JP2000028433A - Spectroscopic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spectroscopic device which has a simple constitution and can obtain a luminous flux having a prescribed wavelength with less flare and high accuracy. SOLUTION: In a spectroscopic device which is provided with a slit for passing luminous flux and a diffracting optical element G which diffracts the luminous flux made incident through the slit and emits a prescribed part of the diffracted light from the optical element G through the slit, the slit has at least first to fourth openings SLA, SLD, SLC, and SLB. The device is also provided with re-input optical systems M3 and M4 which emits the light made incident through the first opening SLA from the second opening SLD after the light is diffracted by means of the optical element G and lead the light emitted from the second opening SLD to the third opening SLC and emits the light made incident through the third opening SLC from the fourth opening SLB after diffracting the light by means of the optical element G.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectroscope, and more particularly to a spectroscope for extracting monochromatic light having a predetermined wavelength from light having a wavelength width.

[0002]

2. Description of the Related Art Conventionally, a spectroscope using a diffraction grating (grating) or a prism element has been used to separate a light beam from a light source having a wide wavelength distribution such as white light. In particular, a diffraction grating is used for high-precision spectroscopy. FIG. 4 shows a configuration of a simple spectroscope. The light beam from the white light source LS is made incident on the slit SL1 and collimated by the collimator mirror M1, and then incident on the diffraction grating G. Then, the light is diffracted by the diffraction grating G at different angles depending on the wavelength, is reflected by the condenser mirror M2, and forms a slit image at a position different for each wavelength. By arranging the slit SL2 on the image plane of the condenser mirror M2, it is possible to extract only light of a specific wavelength.

[0003]

However, in the case of a spectroscope using a diffraction grating, higher-order diffracted light generated by the diffraction grating may be reflected multiple times in the spectroscope. As a result, a so-called flare occurs in which a light beam having an unnecessary wavelength exits from the exit slit of the spectroscope. FIG. 5 is a measurement example showing the relationship between the wavelength (horizontal axis) and the intensity (vertical axis) of the light beam emitted from the spectroscope. As can be seen from FIG. 5, in addition to the light having the wavelength λ = 450.0 nm which is originally desired to be extracted, there is light having a continuous distribution over a wavelength of about 500 to 1100 nm. Flare is a phenomenon that is not preferable from the original purpose of a spectroscope in which only a light beam having a specific wavelength is extracted. In order to reduce flare, a spectroscope in which a second spectroscope is further arranged after the first spectroscope, that is, a so-called double monochromator has been proposed. By transmitting the light beam through the two spectroscopes arranged in series, the wavelength characteristic of the light finally obtained is determined by multiplying the product of the spectral characteristics of the first and second spectroscopes. Become. Therefore,
Flare as shown in FIG. 5 can be reduced. However,
When two spectroscopes are used in combination, there is a problem in that the manufacturing cost of the spectroscope is doubled. The spectroscope extracts a desired wavelength by changing the angle of the diffraction grating. Therefore, when two spectrometers are connected,
When the light L emitted from the first spectroscope enters the second spectroscope, the angle of the diffraction grating of the second spectroscope must be adjusted so that the light L is emitted from the second spectroscope. . That is,
Since the angles of the diffraction gratings of the first and second spectrometers must be adjusted in synchronization with each other with high precision, a highly accurate mechanism is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a spectroscopic device which has a simple structure, has a small flare, and can obtain a light beam of a predetermined wavelength with high accuracy.

[0005]

In order to solve the above-mentioned problems, the invention according to claim 1 has a slit for passing a light beam, and a diffractive optical element for diffracting a light beam incident from the slit. In a spectroscopic device that emits a predetermined portion of light diffracted by a diffractive optical element through the slit, the slit includes at least a first, a second, and a third.
And light incident from the first opening is emitted from the second opening after being diffracted by the diffractive optical element, and emitted from the second opening. A re-incident optical system for guiding the light to the third opening, and the light incident from the third opening exits from the fourth opening after being diffracted by the diffractive optical element. It is characterized by doing.

In the invention according to claim 2, the diffractive optical element is a diffraction grating having linear gratings arranged at a predetermined interval, and enters the diffractive optical element through the incident side slit. A line obtained by projecting a light beam onto the diffractive optical element is different from a longitudinal direction of the linear grating.

[0007] According to the invention described in claim 3, in the first aspect, the first
Each of the fourth to fourth opening portions is located at each of four independent opening portions.

[0008] According to the invention described in claim 4, in the first aspect, the first
And the fourth opening is located on one opening, and the second and third openings are located on another opening different from the one opening. And

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a spectroscopic device according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG.
(A)-(C) is a figure which shows schematic structure of the optical system of the spectroscopy apparatus concerning embodiment of this invention. This spectrometer is
As seen from the light source side Z direction, as shown in FIG. 2, it has four rectangular slits SLA, SLB, SLC, and SLD.
In FIGS. 1 and 2, for convenience of understanding, in addition to the XYZ coordinate system, the M and S axes obtained by rotating the Y and X directions by 45 degrees about the Z axis are indicated by broken lines.

