JPH09257579A - Interferometer - Google Patents

Abstract

(57) Abstract: In a Michelson interferometer, by arranging two corner cube prisms at different positions, interference fringes are generated spatially and non-movable spectroscopic analysis can be performed. To realize an interferometer with high utilization efficiency. A light source, a lens that converts light emitted from the light source into parallel light, a beam splitter, and two corner cube prisms that reflect light split by the beam splitter in opposite directions, respectively. In a Michelson interferometer comprising a condenser lens for focusing two lights and causing interference on a photodetector, light travels from one corner cube prism to an equivalent position of the other corner cube prism with respect to the beam splitter. A predetermined amount is shifted in the direction orthogonal to the direction, and interference fringes are generated on the photodetector.

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 spectroscope mainly for use in a non-movable Fourier spectroscope, and in particular, by arranging two corner cube prisms in a staggered manner, spatial interference is caused. The present invention relates to an immovable, inexpensive, interferometer with high light utilization efficiency that generates fringes.

[0002]

2. Description of the Related Art Conventionally, as a non-movable Fourier spectroscopy apparatus, there are 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 “Infrared Raman Workshop” (held in December 1991) of the Spectroscopic Society. In this interferometer, the light from the light source S is collimated by the lens L1 and then split by the light splitting means BS into two, that is, reflected light and transmitted light, and enter the respective reflection mirrors M1 and M2. The reflection mirrors M1 and M2 are each slightly tilted in the opposite direction with respect 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 displaced from the mirror M1 by θx (θ is an angle formed by two light beams) in proportion to the distance x from the optical axis.

When observing the mirrors M1 and M2 with the imaging lens L2, interference fringes caused by the difference in optical path length between the two light beams are obtained on the image plane. By arranging a multi-channel array detector on this image plane, the optical path length difference scanning, which was performed by mechanical driving of the mirror in ordinary Fourier spectroscopy, can be electronically realized.

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

[0005]

By the way, 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 improve the resolution. However, there is a problem that the throughput becomes low.

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

However, in such a Savart plate birefringence interferometer, although the throughput is high, there is a problem that expensive components such as an infrared polarizer and a birefringence crystal are required.

In view of the above points, an object of the present invention is to produce a spatial interference fringe by arranging two corner cube prisms at different positions in a Michelson interferometer using a corner cube prism or the like. In this way, spectroscopic analysis can be performed immovably, and an attempt is made to realize an interferometer with high light utilization efficiency while using general inexpensive optical components.

[0009]

In order to achieve such an object, according to the present invention, a light source, a lens for converting light emitted from the light source into parallel light, and reflection of light from the lens with transmitted light. A beam splitter that splits the light into two, a corner cube prism or a corner cube mirror that reflects the two split lights in opposite directions, and two lights that are reflected by the corner cube prism or the corner cube mirror. In a Michelson interferometer consisting of a condenser lens that causes interference on a photodetector, the direction of travel of light from an equivalent position of the one corner cube prism or corner cube mirror to the other beam splitter of the other corner cube prism or corner cube mirror. Shift by a predetermined amount in the direction orthogonal to Place, characterized by being configured to generate interference fringes on the optical detector.

By shifting one corner cube prism or corner cube mirror (hereinafter referred to as a corner cube prism) from the equivalent position of the other corner cube prism with respect to the beam splitter by a predetermined amount δ in a direction orthogonal to the traveling direction of light, A phase difference occurs between the two lights that enter the condenser lens. Letting the incident angle of the ray be θ, the phase difference ψ = (2π ・ 2δθ) / λ (λ is the wavelength of the light of the light source), and on the photodetector, when ψ = 0, ± 2π, ± 4π, the bright part Cause By observing the interference fringes on this photodetector, the spectrum of the incident light can be known.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a 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 collimating the light from the light source 1, 3 is a beam splitter, 4 and 5 are reflecting means such as a corner cube prism, 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 collimated by the lens 2 and is incident on 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 light emitted from the corner cube prism 4 passes through the beam splitter 3 and the other corner cube prism 5
The emitted light is reflected by the beam splitter 3, is combined, and enters the condenser lens 6. The condenser lens 6 detects this light as a photodetector 7
Focus on top. An image of interference fringes is formed on the photodetector 7. The image on the photodetector 7 is fast Fourier transformed (FF
The spectrum of the incident light can be analyzed by frequency analysis using T) or the like.

