JPS62203024A - Fabry-perot spectroscope - Google Patents

Abstract

PURPOSE:To enhance wavelength resolving power by widening a spectral diffraction wavelength region, by a method wherein the interval and first and second angles of refraction of interference plates are selected properly and a wavelength intensified by the generation of interference is specified to perform the spectral diffraction only of the specified wavelength. CONSTITUTION:The beam emitted from a beam source 20 is converted to a parallel beam by a collimator lens 21 and incident to Fabry-Perot interference plates 17 so as to set a predetermined angle theta1' of refraction. These interference plates 17 are constituted so that half mirrors having high reflectivity are parallelly held on two planes at a predetermined interval by a piezoelectric element and the interval therebetween is made changeable in a predetermined range. The beam transmitted through said interference plates 17 is reflected by reflecting mirrors 23, 24, 25 to be again incident to the interference plates 17 at a predetermined angle theta2'. Then, by condensing the spectrally diffracted beam by a condensing lens 26, the beam of the beam source 20 can be spectrally diffracted.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a spectroscopic device using a Fabry-Perot interference plate. This invention relates to a Fabry-Perot spectrometer characterized by a double-injection type.

[Conventional technology]

Among various spectroscopic devices, the Fabry-Perot spectroscopic device has been well known for a long time as a spectroscopic device with high wavelength resolution.

FIG. 4 is an explanatory diagram of the basic principle of a Fabry-Perot spectrometer.

In the figure, 1 and 3 are high reflection films, 2.degree. 4 are glass plates, 5 is incident light, and 6 is transmitted light. In the Fabry-Perot spectrometer, a Fabry-Perot interference plate is used, which consists of a glass plate 2 provided with a high reflection [1] and a glass plate 4 provided with a similar high reflection film 3, facing each other in parallel with an interval. be done.

When incident light 5 having various wavelengths is made incident on this Fabry-Perot interference plate at a predetermined angle of incidence, the transmitted light 6 is given by the following equation. Transmitted light intensity for incident light intensity (1) of a certain wavelength λG! (t) ratio, transmittance T is.

becomes. Here, n' is the refractive index of the medium, h is the interval between the glass plates 4, θ' is the refraction angle within the medium n', and R is the reflectance of the high reflective films 1 and 2. (Reference: “Pr1ncipl@s
of Opticm"3rd Edition, M,
Born and E, Wolf.

Pergamon Pr@s@e 1965, 327
Page) When the spacing and the refraction angle θ' are constant, the transmittance for the wavelength λ is as shown in FIG. That is, multiple wavelengths are transmitted. According to equation (1) above, T is a periodic function of δ! D, in equation (2), when δ=2πN (where N is an integer), T is maximum, and the wavelength λN at that time is transmitted.

Now, if the medium n'=1, then according to equation (2), the transmitted light λN is as follows.

Specifically, when h=10m and θ'=O, the results are shown in Table 1.

(Table 1) Furthermore, when h=1.6×10'' dew and θ'=06, the results are shown in Table 2.

(Table 2) In other words, the interval between adjacent wavelengths varies greatly depending on the interval.

The wavelength interval is 0.0000125/jm = 0.0125 nm in Table 1, whereas it is 0.07619 μm in Table 2 (N=6 and N
= 7).

As shown in FIG. 5, the wavelength resolution is expressed by the relative finesse F of the half-width ΔλN with respect to the difference in adjacent wavelengths. Finesse F is determined by the following formula.

In other words, finesse F is determined by F in equation (3), and since F is determined by reflectance 8, finesse F is determined by reflectance R. For example, if R = 0.95, then 7' = 61.2. , the wavelength resolution is 0.0125 (μm) 761.2 = 0.0002 n when the above interval h = 10 m
m and the interval h=1.6X10-'m is 0.07619
(μm) 761.2 = 0.0012μm ” 1.2
It has an extremely high resolution of nanometers. However, on the other hand, as in the above-mentioned example, the interval between adjacent wavelengths is small, and the wavelength range is narrow, making it difficult to use as a spectrometer or spectrometer.

Figure 6 shows another spectrometer (''
This shows a device that can measure a specific wavelength with high resolution by combining it with an Im rhythm spectrometer.
Reference: "Pr1nciples of 0ptics".

3rd Eddie trons M, Born & E
@Wolf + Pergamon Press.

(1965, p. 336).

In the same figure, 7 is a light source, 8 is a collimator lens, and 9 is a light source.
10 is a Fabry-Perot interference plate, 10 is an imaging lens, 11 is a pinhole, 12 is a collimator lens, 13 is a prism, 14 is an imaging lens, and 15 is an observation surface.

