JP3275287B2 - Interferometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Michelson-type Fourier spectrometer mainly used for an immovable Fourier spectrometer, and more particularly, to a method of spatially interfering by displacing two corner cube prisms. The present invention relates to a non-movable, inexpensive interferometer with high light use efficiency which generates fringes.

[0002]

2. Description of the Related Art Conventionally, non-movable Fourier spectroscopy apparatuses include a Michelson interferometer and a Savert plate birefringence interferometer. FIG. 5 is a block diagram of a Michelson interferometer for generating spatial interference fringes disclosed in the Infrared Raman Seminar of the Spectroscopic Society (held in December 1991). In this interferometer, light from a light source S is converted into parallel light by a lens L1, and then split into two, reflected light and transmitted light, by a light branching means BS and enters respective reflection mirrors M1 and M2. The reflection mirrors M1 and M2 are slightly inclined in opposite directions to the optical axis. According to such an arrangement, the equivalent position M2a of the mirror M2 at the position of the mirror M1 is shifted by θx (θ is an angle between two light beams) in proportion to the distance x from the optical axis as compared with the mirror M1.

When the mirrors M1 and M2 are observed with the imaging lens L2, interference fringes generated due to the difference in optical path length between the two light beams are obtained on the image plane. If a multi-channel array detector is provided on this image plane, optical path length difference scanning that has been performed by mechanical driving of a mirror in ordinary Fourier spectroscopy can be realized electronically.

From another viewpoint, this means that Young's interference fringes from two pinholes S1 and S2 (corresponding to two real images by the lenses L1 and L2 of the light source S) are observed.

[0005]

In the Michelson interferometer having such a structure, it is necessary to reduce the area of the light source S (for example, to form a slit) in order to increase the resolution. However, there is a problem that the throughput is reduced.

FIG. 6 is a configuration diagram of a Savart plate birefringence interferometer. The Savart plate SP is a combination of two birefringent crystals, and divides the linearly polarized light incident from the light source S through the infrared polarizer P in parallel to the crystal plane into two components, and shifts the parallel polarized light horizontally. It is emitted as two light beams. The two light beams pass through the analyzer A and the lens L3 and form an image on the multi-channel array detector MD.

[0007] However, such a Savart plate birefringence interferometer has a problem that, although the throughput is high, expensive parts such as an infrared polarizer and a birefringent crystal are required.

In view of the foregoing, it is an object of the present invention to generate interference fringes spatially by displacing two corner cube prisms in a Michelson interferometer using a corner cube prism or the like. In this way, the spectroscopic analysis can be performed in a non-movable manner, and it is intended to realize an interferometer having high light use efficiency while using general inexpensive optical components.

[0009]

In order to achieve the above object, the present invention provides a light source, a lens for converting light emitted from the light source into parallel light, and reflecting light from this lens with transmitted light. A beam splitter that splits the light into two light beams; a corner cube prism or a corner cube mirror that reflects the two split light beams in opposite directions; and two light beams that are respectively reflected by the corner cube prism or the corner cube mirror. In a Michelson interferometer comprising a condensing lens for causing interference on a photodetector, a light traveling direction from an equivalent position of the one corner cube prism or corner cube mirror to the beam splitter of the other corner cube prism or corner cube mirror. A predetermined amount in the direction perpendicular to Place, characterized by being configured to generate interference fringes on the optical detector.

[0010]

In order to achieve the above object, the present invention provides a light source, a lens for converting light emitted from the light source into parallel light, and reflecting light from this lens with transmitted light. A beam splitter that splits the light into two light beams, a corner cube prism or a corner cube mirror that reflects the two split light beams in opposite directions, and two light beams respectively reflected by the corner cube prism or the corner cube mirror are collected. In a Michelson interferometer comprising a condensing lens for causing interference on a photodetector, a light traveling direction from an equivalent position of the one corner cube prism or corner cube mirror to the beam splitter of the other corner cube prism or corner cube mirror. A predetermined amount in the direction perpendicular to Arranged to, as well as configured to generate interference fringes on the photodetector, resulting et at the photodetector
The light source or
A means is provided for obtaining the spectrum of the light of the sample inserted in the optical path.
And it said that there were pictures.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the non-movable Fourier spectrometer according to the present invention. In the figure, 1 is a light source such as a halogen lamp, 2 is a lens for converting light from the light source 1 into parallel light, 3 is a beam splitter, 4 and 5 are reflecting means such as corner cube prisms, 6 is a condenser lens, 7
Is a photodetector in which a plurality of CCDs (Charge Coupled Devices) and the like are linearly arranged.

The light from the light source 1 is converted into parallel light by the lens 2 and enters the beam splitter 3. The light reflected by the beam splitter 3 enters the corner cube prism 4, while the transmitted light enters the corner cube prism 5. The output light of the corner cube prism 4 passes through the beam splitter 3 and the other corner cube prism 5
Are reflected by the beam splitter 3, multiplexed and enter the condenser lens 6. The condenser lens 6 converts this light into a photodetector 7
Focus on top. An image of interference fringes is formed on the photodetector 7. The image on the photodetector 7 is converted to a fast Fourier transform (FF).
The spectrum of the incident light can be analyzed by performing frequency analysis as in T).

