Infrared microscope with a multi-element detector of different sizes

Abstract

This infrared microscope (10) allows selection of an optimally sized infrared element depending on the size of the sample, the aperture opening size, or the amount of light received by the detector. The infrared microscope (10) includes a sample stage (22), an upper Cassegrain mirror (24) that collects infrared light from the sample, an aperture (40) positioned to form a sample image, a collecting mirror (50) that collects light passing through the aperture, a mirror mount (60) that moves the collecting mirror (50), and a detector (70) that detects the light collected by the collecting mirror (50). The aperture (40) is selected from a plurality of apertures with different opening sizes, and the detector (70) has multiple infrared elements (76, 78) arranged on the surface of a dewar (72). The multiple infrared elements (76, 78) are different sizes and are spaced apart at intervals of 10 mm or less. The mirror mount (60) is provided to move the collecting mirror (50) so that the position of the aperture image formed by the collecting mirror (50) coincides with the positions of the multiple infrared elements (76, 78).

Description

[Technical Field]

[0001] The present invention relates to an infrared microscope that uses infrared light to obtain optical information of a minute area on a sample. [Background technology]

[0002] An infrared microscope is a device that irradiates a sample placed on a movable stage with infrared light, collects and detects the transmitted light, reflected light, or total reflected light from a small area on the sample, and obtains its infrared spectrum.

[0003] We will now explain the typical optical system (Cassegrain mirror, aperture, and focusing mirror in front of the detector) from the sample on the movable stage of an infrared microscope to the detector. First, a magnified image of a small area on the sample is obtained using the Cassegrain mirror. An aperture is placed at the position of the magnified image, allowing only light from the desired measurement area to pass. The focusing mirror in front of the detector forms an image of the aperture opening on the infrared element of the detector, and the infrared element detects the intensity of the infrared light. The signal processing unit performs a Fourier transform on the intensity signal of the infrared light detected in this way to calculate the infrared spectrum.

[0004] As described in paragraph 0010 of Patent Document 1, the aperture is configured so that the size and shape of the opening can be changed to adjust the measurement area according to the size of a minute part of the sample. For example, if the target substance is minute in size, changing to an aperture with a smaller opening and narrowing the measurement area makes it possible to obtain only the optical information of that substance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-208016 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when only one detector can be installed in an infrared microscope, the size of the infrared element remains the same even if the aperture opening size is reduced, and as shown in Figures 9(A) and (B), the area on the light-receiving surface of the infrared element where light is not detected increases.

[0007] In Figure 9(A), the size of the aperture image is appropriate for the infrared element, enabling highly sensitive measurements with a good S / N ratio. However, if the aperture image is made too small, as in Figure 9(B), the proportion of the area that does not receive light, that is, the proportion of thermal noise relative to the received light signal, becomes excessive, resulting in insufficient detection sensitivity. This problem is not limited to when the aperture opening size is made small; it can also occur when the amount of light received by the detector is small due to the small size of the sample itself.

[0008] So, is it enough to replace the detector with one that has a small-sized infrared element? However, every time a detector with a large-sized element is replaced with a detector with a small-sized element, adjustment work is required to accurately position the small aperture image on the small-sized infrared element, and such adjustment work is very difficult for an ordinary user to perform.

[0009] So, what if we could install two detectors, one with a large element and one with a small element? However, because the detectors are integrated with a cooling mechanism (Dewar) such as liquid nitrogen to avoid errors caused by thermal fluctuations in the infrared elements, a certain amount of space must be reserved for each detector. Therefore, installing two detectors would make the infrared microscope significantly larger. Furthermore, even if two detectors could be installed, the distance between the large and small infrared elements would be several centimeters or more, which would usually increase the time required to switch the optical path, making it difficult to switch the optical path quickly.

[0010] An object of the present invention is to provide an infrared microscope that allows selection of an infrared element of an optimum size according to the size of the sample, the opening size of the aperture, or the amount of light received by the detector. [Means for solving the problem]

[0011] That is, the infrared microscope of the present invention comprises a sample stage on which a sample is placed, an objective mirror that collects infrared light from the sample, an aperture provided at the position of a sample image formed by the objective mirror, a collecting mirror that collects infrared light that has passed through an opening of the aperture, a collecting mirror drive unit that moves the collecting mirror, and a detector that detects the infrared light collected by the collecting mirror, the aperture is selected from a plurality of apertures having different opening sizes or shapes, or is configured so that the opening size or shape is variable; the detector has a detection element holder and a plurality of infrared elements arranged on a surface of the detection element holder, the plurality of infrared elements having different sizes and arranged at intervals of 10 mm or less; The focusing mirror driving unit is configured to move the focusing mirror so that the position of an aperture image formed by the focusing mirror coincides with the positions of the plurality of infrared elements.

