Detachable structure for microscope cassegrain mirror

Abstract

A Cassegrain mirror 10 that can be easily detached from a microscope without requiring optical adjustment comprises: a Cassegrain mirror body 2 having a main mirror 22, a sub-mirror 24, a housing 26 that holds the main mirror 22 and the sub-mirror 24, and a barrel 32 that is provided on the outer side of the housing 26 and forms an optical path to a central hole 28; a slider 4 having a through-hole 42 sized to allow a gap to form when the barrel 32 is fitted therein, and an adjustment screw 46 for adjusting the position of the barrel 32 fitted in the through-hole 42; and a stage 6 configured such that the Cassegrain mirror body 2 can be attached to and detached from the stage 6 together with the slider 4. A through-hole 62 communicating with the through-hole 42 of the slider is formed in the stage 6. Shapes for positioning the slider 4 at a prescribed position with respect to the stage 6 by sliding the slider 4 in a prescribed direction once the slider 4 has been brought into contact with the surface of the stage 6 are respectively formed in the slider 4 and the stage 6.

Description

Detachable structure of Cassegrain mirror for microscope

[0001] The present invention relates to an improved attachment / detachment structure for a Cassegrain mirror for a microscope.

[0002] Microscopes, such as infrared microscopes and ultraviolet-visible-near-infrared microscopes, are devices that irradiate a sample placed on a movable stage with measurement light, collect and detect the transmitted light, reflected light, or total internal reflection light from a small area on the sample, and acquire its spectrum. Such microscopes typically have a pair of Cassegrain mirrors located above and below the sample stage. In transmission measurements, the lower Cassegrain mirror collects measurement light from the light source and directs it toward the sample, while the upper Cassegrain mirror collects the light transmitted through the sample.

[0003] Each pair of upper and lower Cassegrain mirrors has a primary mirror and a secondary mirror, and the upper and lower primary mirrors and secondary mirrors are arranged symmetrically above and below the sample. Because the concave surface of the primary mirror of the lower Cassegrain mirror faces upward, there is a risk that the sample may accidentally fall from the sample stage onto the concave surface of the primary mirror. If the sample falls onto the primary mirror of the lower Cassegrain mirror, the falling object will block the light, adversely affecting the measurement results.

[0004] The infrared microscope of Patent Document 1 is configured so that a disposable paper shutter is placed over the lower Cassegrain mirror to prevent the sample from falling onto the lower Cassegrain mirror. There are also microscopes that have a manually opened and closed mechanical shutter on the sample stage to prevent the sample from falling onto the lower Cassegrain mirror.

[0005] Japanese Patent Application Laid-Open No. 2004-354342

[0006] However, even if a disposable shutter or a mechanical manual shutter as described in Patent Document 1 is provided, if the user forgets to put the shutter on or close it, the shutter's effectiveness cannot be achieved. To overcome this drawback, a mechanism for automatically controlling the opening and closing of the shutter could be considered, so that the shutter opens only during measurement and closes during measurement preparation. However, the space around the sample stage is limited, and installing an automatic control mechanism would increase costs, making it unrealistic.

[0007] If a sample falls onto the primary mirror of the lower Cassegrain mirror, some method must be used to remove it. One possible method for accessing the concave surface of the primary mirror from above the sample stage while the lower Cassegrain mirror is still attached is to use a rod with adhesive tape wrapped around the end, bring the tip of the rod close to the concave mirror surface, and attach the sample to it for removal. However, if the sample is light, sticks to the adhesive tape, and falls in an easily accessible location, the sample may be successfully removed. However, if these conditions are not met, the success rate is low. There is also a risk that components of the adhesive tape will adhere to the primary mirror of the lower Cassegrain mirror. Furthermore, components of the adhesive tape will also adhere to the sample, making it impossible to analyze again.

[0008] The quickest way to reliably remove any fallen objects would be to remove the lower Cassegrain mirror and turn the concave surface of the primary mirror upside down. This would allow for reliable removal of the sample no matter where it falls on the concave mirror surface, without worrying about accidentally soiling the concave surface of the lower Cassegrain mirror or contaminating the sample. To achieve this, it is necessary to make it possible for the user to attach and detach the lower Cassegrain mirror smoothly.

[0009] However, in a microscope ready for measurement, the attached lower Cassegrain mirror is already optically adjusted to the order of μm, and such optical adjustment is not something that users can easily perform. Also, once the lower Cassegrain mirror is removed, the next time it is installed, optical adjustment must be performed again. For this reason, in conventional microscopes, the mounting portion for the lower Cassegrain mirror is not configured so that users can quickly remove and install it.

[0010] For the reasons described above, if a sample were to fall onto the lower Cassegrain mirror, the usual procedure would be to first try to access the sample from above the sample stage, and if this was not possible, to call in an engineer with specialized knowledge to remove the sample.

[0011] Therefore, the inventors have aimed to develop a Cassegrain mirror for a microscope that can be easily removed by the user and that does not require optical adjustment on the order of μm when the user installs it.

[0012] In other words, the Cassegrain mirror for a microscope of the present invention is a Cassegrain mirror for a microscope comprising: a Cassegrain mirror body having a primary mirror with a central hole, a secondary mirror located on the central axis of the primary mirror, a housing that holds the primary mirror and the secondary mirror, and a cylindrical portion provided on the outside of the housing for forming an optical path to the central hole of the primary mirror; a slider having a through hole large enough to create a gap when the cylindrical portion is inserted and an adjustment screw for adjusting the position of the central axis of the cylindrical portion inserted into the through hole; and a base configured to allow the Cassegrain mirror body to be attached and detached together with the slider, wherein the base is configured to be attachable to the microscope and has a through hole that communicates with the through hole of the slider, and the slider and the base are each formed with a shape that allows the slider to be positioned at a predetermined position relative to the base by sliding the slider in a predetermined direction on the surface of the base while in contact with the surface of the base.

[0013] With the above configuration, when the slider and the Cassegrain mirror body, which have been optically adjusted, are detached from the base and then reattached to the base, positioning to the specified position is completed by combining the shapes of the two (slider and base) (such as fitting of concave and convex shapes, or abutment of surface shapes), so the slider can be positioned with high reproducibility relative to the base. Furthermore, there is no need to turn the adjustment screws and redo the optical adjustment of the Cassegrain mirror body every time the slider and the Cassegrain mirror body are attached to the base. Therefore, users can attach and detach the Cassegrain mirror with extremely simple operations.

[0014] The microscope of the present invention is characterized by including the above-mentioned Cassegrain mirror.

[0015] Fig. 5 is an exploded view showing a schematic longitudinal section of a Cassegrain mirror of a first embodiment. Fig. 6 is a schematic view of a detached state of a Cassegrain mirror of a second embodiment. Fig. 7 is a schematic view of an attached state of the Cassegrain mirror. Fig. 8 is a stereoscopic view showing a detached state of a Cassegrain mirror of a third embodiment. Fig. 9 is a diagram for explaining the optical path when performing transmission measurement and reflection measurement using an infrared microscope in which a Cassegrain mirror of the present invention is applied to a lower Cassegrain mirror. Fig. 10 is an explanatory diagram of the optical path when performing ATR measurement using the infrared microscope of Fig. 5.

[0016] A first embodiment of a Cassegrain mirror for a microscope according to the present invention will now be described with reference to the drawings. As shown in Figure 1, a Cassegrain mirror for a microscope 10 according to this embodiment comprises a Cassegrain mirror body 2, a slider 4, and a base 6. The present invention will be described using orthogonal coordinate axes of X, Y, and Z axes that are orthogonal to each other on the drawings.

[0017] First, the Cassegrain mirror main body 2 has a primary mirror 22, a secondary mirror 24 arranged on the central axis of the primary mirror 22 (an axis parallel to the Z axis), and a housing 26 that holds the primary mirror 22 and the secondary mirror 24. A central hole 28 is located on the central axis of the primary mirror 22. A tube portion 32 that communicates with the central hole 28 of the primary mirror 22 is formed integrally with the housing 26 on the lower outer side. Light entering this tube portion 32 travels through an optical path formed by the tube portion 32 and the central hole 28 and reaches the convex mirror surface of the secondary mirror 24. Light reflected from the convex mirror surface of the secondary mirror 24 reaches the concave mirror surface of the primary mirror 22. Light reflected from the concave mirror surface of the primary mirror 22 is focused on the central axis above and outside the secondary mirror 24.

[0018] The slider 4 is a plate-shaped member extending in the plane of the X- and Y-axes and has a through-hole 42 near its center that penetrates in the Z-axis direction. The diameter of the through-hole 42 is large enough to create a gap when the tubular portion 32 of the Cassegrain mirror main body 2 is fitted into it. The side circumferential surface of the plate-shaped member of the slider 4 has multiple optical adjustment holes 44 that are parallel to the plane of the X- and Y-axes. These optical adjustment holes 44 are formed so that the interior of the plate-shaped member of the slider 4 reaches the through-hole 42. Each optical adjustment hole 44 is provided with an adjustment screw 46 whose tip protrudes from the through-hole 42. The adjustment screw 46 is threadedly engaged with the optical adjustment hole 44, and the amount of protrusion into the through-hole 42 is adjusted by rotating the adjustment screw 46. With the tubular portion 32 of the Cassegrain mirror main body 2 fitted into the through-hole 42 of the slider 4, the position of the central axis of the tubular portion 32 is adjusted by rotating the multiple adjustment screws 46 with a dedicated tool or the like.

[0019] Here, the sliding direction when the slider 4 is mounted on the pedestal 6 described below is the negative direction of the X axis on the paper surface of Fig. 1. At the tip of the plate-like member in the sliding direction, a convex portion 48 is formed as a shape for positioning the slider 4 at a predetermined position in the X-axis, Y-axis, and Z-axis directions relative to the pedestal 6 when the slider 4 is mounted.

[0020] When removing the slider 4 from the base 6, the slider 4 is slid in the opposite direction. The plate-like member of the slider 4 is formed so that the tip on the side opposite the convex portion 48 has an L-shaped cross section 52. This L-shaped cross section 52 serves to position the slider 4 at a predetermined position in the X-axis direction relative to the base 6 when the slider 4 is attached.

[0021] The back surface 54 of the slider 4, i.e., the surface facing the surface of the base 6, is the contact surface and also the sliding surface with the surface of the base 6. The back surface 54 serves to position the slider 4 relative to the base 6 in the Z-axis direction.

[0022] The pedestal 6 is a plate-like member extending in the plane of the X-Y axes, and is configured so that the slider 4 can be attached and detached together with the Cassegrain mirror main body 2. The pedestal 6 can be attached to the microscope main body 8 below the sample stage, for example, and has a through-hole 62 that communicates with the through-hole 42 of the slider 4. As described above, the surface 64 of the pedestal 6 functions as a sliding surface that comes into contact with the back surface 54 of the slider 4.

