JPS6130725A - Interferometer - Google Patents

Abstract

PURPOSE:To repeatedly change the light path length of split beam without providing a reciprocal movement mechanism, by rotating a plurality of phase plates arranged on the light path between a beam splitter and a fixed reflective mirror. CONSTITUTION:On the light path between a splitter 11 and a fixed reflective mirror 13, phase plates 14, 15 comprising a material having a refractive index higher than that of the atmosphere of the light path are arranged so that the opposed surfaces of the splitter 11 and the fixed mirror 13 are respectively made vertical to an optical axis O and the opposed surfaces of the phase plates 14, 15 are formed in parallel so as to be inclined at a predetermined angle to the optical axis O. When the phase plates 14, 15 are rotated around axes S, S', which are parallel to the optical axis O and spaced apart by a predetermined distance, by a rotary mechanism, the light path length between the splitter 11 and the fixed mirror 13 is changed continuously and periodically. By this mechanism, the reciprocal movement of on optical system is unnecessary and the light path length of beam split by the splitter can be changed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a Michelson-type interferometer that is optimal for use in a Fourier transform infrared spectrophotometer. 1 shows a Michelson interferometer used in external spectroscopy methods, in which incident infrared light IR is split by a beam splitter 1. The infrared light reflected by the beam splitter 1 is reflected by the fixed reflecting mirror 2 and enters the beam splitter 1 again. The infrared light transmitted through the beam splitter 1 passes through the movable reflecting mirror 3.
The beam is reflected by the beam and enters the beam splitter again.

The infrared light reflected by the reflecting mirrors 2 and 3 interferes on the sample splitter 1, but the interference light is reflected by the sample rail 4.
is detected by a detector (not shown). Here, on the optical path between the movable reflector 3 and the beam splitter 1, a position from which the distance from the beam splitter 1 is equal to the distance between the beam splitter 1 and the fixed reflector 2 is defined as a base point P, and from the base point P Letting the distance to the movable reflector 3 be X, move the movable reflector from X=Q to x=m,
If interference light is detected during this time, a so-called interferogram having a peak at x=Q can be obtained.

FIG. 5 shows the interferometer described in Japanese Patent Application Laid-Open No. 58-727, in which the light reflected by the beam splitter 1 is reflected by the first fixed reflection #! The light reflected by L2 and transmitted through the beam splitter 1 is reflected by the second fixed mirror 5. A pair of rotating phase plates 6.7 are arranged in the optical path between the beam splitter 1 and the fixed reflecting mirror 5. The phase plate 6.7 is rotatably arranged around the axis 0.0- in the direction of the arrow in the figure, and can be changed from the state shown in FIG. 5(a) to the state shown in FIG. 5(b). can.

Comparing the state of FIG. 5(a) and the state of FIG. 5(b), in the latter case, the optical path length of the light passing through the phase plate 6.7 becomes longer, and the refractive index of the phase plate changes along the optical path. By selecting a higher atmosphere than other atmospheres, in the latter case, the substantial optical path length between the beam splitter 1 and the fixed reflecting mirror 5 can be made longer than in the former case. Therefore, by rotating the pair of phase plates symmetrically, that is, by changing the angle θ formed by the two phase plates, the length of one optical path divided by the beam splitter 1 can be continuously changed. be able to. An ink ferrogram can be obtained by detecting the interference light that accompanies this change in optical path length.

[Problems to be Solved by the Invention] If the obtained interferogram is subjected to Fourier transform processing, an infrared absorption spectrum of the sample can be obtained. However, in order to obtain an accurate spectrum by Fourier transform, In the configuration shown in FIG. 4, it is necessary to increase the moving distance of the movable reflecting mirror.

By the way, the reflecting surface of the moving reflector is always perpendicular to the direction of movement in order to maintain good coherence between the infrared light reflected by the fixed reflector and the infrared light reflected by the moving reflector. needs to be preserved.

When the moving distance is short, it is relatively easy to maintain the reflective surface vertically; however, as the distance increases, maintaining the verticality of the reflective surface becomes increasingly difficult.

Furthermore, in order to increase the distance, the bearing and drive mechanism that support the movable reflecting mirror must necessarily become large, and the interferometer itself must also become large. In addition, in the actual device 7, the movable reflector 13 is moved back and forth, but in this case, energy is required to stop and reverse the reflector, which has a considerable mass, making it difficult to move the reflector back and forth at high speed. .

In the configuration shown in FIG. 5, the optical path length is changed by a rotation mechanism. As a result, it is easier to manufacture bearings for the rotating phase plate 6.7 with better precision than linear sliding bearings.
Further, although the optical path length changes depending on the rotation angle θ, increasing this θ does not increase the difficulty in manufacturing the bearing. Furthermore, since the light incident on the fixed reflector 5 is simply the light that has passed through the phase plate, even if the rotational axis accuracy of the phase plates 6 and 7 is poor, the angle of incidence of the light on the fixed reflector will not change. and has little effect on measurements. However, even in the configuration shown in FIG. 5, when θ is increased, the phase plates 6 and 7 become the beam splitter 1. Since the fixed reflector 5 is approached, the phase plates 6 and 7 are rotated back and forth, and large amounts of energy are required to stop and reverse the phase plates.

