JPH0549965B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to spectroscopy, and particularly to a spectroscopic method requiring high resolution and a spectroscopic element used therein.

(b) Background of the technology Spectroscopy is a technology that has been known for a long time and is widely used as a means of analysis, etc., but the range of wavelengths it targets is generally wide. On the other hand, in recent years, technology related to laser light has developed,
Spectroscopy of laser light has become necessary, but since laser light has an extremely narrow wavelength width, it is necessary to increase the resolution when performing spectroscopy, and it is desired that it can be done easily.

(c) Prior art and problems Figure 1 shows an example of a spectroscopic method using a conventional spectroscopic element, and Figure 2 shows another example, where 1 is a prism, and 1a is an incident light beam. 1b is the exit surface, 2 is the diffraction grating surface, 2a is the diffraction grating surface,
A and B are incident beams, Aa is refracted beam, Ab and
Ba indicates the output beam, respectively.

In Figure 1, a prism 1 made of optical glass
has a refractive index that differs depending on the wavelength.
is refracted and split at the entrance surface 1a to become a refracted beam Aa, and further refracted and split at the exit surface 1b to become an output beam.
It becomes Ab and emits. By observing this emitted beam Ab at a distance from the prism 1, the distribution according to wavelength can be determined. The resolution is mainly controlled by the magnitude of the refraction angle formed by the incident beam A and the outgoing beam Ab, and the length of the distance from the prism 1 to the observation position.

In this way, when performing spectroscopy with prism 1,
Although this method is simple, it has the disadvantage that it cannot achieve high resolution because the refraction angle is about 60 degrees and the distance to the observation position cannot be increased arbitrarily.

In the embodiment shown in FIG. 2, a diffraction grating plate 2 is used in place of the prism 1 in the case of FIG. Since the diffraction angle of the diffraction grating on the diffraction grating surface 2a differs depending on the wavelength, the incident beam B is
It undergoes diffraction and spectroscopy at point a to become an outgoing beam Ba, which can be observed in the same manner as in Figure 1. In the case of the diffraction grating plate 2, the diffraction angle is determined by the grating spacing of the diffraction grating, but from a practical standpoint, it is about 120 degrees or less, and although it is a simple method as in the case of prism 1, it still cannot achieve high resolution. There are drawbacks.

(d) Purpose of the Invention In view of the above-mentioned drawbacks of the conventional method, the purpose of the present invention is to provide a spectroscopic method that is as simple as the conventional method but can improve the resolution, and a spectroscopic element used therein. .

(e) Structure of the Invention The above object is to: (1) Arrange three or more diffraction gratings parallel to an axis and radially, and direct a beam to be separated to any one of the diffraction gratings perpendicular to the axis. The diffracted light was incident diagonally to the surface and diagonally to the diffraction grating and diffracted, and the diffracted light was sequentially incident on adjacent diffraction gratings and the diffraction was repeated until it reached at least the first diffraction grating. and (2) three or more diffraction grating surfaces are arranged parallel to the axis and radially, and any one of the diffraction grating surfaces is A spectroscopic element having a diffraction grating that diffracts a beam to be separated that is incident from one of the diffraction grating surfaces on both sides thereof and outputs the beam toward the other diffraction grating surface, or (3) the above-mentioned one in which the diffraction grating surface is a hologram. The spectroscopic element according to item 2, or (4) in the above arrangement, is achieved by the spectroscopic element according to item 2, wherein the space between the surfaces of the diffraction grating is filled with a transparent medium.

In this spectroscopic element, when the beam to be separated is incident at an angle with respect to the axis, the beam travels in a spiral shape while repeating sequential diffraction orders on the plurality of diffraction grating surfaces within the spectroscopic element. If it is extracted as an output beam after diffraction a desired number of times (n times), the degree of spectralization of the output beam is expanded to approximately n times that of one spectral beam, so it is possible to significantly improve the resolution. be.

Further, according to the present invention, it is desirable that the diffraction grating surface of the spectroscopic element is a hologram. This is because the diffraction efficiency (outgoing light amount/incident light amount) is higher than that of other diffraction grating surfaces.

Furthermore, it is desirable that the spaces between the plurality of diffraction grating surfaces be filled with a transparent medium, because the diffraction grating surfaces are generally formed on the surface of a transparent plate, and surface reflection of the transparent plate causes loss of the incident beam. This is because filling the transparent medium makes it possible to reduce the reflection loss, which reduces the amount of light of the emitted beam and increases the influence when there are a plurality of diffraction grating surfaces.

(f) Examples of the invention Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a perspective view a and a plan view b showing an embodiment of a spectroscopic method using an embodiment of the spectroscopic element of the present invention;
Figures 4, 5, and 6 are diagrams showing other embodiments of the spectroscopic element, 3a, 3b, 3c, 3d.
is a diffraction grating plate, 4a, 4d are mirror surfaces, 5a to 5
d, 6a to 6d are transparent media, 7 is a bonding material, 8 is a diffraction grating plate, C is an incident beam, Ca is an output beam,
Z indicates an axis, respectively.