[0023] A portion that protrudes above the surface 64 is formed at the end of the base 6 in the negative direction of the X axis, and this protruding portion is formed with a recessed portion 66 that engages with the protruding portion 48 of the slider 4. The engagement between the protruding portion 48 and the recessed portion 66 positions the slider 4 relative to the base 6 in the X-axis, Y-axis, and Z-axis directions.

[0024] Furthermore, an abutment surface 68 is formed at the end of the base 6 in the positive direction of the X axis for contact with the inner surface of the L-shaped cross section 52 of the slider 4. When the slider 4 is attached, the engagement between the convex portion 48 and the concave portion 66 and the abutment between the inner surface of the L-shaped cross section 52 and the abutment surface 68 occur simultaneously, thereby ensuring reliable positioning of the slider 4 relative to the base 6 in the X-axis, Y-axis, and Z-axis directions.

[0025] A second embodiment of a Cassegrain mirror for a microscope according to the present invention will be described using Figure 2. Components common to the first embodiment will be given the same reference numerals, and duplicated descriptions will be omitted. As shown in Figure 2, the Cassegrain mirror for a microscope 10A of the second embodiment has a pin 56 that protrudes from the back surface 54 of the slider 4A, and a fixing screw 58 is provided in a hole 59 in the L-shaped cross section 52.

[0026] Furthermore, a groove 72 that guides the pin 56 in the sliding direction is formed in the surface 64 of the base 6A, and a screw hole 74 that screws into the fixing screw 58 is formed in the abutment surface 68 of the base 6A. Furthermore, the base 6A has an elevation device 76, which allows it to be raised and lowered relative to the microscope main body 8. The provision of the pin 56 and groove 72 makes it easy to slide the slider 4A, and the provision of the fixing screw 58 makes it possible to fix the slider 4A, once it has been positioned relative to the base 6A, so that it does not shift.

[0027] Here, we will explain the optical adjustment method for the Cassegrain mirror 10A for microscopes of the second embodiment. First, the elevating base 6A is fixed to a predetermined location on the microscope body 8. The tubular portion 32 of the Cassegrain mirror body 2 is fitted into the through-hole 42 of the slider 4A. Next, the slider 4A, together with the Cassegrain mirror body 2, is slid onto the base 6A, positioning the slider 4A relative to the base 6A. In this state, the adjustment screw 46 is turned with a dedicated tool or the like using the microscope's imaging function and / or the monitored value of the light intensity of the microscope's detector to adjust the central axis of the tubular portion 32 so that the central axis of the Cassegrain mirror body 2 coincides with the optical axis of the microscope body 8. Although not shown, it is preferable that the position of the central axis of the tubular portion 32 can be adjusted in the X-Y plane by individually turning multiple adjustment screws 46. In this manner, optical adjustment of the Cassegrain mirror body 2 to the order of μm is completed. Figure 3 shows the mounted state of the Cassegrain mirror 10A after optical adjustment.

[0028] While such optical adjustments may be performed by the microscope user, it is preferable for a maintenance technician with specialized knowledge specific to the device to perform the adjustments. Typically, a maintenance technician visits the microscope installation location to perform the optical adjustments of the Cassegrain mirror 10A. Optical adjustments can also be performed using the above procedure for the microscope Cassegrain mirror 10 of the first embodiment.

[0029] The user can detach the slider 4A together with the optically adjusted Cassegrain mirror body 2 from the base 6A of the optically adjusted Cassegrain mirror 10A shown in Figure 3. Figure 2 above shows the state in which the slider 4A together with the optically adjusted Cassegrain mirror body 2 has been detached from the base 6A. The detached Cassegrain mirror body 2 and slider 4A will remain in their optically adjusted state unless the adjustment screw 46 is moved. Therefore, by simply sliding the slider 4A together with the Cassegrain mirror body 2 back onto the base 6A, it is possible to recreate the Cassegrain mirror 10A that has been optically adjusted to the order of μm.

[0030] For example, by preparing multiple Cassegrain mirror bodies 2 with different focusing characteristics and multiple sliders 4A to be combined with each Cassegrain mirror body 2 and performing the optical adjustment described above for each assembly set of the Cassegrain mirror body 2 and slider 4A, it is possible to prepare multiple assembly sets of optically adjusted Cassegrain mirror bodies 2 and sliders 4A. In this manner, the user can simply select one of the assembly sets (Cassegrain mirror bodies 2 and sliders 4A) with different focusing characteristics that matches the sample state and measurement conditions, slide it onto the base 6A, and immediately perform microscopic measurement without having to perform optical adjustment of the Cassegrain mirror on the order of μm. In other words, the user can replace the Cassegrain mirror body 2 with another Cassegrain mirror body 2 with a different focusing characteristic with a very simple operation.

[0031] 4 shows a stereoscopic view of the Cassegrain mirror for a microscope 10B of the third embodiment. The Cassegrain mirror for a microscope 10B is one of specific configuration examples of the Cassegrain mirror for a microscope 10A of the second embodiment, and has the following structural features.