At this time, an equivalent position 4a of the corner cube prism 4 with respect to the beam splitter 3 as shown in FIG.
Is shifted from the corner cube prism 5 by δ in a direction orthogonal to the optical axis. Each part is a beam splitter 3
Can be expressed in a positional relationship as shown in FIG.

The light from the light source 1 passes through a beam splitter 3
It is divided into three rays, the corner cube prism 4
If the positions of a and 5 are shifted by δ, the trajectories after reflection from the corner cube prism do not match as shown in FIG. An image is formed at the same position above.

Assuming that the incident angle of the light beam is θ, ψ = (2π · 2δθ) / λ where λ is the wavelength of the light from the light source 1 and ψ = 0, ± 2π, ± 4π on the photodetector 7. Since the bright part occurs at the time of
As for the image height H, the following relationship is established when the focal length of the lens 6 is f. A (2δθ) / λ = n ( n is an integer), the image height H _n of the n-th can be expressed as _{H n = fθ = (fnλ)} / (2δ). The interval P from the nth to the (n-1) th of the bright part
Is _{P = H n -H n-1} = (fλ) / (2δ), therefore, the 1 / P = ((2δ) / f) · (1 / λ).

That is, since a frequency component proportional to the wave number 1 / λ is observed as an interference fringe on the photodetector 7, the spectrum of the incident light is obtained by analyzing the image on the photodetector 7 by FFT or the like. Can be analyzed.

Experimental results confirmed in the interferometer of the present invention based on such a principle are as follows. FIG. 3 is an image captured by the photodetector 7, and CC is used as an element of the photodetector 7.
This is an image of an interference fringe imaged using a D camera and superimposed on a filament image of a light source of a halogen lamp.
FIG. 4 shows measured values of interference fringes. The horizontal axis represents the deviation from the optical axis, and the vertical axis represents the interference fringe spatial frequency.

In a spectroscope such as a grating, when the incident angle θ changes, the position of the stripe on the photodetector also changes.
For this reason, if the incident angle is not restricted by a slit or the like, the stripes overlap and the visibility is reduced, and there is a disadvantage that the image is dark. However, the interferometer of the present invention has a feature that it is not necessary to provide a slit in the light source and is bright as in the Savart type. This is because the coordinates of the stripe are determined by the incident angle θ.

The foregoing description of the present invention has been presented by way of illustration and example only, and is given of certain preferred embodiments. Accordingly, the present invention has many modifications, without departing from its essence,
It will be apparent to those skilled in the art that variations can be made. For example,
The reflecting means may be not only a corner cube prism but also a corner cube mirror. The condenser lens 6 may be a concave mirror or the like. Further, the beam splitter may be a half mirror. Further, the interferometer of the present invention can be applied not only to Fourier spectroscopy but also to, for example, aberration measurement of light from a light source.

[0020]

As described above, according to the present invention, in the non-movable Fourier spectroscopy, a Michelson interferometer in which two corner cube prisms are shifted is configured, so that it can be realized only with generally used inexpensive optical components. ,
Moreover, since the slit width can be increased by the Fourier optical system, a spectroscope with high light use efficiency can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an interferometer according to the present invention.

FIG. 2 is a diagram of the equivalent optical system of FIG. 1;

FIG. 3 is a diagram illustrating an example of an image of interference fringes observed by a photodetector.

FIG. 4 is a diagram showing measured values of interference fringes;

FIG. 5 is a configuration diagram of a conventional Michelson interferometer

FIG. 6 is a configuration diagram of a conventional Savart plate birefringent polarization interferometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Lens 3 Beam splitter 4,5 Corner cube prism 6 Condensing lens 7 Photodetector

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 G01J 3/00-3/52 G01J 9 / 00-9/04 G01B 9/00-9/10 ECLA practical file (PATOLIS) Patent file (PATOLIS)

Claims (1)

(57) [Claims] 1. A light source, a lens for converting light emitted from the light source into parallel light, a beam splitter for splitting light from the lens into transmitted light and reflected light, and two beam splitters opposite to each other. A Michelson interferometer comprising a corner cube prism or a corner cube mirror that reflects light in a direction and a condenser lens that collects two lights reflected by the corner cube prism or the corner cube mirror and interferes on a photodetector. the then staggered by a predetermined amount in a direction perpendicular to the traveling direction of the light from the equivalent position relative to the beam splitter of one corner cube prism or a corner cube other corner cube prism or corner cube mirror mirror, said photodetector Configure to generate interference fringes on top And Fourier transforming the signal obtained by the photodetector.
Of the light of the sample inserted into the light source or the optical path.
An interferometer comprising means for obtaining a torque.