[0012] With this configuration, the infrared microscope of the present invention can select an infrared element of an optimal size according to the size of the sample, the aperture opening size, or the amount of light received by the detector. For example, selecting a large-sized infrared element enables bright measurements using a large aperture opening, while selecting a small-sized infrared element enables highly sensitive measurements of a minute area by narrowing the aperture opening. In other words, it is now possible to perform different types of measurements simultaneously.

[0013] Furthermore, since multiple infrared elements of different sizes are arranged in one detection element holder at intervals of 10 mm or less, the installation space for the detector is not increased, and the movement of the focusing mirror by the focusing mirror drive unit is small, allowing for quick and accurate switching of the infrared elements.

[0014] Here, the infrared light from the sample can be infrared light that has been transmitted through the sample, infrared light that has been reflected by the sample, or infrared light that has been totally reflected by the sample. The multiple infrared elements may be arranged parallel to the axis of incidence of the infrared light on the focusing mirror, or may be arranged two-dimensionally with a direction parallel to the axis of incidence of the infrared light on the focusing mirror and a direction perpendicular to the axis of incidence.

[0015] The focusing mirror driver may be configured to move the position or the attitude of the focusing mirror, or both the position and the attitude of the focusing mirror. For example, the focusing mirror driver may be configured to vary the angle of incidence of infrared light onto the focusing mirror. For example, the focusing mirror driver may be configured to translate the focusing mirror along the axis of incidence of infrared light.

[0016] Furthermore, for example, the collecting mirror drive unit may be configured to translate the collecting mirror along the incident axis of infrared light and to rotate the collecting mirror around the incident axis of infrared light. Furthermore, for example, the collecting mirror drive unit may be configured to vary the incident angle of infrared light onto the collecting mirror and to rotate the collecting mirror around the incident axis of infrared light.

[0017] Since the movements of the focusing mirrors exemplified above all require small movements, by using a focusing mirror drive unit, it is possible to quickly and accurately align the aperture image of the infrared light with the respective positions of multiple infrared elements of different sizes arranged one-dimensionally or two-dimensionally on the detector.

[0018] Furthermore, it is preferable that the infrared microscope of the present invention further comprises a computer connected to the focusing mirror drive unit, and the computer is configured to select an infrared element of an optimal size based on information on the opening size of the aperture provided at the position of the sample image, information on the energy value of the infrared light received by the detector, or both, and to control the focusing mirror drive unit so that the focusing mirror focuses the infrared light onto the selected infrared element.

[0019] Alternatively, the infrared microscope of the present invention further includes a computer connected to the focusing mirror drive unit, the computer information on an aperture size range in which the energy value of the infrared light measured in advance for each opening size of the aperture in the absence of a sample exhibits linearity is acquired and stored for each infrared element; It is preferable that the optical system is configured to select an infrared element of an optimal size based on information about the opening size of the aperture provided at the position of the sample image and information about the opening size range indicating the linearity, and to control the focusing mirror drive unit so that the focusing mirror focuses infrared light onto the selected infrared element.

[0020] This automatic infrared element selection function makes it possible to automatically switch to an infrared element of the optimal size depending on the sample size, aperture size, or detector light intensity. Because the focusing mirror is moved by the focusing mirror driver over a very small distance, the infrared element can be switched in a short time, enabling a seamless series of measurements involving the use of multiple infrared elements. Furthermore, because the appropriate infrared element is always selected, high-sensitivity measurements (improved S / N) are possible even without sufficient measurement know-how.

[0021] It is also preferable that the sample stage is configured to be movable in a direction perpendicular to the central axis of the detection-side objective mirror, and that the infrared microscope detects the infrared light by sequentially changing the measurement area on the sample where the infrared light is focused by moving the stage, and acquires spectral data for each measurement area, thereby performing mapping measurement of a predetermined range of the sample.

[0022] Alternatively, the infrared microscope includes a detection-side scanning mirror provided on an optical path from the detection-side objective mirror to the aperture, the detection-side scan mirror is configured so that the orientation of the reflection surface can be changed, and the reflection surface is variable with respect to the incident direction of the infrared light from the detection-side objective mirror, thereby making it possible to change the measurement area on the sample that is detected by the detector; It is preferable that the infrared microscope detects infrared light from the measurement area on the sample, which is sequentially changed by the detection-side scanning mirror, and acquires spectral data for each measurement area, thereby performing mapping measurement of a predetermined range of the sample.

[0023] Here, the infrared microscope includes a light output means for outputting infrared light for irradiating a sample; an irradiation-side scanning mirror for guiding the infrared light from the light output means to a sample; an illumination-side objective mirror for collecting the infrared light from the illumination-side scan mirror and illuminating a predetermined illumination area on the sample; It is preferable that the irradiation side scanning mirror is configured so that the orientation of the reflective surface can be changed, and that the reflective surface is variable with respect to the incident direction of the infrared light from the light output means, so that the irradiation area of ​​the infrared light on the sample can be sequentially changed to match the measurement area.

