JPH08271335A - Diffraction grating, and diffraction grating spectroscope using this diffraction grating - Google Patents

Abstract

PURPOSE: To provide a spectroscope having no astigmatism by using a diffraction grating having a grating pattern recorded and formed by holographic exposure. CONSTITUTION: The grating pattern of a concave diffraction grating 1 having slightly different vertical and horizontal curvatures is formed by holographic exposure. A spectroscope is constituted in such a manner that the image of an incident slit 2 is directly formed on a spectrum image surface by the diffraction grating 1 itself without a collimator mirror. Namely, the part of a line S on a sample 4 is formed on the incident slit 2 by a lens 5. The image of the incident slit 2 is arranged in X-direction every wavelength on an image pickup element 3, the spectrum of each point laid along the line S on the sample 4, for example, a point P on the line S is formed along a line Q on the image pickup element 3. Since this diffraction grating 1 is a toroidal surface-like concave diffraction grating slightly more distorted than a spherical surface, and the grating pattern is formed by holographic exposure, the image can be formed without astigmatism on the end side of the incident slit 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffraction grating spectroscope suitable for spectroscopic measurement of an isometric sample for inspecting the color tone of fabric.

[0002]

2. Description of the Related Art A spectroscope includes a type using a light dispersive element having no image forming property and using a collimator mirror and a camera mirror, and a type using a dispersive element itself without using these mirrors. The type using a collimator mirror or the like has astigmatism because both the collimator mirror and the camera mirror are arranged so as to be inclined from the optical axis. Even in the type using an image-forming diffraction grating, the image forming action of forming the image of the entrance slit at the position of the exit slit is not different from that of a normal mirror, and is used in a state of being tilted from the optical axis as a concave mirror. Astigmatism is inevitable. However, since a single sample is used in ordinary spectroscopic analysis, there is no adverse effect on the resolution even if an astigmatic image extending in the length direction of the slit is formed.

[0003]

In the conventional spectroscope, astigmatism is not a serious problem due to the nature of the object of spectroscopic analysis, but considering surface analysis of planar samples and simultaneous analysis of multiple samples, An image of the planar sample is formed on the entrance slit of the spectroscope, and the distribution of the spectral characteristics along one line of the planar sample is measured. Since the image is formed on the entrance slit, each point in the length direction of the entrance slit needs to be imaged at a corresponding point on the exit slit without astigmatism. Cannot be generous with respect to the astigmatism of the vessel. Therefore, the present invention is intended to provide a spectroscope having no astigmatism by using an imaging diffraction grating.

[0004]

[Means for Solving the Problems] A concave diffraction grating having slightly different vertical and horizontal curvatures is formed by a holographic exposure method, and the diffraction grating is used to scan an image of an entrance slit without a collimator mirror. The spectroscope is configured to be formed directly on the spectral image plane by the diffraction grating itself, and the optimum range of the parameters of the light source arrangement and the arrangement of each part of the spectrograph at the time of recording the grating pattern, that is, the optimum range, that is, the parameter We searched for a range in which the astigmatism of the spectroscope hardly changed even when the spectroscope was changed.

[0005]

Since the present invention is the concave diffraction grating having a toroidal surface shape slightly distorted from the spherical surface, the object point image point relationship is established between each point on the entrance slit and each point on the exit slit.
Such a relationship holds true even for a spherical surface, but since the aspherical surface as described above is used and the grating pattern is formed by the holographic exposure method, the light is emitted without astigmatism not only at the center of the entrance slit but also at the end. An image is formed on the slit.
Since such a diffraction grating is used, it is not necessary to use a collimator mirror or a camera mirror, and each point on the entrance slit can be used as an independent light source for spectral analysis.