[0032] First, the slider 4B in FIG. 4 has two fixing screws 58 spaced apart in the Y-axis direction for fixing the slider 4 to the base 6B. Furthermore, optical adjustment holes 44 are provided at a total of four locations on the side of the plate-like member of the slider 4B, and FIG. 4 shows two of these optical adjustment holes 44 (two on the left and right of the side closest to the page). The remaining optical adjustment holes 44 are similarly formed at two locations on the opposite side. The four optical adjustment holes 44 are formed inside the plate-like member toward the central through-hole 42, and an adjustment screw 46 is built into each optical adjustment hole 44. After optical adjustment of the Cassegrain mirror main body 2 is performed using the adjustment screws 46, the position of the optically adjusted Cassegrain mirror main body 2 is fixed relative to the slider 4B by tightening the fixing screws 55 on a plate portion 57 connected to the lower end of the housing of the Cassegrain mirror main body 2.

[0033] Furthermore, two recessed portions 48A and 48B are formed at the end of the plate-shaped member of the slider 4B in the negative direction of the X axis, and two protruding portions 66A and 66B are formed on the plate-shaped member of the base 6B at positions corresponding to the two recessed portions 48A and 48B. When the slider 4B is slidably mounted on the base 6B, the recessed portion 48A engages with the protruding portion 66A, and the recessed portion 48B engages with the protruding portion 66B, thereby positioning the slider 4B relative to the base 6B in the X-, Y-, and Z-axis directions. In FIG. 1, the protruding portion 48 is formed on the slider 4 side and the recessed portion 66 is formed on the base 6 side. However, as shown in FIG. 4, the recessed portions 48A and 48B may be formed on the slider 4B side and the protruding portions 66A and 66B may be formed on the base 6B side. Here, the recesses of recessed portions 48A and 48B do not penetrate in the Z-axis direction, but have bottoms that are inserted into gaps formed between the convex portions of convex portions 66A and 66B and surface 64 when slidably mounted, thereby restricting movement of Cassegrain mirror body 2 in the Z-axis direction relative to base 6B.

[0034] Furthermore, three magnet mounting holes are formed in a horizontal row on the side surface of the plate-shaped member of slider 4B, midway between the two concave portions 48A, 48B, and one magnet 49 can be embedded in each mounting hole. A sensor 78 capable of detecting the magnetic force of magnet 49 is attached to the inner surface of the plate-shaped member of base 6B, midway between the two convex portions 66A, 66B. When slider 4B is slid onto base 6B, sensor 78 attached to base 6B can determine whether magnets 49 are embedded in each mounting hole on slider 4B. Therefore, by changing the arrangement pattern of the three magnets, it is possible to distinguish between Cassegrain mirror bodies 2 with a total of eight different light-focusing characteristics. The detection signal from sensor 78 can be read by a computer or other control means for the microscope, allowing the type of Cassegrain mirror body 2 currently attached to be automatically recognized.

[0035] When the Cassegrain mirror 10, 10A, 10B configured in each of the above embodiments is used, when the slider 4, 4A, 4B together with the optically adjusted Cassegrain mirror body 2 is detached from the base 6, 6A, 6B and then reattached to the base 6, 6A, 6B, positioning to a predetermined position is completed by combining the shapes of both (slider 4, 4A, 4B and base 6, 6A, 6B) (for example, engagement between the convex portion 48 and the concave portion 66, engagement between the concave portions 48A, 48B and the convex portions 66A, 66B, contact between the back surface 54 and the front surface 64, contact between the L-shaped cross section 52 and the abutment surface 68, etc.), the slider 4, 4A, 4B can be positioned with good reproducibility relative to the base 6, 6A, 6B. Furthermore, there is no need to turn the adjustment screw 46 and redo the optical adjustment of the Cassegrain mirror body 2 every time the slider 4, 4A, 4B is attached to the base 6, 6A, 6B together with the Cassegrain mirror body 2. Therefore, the user can attach and detach the Cassegrain mirror with a very simple operation.

[0036] 5 and 6, a microscope 500 in which the Cassegrain mirror 10 shown in the first embodiment is applied to a lower Cassegrain mirror will be described. The microscope 500 is an infrared microscope configured by connecting a Fourier transform infrared spectrophotometer (hereinafter referred to as FTIR) 520. The FTIR 520 has a built-in infrared light source and a Michelson interferometer, and serves to supply the microscope 500 with an interference wave of infrared light output from the interferometer, and corresponds to the light irradiation means of the present invention.

[0037] The microscope 500 is composed of a microscopic optical unit 530, an aperture 540, a detector 550, various reflecting mirrors, etc. The microscopic optical unit 530 is a part that performs transmission, reflection, or total reflection measurement of a minute area of ​​a sample using infrared light. The detector 550 can be appropriately selected from a single-element detector, a linear array detector, etc. Here, a case where the detector 550 is a single-element detector will be described.

[0038] <Transmission Measurement> First, transmission measurement will be described. A transmission measurement plate 525 is attached to the sample stage 521, and the object to be measured is placed on its surface. In measurements using infrared light, a plate made of an infrared-transmitting material such as potassium bromide or diamond is used as the transmission measurement plate 525.

[0039] The switching mirror 512 in FIG. 5 guides the infrared light from the FTIR 520 to the optical path for transmission measurement (in this order: reflecting mirror 514, transmission measurement mirror 516, and lower Cassegrain mirror 10). The lower Cassegrain mirror 10 for the sample (corresponding to the illumination-side Cassegrain mirror) focuses the infrared light reflected from the transmission measurement mirror 516 and illuminates a predetermined area of ​​the sample placed on the sample stage 521 from below. The light transmitted through the sample is extracted and focused by the upper Cassegrain mirror 524 for the sample (corresponding to the detection-side Cassegrain mirror) and reflected by the detection-side scanning mirror 526 above. An aperture 540 is placed at the imaging position behind the upper Cassegrain mirror 524 to cut out light (such as stray light) generated from areas other than the light-focusing area on the sample and detect only the light transmitted through the desired light-focusing area. Light passing through the opening of the aperture 540 passes through a light-collecting element for the detector (not shown) and forms an image on the detector 550. An electrical signal corresponding to the amount of light received by the detector 550 is Fourier transformed by the signal processing means to become infrared spectrum data.