[0024] Alternatively, the detection-side objective mirror is provided with a high-refractive-index crystal element for contacting with a sample, and infrared light supplied to the detection-side objective mirror, which also serves as an illumination-side objective mirror, is focused on the crystal element and illuminates a minute portion within the contact surface with the sample at an incident angle equal to or greater than a critical angle, the infrared microscope further includes a detection-side scanning mirror provided on an optical path from the detection-side objective mirror to the aperture, the detection-side scanning mirror is configured so that the orientation of the reflecting surface can be changed, and the reflecting surface can be changed with respect to the incident direction of the infrared light from the detection-side objective mirror, thereby making it possible to change the measurement area in a minute portion within the contact surface that is detected by the detector; It is preferable that the infrared microscope detects infrared light from the measurement area in a minute area within the contact surface that is sequentially changed by the detection side scanning mirror, and performs mapping measurement of the minute area within the contact surface by acquiring spectral data for each measurement area.

[0025] Here, the infrared microscope includes a light output means for outputting infrared light for irradiating a sample; an illumination-side scanning mirror for guiding the infrared light from the light output means to the detection-side objective mirror, It is preferable that the irradiation side scanning mirror is configured so that the orientation of the reflective surface can be changed, and that the reflective surface can be changed relative to the incident direction of the infrared light from the light output means, so that the irradiation area of ​​the infrared light at a small location within the contact surface can be sequentially changed to match the measurement area. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a diagram showing the overall configuration of a microscopy system configured by connecting an FTIR to an infrared microscope according to one embodiment of the present invention. [Figure 2] 10(A) to 10(C) are diagrams showing variations in the layout of a plurality of infrared elements used in the detector of the infrared microscope. [Figure 3] 10A and 10B are diagrams illustrating an example of the operation of a collecting mirror in front of a detector of the infrared microscope. [Figure 4] 4(A) and 4(B) are diagrams showing the change in the position of the aperture image due to the movement of the focusing mirror in FIG. 3. [Figure 5] 10A and 10B are diagrams showing another example of the operation of the collecting mirror in front of the detector of the infrared microscope. [Figure 6] 10A and 10B are diagrams showing a holding structure for finely adjusting the attitude of the collecting mirror. [Figure 7] 10A and 10B are diagrams illustrating an example of an automatic switching method for an infrared element. [Figure 8] 10A and 10B are diagrams for explaining another example of an automatic switching method for an infrared element. [Figure 9] 10A and 10B are diagrams showing the relationship between the size of the infrared element of the detector and the size of the aperture image formed on the infrared element. DETAILED DESCRIPTION OF THE INVENTION

[0027] An embodiment of an infrared microscope according to the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing the overall configuration of a microscopy system configured by connecting an infrared microscope 10 of this embodiment to a Fourier transform infrared spectrophotometer (hereinafter referred to as FTIR) 20. The FTIR 20 has a built-in infrared light source and a Michelson interferometer, and supplies an interference wave of infrared light output from the interferometer to the infrared microscope 10, and corresponds to the light output means of the present invention.

[0028] The infrared microscope 10 is composed of a microscopic optical section 30, an aperture 40, a focusing mirror 50 in front of the detector, a focusing mirror drive section (referred to here as a mirror mount 60), a detector 70, and various reflecting mirrors. The microscopic optical section 30 is a section that performs transmission, reflection, or total reflection measurement of a minute area of ​​a sample using infrared light.

[0029] First, the optical system for transmission measurement shown in Figure 1 will be described. Switchable mirror 12 guides infrared light from FTIR 20 to the optical path for transmission measurement (reflector 14, transmission measurement mirror 16, and lower Cassegrain mirror 18, in that order). Lower Cassegrain mirror 18 (corresponding to the illumination-side objective mirror) focuses the infrared light reflected from transmission measurement mirror 16 and illuminates a predetermined area of ​​the sample placed on sample stage 22 from below. Light transmitted through the sample is extracted and focused by upper Cassegrain mirror 24 (corresponding to the detection-side objective mirror) and reflected by detection-side scanning mirror 26 above. An aperture 40 is placed at the imaging position behind upper Cassegrain mirror 24 to cut out light (such as stray light) generated from areas other than the measurement area on the sample and detect only the light transmitted through the desired measurement area. The light passing through the opening of the aperture 40 is focused again by the reflecting mirror 28 and the focusing mirror 50 in front of the detector, and illuminates the infrared elements 76, 78 of the detector 70 located at the confocal point of the aperture 40. The light is converted into an electrical signal, which is then Fourier transformed in the signal processing means to produce an infrared spectrum.

