JPH02291939A - Apparatus for measuring diffraction efficiency of diffraction grating - Google Patents

Abstract

PURPOSE:To make it possible to measure the diffraction efficiency of a diffraction grating highly accurately by one operation by providing a slide mirror which is slidden along an optical axis, a rotary stage which supports the diffraction grating to be measured and is rotated, and a switching mirror. CONSTITUTION:A diffraction grating 3 to be measured is arranged on a rotary stage 10. The light from a light source is reflected with a slide mirror 2 and a switching mirror 4 through a fixed mirror 1 as shown with a continuous line. The light is adjusted and measured with a photoelectric detector 12 so that the light intensity becomes 100. Then, the mirror 2 is moved along the optical axis from the mirror 1. The light from the mirror 1 is reflected to the grating 3 at a position 2'. The grating 3 generates 0-order diffracted light 20, first-order diffracted light 21.... At this time, the first-order diffracted light 21 becomes the optical axis light 22. The light 22 is reflected at a position 4' and reaches the detector 12. The light intensity is measured as the diffraction efficiency. The light intensity is measured as the ratio between the light intensity which is measured through the path of the continuous line and the light intensity which is measured through the path of a dotted line. Since the lengths of the light paths are equal, the diffraction efficiency of the grating 3 can be measured highly accurately by one operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diffraction efficiency measuring device for determining the diffraction efficiency of a diffraction grating.

[Conventional technology]

Diffraction efficiency is one of the important indicators regarding the performance of a diffraction grating, and a conventional method of determining diffraction efficiency that is generally used will be explained with reference to FIG. Here, the diffraction efficiency refers to the ratio of the intensity of the diffracted light to the incident light of the diffraction grating.

In FIG. 2, 5 is an entrance slit, 1 and 11 are fixed mirrors, 6 is a switching collimator mirror, 3 is a diffraction grating to be measured, 8 is an exit slit, and these constitute a so-called Littrow type monochromator. The switching collimator mirror 6 can be switched to be located on the side of the measured grating 3 constituting the monochromator, as shown by the dotted line, or on the reference mirror side, as shown by the solid line. In the determination, the switching collimator 6 is first set on the reference mirror side.The light passing through the entrance slit 5 passes through the fixed mirror 1, the switching collimator mirror 6, and is projected onto the λ quasi-mirror 7. The light reflected by the reference mirror passes through the switching collimator mirror 6, fixed mirror 11, and exit slit 8 again and is detected by the photoelectric detector 12.If the output of the photoelectric detector 12 at this time is 100, then the switching The collimator mirror 6 is switched to the side of the diffraction grating 3 to be measured, and the diffraction grating 3 to be measured is rotated to detect the photoelectric detector 12 at each wavelength order.
The output reading is the diffraction efficiency and is expressed in %.

The diffraction efficiency measured in this manner is a measurement value when the reflectance of the reference mirror 7 is taken as 100%, and is called relative diffraction efficiency. However, in reality, the reflectance of this reference mirror is not necessarily 100%, so the reflectance of the reference mirror must be determined separately.

As a method for measuring the reflectance of such a reference mirror, the example shown in FIG. 3 and the example shown in FIG. 4 are known, for example, from Japanese Unexamined Utility Model Publication No. 61-158844.

In FIG. 3, the switching mirror 4 slides to the position indicated by the solid line, and the light that has passed through the fixed mirrors 1 and 11 goes directly from the switching mirror 4 to the photoelectric detector 12 as shown in the figure, and the output of the photoelectric detector 12 at this time is 100 shall be. Next, the switching mirror 4 rotates and slides to the position 4' indicated by the dotted line, and after the light that has passed through the fixed mirrors 1 and 11 is reflected by the mirror 9 to be measured, it heads toward the Kyuden detector 12 from the switching mirror position 4'. If you read the output of the photoelectric detector 12, the standard Mi? can measure the reflectance of This measurement method based on the fixed method does not use a reference mirror, so it is called absolute reflectance. However, in the measurement method shown in FIG. 3, since the optical path length changes by switching the switching mirror 4, highly accurate measurement cannot be expected.