[0040] The specimen stage 521 is configured so that the stage surface can be raised and lowered relative to the upper Cassegrain mirror 524 (which is usually attached to a revolver together with an objective lens, etc.). A driving means for raising and lowering the specimen stage 521 is indicated by the reference numeral 610. The lower Cassegrain mirror 10 is also configured so that it can be raised and lowered by an elevator device 76 in order to adjust the distance between it and the specimen stage 521.

[0041] The control means 612, which controls the raising and lowering operations of the sample stage 521 and the lower Cassegrain mirror 10, can automatically raise the sample stage 521 to its upper limit and automatically lower the lower Cassegrain mirror 10 to its lower limit when attaching or detaching the slider 4 together with the Cassegrain mirror main body 2 shown in Figure 1 from the lower Cassegrain mirror 10.

[0042] The magnification of the sample Cassegrain mirror can be selected from a range of 4 to 100 times. The opening size of the aperture 540 indicates the size of the light-collecting area on the sample. Even if the aperture is the same, the size of the measurement area on the sample varies depending on the magnification of the sample Cassegrain mirror 10, 524 to be combined. Even if the magnification of the sample Cassegrain mirror 10, 524 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 an aperture with the desired shape and opening size can be selected and used depending on the measurement conditions. An aperture equipped with a mechanism for changing the opening shape and size can also be used.

[0043] For example, if the magnification of the Cassegrain mirror to be used needs to be changed depending on the object being measured in transmission measurement, the upper Cassegrain mirror 524 can be easily changed to a Cassegrain mirror with the desired magnification by operating the revolver. Even if it is difficult to set up a revolver for the lower Cassegrain mirror due to space constraints, the use of the lower Cassegrain mirror 10 of this embodiment allows the slider 4 to be easily attached and detached together with the Cassegrain mirror body 2. Furthermore, since the slider 4 can be attached to the base 6 with good positional repeatability, there is no need to optically adjust the Cassegrain mirror each time it is attached. Furthermore, when replacing the Cassegrain mirror body of the lower Cassegrain mirror 10, the control unit 612, which controls the elevation operations of the sample stage 521 and the lower Cassegrain mirror 10, can automatically raise the sample stage 521 to its upper limit and automatically lower the lower Cassegrain mirror 10 to its lower limit. This ensures sufficient replacement space below the sample stage 521, allowing for smooth replacement.

[0044] Furthermore, it is easy to measure the same position at high magnification as that measured at low magnification (for example, 16x) by replacing the lower Cassegrain mirror 10 with a high magnification (for example, 32x) one while the sample is placed on the sample stage 521. In other words, a single infrared microscope can seamlessly perform wide-field measurement with a low-magnification Cassegrain mirror and high S / N measurement of a minute area with a high-magnification Cassegrain mirror.

[0045] Furthermore, even if a sample falls onto the concave mirror surface of the primary mirror 22 of the lower Cassegrain mirror 10, the slider 4 can be removed together with the Cassegrain mirror body 2, so the sample can be removed immediately.

[0046] <Switching to Reflection Measurement> Next, a method for switching from the optical configuration for transmission measurement shown in Figure 5 to the optical configuration for reflection measurement will be described. In reflection measurement, a reflection measurement plate is attached to the sample stage 521, and the measurement object is placed on its surface. Note that, in measurements using infrared light, it is preferable to use a plate made of a material that reflects infrared light (aluminum, gold, stainless steel, etc.) as the reflection measurement plate. In reflection measurement, the switching mirror 512 in Figure 5 is rotated 90 degrees so that the infrared light from the FTIR 520 is guided to the optical path for reflection measurement (in the order of reflecting mirror 532, reflection measurement mirror 534, and upper Cassegrain mirror 524).

[0047] In reflection measurement, the upper sample Cassegrain mirror 524 (corresponding to the illumination-side Cassegrain mirror) focuses the infrared light reflected from the reflection measurement mirror 534 and illuminates a predetermined area of ​​the sample placed on the sample stage 521 from above. The light reflected from the sample is again extracted and focused by the upper sample Cassegrain mirror 524 (which also serves as the detection-side Cassegrain mirror) and directed to the detection-side scanning mirror 526 above. The components from the detection-side scanning mirror 526 onwards are the same as those for transmission measurement.

[0048] Here, the reflection measurement mirror 534 is located in half of the area divided by a boundary line passing through the optical axis connecting the upper Cassegrain mirror 524 and the detection-side scanning mirror 526 on a cross section perpendicular to the optical axis, and is not located in the other half; therefore, it is also called a half mirror. In reflection measurement, infrared light from the reflecting mirror 532 reflects off the reflection measurement mirror 534 and travels toward the upper Cassegrain mirror 524, irradiating the sample. The reflected light from the sample is collected by the upper Cassegrain mirror 524 and then travels through the space where the reflection measurement mirror 534 is not located to the detection-side scanning mirror 526. In addition, in reflection measurement, by removing the slider 4 along with the Cassegrain mirror body 2 from the base 6 of the lower Cassegrain mirror 10, the absence of the Cassegrain mirror body 2 and slider 4 allows the stage movement width in the Z direction to be increased. In other words, the working distance can be extended. This effect can also be obtained in ATR measurement, which will be described later.