[0030] The magnification of each Cassegrain mirror can be selected from a range of 4 to 100x, preferably from a range of 15 to 32x. The opening size of the aperture 40 indicates the size of the measurement area on the sample. Even if the aperture is the same, the size of the measurement area on the sample will vary depending on the magnification of the upper Cassegrain mirror 24 it is combined with. Even if the magnification of the upper Cassegrain mirror 24 is fixed, it is preferable to configure the opening size and shape to be changeable so that the measurement area on the sample can be adjusted. For example, multiple apertures with different shapes and opening sizes can be prepared, and the desired shape and opening size can be selected and used depending on the measurement conditions. An aperture equipped with a mechanism that allows the opening shape and size to be changed can also be used.

[0031] Next, the optical system for reflectance measurement will be described. The reflective surface of the switching mirror 12 is rotated 90 degrees so that the switching mirror 12 guides infrared light to the optical path for reflectance measurement (reflector 32, reflectance measurement mirror 34, and upper Cassegrain mirror 24). The upper Cassegrain mirror 24 serves both the function of irradiating a predetermined area of ​​the sample from above with infrared light (function as an illumination-side objective mirror) and the function of extracting and focusing the light reflected from the sample (function as a detection-side objective mirror). The reflectance measurement mirror 34 is located in half of the area divided by a boundary line passing through the optical axis on a cross section perpendicular to the optical axis connecting the upper Cassegrain mirror 24 and the detection-side scanning mirror 26, and is not located in the other half. Therefore, it is also called a half mirror. In other words, in reflectance measurement, infrared light from the reflector 32 reflects off the reflectance measurement mirror 34 and travels toward the upper Cassegrain mirror 24, irradiating the sample. The infrared light reflected from the sample and collected by the upper Cassegrain mirror 24 then passes through the space where the reflection measurement mirror 34 is not located and proceeds to the detection-side scanning mirror 26. The formation of the optical path after the detection-side scanning mirror 26 and the signal processing after the detector 70 are the same as for transmission measurement.

[0032] The optical system for total reflection measurement will now be described. The upper Cassegrain mirror 24 is switched to an upper Cassegrain mirror equipped with a high-refractive-index crystal element (ATR prism), bringing the ATR prism into contact with the sample. Infrared light is guided to the optical path for reflection measurement and supplied to the upper Cassegrain mirror equipped with an ATR prism. The infrared light passes through the ATR prism of the upper Cassegrain mirror and irradiates a minute area within the contact surface with the sample at an incident angle equal to or greater than the critical angle. The total reflected light from the sample passes through the ATR prism, is collected again by the upper Cassegrain mirror, and is sent to the detection-side scanning mirror 26.

[0033] The following describes mapping measurement of a predetermined area on a sample using the infrared microscope 10 configured as described above. The infrared microscope 10 enables spectral measurement at high magnification, but when it is desired to capture the entire sample to be measured, mapping measurement is performed to capture the entire sample or a specific area in a unified manner.

[0034] The first method is mapping measurement involving the operation of the sample stage 22, which has an electronically controlled automatic stage. In this method, the sample is placed on the automatic stage of the sample stage 22, and the measurement area on the sample is changed in sequence by moving the automatic stage. Spectral data is acquired for each measurement area, and mapping data for a specified range of the sample is created.

[0035] In the second method, the measurement area on the sample is changed sequentially by moving the detection-side scanning mirror 26 while the sample stage 22 is fixed, and spectral data for each measurement area is acquired to create mapping data for a predetermined range of the sample. In this embodiment, the switching mirror 12, which switches between transmission measurement and reflection measurement as described above, also serves as the illumination-side scanning mirror. In other words, the switching mirror 12 has both the function of switching between transmission measurement and reflection measurement by rotating the reflective surface 90 degrees, and the scanning function of sequentially moving the illumination area on the sample by minutely controlling the orientation of the reflective surface with a controller in each position after the 90-degree rotation (for both transmission measurement and reflection measurement).

[0036] The orientation of the reflective surface of detection-side scanning mirror 26 is adjusted so that only light from a specific measurement area on the sample is directed toward the opening of aperture 40. By controlling the orientation of the reflective surface of detection-side scanning mirror 26 with a controller, the measurement area on the sample can be moved to match the opening of aperture 40. The orientation of the reflective surface of switching mirror (illumination-side scanning mirror) 12 is changed to move the irradiation area on the sample, and at the same time, the orientation of the reflective surface of detection-side scanning mirror 26 is also changed so that the measurement area moves in the same direction as the irradiation area. By repeating spectral measurements for all of these moved positions of the measurement area and irradiation area, two-dimensional mapping measurement of a certain range on the sample can be performed.

[0037] As described above, by synchronizing the operation of the switching mirror (illumination-side scanning mirror) 12 with the operation of the detection-side scanning mirror 26, when a wider XY plane range (here, the mounting surface of the sample stage is referred to as the XY plane) is set as the mapping measurement range, it is possible to acquire spectral data with high energy values ​​throughout the entire mapping measurement range. In other words, two-dimensional mapping measurement based on high-quality spectral data acquired over a wider XY plane range becomes possible.