[0006]

FIG. 1 shows an embodiment of the spectroscope of the present invention. In the figure, 1 is a diffraction grating, which is the main part of the present invention, 2 is an entrance slit, 3 is a two-dimensional image pickup device placed on the spectrum image plane, and the size is 15 × 15 mm. 4 is the sample and the line S on the sample
Is formed on the entrance slit 2 by the lens 5. The images of the entrance slits 2 are formed on the image pickup device side by side in the x direction in the figure for each wavelength, and the spectral spectrum of each point along the line S on the sample is, for example, the point P on S is the line Q on the image pickup device 3 on the image pickup device 3. Will be exhibited along.

FIG. 2 is a diagram showing various parameters at the time of holographic exposure for obtaining the grating pattern of the diffraction grating 1. In FIG. 1, reference numeral 1 denotes a material of a diffraction grating, and a photosensitive resist layer is provided on the material, and the grating pattern is baked and developed by holographic exposure to perform etching treatment to obtain the diffraction grating in FIG. As shown in the figure, this diffraction grating has a radius of curvature R2 in a plane parallel to the lattice groove, that is, in the yz plane, and a radius of curvature R1 in the xz plane. In FIG. 2, C and D denote the point light sources for exposure, which are obtained by dividing the beam emitted from the laser light source into two and converging the beams at points C and D, respectively, and having a wavelength of 457.93.
nm. Below, the value of each parameter regarding exposure is shown about two examples. In the following numerical values, E + 1 after the numerical value is the numerical value plus 1. (If it's E-2, it's the -2 power)
Means to say. The numerical value regarding the length is in mm, but this may be considered as a relative value. The angle is in degrees.
Further, for reference, the case of setting a parameter apart from the present invention was also examined, and the parameter is shown as a reference example in the third column. Example 1 Example 2 Reference Example R1 1.0295E + 2 1.0657E + 2 1.2462E + 2 R2 1.0252E + 2 1.0529E + 2 1.2254E + 2 γ 2.8054E + 1-1.3201E-1 -2.6551E + 0 rc 1.2007E + 3 1.2000E + 01 .1426E + 3 δ 1.7819E + 1 8.0808E + 0 5.5405E + 0 rd 1.1992E + 3 1.1999E + 3 8.4085E + 2

FIG. 1 shows each parameter of the spectroscope incorporating the diffraction grating manufactured as described above. Regarding the position of the spectral image, the two-dimensional image pickup element in the xz plane, that is, the straight line cut by the image plane is represented by the numerical values of a and b as a linear expression x = az + b on the xz plane. The value of each parameter is shown for the first and second embodiments and the reference example. Example 1 Example 2 Reference Example a-3.4323E + 0-1.6652E + 1-5.5284E + 0 b 3.0913E + 2 1.5304E + 3 6.4834E + 2 ra 1.1448E + 2 1.2339E + 2 1.2590E + 2 α 6.7963E + 0 1.014E + 1 1. 1596E + 1

FIG. 3 shows the wavelength 380n of the spectroscope of the first embodiment.
In the spectral images for three wavelengths of m, 540 nm, and 700 nm, the image plane is developed within a height of 15 mm and a width of 15 mm, and the position of the entrance slit is on the vertical axis, and the shape of the image of each point on the entrance slit is shown. The point image is shown for 11 points (one of them is on the xz plane) arranged above and below the xz plane at 1 mm intervals on the entrance slit. Similarly, FIG. 4 shows the second embodiment and FIG. 5 shows the reference example.

Comparing FIGS. 3, 4 and 5, Examples 1 and 2
It can be seen that there is almost no difference in performance between and. On the other hand, in the reference example, the astigmatism is generally larger than that of the present invention, and the astigmatism is particularly large on the short wavelength side. The values of a and b relating to the arrangement of the imaging surface are greatly different depending on the parameters shown in Examples 1 and 2, but this is between the diffraction grating center and the entrance slit and between the center of the image sensor and the diffraction grating center. This is related to the method of setting the distance between them, and the spectral image plane of Example 2 is closer to the diffraction grating than that of 1. Generally, when the entrance slit position is moved away from the diffraction grating, the spectral image plane approaches the diffraction grating. In other words, a, b, and ra are selection elements of the recorder selected from the requirements on the outer shape of the spectroscope, and even if this changes considerably within the range of the embodiment, other parameters are set within the range of the values of the first and second embodiments. The effect of reducing astigmatism can be obtained by adopting