The light emitted from the light source is collimated by a collimator lens 8, separated by a Fabry-Perot interference plate 9, and focused onto a pinhole 11 by an imaging lens 10. The light cut off from the pinhole 11 on the optical axis is
The collimator lens 12 converts the light into parallel light, and the prism 13 changes the output angle of each wavelength. The imaging lens 14 positions the focal point of each wavelength on the observation surface 15. Separated. In this way, the aforementioned adjacent wavelengths can be separated.

[Problem that the invention seeks to solve]

However, in the above-mentioned spectroscopic device, it is essential to use another spectrometer, a prism spectrometer, and it is necessary to match the two spectrometers (optical axis alignment, aberration correction, etc.). J? The problem of loss of tact was solved.

Therefore, the Fabry-Berrot optical devices that are mainly in practical use are currently limited to the measurement of the longitudinal mode of Rede light with a narrow spectral range.

[Means for solving problems]

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a Fabry-Perot spectrometer that has a wide spectral wavelength range without using other spectrometers in combination.

A Fabry-Bello spectrometer of the present invention that achieves the above objects includes a Fabry-Perot interference plate, a control means for changing the interval of the Fabry-Perot interference plate, and a first a first optical means for making the light beam incident at a refraction angle; and a first optical means for making the light beam that has passed through the Fabry-Perot interference plate enter the Fabry-Perot interference plate again at a second refraction angle different from the first refraction angle. It is characterized by having a second optical means.

[Effect]

According to the above-mentioned apparatus, the distance between the Fabry-Perot interference plates and the first refraction angle θ, for example, when two incidences are used,
By appropriately selecting the refraction angle θ'1 and the second refraction angle θ'2, the wavelength at which interference occurs and is strengthened can be specified, making it possible to perform spectroscopy of only a specific wavelength, thereby expanding the usable wavelength range. .

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the Fabry-Bello spectrometer according to the present invention will be explained in detail based on the drawings.

FIG. 1 shows a principle diagram of the present invention.

In the figure, 17 is a Fabry-Perot interference plate, 40 is a first human radiation beam, 41 is a second human radiation beam, and 42 and 43 are reflecting mirrors, respectively.

The Fabry-Perot spectrometer of the present invention allows light to enter the Fabry-Perot interference plate 17 multiple times at different refraction angles,
It is a spectroscopic device that is characterized by transmitting only a predetermined wavelength. The light flux (first human incident light 40) is incident on the spaced Fabry-Perot interference plate 17 at a first refraction angle θ'1, and the transmitted light is reflected again by the reflecting mirror 42.43. A second refraction angle θ' is applied to the Fabry-Perot interference plate 17.
By making the incident light beams 2 (second human incident light 41 is shown), adjacent wavelengths can be removed.

For example, if the interval is 1.6 μm, the first refraction angle θ/
When 1==O', from Table 1 mentioned above, 064 to 0.
Five wavelengths are transmitted in the 8 μm wavelength range. Therefore, when light is incident so that the second refraction angle θ'2t of the second human light 41 is 36.87°, the wavelengths shown in Table 3 below are transmitted in the wavelength range of 0.4 to 0.8 μm.

(Table 3) As is clear from the comparison with Table 1 and Table 2, only the wavelength of 0.64 μm matches. Therefore 0.4～
Only specific wavelengths in the 0.8 μm wavelength range can be spectrally analyzed, expanding the usable wavelength range.

In Figure 3, the order N1 (solid line) when the refraction angle θ'1 = 09 and the order N2 (dotted line) when the refraction angle θ'1 = 36.87° are used as parameters, and the transmission wavelength ) and the distance h (vertical axis) between the interference plates 17.

The spacing is in the range of 1°0 to 2.0pm, and 0.4 to 0.
．． The reason why the dotted line and the solid line match in the 8 μm wavelength range is N
1; 5, only when N2=4.

Therefore, the spacing can be reduced to 1.0 μm to 2 μm using piezo elements, etc.
．． If you change it continuously to 0μm, it will change from 0.4μm to 0
．． It is possible to continuously separate light of 8 μm.

FIG. 2 is a diagram for more specifically explaining the spectroscopic apparatus of the present invention.

In the figure, 20 is a light source that emits a beam to be separated, 21 is a collimator lens, 22 is a minute distance moving means such as a piezo element, 17 is a Fabry-Perot interference plate, and 2
3, 24, and 25 are reflecting mirrors, 26 is a condensing lens, 27 is a light source such as a light emitting diode, 28 is a collimator lens, 29 is a condensing lens, and 30 is a photoelectric conversion element.