In the method of measuring the absolute reflectance of the reference mirror shown in FIG. 4, even if the position of the slide mirror 2 is moved as shown in 2 and 2' in the figure and the optical path changes as shown by the solid line and dotted line, the optical path length remains unchanged.

In other words, when the slide mirror 2 and switching mirror 4 are arranged as shown in the figure and the light travels as shown by the solid line, and when the slide mirror 2 is placed at the 2' position and the switching mirror 4 is placed at the 4'' position as shown in the figure, the light travels as shown by the dotted line. The absolute reflectance can be determined by measuring the light traveling as shown in FIG.

As described above, the conventional measurement of the diffraction efficiency of a diffraction grating is carried out in advance using a measuring device as shown in FIGS. 3 and 4, as described above. (After measuring the absolute reflectance of the quasi-mirror, the diffraction efficiency was measured using the apparatus shown in FIG. 2, which required two steps and was very inefficient.

[The problem that the invention attempts to solve]

An object of the present invention is to provide an efficient apparatus for measuring the diffraction efficiency of a diffraction grating that solves these problems.

[Effect]

When the sliding mirror is moved to the first sliding position,
Since the same slide mirror is used and the optical path length is the same when moving to the second slide position, the diffraction efficiency of the diffraction grating can be measured with high accuracy in a single operation.

〔Example〕

An embodiment of the present invention will be described using FIG. The diffraction grating 3 to be measured is placed on a rotatable rotation stage 10, and is rotated according to the order of the diffracted light of the diffraction grating 3 to be measured. The light from the light source is reflected by the fixed mirror 1, then reflected by the slide mirror 2 and then by the switching mirror 4 as shown by the solid line, and reaches the photoelectric detector 12. regulated and measured. Next, the slide mirror 2 is moved along the direction of the light from the fixed mirror 1 to a position 2', and at the position 2', the light from the fixed mirror 1 is reflected onto the diffraction grating 3 as shown by the dotted line. The diffraction grating 3 has O-order light 2o, 1
Diffracted light of the order light 21... is generated. The diffracted light selected as the optical axis light 22 from the diffraction grating 3 to the switching mirror 4 is selected depending on the rotation angle of the rotary stage 10. In the figure, the primary light 21 becomes the optical axis light, is reflected at the switched position 4' of the switching mirror 4, reaches the photoelectric detector 12, and its light intensity is measured as the diffraction efficiency. This light intensity is measured as the ratio of the light intensity when measured via the dotted line route to the light intensity when measured via the solid line route in the figure, and is therefore expressed as a percentage.

In the figure, the slide mirror 2 slides along the optical axis from the fixed mirror 1 without changing its angle, so the optical axis of the light from the slide mirror 2 to the switching mirror 4 and the position 2' of the slide mirror 2 to the diffraction grating 3. The optical axes of the light leading to are parallel. Further, the optical axis from the fixed mirror 1 and the optical axis of the diffracted light from the diffraction grating 3 to the position 4' of the switching mirror 4 are parallel.

Note that the fixed mirror 1 is not necessarily necessary in the present invention, and the light from the light source is directly transmitted to the slide mirror 2 or 2'.
There is no difference in the effect of the present invention even if it is introduced in In the best embodiment of the present invention, two of the slide mirrors 2
The optical path length of the light from 2' to 2 and the optical path length of the reflected light from 2' of the slide mirror 2 to the diffraction grating 3 are equal. In other words, the optical path length of the diffracted light from the diffraction grating 3 through the switching mirror 4'' to the optical detector 12 is equal to the optical path length of the reflected light from the slide mirror 2 through the switching mirror 4 to the photoelectric detector 12. .At this time, the optical axis path 2' -2
The shape made by -4 and 2'-3-4' is a rhombus. The diffracted light from the diffraction grating 3 is diffusely reflected depending on its diffraction order, and the diffracted light directed toward the switching mirror 4' along the optical axis 22 is very weak, so the photoelectric detector 1 is used based on the difference in optical path length.
The amount of unbalance in the light taken into 2 has a large effect on the measurement accuracy of diffraction efficiency. Therefore, the optical path length is 3-4'-1
When 2 and the optical path length 2-4-12 are equal, the measurement accuracy of the diffraction efficiency of the diffraction grating to be measured can be maximized. An example of application of the present invention is shown in FIG. By connecting a monochromator 31 to the light source of the diffraction efficiency measuring device for a diffraction grating shown in FIG. 1, the diffraction efficiency of each wavelength component can be measured.