[0038] Even if the switching mirror (illumination side scanning mirror) 12 is fixed and only the detection side scanning mirror 26 is operated, spectral data with a relatively high energy value can be acquired within a certain range of the XY plane near the center of the illumination light, making it possible to perform two-dimensional mapping measurements.

[0039] Even when using an upper Cassegrain mirror with an ATR prism instead of the upper Cassegrain mirror 24 to measure the total reflection of a sample, two-dimensional mapping measurement can be performed without moving the sample stage 22 by using the detection-side scanning mirror 26 or by using both the detection-side scanning mirror 26 and the switching mirror (illumination-side scanning mirror) 12. That is, in total reflection measurement, the measurement area in the minute area within the contact surface between the ATR prism and the sample is sequentially changed by the operation of the detection-side scanning mirror 26. Furthermore, by adding the operation of the switching mirror (illumination-side scanning mirror) 12, the irradiation area in the minute area within the contact surface between the ATR prism and the sample is sequentially changed to match the measurement area.

[0040] Next, the detector 70 and its peripheral optical system, which are characteristic of this embodiment, will be described.

[0041] The detector 70 is, for example, a semiconductor detector such as an MCT detector or an InGaAs detector. Generally, semiconductor detectors are susceptible to thermal fluctuations and must be kept at a low temperature to maintain high-sensitivity measurements. In this embodiment, a detector element holder 74 is provided on the side of a container (Dewar 72) that contains a refrigerant such as liquid nitrogen, and multiple infrared elements 76 to 79 are closely attached to the vertical surface of this detector element holder 74 in a layout such as that shown in Figures 2(A) to 2(C), allowing the infrared elements 76 to 79 to be used while maintained at a low temperature.

[0042] The multiple infrared elements 76-79 that make up the detector 70 are squares with sides measuring 5-500 μm and are different sizes. For example, in the layout of Fig. 2(A), the large infrared element 76 has a side length of 200-300 μm, and the small infrared element 78 has a side length of 50-100 μm, and the two infrared elements 76, 78 are arranged horizontally (for example, in a direction parallel to the axis of incidence of infrared light on the reflecting mirror 28) at intervals of 50 μm-10 mm. Similarly, in the layout of FIG. 2(B), three infrared elements 76 to 78 of large, medium and small sizes are arranged in the horizontal direction. Similarly, in the layout of Figure 2(C), four infrared elements 76 to 79 of large, medium, small and minute sizes are arranged two-dimensionally in the horizontal and vertical directions (for example, in a direction perpendicular to the axis of incidence of infrared light on the reflecting mirror 28). In all layouts, the intervals between adjacent infrared elements 76 to 79 are 50 μm to 10 mm in both the horizontal and vertical directions, and the elements themselves and the intervals between the elements are small.

[0043] The infrared light that passes through the opening of aperture 40 is converted into a parallel beam by reflecting mirror 28 (parabolic mirror) and travels toward collecting mirror 50 (parabolic mirror) in front of the detector. Note that the infrared light that passes through the opening of aperture 40 may also be configured to be directly received by collecting mirror 50 in front of the detector (in this case, an ellipsoidal mirror is used).

[0044] FIG. 3 shows an example of a mechanism for switching between the infrared elements 76 and 78.

[0045] The positional relationship between the collecting mirror 50 in front of the detector and the small infrared element 78 is that of a paraboloid and its focal point, as shown by the dashed line in Figure 3, and the parallel light beam incident on the paraboloid of collecting mirror 50 is collected on the small infrared element 78 located at the focal point of the paraboloid. The position of the small infrared element 78 is also confocal with the opening of aperture 40, and an image of the opening of aperture 40 is formed on the small infrared element 78 (see Figure 4(A)). For convenience of explanation, it is assumed here that the parallel light beam of infrared light in Figure 3 is horizontal, and that the plane defined by this parallel light beam and the focal point of the paraboloid is also horizontal.

[0046] The collecting mirror 50 in front of the detector is held by a mirror mount 60 equipped with an actuator, and an external computer 80 connected to this mirror mount 60 by wire or wirelessly remotely controls the actuator, thereby changing the tilt of the parabolic surface of the collecting mirror 50. This mirror mount 60 equipped with an actuator corresponds to the collecting mirror drive unit of the present invention. Known actuators can be used, such as a piezoelectric actuator, a DC motor with a rotary encoder, an ultrasonic vibrator, or a stepping motor.

[0047] In FIG. 3, the mirror mount 60 tilts the focusing mirror 50 by a small angle about a vertical axis (an axis perpendicular to the plane of the paper in FIG. 3), thereby changing the angle of incidence of the parallel light on the focusing mirror 50, and the focusing position of the parallel light beam by the focusing mirror 50 can be shifted slightly (for example, by 500 μm or less) in the horizontal direction from the position of the small infrared element 78, as shown by the solid line in FIG. 3.