At this time, as shown in the figure, the equivalent position 4a of the corner cube prism 4 to the beam splitter 3 is shown.
Is displaced from the corner cube prism 5 by δ in the direction orthogonal to the optical axis. Beam splitter 3
Can be expressed equivalently by the positional relationship shown in FIG.

The light from the light source 1 is passed through the beam splitter 3 to 2
Divided into rays of a book, corner cube prism 4
When the positions of a and 5 are deviated by δ, the loci after reflection from the corner cube prism do not match as shown in FIG. 2, and a phase difference ψ occurs and the light is incident on the lens 6. The image is formed at the same position above.

When the incident angle of this ray 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. Because the bright part occurs when
Regarding the image height H, the following relationship holds when the focal length of the lens 6 is f. (2δθ) / λ = n (n is an integer), and the nth image height H _n can be expressed as H _n = fθ = (fnλ) / (2δ). Interval P from nth to n-1th 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 interference fringes on the photodetector 7, the spectrum of the incident light is obtained by frequency analysis of the image on the photodetector 7 by FFT or the like. Can be analyzed.

Experimental results confirmed by the interferometer of the present invention based on such a principle are shown below. FIG. 3 is an image captured by the photodetector 7, and the elements of the photodetector 7 are CCs.
The image was taken by using a D camera and is an image of interference fringes superimposed on the filament image of the light source of the halogen lamp.
FIG. 4 shows measured values of interference fringes. The horizontal axis is the deviation from the optical axis, and the vertical axis is the interference fringe spatial frequency.

In a spectroscope such as a grating, the position of the stripe on the photodetector changes as the incident angle θ changes.
For this reason, if the incident angle is not limited by a slit or the like, the stripes are overlapped with each other to reduce the visibility. However, the interferometer of the present invention has a feature that it does not require slits in the light source and is bright, like the Savart type. This is because the incident angle θ determines the stripe coordinates.

The foregoing description of the invention has been shown by way of illustration only of particular preferred embodiments for purposes of illustration and illustration. Accordingly, the invention is subject to 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. The beam splitter may be a half mirror. Furthermore, the interferometer of the present invention can be applied not only to Fourier spectroscopy but also to, for example, measurement of aberration of light from a light source.

[0020]

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

[Brief description of drawings]

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

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

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

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

FIG. 5: Configuration diagram of a conventional Michelson interferometer

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

[Explanation of symbols]

 1 light source 2 lens 3 beam splitter 4,5 corner cube prism 6 condensing lens 7 photodetector

Claims (3)

[Claims] 1. A light source, a lens that converts light emitted from the light source into parallel light, a beam splitter that splits the light from the lens into transmitted light and reflected light, and two split light beams are opposite to each other. In a Michelson interferometer consisting of a corner cube prism or corner cube mirror that reflects in one direction and a condenser lens that collects the two lights respectively reflected by this corner cube prism or corner cube mirror and causes them to interfere on the photodetector. , One of the corner cube prisms or corner cube mirrors is offset from the equivalent position of the other corner cube prism or corner cube mirror with respect to the beam splitter in a direction orthogonal to the traveling direction of light by a predetermined amount, and is placed on the photodetector. That it is configured to generate interference fringes Characteristic interferometer. 2. The interferometer of claim 1, wherein the photodetector is a multi-channel photodetector or film. 3. A means for obtaining the spectrum of the light of the sample inserted in the light source or the optical path by Fourier-transforming the signal obtained by the photodetector. Interferometer described.