JPH083448B2 - Movable mirror unit for Michelson interferometer and integrated micro Fourier infrared spectrophotometer using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a movable mirror unit used in a Michelson interferometer, and a Fourier-infrared spectrophotometer and an infrared microscope using the same. Body microscope Fourier infrared spectrophotometer.

[Prior Art] FIG. 6 shows a Michelson interferometer using a movable double-corner cube mirror (JP-A-63-175734).

The light emitted from the infrared light source 10 is collimated by a collimator 12 and split into two by a beam splitter 14, and one of the light fluxes thereof is a fixed mirror 16 and one of the corner cube mirror 20 and the fixed mirror 16 of the double corner cube mirror 20. Are sequentially reflected by the beam splitter 14 and returned to the beam splitter 14, and the other light flux is sequentially reflected by the fixed mirror 18, the other corner cube mirror 20b of the double corner cube mirror 20 and the fixed mirror 18, and the beam splitter 1
The beams are returned to 4, and the returned beams are combined and interfered by the beam splitter 14 to be emitted to the outside.

In the double-corner cube mirror 20, corner cube mirrors 20a and 20b are connected back-to-back with each other and mounted on a slider, and the slider is guided by a guide to connect a fixed mirror 16 and a fixed mirror 18 in a linear direction ( It is reciprocally driven by a driving device in the X direction in the drawing). A bearing for reducing sliding resistance is interposed between the slider and the guide.

Here, the stability and reproducibility, which are important for the interferometer, are greatly affected by the sliding portion between the slider and the guide of the interferometer. In order to constantly and stably scan the double-corner cube mirror 20, it is required that the sliding resistance of this sliding portion is always constant and that the sliding portion has no backlash.

However, if the clearance of the sliding portion is increased, the sliding resistance is reduced, but the play is increased and the double-corner cube mirror 20 is laterally shaken to deteriorate the stability. Further, if the clearance of the sliding portion is reduced, the backlash is reduced, but the sliding resistance is large and non-uniform, so that the scanning speed cannot be stabilized and the reproducibility is deteriorated.

On the other hand, in the case of measurement by microscopic Fourier infrared spectroscopy, conventionally, an infrared microscope is mounted on the case of a Fourier infrared spectrophotometer, and the interference light flux emitted from the Fourier infrared spectrophotometer is collected by the infrared microscope. It was guided to a mirror and the luminous flux emitted from the infrared microscope was guided to the detector of the Fourier infrared spectrophotometer.

However, in use, the optical adjustment between the Fourier infrared spectrophotometer and the infrared microscope must be performed, and when the infrared microscope is removed from the Fourier infrared spectrophotometer, the two will be connected later. However, it was inconvenient because it required optical adjustment again.

Therefore, when an attempt is made to integrate the Fourier infrared spectrophotometer and the infrared microscope, the Fourier infrared spectrophotometer has a planarly spread configuration, as is apparent from the configuration of the interferometer shown in FIG. On the other hand, since the infrared microscope is configured to extend in the vertical direction, there is a problem that it becomes large as a whole and cannot be downsized. For this reason, a combination of the two is not commercially available.

There is a structure in which one end of a pendulum column is rotatably supported by a bearing, a retroreflecting mirror as a movable mirror for Michelson interferometer is fixed to the other part of the pendulum column, and the pendulum column is vibrated by an exciting magnet. Although proposed (Japanese Patent Laid-Open No. 56-129826), since the pendulum column is supported by a bearing, the above problem occurs. That is, if the clearance of the bearing sliding portion is increased, the sliding resistance is reduced, but the backlash is increased and the retro-reflecting mirror is laterally shaken to deteriorate the stability. Further, if the clearance of the bearing sliding portion is reduced, the backlash is reduced, but the sliding resistance becomes large and non-uniform, so that the scanning speed of the retroreflecting mirror cannot be kept stable and the reproducibility deteriorates.

[Problems to be Solved by the Invention] In view of the above-mentioned conventional problems, a first object of the present invention is to provide a movable mirror unit for a Michelson interferometer capable of scanning a movable mirror stably and with good reproducibility. It is in.

A second object of the present invention is to provide an integrated microscopic Fourier infrared spectrophotometer which is miniaturized by using this movable mirror unit.