[0048] Therefore, by arranging the two infrared elements 76, 78 so that the position of the large-sized infrared element 76 is the focusing position after tilting the focusing mirror 50, it becomes possible to switch between the infrared elements 76, 78 by driving the mirror mount 60. This switching causes the opening image of the aperture 40 to be formed on the large-sized infrared element 76 as well. FIG. 4(B) shows the state in which the opening size of the aperture 40 is increased and the mirror mount 60 is driven to switch the focusing position to the large-sized infrared element 76, whereby the opening image is formed on the large-sized infrared element 76. The example in FIG. 3 is suitable when the spacing between adjacent infrared elements is small (for example, 500 μm or less), particularly when the spacing is between 50 μm and 150 μm.

[0049] FIG. 5 shows another example of a mechanism for switching between the infrared elements 76 and 78.

[0050] When the spacing between adjacent infrared elements is relatively large (for example, greater than 500 μm), the angle of the collecting mirror 50 must be changed significantly, causing the collecting position of the infrared light to deviate significantly from the focus of the paraboloid, resulting in poor collecting performance. Therefore, as shown in the switching mechanism of FIG. 5, it is preferable to translate the collecting mirror 50 along the optical axis of the parallel light beam without changing its orientation. Because the angle of incidence of the parallel light beam on the collecting mirror 50 does not change before and after the translation, the collecting position of the infrared light remains at the focus of the paraboloid, maintaining collecting performance. This is particularly suitable when the spacing between the infrared elements is 2 mm or more, preferably 3 mm or more.

[0051] The parallel movement of the focusing mirror 50 can be achieved by using a mirror mount 60 with an actuator, as in FIG.

[0052] When multiple infrared elements of different sizes are arranged two-dimensionally, it is preferable to use a mirror mount 60 that has both the function of tilting and the function of translating the collecting mirror 50. Alternatively, it is preferable to use a mirror mount 60 that is configured to be able to translate the collecting mirror 50 along the incident axis of the infrared light and to be able to rotate the collecting mirror 50 around the incident axis of the infrared light. Alternatively, it is preferable to use a mirror mount 60 that is configured to be able to change the incident angle of the infrared light onto the collecting mirror 50 and to be able to rotate the collecting mirror around the incident axis of the infrared light.

[0053] Since the movements of the focusing mirror 50 in these examples all require small movements, by using the mirror mount 60, it is possible to quickly and accurately align the aperture image of the infrared light with the respective positions of multiple infrared elements of different sizes arranged one-dimensionally or two-dimensionally on the detector 70.

[0054] Furthermore, the size of the infrared element attached to detector 70 is very small, ranging from 5 to 500 μm. Therefore, when assembling infrared microscope 10, fine adjustment is required to accurately position the minute infrared element at the focus of the parabolic surface of collecting mirror 50. Therefore, Fig. 6 shows a holding structure for finely adjusting the attitude of collecting mirror 50, in which collecting mirror 50 is suspended together with mirror mount 60.

[0055] 6 has a wall plate 44 standing on one end of a horizontally placed base plate 42 and two supports 46, 48 standing on the other end, with a top plate 52 supported by the wall plate 44 and the two supports 46, 48. A mirror mount 60 is attached to the underside of the top plate 52, and in this way, the collecting mirror 50 is suspended below the top plate 52.

[0056] Fine adjustment of the attitude of collecting mirror 50 is usually performed using a screw provided on the back surface of collecting mirror 50 to hold collecting mirror 50 to the movable part of mirror mount 60, but it may also be performed by, for example, using adjustment screw 54 connecting top plate 52 to wall plate 44 and adjustment screws 55, 56 connecting top plate 52 to two supports 46, 48, and adjusting the tightening of adjustment screws 54 to 56. Adjustment may also be performed using an adjustment screw (not shown) provided on the back surface of collecting mirror 50.

[0057] Next, a method for automatically selecting an optimum infrared element from a plurality of infrared elements 76, 78 of different sizes attached to the detector 70 using the computer 80 will be described.

[0058] The first method is to select an infrared element according to the opening size of the aperture 40. For example, 400 to 900 μm 2 A threshold value is set in the range of 100 μm, and if the opening area of ​​aperture 40 is larger than the threshold, large-sized infrared element 76 is selected; if it is equal to or smaller than the threshold, small-sized infrared element 78 is selected. If the opening is square, the threshold value can be set in the range of 20 to 30 μm, and the length of one side of the opening can be compared with the threshold. In other words, computer 80 connected to mirror mount 60 recognizes information about the opening size of aperture 40, compares it with the threshold, determines the infrared element of the size to be selected, and controls mirror mount 60 to switch to the determined infrared element. To set the threshold, a reference sample may be measured with different aperture sizes for each infrared element, and the S / N ratios of the large-sized infrared element 76 and the small-sized infrared element 78 may be compared for each aperture size, and the aperture size at which the S / N ratios become approximately the same may be set as the threshold.