Furthermore, if white light is used as a light source, it is possible to determine the diffraction efficiency of a specific wavelength with respect to the total energy of the light source.

〔Effect of the invention〕

The diffraction efficiency measuring device for a diffraction grating of the invention includes a slide mirror that slides along the optical axis from a light source, a rotation stage that supports and rotates the diffraction grating to be measured, and a switching mirror, and a first slide of the slide mirror. The light intensity when the light from the light source reflected at the position is reflected to the photoelectric detector by the switching mirror, and the light from the light source reflected at the second slide position of the slide mirror is determined by the trained target. Since the ratio of the light diffracted by the diffraction grating and guided to the switched switching mirror is taken, the diffraction efficiency of the diffraction grating can be measured with high precision in a single operation.

[Brief explanation of the drawing]

Figure 1 shows an embodiment of the diffraction efficiency measuring device for a diffraction grating according to the present invention. FIG. 2 shows a conventional example of a diffraction efficiency measuring device for a diffraction grating. FIGS. 3 and 4 show a conventional example of a measuring device based on a device for measuring the diffraction efficiency of a diffraction grating. FIG. 5 shows an example of an application of the apparatus for determining the diffraction efficiency 81 of a diffraction grating according to the present invention. 1, 11...Fixed mirror 2, 2'...Sliding mirror 3...Diffraction grating to be measured 4, 4'...Switching mirror 5, 8...Slit 6...Switching collimator mirror 7・
・Reference mirror 9 ... Mirror to be measured 10 ... Rotation stage 20 ... 0th order diffracted light 21 ... 1st order diffracted light 22 ... Optical axis light ... Diffraction efficiency measuring device ... Monochromator No. 1 Figure 1.11... Fixed mirror 3... Diffraction grating 6... Collimator mirror 7...
...Reference mirror coverage measuring device

Claims (1)

[Claims] 1. A slide mirror that slides along the optical axis from the light source and moves to first and second slide positions, and a light source that is reflected by the slide mirror at the first slide position. It consists of a switching mirror that reflects light to a photoelectric detector, and a rotation stage that rotates on which a diffraction grating to be measured is mounted, and the slide mirror reflects light from the light source reflected at the second slide position to the target. A diffraction efficiency measurement device for a diffraction grating, characterized in that the diffraction grating is diffracted by a measurement diffraction grating, then reflected by the switched mirror and guided to the photoelectric detector. 2. Diffraction according to claim 1, wherein the optical path length from the second sliding position of the slide mirror to the first sliding position is equal to the optical path length from the second sliding position to the measured diffraction grating. Grating diffraction efficiency measuring device. 3. The diffraction efficiency measuring device for a diffraction grating according to claim 1, wherein a monochromator is arranged as the light source and the diffraction efficiency of each wavelength of the diffraction grating is measured. 4. The diffraction efficiency measuring device for a diffraction grating according to claim 1, wherein a white light source is arranged as the light source and the diffraction efficiency of a specific wavelength component with respect to the total energy from the diffraction grating is measured. 5. The optical path from the second slide position to the first slide position and the optical path from the diffraction grating to the switching mirror are parallel, and the optical path from the second slide position to the switching mirror and the optical path from the second slide position to the switching mirror are parallel. 2. The diffraction efficiency measuring device for a diffraction grating according to claim 1, wherein the optical paths from the first slide position to the diffraction grating are parallel. 6. An optical path from the second slide position to the first slide position, an optical path from the diffraction grating to the switching mirror, an optical path from the second slide position to the switching mirror, and the first slide. 2. The diffraction efficiency measuring device for a diffraction grating according to claim 1, wherein an optical path from a position to said diffraction grating forms a rhombus.