Therefore, a main object of the present invention is to provide an interferometer that can repeatedly change the length of one optical path divided by a beam splitter without the need for a reciprocating mechanism.

[Means for Solving the Problems] The interferometer based on the present invention splits light into two types of light by a beam splitter, and reflects each of the split lights by first and second reflecting mirrors. , in an interferometer configured to cause the reflected light to interfere on the beam splitter, an optical path between the beam splitter and one fixed reflecting mirror has a different atmosphere and refractive index. A plurality of plate-like members made of a material are rotatably arranged, and opposing surfaces of each of the plurality of plate-like members are parallel to each other,
It is characterized in that the surface of the plate-like member facing the beam splitter and the surface of the plate-like member facing the one fixed reflecting mirror are formed parallel to each other.

[Example] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which the incident light IR
is split into two beams by the beam splitter 11.

The light reflected by the beam splitter 11 is
It is reflected by the fixed reflection #R12 and re-enters the beam splitter 11.

The light that has passed through the beam splitter 11 is incident on the second fixed reflecting mirror 13 and reflected, and the light passes through the beam splitter 11.
to be re-injected. The two types of light re-entering the beam splitter are interfered with each other, and the interference light IL is irradiated onto a sample cell (not shown). The beam splitter 11 and the second fixed reflecting mirror 1
Two phase plates 14 and 15 are arranged on the optical path between the two phase plates 14 and 3. The phase plates 14 and 15 are made of a material having a higher refractive index than the atmosphere in the optical path. The surface of the phase plate 14 facing the throat splitter 11 and the surface of the phase plate 15 facing the fixed reflecting mirror 13 are formed perpendicular to the optical axis,
Opposing surfaces of the phase plates 14 and 15 are formed parallel to and inclined at a predetermined angle with respect to the optical axis. Furthermore, the phase plate 1
4.15 is rotated around axes s, s'' parallel to the optical axis O and separated by a predetermined distance by a rotation mechanism (not shown).

2(a) to 2(d) show the state in which the phase plates 14 and 15 of FIG. 1 are rotated around the axes s and s', respectively.
(a) is the same state as in FIG. 1, (b).

(C) and (d) show the states in which the phase plate 14°15 is rotated 90°, 180", and 270° from (a), respectively.
There is C. As is clear from FIG. 2, the phase plate 14.1
The length of the optical path passing through 5 is the shortest in the state shown in FIG. be done. Since the change in the length L substantially corresponds to the change in the optical path length between the beam splitter 11 and the fixed reflecting mirror 13, the two phase plates 1
By means of a rotation of 4.15, the optical path length can be varied continuously and periodically. Note that since the opposing surfaces of the phase plates 14.15 are formed at the same angle with respect to the optical axis, the angle at which the light transmitted through the two phase plates 14.15 enters the fixed reflecting mirror 13 is as follows. It does not change even if the phase plate rotates.

In the above embodiment, the phase plate is configured to rotate around an axis parallel to the optical axis, but the phase plate may also be rotated around an axis tilted at a predetermined angle with respect to the optical axis. good. Further, the number of phase plates disposed on the optical path between the beam splitter and one of the fixed reflecting mirrors is not limited to two, but may be three or more.

In that case, in order to always keep the incident angle of light incident on the fixed mirror constant, the surface of the phase plate facing the beam splitter and the surface of the phase plate facing the fixed reflecting mirror should be parallel. , the opposing surfaces of the phase plates must be parallel. FIG. 3 shows an example of a configuration using three phase plates 20, 21, and 22. The three phase plates 20
, 21, 22 are arranged rotatably around rotation axes s, s', s'', respectively.

[Effects] As detailed above, the interferometer according to the present invention is configured such that a plurality of phase plates are arranged on the optical path between the beam splitter and the fixed reflecting mirror, and the phase plates are rotated. It has all the advantages of the conventional rotary drive method, and furthermore, by continuously rotating the optical system in the same direction, the light split by the beam splitter can be transmitted without the need for reciprocating the optical system. The optical path length can be changed repeatedly. Therefore, the drive mechanism for changing the optical path length can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing a state in which the phase plate of FIG. 1 is rotated, FIG. 3 is a diagram showing another embodiment of the present invention, and FIG. FIG. 5 is a diagram showing a conventional interferometer. 11...Beam splitter 12.13...Fixed reflecting mirror 14.15...Phase plate

Claims (1)

[Claims] The light is split into two types of light by a beam splitter, each of the split lights is reflected by a first and second reflecting mirror, and the reflected lights are caused to interfere on the beam splitter. In this interferometer, a plurality of plate-like members made of materials having different refractive indexes from the atmosphere of the optical path are rotatably arranged on the optical path between the beam splitter and one of the fixed reflecting mirrors. The opposing surfaces of each of the plurality of plate-like members are formed parallel to each other, and the surface of the plate-like member facing the beam splitter and the surface of the plate-like member facing the one fixed reflecting mirror are formed parallel to each other. interferometer.