The diffraction element shown in FIG. 3 is a hologram and includes four diffraction grating plates 3a to 3a having the same diffraction grating surface.
3d are arranged radially at 90 degree intervals as shown in the figure,
In between is a transparent medium 5a such as lens bond.
Filled with ~5d. Here, the diffraction grating on the diffraction grating surface is such that, for example, as shown in FIG. The diffraction grating is such that the light is emitted at an output angle of approximately 45 degrees toward the diffraction grating plate 3c. Furthermore, although the transparent media 5a, 5b, and 5c fill the entire surfaces of the diffraction grating plates 3a to 3d, the filling of the transparent medium 5d covers the upper and lower surfaces of the diffraction grating plates 3d and 3a, as shown in Figure a. The remaining diffraction grating plate 3
Mirror surfaces 4d and 4a for reflecting the beam are formed on the upper surface of d and the lower surface of 3a, respectively.

In order to perform spectroscopy using the diffraction element having this configuration, as shown in FIG.
d Slightly inclined with respect to the plane perpendicular to the axis Z of the arrangement,
Moreover, the incident beam C, which is the beam to be separated, may be projected so that the beam reflected by the mirror surface 4d is incident on the diffraction grating plate 3a at an incident angle of approximately 45 degrees. The incident beam C undergoes the first diffraction at the diffraction grating plate 3a, and then repeats the diffraction in steps 3b, 3c, etc. In the illustrated example, it rotates through this diffraction element three times, performs the 12th diffraction at 3d, and becomes an output beam. It becomes Ca, is reflected on the mirror surface 4a, and is drawn out. In this case, the hologram with good diffraction efficiency is placed on the diffraction grating plates 3a to 3d.
transparent medium 5a that suppresses surface reflection.
Since the filling is ~5d, the output beam
Ca has a sufficient amount of light despite being diffracted 12 times. Therefore, the degree of spectralization of this output beam Ca is approximately 12 times that of one spectral beam,
Since the amount of light is also sufficient, it is possible to easily observe the distribution of light even if the wavelength width is small, such as laser light.

Other embodiments of the diffraction element will be listed below, but in any case, the principle and method of spectroscopy are the same as above.

FIG. 4 shows a case in which the transparent media 5a to 5d in the case of FIG. 3 are not filled, and the surface reflection of the diffraction grating plates 3a to 3d is larger than in the case in FIG. limited.

In FIG. 5, the transparent media 5a to 5d in FIG. 3 are replaced with optical glass 6a to 6d, and in this case, a bonding material 7 such as lens bond is used between the diffraction grating plates 3a to 3d. It is better to join.

Figure 6 shows an example composed of three diffraction grating plates 8.
The form of the structure may be any of those shown in FIG. 3, FIG. 4, and FIG. 5. However, since the angle of diffraction is different, it is necessary to change the spacing of the diffraction gratings.

Note that the diffraction elements configured according to the present invention cannot be used in a wide range of wavelengths, so it is necessary to prepare a diffraction element that matches the wavelength of the incident beam to be observed. It is not a burden, and the simplicity of the spectroscopic method is a greater advantage.

(g) Effects of the Invention As explained above, the configuration of the present invention provides a spectroscopic method that is as simple as the conventional method but can improve resolution, and a spectroscopic element used therein. For example,
This has the effect of making it possible to easily observe the distribution of even light with a small wavelength width, such as laser light.

[Brief explanation of the drawing]

Fig. 1 shows an example of a spectroscopic method using a conventional spectroscopic element, Fig. 2 shows another example, and Fig. 3 shows a spectroscopic method using an embodiment of the spectroscopic element of the present invention. A perspective view a and a plan view b showing one embodiment, and FIGS. 4, 5, and 6 are views showing other embodiments of the spectroscopic element, respectively. In the drawing, 1 is a prism, 1a is an entrance surface,
1b is an output surface, 2, 3a to 3d, 8 are diffraction grating plates, 2a is a diffraction grating surface, 4a, 4b are mirror surfaces,
5a to 5d, 6a to 6d are transparent media, 7 is a bonding material, A, B, C are incident beams, Aa is a refracted beam,
Ab, Ba, and Ca indicate the output beam, and Z indicates the axis, respectively.

Claims (1)

[Claims] 1. Three or more diffraction gratings are arranged parallel to an axis and radially, and a beam to be separated is directed to any one of the diffraction gratings at an angle with respect to a plane perpendicular to the axis. The diffraction light is incident obliquely on the diffraction grating and diffracted, and the diffraction light is sequentially incident on adjacent diffraction gratings until it reaches at least the first diffraction grating, and then the diffraction light is A spectroscopic method characterized by the extraction of 2. Three or more diffraction grating surfaces are arranged parallel to the axis and radially, and any one of the diffraction grating surfaces is capable of absorbing light incident from one of the adjacent diffraction grating surfaces on both sides. diffract the spectral beam,
A spectroscopic element characterized by having a diffraction grating that emits light toward the other diffraction grating surface. 3. The spectroscopic element according to claim 2, wherein the diffraction grating surface is a hologram. 4. The spectroscopic element according to claim 2, wherein in the arrangement, a space between the surfaces of the diffraction grating is filled with a transparent medium.