JPH03220430A - Interferometer - Google Patents

Abstract

PURPOSE:To prevent other light than the light from a light source which causes variations from entering in the direction of an incident light by making lights from the same light source enter simultaneously the position of two different incident lights. CONSTITUTION:This interferometer is in such a structure that the direction of the light from a semi-transparent mirror 1 to a fixed mirror 2 to a moving mirror 3 is different from that of the incident light from the mirrors 2, 3 to the mirror 1. Since the projecting light is generated at two points centering the mirror 1, two detectors I, II are arranged at the corresponding points. One incident light projected from a light source 9 is allowed to enter the detectors I, II through reflecting mirrors M1, M2 in a direction I, while the other incident light projected from the same light source 9 is made to enter the detectors I, II through reflecting mirrors M3, M4 in a direction II. The light source 9 is generally similar to a black body at a fixed temperature, so that the light other than the light from the light source 9 which is a cause of variations is prevented from entering in the directions I, II. Since it is possible to obtain a signal corresponding to the spectral characteristic of a sample by adding interferogram signals obtained by the detectors I, II, the characteristic of the sample can be easily detected with high accuracy.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention consists of a semi-transparent mirror, a fixed mirror system and a movable mirror system that respectively reflect the light transmitted through the cough semi-transparent mirror and the reflected light towards the semi-transparent mirror. , in particular, relates to interferometers suitable for use in Fourier transform infrared spectrophotometers.

Prior Art] Figure 6 shows the configuration of a conventional Michelson interferometer. In the figure, 1 is a semi-transparent mirror, 2 is a fixed mirror, and 3 is a movable mirror. In the conventionally well-known Michelson interferometer, as shown in FIG. 6, part of the input light and the output light enter and exit in the same direction. That is, the incident light is split into reflected light and transmitted light by the semi-transparent mirror 1, reflected by the fixed mirror 2 and the movable mirror 3, respectively, and then enters the semi-transparent mirror 1 again to form interference light. In such an interferometer, when using an interference signal called an interferogram generated by the difference between the optical path length on the fixed mirror 2 side and the optical path length on the movable mirror 3 side, half of the emitted light returns to the direction of the incident light. Since it is difficult to separate the emitted light, the remaining half of the emitted light is used for measurement. Furthermore, the light that returns in the direction of the incident light may have a negative effect on the light source and the like.

Apart from this point, according to the configuration shown in Fig. 6, when the detector is placed in the direction of the emitted light H, the light from the detector returns to the detector itself through the interferometer and becomes the signal light. This can cause fluctuations in the interferodalum signal obtained from the detector. Therefore, by placing a slit or aperture between the interferometer and the detector, or by placing the sample in a slit or aperture-shaped sample holder, it is possible to prevent the light from the detector from entering the interferometer. However, there is also a possibility that the light from the detector hits the slit or the aperture (also, the slit or aperture-shaped sample holder) and is reflected and enters the detector as well. Therefore, when there are temperature fluctuations around the detector, or when there are temperature fluctuations in the slit or aperture, these temperature fluctuations cause interferometer output fluctuations.

As mentioned above, in order to avoid half of the emitted light returning to the direction of the incident light, which is a drawback of conventional Michelson interferometers,
The present inventor published Utility Model Application No. 60 72511),
As shown in FIG. 7, the fixed mirror 2 and the movable mirror 3 are constructed with two mirrors, and the incident direction from the semi-transparent mirror 1 to each mirror 2.3 and the half of the reflected light from each mirror 2.3 are shown. By configuring the transmissive mirror 1 in a different direction from the incident direction, it is possible to separate and use the emitted light ■ returning to the incident light ■ side from the incident light ■ without increasing the area of the semi-transparent mirror 1, thereby improving measurement accuracy. let me,
We also proposed an interferometer that eliminates the negative effects of emitted light on the light source.

However, even in the case where the emitted light ■ returning to the incident light I side can be used for measurement as shown in Figure 7, as shown in Figure 8, the incident light from either side of the detector ■ or Light ■
Since the incident light appears to be coming from two places, i.e., incident light H and
), and the output of the interferometer may fluctuate (in Fig. 8,
The arrow indicates the interferometer viewed from the detector ■. ).

Therefore, by having a plurality of incident light directions as shown in FIG.
In an interferometer where the direction of the incident light and the direction of the output light are separated, in order to prevent the unused direction of the incident light from being affected by temperature changes, etc., a constant-temperature black body is placed in that direction so that the incident light does not enter. Bank ground light with large fluctuations can be prevented from entering from the incident light side.

To further explain this point with reference to FIG. You can also put it in from
Normally, the incident light enters from one of the positions (in the case shown, it enters from the direction of the incident light I''), and the other incident light (in the case shown, the incident light ■) enters the position. Even if nothing is placed, as explained in Figure 8 (a), light that includes the effects of temperature fluctuations etc. may enter the detectors ■ and ■ from this direction and affect the measurements. Therefore, the constant-temperature black body 4 is placed in this direction.When looking into the interferometer from the detector ■ or the detector ■ side as shown in the figure, the interferometer, the incident light I, and the constant-temperature black body 4 are all aligned. Therefore, by placing the constant temperature black body 4 on the side of the incident light (1), it is possible to prevent background light with large fluctuations from entering from the side of the incident light (2). Use an integrating sphere whose inner surface is painted black, or a similar cone.

By the way, in the interferometer as shown in FIG. 7, another light source having the same effect as the constant temperature black body may be placed in place of the constant temperature black body 4 in the direction of the incident light (1).

Therefore, the object of the present invention is to provide two sources of incidence.

An object of the present invention is to provide an interferometer in which light that is a variable factor other than light from a light source is prevented from entering from the direction of the incident light in an interferometer in which the direction of the incident light and the direction of the outgoing light are separated. .

[Means to solve the problem]

For this purpose, the interferometer of the present invention consists of a semi-transparent mirror, a fixed mirror system and a movable mirror system that reflect the light transmitted through the semi-transparent mirror and the reflected light toward the semi-transparent mirror, respectively, and the direction of the incident light and the output light In an interferometer, the directions of which are separated, and both the incident light and the outgoing light can take two different positions, the interferometer is configured so that light from the same light source is simultaneously incident on two different incident light positions. It is characterized by:

[Effect]

In the interferometer of the present invention, a light source that has the same effect as a constant-temperature black body is placed in both directions of incident light, so that light that causes fluctuations other than the light from the light source enters from the incident light side. It can be prevented. Furthermore, since these light sources are the same light source, the characteristics of the sample can be easily measured with high precision by arranging detectors at two different emission light positions and adding the outputs.

〔Example〕

Embodiments of the present invention will be explained below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of one embodiment of the interferometer according to the present invention, where 1 is a semi-transparent mirror, 2 is a fixed mirror, 3 is a movable mirror, 9 is a light source, and M and -M are reflective mirrors. Each is shown below.

The configuration of the interferometer itself shown in FIG. 1 was proposed by the inventor in Japanese Utility Model Application Publication No. 1983-72511 as mentioned above, and in the Michelson interferometer, the fixed mirror 2 and the movable mirror 3 are Consisting of plane mirrors, each mirror 2.
Direction of light towards 3 and each mirror 2.3 to semi-transparent mirror l
The direction of the incident light is different from that of the incident light I, and the outgoing light that returns to the incident light I side is separated from the incident light I.

In this interferometer, since the emitted light is generated at two locations with the semi-transparent mirror 1 as the symmetrical surface, a detector I and a detector (2) are placed at each location. Regarding the incident light, the incident light I shown in
Although the incident light H may enter from any of the two positions, based on the present invention, the light emitted from the same light source 9 in different directions is reflected by the reflecting mirror M, , for one direction of the incident light. M
, and for the incident light direction, the reflecting mirror M3,
M.

It is made incident through the . When arranged in this manner, the light source 9 is generally close to a constant-temperature blackbody, so that it is possible to prevent light from entering from the light source that causes fluctuations other than the light from the direction of the incident light I and (2). Note that in such an interferometer that separates the incident light (1) and the output light I, the light from the detectors (2) and (2) themselves enters the interferometer and reaches the light source 9, but its influence is small.

By the way, in such an interferometer, the interferogram signal obtained from detector I and the interferogram signal obtained from detector H have opposite phases (this is because the sum of their energies is constant). (It's easy to understand.)

Therefore, if no sample is inserted into either of the two optical paths from the light source 9 to the semitransparent mirror l, the interferogram signal obtained from the detector I and the interferogram signal obtained from the detector When added, it becomes zero.

However, when a measurement sample is placed in one of the optical paths, a signal corresponding to the spectral characteristics of the sample is obtained from this added signal. Therefore, since this added signal has a lower peak value than the signal from a conventional interferometer, the number of bits required for A/D conversion and Fourier transformation is small, and processing is easy. Although not necessarily required, it is desirable that the two optical paths from the light source 9 to the semi-transparent mirror 1 be arranged symmetrically with respect to the semi-transparent mirror l.

Note that the present invention is not limited to the above-mentioned interferometer shown in FIG. 7, but can be applied to any interferometer in which the direction of the incident light and the direction of the outgoing light are separated, and two positions are possible for both the incoming light and the outgoing light. . Examples of such interferometers are shown in FIGS. 2 to 5.

The interferometers in Figure 2 are J, F, James, R, S.
, 5ternberry''The Design of
0ptical Spectrometers p,
139 (Chapman and Hall, 19
69), in which two or three mirrors (corner cube mirrors) orthogonal are used as a fixed mirror 2 and a movable mirror 3, and a semi-transparent mirror 1 is used to control the optical path passing through the fixed mirror 2 and the movable mirror. In order to have the same characteristics for the optical path passing through the crystal plate 10, a semi-transparent film 11 on the optical path of the incident light I and a semi-transparent film 12 on the optical path of the output light are separately deposited on the front and back sides of the crystal plate 10. In this case as well, as is clear from the drawing, there are two possible positions for the incident light, I and H, and the detectors I and ■ can be placed in the same way. By inputting light from the incident light I and ■ directions, it is possible to prevent light from entering that causes fluctuations other than light from the light source, and also to prevent the signal obtained from the detector ■ and the signal obtained from the detector ■ from entering. By adding the signals, a highly accurate signal that can be easily processed can be obtained.

Furthermore, the interferometer shown in FIG.
Haseth “Fourier Transform”
Infrared Spectroscopy, 59
5 (John Wiley & 5ons, 198
6), which is a Michelson interferometer in which the incident light is shifted from perpendicular to the fixed mirror 2 and movable mirror 3, and the incident light and the outgoing light are separated. It is. In this case as well, as is clear from the drawing, there are two possible positions for the incident light: ■ and H, and detectors I and ■ can be placed in the same way, so that the two positions of the incident light from the same light source are possible. By inputting light from the incident light direction ■ and ■, it is possible to prevent light that is a fluctuation factor other than the light from the light source from entering, and the signal obtained from detector I and the signal obtained from detector ■ can be prevented from entering. By adding these, a highly accurate signal that can be easily processed can be obtained.

Furthermore, the interferometer shown in FIG.
This is one of the proposals proposed in No. 1, and is a modification of the interferometer shown in Figure 1 so that it is spatially arranged three-dimensionally.
In order to make the human output light as perpendicular to the semi-transparent mirror I as possible, the incident light I is arranged so that the plane containing the incident light and reflected light on the fixed mirror 2 forms a different plane from the plane containing the incident light and reflected light on the movable mirror 3. , and the arrangement angles of the fixed mirror 2 and movable mirror 3. In this case as well, as is clear from the drawing, there are two possible positions for the incident light, I and ■, and the detector is also located at the detector I.
and ■ can be arranged, so the light from the same light source can be input into
■ By letting the light enter from the direction, it is possible to prevent light that is a variable factor other than the light from the light source from entering, and
By adding the signal obtained from detector I and the signal obtained from detector 2, a highly accurate signal that can be easily processed is obtained. Note that in other interferometers of the above-mentioned application, the light sources can be similarly arranged to obtain the same effect.