After the light emitted from the light source 20 is made into a parallel beam by the collimator lens 21, the Fabry-Perot interference plate 17
is made incident at a predetermined refraction angle θ'1, for example, 36.87° as mentioned above. The Fabry-Perot interference plate 17 has two planar semi-transparent mirrors with a high reflectivity held in parallel at a predetermined interval by a piezo element, etc.
The thickness can be changed from 1.0 μm to 2.0 μm. The light beam that has passed through the Fabry-Perot interference plate 17 is incident on the Fabry-Perot interference plate 17 again by the reflecting mirrors 23, 24, and 25 at a predetermined refraction angle θ'2, for example, 00 as described above. Then, the separated transmitted light is passed through a condensing lens 26.
By concentrating the light, the light source 20 can be divided into spectra.

What is particularly important here is the Fabry-Perot interference plate 17.
This is interval management and maintenance. This management.

For maintenance purposes, a standard interval detection system consisting of a light source with a wavelength that is transmitted when it is incident at a predetermined refraction angle, its optical system, and a detection system is used only when the interval between the Fabry-Perot interference plates 17 increases. Optical system of 27.28, 29.30
has been established. That is, a light source, for example a light emitting diode 27
After collimating the light emitted from the collimator lens 28 into a parallel light beam, the light is made to enter the Fabry-Perot interference plate 17 at a predetermined refraction angle, and the transmitted light beam is passed through the condenser lens 29.
By focusing the light onto the photoelectric conversion element 30, the spacing between the optical interference plates 17 can be controlled from the output from the photoelectric conversion element 30.

For example, the center wavelength of the light emitting diode 27 is 0.65 μm,
When the refraction angle is 45°, the interval is 2.298 μm (order 5
).

1.838μm (order 4), 1.379μm (order 3)
.

It is transmitted at 0.919 μm (order 2). Therefore, by managing and maintaining these intervals, accurate spectroscopy can be performed at all times.

Another advantage of the method of the present invention is that wavelength resolution is significantly improved compared to conventional methods by making the light incident on the 7-hole Burri-Perot interference plate 17 at least twice. This is because the half-width ΔλN becomes small when the beam is incident twice, and the resolution determined by the difference in adjacent wavelengths and the magnitude of the half-width ΔλN can similarly be detected down to a small value.

The method of the present invention is not limited to the above embodiments, and various modifications are possible.

For example, in the embodiment described above, the light is made to enter the Fabry-Perot interference plate twice at different refraction angles, but it is also possible to make the light enter the Fabry-Perot interference plate twice or more.

For example, as shown in Fig. 3, by attaching a human beam to the Fabry-Perot interference plate so that the refraction angle is 51.13°, the order when the refraction angle is θ0.36.87° is 3rd order. 5.4, the conditions are even stricter than in the case of double incidence, and since the other orders do not match, it is possible to prevent the mixing of higher wavelengths.

〔Effect of the invention〕

As explained above, according to the spectroscopic device of the present invention that can make light beams with different refraction angles enter the Fabry-Perot interference plate multiple times, it is possible to cut adjacent wavelengths and widen the spectral wavelength range. can.

Furthermore, by making the light incident multiple times, the wavelength resolution can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of a Fabry-Perot spectrometer according to the present invention, and FIG. 2 is a schematic diagram showing a specific embodiment thereof. FIG. 3 is a graph showing the relationship between the transmission wavelength λ and the interval between interference plates. Figure 4 is a diagram showing the basic principle of a conventional 7-application-P4 spectrometer, Figure 5 is a graph showing the relationship between wavelength λ and transmittance T, and Figure 6 is a conventional Fabry-Bello spectrometer. This is a structural diagram showing a spectroscopic device that compensates for the shortcomings of . 17...Fapri-Bello interference plate, 40...First incident light, 41...Second human incident light, 42.43, 23°24
．． 15...Reflection mirror, 20.27...Light source, 21
．． 28... Collimator lens, 26. 29... Condensing lens, 22... Minute distance moving means, 30... Photoelectric conversion element. Agent Patent Attorney Johei Yamashita Figure 1 Figure 2

Claims (1)

[Claims] (1) A Fabry-Perot interference plate, a control means for changing the interval between the Fabry-Perot interference plates, a first optical means for making a light beam incident on the Fabry-Perot interference plate at a first refraction angle, and the Fabry-Perot interference plate; - A Fabry-Perot spectrometer comprising: second optical means for making the light beam that has passed through the Perot interference plate enter the Fabry-Perot interference plate again at a second refraction angle different from the first refraction angle.