[0049] <ATR Measurement> Next, ATR measurement will be described. Mapping measurement (high-speed imaging) in ATR measurement will also be described. By selecting a linear array detector 560, in which multiple detection elements are arranged in a row, it is possible to simultaneously measure spectra at multiple measurement positions within the focused region on the sample, thereby shortening the time required for mapping measurement.

[0050] When changing from transmission measurement to ATR measurement, the operator replaces the transmission measurement plate 525 on the sample stage 521 with the ATR measurement plate 528 and places the object to be measured on its surface. In addition, the operator rotates the revolver above the sample stage 521 to select the Cassegrain mirror 523 with the ATR prism 522 as the upper Cassegrain mirror.

[0051] The reflective surface of the switching mirror 512 is rotated 90 degrees so that the switching mirror 512 guides the infrared light to the optical path for reflection measurement (reflecting mirror 532, reflection measurement mirror 534, and Cassegrain mirror 523 with ATR prism). The Cassegrain mirror 523, which has an ATR prism 522, a high-refractive-index crystal element, serves two functions: irradiating a predetermined focusing area within the contact surface between the sample and the ATR prism 522 at an incident angle equal to or greater than the critical angle (function of the illumination-side Cassegrain mirror), and also focusing the total reflected light from the sample again on the Cassegrain mirror via the ATR prism (function of the detection-side Cassegrain mirror). The reflection measurement mirror 534 is located in one 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 Cassegrain mirror 523 with ATR prism and the detection-side scanning mirror 526, and is therefore not located in the other half. Therefore, it is also called a half mirror. That is, in total reflection measurement, infrared light from reflecting mirror 532 is reflected by reflecting measurement mirror 534, travels toward Cassegrain mirror with ATR prism 523, and irradiates the sample. Then, the total reflected light from the contact surface between the sample and ATR prism 522 is collected and travels toward detection-side scanning mirror 526 through a space where reflecting measurement mirror 534 is not located.

[0052] In order to cut out light (stray light, etc.) generated from areas other than the designated light-collecting area and detect only the total reflected light from the desired light-collecting area, an aperture 540 is placed at the imaging position behind the Cassegrain mirror 523 with an ATR prism. Light that passes through the opening of the aperture 540 forms an image on a linear array detector 560 via a light-collecting element for the detector (not shown). An electrical signal corresponding to the amount of light received by each detecting element of the linear array detector 560 is Fourier transformed by a signal processing means to become infrared spectrum data.

[0053] The total magnification of the Cassegrain mirror with ATR prism 523 may be selected from the range of 4 to 100 times. The opening size of the aperture 540 corresponds to the size of the contact area where the total reflected light is to be focused. Even if the aperture is the same, the size of the contact area where the total reflected light is to be focused varies depending on the magnification of the Cassegrain mirror with ATR prism 523 to be combined. Even if the magnification of the Cassegrain mirror with ATR prism 523 is fixed, it is preferable that the size and shape of the opening be changeable so that the desired contact area can be adjusted. For example, multiple apertures with different shapes and opening sizes may be prepared, and an aperture with the desired shape and opening size may be selected and used depending on the measurement conditions. An aperture equipped with a mechanism that allows the shape and size of the opening to be changed may also be used.

[0054] A detailed description will be given of mapping measurement of a predetermined area on a sample using the infrared microscope 500 configured as described above. The infrared microscope 500 enables spectrum 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.

[0055] The first method is mapping measurement involving the operation of a sample stage 521 having an electronically controlled automatic stage. In this method, a sample is placed on the automatic stage of the sample stage 521, and the light-collecting region on the sample is sequentially changed by moving the automatic stage. Here, a single-element detector 550 may be selected as the detector, and an aperture 540 corresponding to the single-element detector 550 may be used to perform spectral measurement for each light-collecting region. Alternatively, a linear array detector 560 may be selected, and an aperture 540 corresponding to the linear array detector 560 may be used to simultaneously perform spectral measurement of multiple points within the light-collecting region. These methods can be used to acquire spectral data of the light-collecting region and create mapping data for a predetermined range of the sample.

[0056] The second method involves moving the detection-side scanning mirror 526 while keeping the sample stage 521 fixed, thereby sequentially changing the light-focusing area on the sample, acquiring spectral data on the light-focusing area, and creating mapping data for a specified range of the sample. In this case, either the single-element detector 550 or the linear array detector 560 can be used. In this embodiment, the switching mirror 512, which switches between the transmission measurement and reflection measurement (including total reflection measurement) described above, also serves as the illumination-side scanning mirror. In other words, the switching mirror 512 has two functions: a function to switch between transmission measurement and reflection measurement (including total reflection measurement) by rotating the reflective surface 90 degrees, and a scanning function to sequentially move the illumination area on the sample by minutely controlling the orientation of the reflective surface with a controller at each 90-degree rotation.

[0057] The orientation of the reflective surface of the detection-side scanning mirror 526 is adjusted so that only light from a specific light-collecting region on the sample is directed toward the opening of the aperture 540. By controlling the orientation of the reflective surface of this detection-side scanning mirror 526 with a controller, the light-collecting region on the sample can be moved to match the opening of the aperture 540. The orientation of the reflective surface of the switching mirror (illumination-side scanning mirror) 512 is changed to move the illumination region on the sample, and at the same time, the orientation of the reflective surface of the detection-side scanning mirror 526 is also changed so that the light-collecting region moves in the same direction as the illumination region. Repeated spectral measurements of the light-collecting region for all of these moving positions of the light-collecting region and illumination region using either the single-element detector 550 or the linear array detector 560 enable two-dimensional mapping measurements of a certain area on the sample.