[Means for Solving the Problem and Its Function and Effect] The first purpose is to support one end of the pendulum post by a supporting member, and to the other part of the pendulum post toward the pendulum post. Two corner cube mirrors for reflecting each of the two light beams incident from the vibration direction and the opposite direction to each other in the opposite direction to the incident direction are fixed, and the pendulum column is moved in the vibration direction in a non-contact manner by electromagnetic force or electrostatic force. In the vibrating movable mirror unit for Michelson interferometer, the one end of the pendulum column and the supporting member are connected to each other through each of first and second leaf springs, and the first leaf spring and the first leaf spring are connected to each other. The second leaf springs intersect with each other at a distance from each other, and the sum of the number of the first leaf springs and the number of the second leaf springs spaced from each other is 3 or more,
When the pendulum column is vibrated in the vibration direction, the spring constant from the neutral position of the pendulum column to one side of the vibration direction and from the neutral position of the pendulum column to the opposite side of the one side of the vibration direction. This is achieved by a movable mirror unit for Michelson interferometer, characterized in that the shape and the number of the leaf springs are determined so that the spring constants thereof are equal to each other.

In the present invention, since the pendulum column has such a supporting structure, there is no sliding portion, and the rigidity in the vibration direction with respect to the torsional rigidity can be reduced, so that the movable mirror can be stably and reproducibly scanned.

Here, since the movable mirror unit extends in the vertical direction, the occupied area in the horizontal direction becomes smaller than in the conventional case. on the other hand,
The infrared microscope extends vertically because it is necessary to increase the focal length of the objective mirror and increase the magnification.

Therefore, a second object of the present invention is to provide an infrared light source, a Michelson interferometer which is provided with the movable mirror unit and on which radiation emitted from the infrared light source is incident, and which is arranged beside the Michelson interferometer. An infrared microscope that guides the light emitted from the interferometer and focuses it on a sample is integrated with a photodetector that is arranged above the Michelson interferometer and detects the intensity of light emitted from the infrared microscope. It is achieved by an integrated microscopic Fourier infrared spectrophotometer.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

(1) Movable Mirror Unit for Michelson Interferometer FIG. 1 shows a movable mirror unit 21 in which the moving mechanism of the double-corner cube mirror 20 of the Michelson interferometer shown in FIG. 6 is improved.

The corner cube mirrors 20a and 20b are fixed back to back on the slope of the mirror base 22. The corner cube mirrors 20a and 20b and the mirror base 22 that are integrated are
As shown in FIG. 2B, an inverted U formed on the lower end of the pendulum column 24.
The side surface of the mirror base 22 is fixed to the side surface of the cutout portion 24a by being fitted into the character cutout portion 24a.

The upper end of the pendulum pole 24 is a support pole via a cross leaf spring 26.
It is connected to the lower end of 28.

That is, as shown in FIGS. 2A and 2B, the upper end of the quadrangular prism-shaped pendulum column 24 and the lower end of the quadrangular prism-shaped support column 28 are obliquely cut at a pair of facing side portions, respectively, to form a pendulum column. Slopes 24a and 24b are formed on 24, and slopes 28a and 2 are formed on the support column 28.
8b is formed. One end of the leaf springs 26a and 26c is screwed to the slope 24a with a screw 30, and the leaf springs 26a and 26c are attached to the slope 28b.
The other end of is fixed by a screw 30. Also, this leaf spring
Leaf springs 26b and 26b are provided on the slope 24b so as to cross 26a and 26c.
One end of d is screwed with a screw 30 and the leaf springs 26b, 2
The other end of 6d is screwed with a screw 30. In the state where the pendulum column 24 hangs down and is stationary, the leaf springs 26a to 26d are inclined by 45 degrees with respect to the horizontal plane. Further, the leaf springs 26a and 26b cross to form a set of cross leaf springs, and the leaf springs 26c and 26d
And cross to form another set of cross leaf springs. In order to oscillate the pendulum column 24 stably and reproducibly in the lateral direction of FIG. 2A, generally at least two sets of cross leaf springs are required. However, if the width of the leaf spring 26b is approximately twice the width of the leaf springs 26a and 26c, the cross leaf spring may be composed of three leaf springs excluding the leaf spring 26d.

As shown in FIG. 1, the upper surface of the support column 28 is fixed to the center of the lower surface of the upper lid 31. The peripheral portion of the upper lid 31 is a solid square tube so that the support column 28 does not slightly move due to the vibration of the pendulum column 24.
It is screwed to the upper end surface of 32. Holes 32a, 32b for passing a light beam are formed corresponding to the corner cube mirrors 20a, 20b on a pair of opposing surfaces of the rectangular tube 32 corresponding to the vibration direction of the pendulum column 24. The light flux that has entered the corner cube mirror 20a through the hole 32a is reflected in the direction opposite to the incident direction.
The light flux which has passed through 32b and has entered the corner cube mirror 20b is reflected in the direction opposite to the incident direction.