Comparing Examples 1 and 2, there is almost no difference in effect. This means that there is one best combination point for astigmatism reduction in the range of the values of the parameters shown in Examples 1 and 2. Further, since there is almost no difference in the effect between the first and second embodiments, the object of the present invention is substantially achieved even if each parameter is slightly out of the range of the first and second embodiments. Therefore, in the claims, each parameter has a value with respect to each value of the embodiment, the larger side is rounded up from the fifth digit from the top, and the smaller side is rounded down from the fifth digit. Regarding R1 and R2, if the values are combined in such a way that the values are large and small, the relationship between the curvatures will be reversed, but the horizontal cross-section rate radius R1 of the lattice must be larger than R2. Therefore, the values of R1 / R2 are specified.

[0012]

The diffractive grating of the present invention has an image-forming property and can be constructed without using a collimator mirror or a camera mirror. Therefore, the spectroscope can be structurally simple and can be arranged in the direction of light dispersion. The image of each point on the entrance slit is formed at the corresponding point on the exit slit without any astigmatism in the direction of the right angle, that is, at each point on the entrance / exit slit, so that the sample surface is cut along one line at a time. It has the effect of being able to analyze and to efficiently perform spectroscopic measurement of the entire surface or spectroscopic measurement of a large number of samples.

[Brief description of drawings]

FIG. 1 is a perspective view of a spectroscope according to an embodiment of the present invention.

FIG. 2 is a perspective view of a diffraction grating used in the spectroscope at the time of recording a grating pattern.

FIG. 3 is a diagram of a spectrum image of the first embodiment of the present invention.

FIG. 4 is a diagram of a spectrum image of a second embodiment of the present invention.

FIG. 5 is a spectrum diagram of a spectroscope having different parameter values from the spectroscope of the present invention.

[Explanation of symbols]

 1 Diffraction grating 2 Incident slit 3 Image sensor 4 Sample

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 20, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

Title: Diffraction grating and diffraction grating spectrometer using the same

Claims (2)

[Claims] 1. A diffractive grating in which a grating pattern is recorded and formed by a holographic exposure method, and a radius of curvature R2 in a plane parallel to a lattice groove of the lattice surface and a radius of curvature R in a plane orthogonal to the lattice groove.
1 is R1 = 102.9 to 106.6 R2 = 102.5 to 105.2 R1 / R2 = 1.004 to 1.010 and the exposure wavelength is 458 nm, the diffraction grating center O and the first light source are As the distance rc, the distance rd between the O and the second light source, the separation angle γ between the diffraction grating center normal and the first light source, and the separation angle δ between the diffraction grating normal and the second light source, rc = 1200 to 1201 rd = 1990 to 1200 γ = −0.1320 to 2.806 δ = 8.080 to 18.20 However, the length is a relative value and the angle is a diffraction grating characterized by being degrees. 2. A diffraction grating, an entrance slit, and an exit slit or an imaging device arranged on the spectrum image plane directly formed by the diffraction grating, wherein the diffraction grating according to claim 1 is used. , The parameter of the arrangement of each part of the spectroscope is the distance between the diffraction grating center O and the entrance slit center is ra, the angle of separation from the diffraction grating center normal of the entrance slit is α, and the spectrum image plane is the diffraction grating center normal. When z = axis and an axis orthogonal to z in the light dispersion direction is x-axis and expressed by x = az + b, ra = 114.8 to 123.4 a = -3.432 to -16.66 b = 309.1. The diffraction grating spectroscope using the diffraction grating according to claim 1, wherein .alpha. = 1531.alpha. = 6.796 to 10.02 (however, the length is a relative value and the angle is degree).