[0058] As described above, by synchronizing the operation of the switching mirror (illumination-side scanning mirror) 512 with the operation of the detection-side scanning mirror 526, 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.

[0059] Even when the switching mirror (illumination-side scanning mirror) 512 is fixed and only the detection-side scanning mirror 526 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 measurement.

[0060] Even when the ATR prism-equipped Cassegrain mirror 523 is used instead of the upper Cassegrain mirror 524 to measure the total reflection of a sample, two-dimensional mapping measurement can be performed without moving the sample stage 521 by using the detection-side scanning mirror 526 or by using both the detection-side scanning mirror 526 and the switching mirror (illumination-side scanning mirror) 512. That is, in total reflection measurement, the light-collecting area within the contact surface between the ATR prism and the sample is sequentially changed by the operation of the detection-side scanning mirror 526. Furthermore, by adding the operation of the switching mirror (illumination-side scanning mirror) 512, the irradiation area within the contact surface between the ATR prism and the sample is sequentially changed to match the light-collecting area.

[0061] By using the linear array detector 560 to simultaneously acquire spectral data from multiple points within the light collection area, and repeating this process for each moving light collection area, two-dimensional mapping measurement can be performed at high speed. This type of mapping measurement is particularly called "imaging measurement."

[0062] 5 and 6 illustrate the case where the present invention is applied to a lower Cassegrain mirror, but when the present invention is applied to an upper Cassegrain mirror, for example, the Cassegrain mirror in Fig. 4 can be attached upside down to microscope 500. When the present invention is applied to a focusing mirror in front of a detector, the Cassegrain mirror in Fig. 4 can be attached to microscope 500 with an angle tilted by 90 degrees. The Cassegrain mirror of the present invention can be applied not only to infrared microscopes but also to other microscopes such as ultraviolet-visible-near-infrared microscopes.

[0063] DESCRIPTION OF SYMBOLS 2 Cassegrain mirror body 4 Slider 6 Base 8 Microscope body 10 Lower Cassegrain mirror (illumination-side Cassegrain mirror) 22 Primary mirror 24 Secondary mirror 26 Housing 28 Central hole 32 Cylinder portion 42 Slider through-hole 44 Optical adjustment hole 46 Adjustment screw 48 Convex portion (shape for positioning the slider at a predetermined position relative to the base) 52 L-shaped cross section (shape for positioning the slider at a predetermined position relative to the base) 54 Back surface of slider (shape for positioning the slider at a predetermined position relative to the base) 56 Pin 62 Base through-hole 64 Surface of base (shape for positioning the slider at a predetermined position relative to the base) 66 Concave portion (shape for positioning the slider at a predetermined position relative to the base) 68 Abutment surface of base (shape for positioning the slider at a predetermined position relative to the base) 72 Groove 76 Elevating device 500 Infrared microscope (microscope) 512 Switchable mirror also serving as irradiation-side scanning mirror 516 Transmission measurement mirror 520 FTIR (light irradiation means) 521 Sample stage 522 ATR prism (total reflection crystal element) 523 Cassegrain mirror with ATR prism (serves as both irradiation-side and detection-side Cassegrain mirror) 524 Upper Cassegrain mirror (serves as both irradiation-side and detection-side Cassegrain mirror) 525 Transmission measurement plate 526 Detection-side scanning mirror 528 ATR measurement plate 534 Reflection measurement mirror 540 Aperture 550 Single-element detector (light detection means) 560 Linear array detector (light detection means) 610 Drive means for sample stage 612 Control means

Claims

1. A Cassegrain mirror for a microscope comprising: a Cassegrain mirror body having a primary mirror with a central hole, a secondary mirror located on the central axis of the primary mirror, a housing that holds the primary mirror and the secondary mirror, and a cylindrical section provided on the outside of the housing for forming an optical path to the central hole of the primary mirror; a slider having a through-hole large enough to create a gap when the cylindrical section is fitted into the through-hole and an adjustment screw for adjusting the position of the central axis of the cylindrical section fitted into the through-hole; and a base configured so that the Cassegrain mirror body can be attached and detached together with the slider, wherein the base is configured to be attachable to a microscope and has a through-hole that communicates with the through-hole of the slider, and the slider and the base are each formed with a shape that allows the slider to be positioned at a predetermined position relative to the base by sliding the slider in a predetermined direction on the surface of the base while in contact with the surface of the base.

2. A Cassegrain mirror for a microscope as described in claim 1, characterized in that the Cassegrain mirror body can be optically adjusted by using the adjustment screw to adjust the position of the central axis of the cylindrical portion fitted into the through hole of the slider when the slider is attached to the base attached to the microscope and positioned at the predetermined position.

3. The Cassegrain mirror for a microscope according to claim 2, characterized in that the slider is configured to be detachable from the base together with the Cassegrain mirror body that has been optically adjusted.

4. A Cassegrain mirror for a microscope as described in claim 3, characterized in that it has another Cassegrain mirror body having different light-gathering characteristics from the Cassegrain mirror body, and the other Cassegrain mirror body is configured to be optically adjustable in the same way as the Cassegrain mirror body using a slider other than the slider, and the Cassegrain mirror body is configured to be replaceable by detaching the slider together with the optically adjusted Cassegrain mirror body from the base, and then attaching the other slider together with the optically adjusted other Cassegrain mirror body to the base.