[0059] The second method is to select an infrared element based on the amount of light received by the detector 70, i.e., the light energy value. The detector gain is adjusted in advance so that the energy value E is 25,000 when the entire infrared element is illuminated by light (for example, when the light spot focused on a square element forms an inscribed circle). For example, a graph showing the relationship between the opening size of the aperture 40 and the energy value E, as shown in FIG. 7, is obtained for each infrared element. The computer 80 sets a threshold value, for example, in the range of 1,000 to 3,000, and switches to the small-sized infrared element 78 when the energy value E information of the currently selected large-sized infrared element 76 is smaller than the threshold value. As a result, the large-sized infrared element 76 is selected for opening sizes A and B, and the small-sized infrared element 78 is selected for opening sizes C and D.

[0060] The third method, like the second method, utilizes the light energy value E. However, in this case, the infrared element is switched depending on the linearity range of each infrared element (the aperture size range in which the relationship between the aperture size of the aperture 40 and the energy value E is linear). With actual infrared elements, the range in which the relationship between the aperture size of the aperture 40 and the energy value E is linear is limited, as shown in FIG. 8 . Therefore, the computer 80 acquires and stores, for each infrared element, information on the aperture size range in which the infrared light energy value is linear, measured in advance for each aperture size of the aperture 40 in the absence of a sample. Then, an infrared element of optimal size may be selected based on the information on the current aperture size of the aperture 40 and the information on the aperture size range in which linearity is exhibited. For example, if a small-sized infrared element 78 is currently being used, if the aperture size becomes too large, the detection capability will saturate and linearity will no longer be obtained. Therefore, the infrared element is switched to a large-sized infrared element 76 just before linearity is no longer obtained. Conversely, if large-sized infrared element 76 is currently being used, an excessively small aperture size will increase noise and make it impossible to obtain linearity, so the system will switch to small-sized infrared element 78 just before linearity is no longer obtainable. In Figure 8, for aperture sizes C and D, the small-sized infrared element is selected because it is within the range in which the small-sized infrared element exhibits linearity, and for aperture sizes A and B, the large-sized infrared element is selected because it is within the range in which the large-sized infrared element exhibits linearity.

[0061] In addition to these three methods, the computer 80 may select an infrared element of an optimum size using, for example, both the aperture size information and the energy value E information.

[0062] Furthermore, when a sample is on the stage, there may be a situation where the aperture size is relatively large but the energy value E is small. For example, this may occur when the reflectance of the sample is low during reflection measurement. In this case, even if the aperture size is larger than the threshold value in the first method, a small-sized infrared element 78 should be selected. This is because measurement using a large-sized infrared element 76 may result in large noise and an unsatisfactory spectrum. Using a small-sized infrared element 78 will only obtain information from the center of the focused spot of infrared light, but it will provide better S / N than a large-sized infrared element 76.

[0063] According to this embodiment, it is possible to automatically switch to an infrared element of the optimum size depending on the measurement conditions (such as the size of the sample, the opening size of the aperture 40, or the amount of light received by the detector 70), making it possible to coexist different types of measurements. For example, it is possible to coexist a measurement that obtains a large amount of received light (bright measurement) with a highly sensitive measurement of a minute area, or a measurement that obtains a small amount of received light but has a good S / N ratio. It is also possible to cope with measurements with a wide dynamic range (large changes in the area of ​​the measurement area).

[0064] Since the movement of the focusing mirror 50 by the mirror mount 60 is only a small distance, the infrared element can be switched in a short time, and as a result, a series of measurements involving the use of multiple infrared elements can be performed seamlessly. In addition, by always selecting the appropriate infrared element, high-sensitivity measurements (improved S / N) are possible even if you do not have sufficient measurement know-how. [Explanation of symbols]

[0065] 10. Infrared microscope 12 Switchable mirror that also serves as the irradiation side scanning mirror 16 Transmission measurement mirror 18 Lower Cassegrain mirror (illumination side objective mirror) 20 FTIR (light output means) 22 Sample stage 24 Upper Cassegrain mirror (illumination side objective mirror, detection side objective mirror) 26 Detector side scanning mirror 34 Reflection measurement mirror 40 aperture 50 Condenser mirror 60 Mirror mount (focusing mirror drive unit) 70 detectors 72 Dewar 74 Detector element holder 76, 77, 78, 79 Infrared elements 80 Computer

Claims

1. An infrared microscope comprising: a sample stage on which a sample is placed; a detection-side objective mirror that collects infrared light from the sample; an aperture provided at the position of a sample image formed by the detection-side objective mirror; a collecting mirror that collects infrared light that has passed through an opening of the aperture; a collecting mirror drive unit that moves the collecting mirror; and a detector that detects the infrared light collected by the collecting mirror, the aperture is selected from a plurality of apertures having different opening sizes or shapes, or is configured so that the opening size or shape is variable; the detector has a detection element holder and a plurality of infrared elements arranged on a surface of the detection element holder, the plurality of infrared elements having different sizes and arranged at intervals of 10 mm or less; The infrared microscope is characterized in that the focusing mirror drive unit is configured to move the focusing mirror so that the position of an aperture image formed by the focusing mirror coincides with the positions of each of the plurality of infrared elements.

