ATR measurement, as shown in FIG. 3A, a spectrum at a position in contact with the prism 60 is obtained separately from the setting of the aperture 16, so that the center of the observation visual field S or the aperture opening center ( When the position indicated by the symbol T in the figure and the center of the contact position of the prism 60 (position indicated by the symbol A in the figure) coincide with each other, the measurement object can be accurately measured. If there is a difference between the measurement object and the measurement object, measurement is performed at a position different from the measurement object, and an accurate spectrum cannot be obtained.

  In the present invention, the deviation (X, Y) between the two confirmed in advance is stored in the storage unit 52, and the sample stage 12 is automatically moved and corrected as shown in (B). Thus, a state in which the center of the observation visual field S or the aperture opening center T and the contact position center A of the prism 60 coincide with each other is realized, and as a result, the measurement object can be accurately measured.

  FIG. 4 shows a spectrum obtained by measuring a sample in which resin beads (styrene-based) having a diameter of 10 μm are placed on glass according to this example. The ATR objective mirror used for the measurement is equipped with a germanium prism having a curved contact surface with the sample, and has a spatial resolution of about 20 μm. For this reason, although the measurement result of beads is influenced by glass, it clearly shows a styrene-based ATR spectrum.

An embodiment of a method for determining the measurement position by the ATR prism will be described.
As shown in FIG. 5A, a linear sample 70 having a width smaller than the spatial resolution of the prism is fixed on the sample stage 12 of the microscope, and the sample stage 12 is moved to move the linear sample 70 in the width direction. The ATR spectrum at each position is measured. In the figure, the square frame represents the observation field of view, and the linear sample 70 moves in the direction of the arrow as the sample stage 12 moves. The amount of movement is the same as or smaller than the line width of the linear sample 70. The position where the ATR spectrum of the linear sample is obtained is searched by repeating the movement and measurement. If the position where the ATR spectrum of the linear sample can be obtained can be confirmed, the actual measurement position exists at a certain position (on the line) 70a of the linear sample at that time. The coordinates of the sample stage 12 at that time are obtained.

Next, as shown in (B), the sample 54 is rotated 90 ° to rotate the linear sample 70 90 °, and the same operation is repeated to obtain the position 70b where the ATR spectrum of the linear sample 70 is obtained again. The coordinates of the sample stage 12 at that time are obtained.
As a result of the above, the point where the two lines 70a and 70b obtained are the points at which the prism 60 is actually in contact with the sample. The position can be obtained from the coordinates of the sample stage obtained in the above two steps (A) and (B).

  As a linear sample, a film cross section produced by embedding a wrap film (thickness of about 10 μm) or a multilayer film having a thickness of about 10 μm with a resin such as epoxy and cutting with a microtome or the like can be used. . The type of film is not particularly limited. It is sufficient that the difference between the spectrum of the film and the spectrum of the adjacent substance is clear. It can also be used in the same way with fibers pressed on a filter.

  FIG. 6 shows a linear sample prepared by embedding a vinylidene chloride film F (thickness of about 10 μm and width of about 50 μm) with two types of epoxy resins R1 and R2, and cutting in the width direction with a microtome. The size of the sample (embedded vinylidene chloride film cross section) surrounded by a frame is 10 μm × 50 μm.

FIG. 7 shows an ATR spectrum obtained by moving the linear sample in the width direction of the film. The spectrum which can be discriminated by the embedding resins 1 and 2 and the film is obtained. By using this linear sample, the measurement position in the ATR measurement mode can be obtained by the method shown in FIG.
A method of obtaining the sample observation position by visible light or infrared light in the observation mode not via the prism can be performed in the same manner as in FIG.

  Infrared spectroscopic analysis using the infrared microscope of the present invention can be widely used for identification analysis of substances. For example, it can be widely used not only for organic substances such as chemical substances, pharmaceuticals, and electronic materials, but also for inorganic substances.

It is a block diagram which shows the infrared microscope of one Example. It is front sectional drawing which shows the part of the sample stage and reflective objective mirror in the Example. It is a figure explaining operation | movement of the Example. It is a figure which shows the spectrum acquired in the Example. It is a figure explaining operation | movement of the Example which calculates | requires a measurement position. It is an image showing the linear sample used in an Example. It is a figure which shows the ATR spectrum obtained by moving the same linear sample to the width direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reflective objective mirror 12 Sample stage 14 Focus position of reflective objective mirror 16 Aperture 26 Infrared detector 46,48 Eyepiece 50 Stage movement control part 52 Memory | storage part 70 Linear sample

Claims (3)

The prism is brought into contact with the sample on the sample stage, and infrared light is irradiated through the prism toward the sample surface at an incident angle equal to or greater than the total reflection critical angle, and the absorption spectrum of the infrared light reflected from the sample surface. In an infrared microscope having an ATR measurement mode for measuring
In the observation mode not via the prism, a linear sample having a width smaller than the spatial resolution of the prism is observed, and the sample stage coordinates when the sample stage is positioned so that the linear sample crosses the observation field center, and The sample is rotated by 90 ° from the state, and the sample observation position coordinates are obtained from the coordinates of the sample stage when the sample stage is positioned again so that the linear sample crosses the observation field center;
Measure the linear sample in the ATR measurement mode, scan the linear sample in its width direction, rotate the sample 90 degrees from the coordinates of the sample stage coordinates when the linear sample is detected, and again Scanning the linear sample in the width direction and obtaining the measurement position coordinates of the sample in the ATR measurement mode from the coordinates of the sample stage when the linear sample is detected,
A method of obtaining a deviation amount between the sample observation position coordinates and the measurement position coordinates and determining a measurement position of the sample based on the sample observation position coordinates and the deviation amount at the time of sample measurement in the ATR measurement mode . The prism is brought into contact with the sample on the sample stage, and infrared light is irradiated through the prism toward the sample surface at an incident angle equal to or greater than the total reflection critical angle, and the absorption spectrum of the infrared light reflected from the sample surface. In an infrared microscope having an ATR measurement mode for measuring
A storage unit for storing a deviation amount between the sample observation position in the observation mode not via the prism and the sample measurement position in the ATR measurement mode;
An infrared, comprising: a stage movement control unit configured to move the sample stage by a deviation amount stored in the storage unit so that the sample observation position and the sample measurement position coincide with each other in the ATR measurement mode. microscope.   The infrared microscope according to claim 2, wherein a difference between the observation position coordinates and the measurement position coordinates in the method according to claim 1 is used as the shift amount stored in the storage unit.

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