5. A Cassegrain mirror for a microscope as described in claim 1, characterized in that the shape for positioning the slider at a predetermined position relative to the base includes: a shape for positioning the slider at a predetermined position in a predetermined direction in which the slider is slid; a shape for positioning the slider at a predetermined position in a direction perpendicular to the predetermined direction and parallel to the surface of the base; and a shape for positioning the slider at a predetermined position in a direction perpendicular to the predetermined direction and also perpendicular to the surface of the base.

6. A Cassegrain mirror for a microscope according to claim 5, characterized in that a protruding pin is formed on the surface of the slider facing the base, and a groove is formed in the base to guide the pin in a predetermined direction in which the slider slides.

7. A microscope comprising a Cassegrain mirror according to any one of claims 1 to 6.

8. A microscope for measuring the spectrum of a minute region of a sample, comprising: a sample stage; an upper Cassegrain mirror provided above the sample stage; a lower Cassegrain mirror provided below the sample stage; and light detection means for detecting transmitted light, reflected light, or total reflected light from the sample collected by the upper Cassegrain mirror via an aperture located downstream of the upper Cassegrain mirror, wherein the sample stage is configured so that the stage surface can be raised and lowered relative to the upper Cassegrain mirror, and the lower Cassegrain mirror is capable of raising and lowering to adjust the distance between it and the sample stage and is configured as a Cassegrain mirror as defined in any one of claims 1 to 6, and wherein control means for controlling the raising and lowering operations of the sample stage and the lower Cassegrain mirror raises the sample stage to its upper limit and lowers the lower Cassegrain mirror to its lower limit when attaching or detaching the slider together with the Cassegrain mirror body from the lower Cassegrain mirror.

9. A microscope for measuring the spectrum of a minute region of a sample, comprising: a sample stage; an upper Cassegrain mirror provided above the sample stage; a lower Cassegrain mirror provided below the sample stage; and light detection means for detecting transmitted light, reflected light, or total reflected light from the sample collected by the upper Cassegrain mirror via an aperture located downstream of the upper Cassegrain mirror, wherein the lower Cassegrain mirror is a Cassegrain mirror as defined in any one of claims 1 to 6.

10. A microscope according to claim 9, characterized in that a detection-side Cassegrain mirror that collects transmitted light, reflected light, or total reflected light from the sample is provided between the sample and the aperture, the sample stage is configured to be movable in a direction perpendicular to the central axis of the detection-side Cassegrain mirror, and the microscope sequentially changes the light-collecting area of ​​the sample by moving the sample stage, detects transmitted light, reflected light, or total reflected light from the light-collecting area, and obtains spectral data of the light-collecting area, thereby performing mapping measurements of a predetermined measurement area of ​​the sample.

11. A microscope according to claim 9, characterized in that: between the sample and the aperture, there are provided a detection-side Cassegrain mirror that focuses transmitted or reflected light from the sample, and a detection-side scanning mirror that reflects light from the detection-side Cassegrain mirror toward the aperture; the detection-side scanning mirror has a reflective surface whose orientation relative to the incident direction from the detection-side Cassegrain mirror is variable, thereby making it possible to change the focused area of ​​the sample detected by the light detection means; and the microscope detects transmitted or reflected light from the focused area that is sequentially changed by the detection-side scanning mirror, and obtains spectral data of the focused area, thereby performing mapping measurements of a predetermined measurement area of ​​the sample.

12. A microscope according to claim 11, comprising: an illumination-side scanning mirror for guiding light to a sample; and an illumination-side Cassegrain mirror for focusing the light from said illumination-side scanning mirror and illuminating a predetermined illumination area on the sample, wherein the orientation of the reflection surface of said illumination-side scanning mirror is variable relative to the direction of incidence of light onto said illumination-side scanning mirror, thereby making it possible to sequentially change said illumination area to match said light-focusing area.

13. The microscope according to claim 9, characterized in that: between the sample and the aperture, there are provided a detection-side Cassegrain mirror that collects the total reflected light from the sample, and a detection-side scanning mirror that reflects the total reflected light from the detection-side Cassegrain mirror toward the aperture; the detection-side Cassegrain mirror has a high-refractive index total reflection crystal element for contacting the sample, and light supplied to the detection-side Cassegrain mirror, which also serves as an illumination-side Cassegrain mirror, is collected on the total reflection crystal element and is configured to illuminate a predetermined illumination area within the contact surface with the sample at an angle of incidence equal to or greater than the critical angle; the detection-side scanning mirror has a variable reflecting surface orientation relative to the direction of incidence from the detection-side Cassegrain mirror, thereby making it possible to change the light-collecting area within the contact surface detected by the light detection means; and the microscope detects the total reflected light from the light-collecting area that is sequentially changed by the detection-side scanning mirror and obtains spectral data of the light-collecting area, thereby performing mapping measurements of minute areas within the contact surface.

14. A microscope as described in claim 13, characterized in that it is provided with an illumination-side scanning mirror for guiding light to the sample to the detection-side Cassegrain mirror, and the illumination-side scanning mirror has a reflective surface whose orientation can be changed relative to the direction of light incidence on the illumination-side scanning mirror, thereby making it possible to sequentially change the light irradiation area at a minute location within the contact surface to match the light-collecting area.

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