2. 2. The infrared microscope according to claim 1, wherein the focusing mirror drive unit is configured to vary the angle of incidence of the infrared light onto the focusing mirror.

3. 2. The infrared microscope according to claim 1, wherein the focusing mirror drive unit is configured to be able to translate the focusing mirror along the axis of incidence of the infrared light.

4. a computer connected to the focusing mirror drive unit; 2. The infrared microscope according to claim 1, wherein the computer is configured to select an infrared element of an optimal size based on information about the opening size of the aperture provided at the position of the sample image, information about the energy value of the infrared light received by the detector, or both of these, and to control the focusing mirror drive unit so that the focusing mirror focuses the infrared light onto the selected infrared element.

5. a computer connected to the focusing mirror drive unit; The computer information on an aperture size range in which the energy value of the infrared light measured in advance for each opening size of the aperture in the absence of a sample exhibits linearity is acquired and stored for each infrared element; 2. The infrared microscope according to claim 1, wherein the microscope is configured to select an infrared element of an optimal size based on information about the opening size of the aperture provided at the position of the sample image and information about the opening size range indicating the linearity, and to control the focusing mirror drive unit so that the focusing mirror focuses infrared light onto the selected infrared element.

6. An infrared microscope according to any one of claims 1 to 5, characterized in that the sample stage is configured to be movable in a direction perpendicular to the central axis of the detection-side objective mirror, and the infrared microscope detects the infrared light by sequentially changing the measurement area on the sample where the infrared light is focused by moving the stage, and acquires spectral data for each measurement area, thereby performing mapping measurement of a predetermined range of the sample.

7. a detection-side scanning mirror provided on an optical path from the detection-side objective mirror to the aperture, the detection-side scan mirror is configured so that the orientation of the reflection surface can be changed, and the reflection surface is variable with respect to the incident direction of the infrared light from the detection-side objective mirror, thereby making it possible to change the measurement area on the sample that is detected by the detector; An infrared microscope as described in any one of claims 1 to 5, characterized in that the infrared microscope detects infrared light from the measurement area on the sample which is sequentially changed by the detection side scanning mirror, and acquires spectral data for each measurement area, thereby performing mapping measurement of a predetermined range of the sample.

8. a light output means for outputting infrared light for irradiating the sample; an irradiation-side scanning mirror for guiding the infrared light from the light output means to a sample; an illumination-side objective mirror for collecting the infrared light from the illumination-side scan mirror and illuminating a predetermined illumination area on the sample; The infrared microscope according to claim 7, characterized in that the direction of the reflective surface of the irradiation side scanning mirror is changeable, and the reflective surface is variable relative to the incident direction of the infrared light from the light output means, so that the irradiation area of ​​the infrared light on the sample can be sequentially changed to match the measurement area.

9. the detection-side objective mirror is provided with a high-refractive-index crystal element to be brought into contact with a sample, and infrared light supplied to the detection-side objective mirror, which also serves as an illumination-side objective mirror, is focused on the crystal element and irradiates a minute portion within the contact surface with the sample at an incident angle equal to or greater than a critical angle; the infrared microscope further includes a detection-side scanning mirror provided on an optical path from the detection-side objective mirror to the aperture, the detection-side scanning mirror is configured so that the orientation of the reflecting surface can be changed, and the reflecting surface can be changed with respect to the incident direction of the infrared light from the detection-side objective mirror, thereby making it possible to change the measurement area in a minute portion within the contact surface that is detected by the detector; An infrared microscope as described in any one of claims 1 to 5, characterized in that the infrared microscope detects infrared light from the measurement area in a minute area within the contact surface that is sequentially changed by the detection side scanning mirror, and performs mapping measurements of the minute area within the contact surface by acquiring spectral data for each measurement area.

10. a light output means for outputting infrared light for irradiating the sample; an illumination-side scanning mirror for guiding the infrared light from the light output means to the detection-side objective mirror, The infrared microscope of claim 9, characterized in that the irradiation side scanning mirror is configured so that the orientation of the reflective surface can be changed, and since the reflective surface is variable with respect to the incident direction of the infrared light from the light output means, it is possible to sequentially change the irradiation area of ​​the infrared light in a small area within the contact surface to match the measurement area.