Referring to FIGS. 1 (A) to 1 (C), a description will be given of a route along which a light beam emitted from the light source LS travels. FIG. 1 (A)
, The luminous flux from the white light source LS passes through the slit SLA
, And after being incident on the collimating mirror M1 and converted into a parallel light flux, it is diffracted by a diffraction grating G having a linear grating at a predetermined interval P. After being reflected by the mirror M2, the diffracted light is collected at the position of the slit SLD. Slit S
At the LD position, the slit SL is located at a different position for each wavelength.
An image of A is formed. Then, a slit SLD is provided so as to pass only a light beam of a specific wavelength. Slit S
The LA and the slit SLD are disposed so as to have a conjugate relationship with respect to the optical system including the collimating mirror M1, the diffraction grating G, and the mirror M2.

Next, as shown in FIG. 1B, the light beam that has passed through the slit SLD is converted into a parallel light beam by the mirror M3, and is incident on the mirror M4. Then, the light beam reflected by the mirror M4 is guided to the slit SLC and enters the mirror M2. Here, the mirrors M3 and M4 constitute a re-incident optical system for causing the light flux once emitted from the slit SLD to enter the slit SLC again. Further, the slits SLC and SLD are disposed so as to be conjugate with respect to the re-incident optical system. Then, as shown in FIG. 1C, the light beam passing through the slit SLC is reflected by the mirror M
After being reflected by 2 and converted into a parallel light flux, it is diffracted again by the diffraction grating G. The light beam diffracted again is reflected by the mirror M1 and exits from the slit SLB. The slits SLB and SLC are arranged so as to be conjugate with respect to the optical system including the mirror M2, the diffraction grating, and the mirror M1.

When the light passes through the slit SLA and enters the diffraction grating G or passes through the slit SLC and reenters the diffraction grating G, the light incident on the diffraction grating G is projected on the diffraction grating G. The rays are incident on the diffraction grating from an oblique direction so as to be different from the longitudinal direction (Y direction) of the linear grating of the diffraction grating.

In the spectroscopic device having such a configuration, the light beam emitted from the light source LS is diffracted by the diffraction grating G and is slit SL
At D, the first spectroscopy is performed. Then, the light flux is again guided to the spectroscopic device by the re-incident optical system, diffracted again by the diffraction grating G, and the second spectroscopy is performed by the slit SLB. Therefore, with respect to the luminous flux finally emitted from the slit SLB, the same spectral characteristics as in the case where two conventional spectral devices having a single diffraction grating G are connected can be obtained. For this reason, light having few flare and sharp wavelength characteristics can be extracted from the slit SLB.

Although the spectroscope of this embodiment has four rectangular slits SLA to SLD, the present invention is not limited to this, and as shown in FIG. You may comprise so that it may have AA and BB. In this case, the upper part of the slit AA is slit SL
A, the lower part is used as a slit SLB, the upper part of the slit BB is used as a slit SLC, and the lower part is used as a slit SLD. Further, in the spectroscopic device of the present embodiment, since the light beam is incident on the diffraction grating from an oblique direction, the slit image is curved. Thus, for example, FIG.
More preferably, the slit is a curved slit as shown in (B) or a rectangular slit inclined with respect to the longitudinal direction of the lattice.

FIG. 1 shows the re-incident optical system.
Instead of the reflecting optical system including the mirrors M3 and M4 as shown in FIG. 6B, an optical fiber optical system L as shown in FIG.
F may be used.

[0016]

As described above, the spectroscopic device of the present invention can perform spectroscopy at a predetermined wavelength with a simple configuration, at a low cost, with little flare, and with high accuracy.

[Brief description of the drawings]

FIGS. 1A to 1C are diagrams showing an optical system of a spectroscopic device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of the spectroscopic device according to the embodiment of the present invention as viewed from a light source side.

FIGS. 3A and 3B are diagrams showing modified examples of a slit.

FIG. 4 is a diagram showing a configuration of a conventional spectroscope.

FIG. 5 is a diagram showing wavelength characteristics of a conventional spectroscope.

FIG. 6 is a diagram showing a configuration of a modification of the embodiment of the present invention.

[Explanation of symbols]

 LS light source M1, M2 mirror M3, M4 mirror (re-entry optical system) G diffraction grating SLA-SLD slit LF optical fiber optical system

Claims (4)

[Claims] An optical element for diffracting a light beam incident from the slit; and a spectroscopic element for emitting a predetermined portion of the light diffracted by the diffractive optical element through the slit. In the apparatus, the slit includes at least a first, a second, a third, and a fourth.
The light incident from the first opening is emitted from the second opening after being diffracted by the diffractive optical element, and the light emitted from the second opening is provided. To the third opening, and the light incident from the third opening is emitted from the fourth opening after being diffracted by the diffractive optical element. Characteristic spectrometer. 2. The diffractive optical element is a diffractive grating having linear gratings arranged at a predetermined interval, and projects a light beam that passes through the incident side slit and enters the diffractive optical element to the diffractive optical element. 2. The spectroscopic device according to claim 1, wherein the drawn line is different from a longitudinal direction of the linear grating. 3. The spectroscopic apparatus according to claim 1, wherein each of the first to fourth opening portions is located at each of four independent opening portions. 4. The first and fourth opening portions are located on one opening, and the second and third opening portions are on another opening different from the one opening. The spectroscopic device according to claim 1, wherein the spectroscopic device is located at: