JPH07117456B2 - Diffraction grating spectrometer - Google Patents

Description

The present invention relates to a reflection type diffraction grating spectroscope used in a spectrophotometer.

(Prior Art) Generally, an Echelette type reflection diffraction grating, which is widely used, is formed by engraving a number of parallel triangular grooves G on a substrate 1 as shown in FIG. A is installed, and this type of diffraction grating has the advantage that high diffraction efficiency can be obtained in a certain wavelength range, but on the other hand, depending on the purpose of use, the measurement wavelength range is so wide that one grating cannot cover it. was there.

Therefore, conventionally, two types of diffraction gratings are switched and used in order to cover a required wavelength range, but two diffraction gratings are required and the switching mechanism is complicated, resulting in high cost and switching mechanism. The accuracy of was often a problem.

(Problems to be Solved by the Invention) In view of the above points, the present invention can cover a wide wavelength range, which conventionally requires two diffraction gratings, and has a simple switching mechanism. Therefore, it is an object of the present invention to provide an inexpensive and highly accurate echelette type reflection diffraction grating.

(Means for Solving the Problems) In order to achieve the above object, the diffraction grating according to the present invention comprises:
A large number of triangular grooves G formed by two inclinations 3 and 4 having different inclination angles θ ₁ and θ ₂ are engraved in parallel to form a lattice plane, and 180 degrees is inverted by a rotation axis 5 perpendicular to the lattice plane. It is a shaft that can be switched freely.

(Function) Since the two inclined surfaces having different inclination angles of the triangular groove G forming the lattice are used as reflecting surfaces, and two inclination angles θ ₁ and θ ₂ can be used as the blaze angle, two sheets are conventionally used. Since it is possible to cover the wavelength range covered by the diffraction grating of No. 1 with one sheet and to invert by the rotation axis 5 perpendicular to the grating surface, the structure can be simplified and the accuracy can be improved. .

(Embodiment) FIG. 1 shows an example of the structure of a diffraction grating main body. The upper surface of a glass substrate 1 forming an optical plane is opposed to each other by a photoresist 2 and tilt angles θ ₁ and θ ₂ are provided. The groove G is formed by different slopes 3 and 4, and the slopes 3 and 4 are different from each other.
The light reflection coatings A ₁ and A _{2 made of} different materials on the surface of the
Are formed. The photoresist 2 is a case of a holographic diffraction grating, and in the case of a replica diffraction grating, the portion of the photoresist 2 is formed of a thermosetting resin layer such as an epoxy resin. In the holographic diffraction grating in which the groove is directly formed on the substrate 1, 2 is made of the same material as the substrate 1.

FIG. 2 shows a supporting structure of the diffraction grating main body, in which the diffraction grating main body is supported by the rotating shaft 5 projecting from the back surface of the substrate 1 perpendicularly to the grating surface so that the diffraction grating main body can be rotated 180 degrees in the grating surface. And the blaze angle of the lattice is θ ₁ , θ due to this inversion.
_It can be switched to 2 or 2, and at the same time, the light reflection film on the surface can be switched to 2 or ₁ of A ₁ and A ₂ .

As a specific example, when the lattice constant is 1600 lines / mm, the blaze angle is θ ₁ = 21 °, the blaze wavelength is 448 nm, and the θ ₂ = 45 ° is 884.
nm, which are suitable conditions in the visible region and near infrared region, respectively. Also, the reflectance of aluminum is high in the visible infrared region, and the reflectance of aluminum sharply decreases in the extremely short ultraviolet region (1000 Å or less), but gold has a relatively high reflectance,
When it is desired to cover the visible or near-infrared region from the ultra short ultraviolet, these materials are selected as the light reflecting coatings A ₁ and A ₂ .

(Effects of the Invention) As described above, the diffraction grating according to the present invention forms a light-reflecting film made of different substances on both slopes of a triangular groove formed of two slopes having different tilt angles, and also has a grating surface. Since it is pivotally supported in 180 degree inversion switching inside, the inclination angle of both slopes can be used as the blaze angle, so that the wavelength range previously covered by two diffraction gratings can be covered by one. In addition, the structure is extremely simple compared to the method in which two diffraction gratings are slid alternately and the method in which they are replaced, because the rotation axis perpendicular to the grating surface is used for inversion. Can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a main body of a diffraction grating according to the present invention, FIG. 2 is a perspective view showing a supporting structure of the same, and FIG. 3 is a perspective view of a conventional example. 1 ... Substrate, 2 ... Photoresist, 3,4 ... Slope, 5 ...
… Rotation axis, A ₁ , A ₂ …… Light-reflecting film, θ ₁ , θ ₂ …… Inclination angle.

Claims (1)

[Claims] 1. An Echelette type reflection diffraction grating having a lattice surface formed by engraving a large number of triangular grooves formed by two inclined surfaces having different inclination angles in parallel with each other by a rotation axis perpendicular to the lattice surface.
A diffraction grating spectroscope that is pivotally supported so that it can be inverted 180 degrees.