The lower end surface of the square tube 32 is screwed onto a sub base plate 34, and a C-shaped yoke 38 is fixed on the sub base plate 34 in the square tube 32 via a bracket 36.
A columnar magnet 38a is fixed to the center of 38 with its center line parallel to the sub-base plate 34. On the other hand, an inverted L-shaped bracket 40 is provided on the bottom surface of the mirror base 22.
The cylindrical voice coil 42 is fixed via the shaft with its axial direction aligned with the vibration direction of the pendulum column 24. In the voice coil 42, the central protruding portion of the magnet 38a is concentrically inserted.

Therefore, when an alternating current is applied to the voice coil 42, the pendulum pole 24 is moved around the intersection of the cross leaf springs 26 by the electromagnetic force acting between the voice coil 42 and the magnet 38.
It vibrates in the horizontal direction in the figure.

In this embodiment, since the cross leaf spring 26 is used in place of the conventionally used sliding portion, the scanning of the double-corner cube mirror 20 is stable and the reproducibility is improved.

Further, since the pendulum column 24 is vertically long and the drive device is provided below the pendulum column 24, the area occupied by the movable mirror unit 21 on the horizontal plane can be made much smaller than in the conventional case.

The concrete dimensions of the pendulum post 24 are 100 mm in length and 2 in width in the vibration direction.
The width is 0 mm and the width is 55 mm in the direction perpendicular to the vibration direction. The specific dimensions of the leaf springs 26a to 26d are 10 mm × 25 mm. Furthermore, the resolution of the spectrophotometer is a double-corner cube mirror.
Although it is proportional to the scanning distance of 20, the resolution required for measurement by the microscopic Fourier infrared spectroscopy is about 4 to 8 cm ^-1 , and it is sufficient to scan the double-corner cube mirror 20 for about 1 mm. Therefore, with the above dimensions, the double-corner cube mirror 20 scans on a substantially straight line.

Generally, a rotary bearing is used at the starting point of the pendulum, but since there is clearance in its sliding part,
When a rotary bearing is used instead of the cross leaf spring 26, the above-mentioned problems occur. Further, it is possible to use a pivot bearing instead of the rotary bearing, but since a sliding member is present as in the rotary bearing, the pendulum cannot be vibrated stably for a long period of time. Further, when a leaf spring was attached in parallel to the pair of side faces of the pendulum column 24 and the support column 28 in place of the cross leaf spring 26, a test was conducted, but the stability of vibration was insufficient and it could not be executed.

(2) Integrated Micro Fourier Infrared Spectrophotometer FIG. 3 shows a microscopic Fourier infrared spectroscope in which a Fourier infrared spectrophotometer 46 equipped with the movable mirror unit 21 and an infrared microscope 48 are compactly integrated. Shows a photometer.

Since the movable mirror unit 21 extends in the vertical direction, the occupied area in the horizontal direction becomes smaller than in the conventional case. On the other hand, infrared microscope
The reference numeral 48 extends in the vertical direction because it is necessary to increase the focal length of the objective mirror 82 to increase the magnification. In consideration of such properties, the integrated microscopic Fourier infrared spectrophotometer is constructed compactly.

The Fourier infrared spectrophotometer 46 is arranged in the right half of FIG. 3, and the infrared microscope 48 is arranged in the left half of FIG. The right half of FIG. 3 of the housing 50 integrally formed by casting except the lid is partitioned by horizontal base plates 50a and 50b to form a lower chamber 52, a middle chamber 54 and an upper chamber 56.

A reflecting mirror 58 is arranged in the lower chamber 52, and an interferometer unit 60 and reflecting mirrors 62 and 64 are arranged in the middle chamber 54.

The interferometer section 60 is mounted on the L-shaped mounting plate 66 as shown in FIGS.
They are arranged as shown in the figure. The interferometer unit 60 includes a Michelson interferometer having basically the same configuration as that in FIG. 6, a sampling signal generation system that shares this Michelson interferometer, and a visible light source.

The sampling signal generation system is configured as follows. That is, the He-Ne laser 1 and the reflecting mirror 2 are fixedly mounted on the side surface 66b of the mounting plate 6, and the laser beam emitted from the He-Ne laser 1 is deflected by the reflecting mirror 2 toward the Michelson interferometer side. . On the other hand, on the bottom plate 66a, a small reflecting mirror 3 is erected at the lower height of the beam splitter 14 by the beam splitter 14, and this laser beam is reflected by the reflecting mirror 3.
Is deflected to the lower side of the beam splitter 14 and enters the beam splitter 14 at an incident angle of 45 °, and then passes through the same optical path as the above infrared light flux. However, the laser beam has a sufficiently smaller cross-sectional area than the infrared light flux, and since the infrared light flux passes through the central portion of the beam splitter 14, the laser beam passes through the lower portion of the beam splitter 14, so the split laser beam The two beams of light are reflected by the reflecting mirrors 16 and 18 and the double-corner cube mirror 20 and returned to the beam splitter 14 at the upper part of the beam splitter 14. The laser beam, which has been combined and interfered at this position, passes through the beam splitter 14 and is deflected toward the photodiode 5 side above the reflecting mirror 4 standing parallel to the beam splitter 14, and the light intensity is photoelectrically converted by the photodiode 5. It An elliptical aperture 4a is formed in the center of the reflecting mirror 4, and infrared interference light passes through this elliptic aperture.

The visible light source is composed of a miniature lamp and a collimator 7 for collimating the divergent light of the miniature lamp 6, and the visible light flux from the collimator 7 is converted into a fifth light by a switching mirror 8 standing parallel to the reflecting mirror 4. It is deflected to the left in the figure. The switching mirror 8 is switched by the rotary solenoid into and out of the optical path.

A case 68 accommodating the infrared light source 10 is screwed to the side plate 66b of the mounting plate 66. A cover for covering the He-Ne laser 1 and the reflecting mirror 2 is omitted in the drawing.

With the above configuration, it is possible to take out the interferometer unit 60 and the infrared light source 10 integrally from the housing 50 and perform optical adjustment.

The bottom plate 66a of the mounting plate 66 is screwed to the base plate 50a, and the side plate 66b is screwed to the side surface of the housing 50.

As shown in FIG. 3, an ellipsoidal mirror 70 and a photodetector 72 are arranged in the upper chamber 56 above the middle chamber 54. This photo detector
In the case of 72, liquefied N ₂ gas is injected into the cooling chamber 72b having the vacuum wall 72a to cool the MCT detection element to a temperature of 77K.

The control device such as the visible mirror unit, the data processing device, the display device, and the recorder are not integrated in the housing 50 but are separate bodies.

The infrared microscope 48 has a well-known configuration, 77 is a reflecting mirror, 78 is a Cassegrain type condensing mirror, 80 is a cover glass on which a sample is placed, 82 is a Cassegrain objective mirror, and 84 is an optical path that moves in the direction perpendicular to the paper surface. A switchable mirror that can be retracted from, 86 is an aperture that can adjust the opening, 88 is a reflecting mirror, 90 is a switchable mirror that can be retracted from the optical path after moving in the direction perpendicular to the paper surface, 92 is an eyepiece, and 94 is not shown. It is a lens barrel connected to a TV camera.

Next, the operation of the integrated microscopic Fourier infrared spectrophotometer configured as described above will be described.

Since infrared light is not visible, observe the sample with visible light before measurement. That is, turn on the bean lamp 6,
The switching mirror 8 is placed in the optical path as shown in FIGS. 4 and 5,
The switching mirror 90 is moved into the optical path, and visible light is reflected downward by the reflecting mirror 62. Further, in the case of transmission observation, the switching mirror 62
In the state shown in FIG. 3 and moving the switching mirror 84 out of the optical path, and in the case of reflection observation, the switching mirror 62 is rotated 90 ° from the state shown in FIG. 3 and the switching mirror 84 is moved into the optical path. .

In the case of transmission observation, visible light is switched mirror 8, 62, reflector
The light is reflected in this order at 58 and 77, is focused on the sample on the cover glass 80 by the Cassegrain condensing mirror 78, is then converged at the aperture position of the aperture 86 by the Cassegrain objective 82, and then the reflecting mirror 88 and the switching mirror 90. Eyepieces reflected by
92 and is guided by a TV camera and observed. By this observation, the height of the Cassegrain condensing mirror 78, the measurement position of the sample, and the opening of the aperture 86 are adjusted.

In the case of reflection observation, visible light is switched mirrors 8 and 62, a reflector.
64, Cassegrain-type objective mirror that is reflected in this order by the switching mirror 84
The interference light is converged on the sample in the right half of FIG. 3 of FIG. 3, and the reflected light is converged at the aperture position of the aperture 86 in the left half of FIG. 3 of the Cassegrain type objective mirror 82. Other points are the same as in the case of the above-mentioned transmission observation.

Next, in order to perform the measurement, the mini lamp 6 is turned off, the switching mirrors 8 and 90 are moved out of the optical path, the infrared light source 10 is turned on, and He
-The Ne laser 1 is turned on, and an alternating current is passed through the voice coil 42 to vibrate the double-corner cube mirror 20. The infrared interference light passes through the elliptical aperture 4a of the reflection mirror 4, is reflected by the switching mirror 62, is then reflected by the reflection mirror 88 along the same optical path as the visible light, and is then detected by the ellipsoidal mirror 70 as a photodetector. The light intensity is detected by being focused on 72. This light intensity is read at the timing of a pulse obtained by waveform-shaping the output of the photodiode 5. This pulse is generated once every time the double-corner cube mirror 20 moves 1/4 of the wavelength of the laser light.

In this embodiment, the movable mirror unit 21 is used for the interferometer section 60 to make the area of the bottom plate 66a smaller than that of the conventional configuration, and the photodetector 72 is arranged above the interferometer section 60, so that the size is small. Can be configured as an integrated microscopic Fourier infrared spectrophotometer.

The dimensions of the prototype Fourier-microscope infrared spectrophotometer were 400 m at the bottom of the housing 50 (left and right in Fig. 3).
m × width 250 mm and housing 50 height 700 mm. The bottom plate 66a of the base 66 has a depth of 170 mm × width of 240 mm, and the movable mirror unit 21 has a height of 250 mm. By using the movable mirror unit 21, the size and depth of the bottom plate 66a can be reduced to about 2/3 of the conventional case, respectively, as compared with the case of using the conventional configuration.

[Brief description of drawings]

1 to 5 relate to an embodiment of the present invention, in which FIG. 1 is a partially longitudinal sectional front view of a movable mirror unit for a Michelson interference system, and FIG. 2A is a front view showing an arrangement of crossed leaf springs. Fig., Fig. 2B is a side view of Fig. 2A, Fig. 3 is a side view of a part of a longitudinal section showing the arrangement of the optical system of the integrated microscopic Fourier infrared spectrophotometer, and Fig. 4 is an interferometer of Fig. 3. FIG. 5 is a partial vertical cross-sectional side view showing an enlarged part, and FIG. 5 is a schematic plan view showing the arrangement of the optical system of the interferometer part of FIG. FIG. 6 is a layout diagram of an optical system of a Michelson interferometer for explaining the conventional problems. In the figure, 1 is a He-Ne laser 2, 3, 16, 18, 58, 64, 77, 88 is a reflecting mirror 4 is a reflecting mirror with an elliptical aperture 5 is a photodiode 6 is a tungsten lamp 8, 62, 84, 90 are switchable Mirror 10 is an infrared light source 14 is a beam splitter 20 is a double-corner cube mirror 20a, 20b is a corner-cube mirror 21 is a movable mirror unit 24 is a pendulum pillar 26 is a cross leaf spring 26a to 26d is a leaf spring 28 is a support pillar 32 is a square. The cylinder 38a is the magnet 42 is the voice coil 46 is the Fourier infrared spectrophotometer 48 is the infrared microscope 50 is the housing 60 is the interferometer 72 is the photodetector 78 is the Cassegrain-type condenser mirror 80 is the sample 82 is the Cassegrain-type objective mirror 86 is an aperture 92 is an eyepiece

Claims (2)

[Claims] 1. One end of a pendulum pole is supported by a support member, and two light fluxes that are incident on the other part of the pendulum pole from the directions of vibration of the pendulum pole and mutually opposite directions. In a movable mirror unit for a Michelson interferometer, two corner cube mirrors for reflecting in a direction opposite to an incident direction are fixed, and the pendulum column is vibrated in the vibrating direction in a non-contact manner by an electromagnetic force or an electrostatic force. The one end of the pillar and the support member are connected to each other via each of first and second leaf springs, and the first leaf spring and the second leaf spring are connected to each other.
Of the first leaf springs and the second leaf springs spaced apart from each other, the sum of the number of the first leaf springs and the number of the second leaf springs is 3 or more, A spring constant from the neutral position of the pendulum pillar to one side of the vibration direction and a spring constant from the neutral position of the pendulum pillar to the opposite side of the vibration direction when vibrating in the vibration direction. A movable mirror unit for a Michelson interferometer, characterized in that the shape and the number of the leaf springs are determined so that they are equal to each other. 2. An infrared light source, a movable mirror unit for the Michelson interferometer according to claim 1, and a Michelson interferometer on which radiation light from the infrared light source is incident, and a lateral side of the Michelson interferometer. And an infrared microscope which guides the light emitted from the interferometer and converges on a sample, and a photodetector which is arranged above the Michelson interferometer and detects the intensity of the light emitted from the infrared microscope. An integrated microscopic Fourier infrared spectrophotometer, which is characterized by integrating and.