Furthermore, the interferometer shown in FIG. is fixed mirror I5,
It is arranged so that it returns to the same position on the semi-transparent mirror I via the fixed mirror II6. Further, half of the incident light transmitted through the semi-transparent mirror 1 is arranged so as to return to the same position on the semi-transparent mirror 1 via the movable mirror 7 and the movable mirror I8. Both lights that have returned to the position of the semi-transparent mirror 1 interfere with each other on the front and back sides of the semi-transparent mirror 1, and the output light 11
The emitted light H is emitted in two directions. As is clear from the figure,
The optical path from the semi-transparent mirror 1 through the fixed mirror I5 and the fixed mirror ■6 and the optical path from the semi-transparent mirror 1 through the movable mirror ■7 and the movable mirror I8 are parallel to each other in the same space and exist on the same plane. Therefore, even if there is a change in the refractive index due to a change in the atmosphere on one side of the space bordering the semi-transparent mirror, such as a change in temperature, this interferometer can automatically compensate for this effect. . In this case as well, as is clear from the drawing, there are two possible positions for the incident light, I and H, and the detectors I and ■ can be placed in the same way. By making light incident from the incident light I and ■ directions, it is possible to prevent light that is a fluctuation factor other than the light from the light source from entering, and the signal obtained from the detector r and the signal obtained from the detector ■ can be prevented from entering. By adding , we can obtain an easily processable high-precision signal: ' = double signal. Note that the same effects can be obtained in other interferometers of the above-mentioned application by arranging the light sources in the same manner.

The above are examples of the present invention, and the present invention is not limited to these examples.The direction of the other incident light and the direction of the output light are separated, and both the input light and the output light have two positions. Applicable to all possible interferometers.

〔Effect of the invention〕

As is clear from the above explanation, in the present invention, a light source that has the same effect as a constant-temperature black body is arranged in either direction of incident light, so that fluctuation factors other than light from the light source are removed from the incident light side. It can prevent light from entering. Furthermore, since these light sources are the same light source, the characteristics of the sample can be easily measured with high precision by arranging detectors at two different emission light positions and adding the outputs.

Therefore, especially when the interferometer of the present invention is used in a Fourier transform infrared spectrophotometer, measurement accuracy is improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of the interferometer according to the present invention, FIGS. 2 to 5 are diagrams showing the configuration of another embodiment of the present invention, and FIG. Figure 7 is a diagram showing the configuration of an interferometer, Figure 7 is a diagram showing the configuration of another conventional interferometer, Figure 8 is a diagram explaining the operation of the interferometer in Figure 7, Figure 9 is a diagram showing the direction of incident light. FIG. 3 is a diagram for explaining the effect when a constant-temperature blackbody is placed on one side of the screen. 1. Semi-transparent mirror, 2.5.6... Fixed mirror, 3.7.8.
...Moving mirror, 4... Constant temperature black body, 9... Light source, lO.
...Crystal plate, 11...Semipermeable membrane, 12...Semipermeable membrane exit
Applicant JEOL Ltd.

Claims (1)

[Claims] (1) A semi-transparent mirror, consisting of a fixed mirror system and a movable mirror system that reflect the light transmitted and reflected by the semi-transparent mirror toward the semi-transparent mirror, and the direction of the incident light and the direction of the emitted light are separated, and An interferometer capable of taking two different positions for both incident light and output light, characterized in that the interferometer is configured so that light from the same light source is simultaneously incident on two different positions of the incident light.