JPH07243967A - Optical path length adjuster - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain an inexpensive optical path length adjusting device which does not cause a deviation of the optical axis without restricting a light ray traveling in an optical path to be adjusted. [Structure] Two parallel plane plates 103 and 104, which are transparent or highly transparent to incident light and are optically isotropic substances, are arranged such that a plane perpendicular to an optical axis 101 of incident light is a plane of symmetry 105. Install.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical path length adjusting device for use in an optical instrument such as an interferometer which requires adjustment of the optical path length.

[0002]

2. Description of the Related Art A conventional technique for adjusting an optical path length in an optical device will be described with reference to the drawings. Figure 4 shows the simplest method of the above technology.
Reference numeral 01 is a light ray traveling on the optical path to be adjusted, 402 is a plane-parallel plate made of a substance transparent or highly transmissive to the wavelength of the light ray, and 403 is a ray of light passing through the plane-parallel plate 402. The optical path length can be adjusted by adjusting the angle formed by the light beam 401 and the plane-parallel plate 402. However, although the above method has the advantage of being simple and inexpensive, the optical path length is adjusted by the angle between the light ray 401 and the plane parallel plate 402, as is apparent from FIG. Ray 4 before and after passing
01 and light ray 403 do not match. That is, there is a serious drawback that the optical axis is displaced.

FIG. 5 is a diagram for explaining another technique conventionally used for adjusting the optical path length. Reference numeral 501 is a light ray traveling on the optical path to be adjusted, 502 and 503 are wedge-shaped objects of a uniaxial medium, and 504 is a plane parallel plate of a uniaxial medium. The wedge-shaped object 503 and the plane-parallel plate 504 are made so that the anisotropic axes coincide with each other, and the wedge-shaped object 502 is made so that the anisotropy axis is orthogonal to the wedge-shaped object 503 and the plane-parallel plate 504. ing. The optical path length is adjusted by moving the wedge-shaped object 502. According to the above method, the deviation of the optical axis does not occur. However, the uniaxial medium is expensive and the processing is complicated, and the overall cost is extremely high. further,
The condition is that the light ray 501 is linearly polarized light that makes a specific angle with the anisotropic axis.

[0004]

As described above, in the prior art, the method in which the light beam traveling in the optical path to be adjusted is not restricted and the device is inexpensive has a serious drawback in that the optical axis shifts. However, the method in which the optical axis deviation does not occur has a drawback in that severe restrictions are imposed on the light rays traveling along the optical path to be adjusted and the apparatus becomes expensive.

It is an object of the present invention to obtain an optical path length adjusting device which does not cause a deviation of the optical axis and which is an inexpensive device in which there are no restrictions on the light rays traveling along the optical path to be adjusted.

[0006]

The above-mentioned object is to provide two parallel plane plates made of an optically isotropic substance, which are transparent or have a high transmittance with respect to the wavelength of the incident light, to the light of the incident light. It is achieved by arranging the plane perpendicular to the axis as a plane of symmetry. Further, the parallel plane plate has a single-layer or multi-layer dielectric thin film formed on the surface thereof, and further has means for detecting the position on the optical axis, and the means has a wavelength of incident light in a visible region or an ultraviolet region. Which is achieved by having a mark such as a pattern on the surface, or the means is a two-dimensional photoelectric conversion device provided in the optical path. It is achieved by Further, it is achieved by having a mechanism capable of inserting or removing the optical axis position detecting means in the optical path.

[0007]

According to the present invention, two parallel plane plates made of an optically isotropic substance are installed so that a plane perpendicular to the optical axis is a plane of symmetry in the optical path for adjusting the optical path length. With this as a basic configuration, the optical path deviated from the optical axis by one of the parallel plane plates is returned to the original optical axis by the other parallel plane plate, so that the optical path length adjusting device can be obtained with an extremely simple configuration at low cost. Moreover, since the two parallel plane plates are made of an optically isotropic material, there is no restriction on the light rays traveling in the optical path to be adjusted. Further, since the two parallel plane plates are installed so as to face each other so that the plane perpendicular to the optical path to be adjusted is a plane of symmetry, the optical axis is not displaced. Further, the surface reflected light of the parallel plane plate that becomes stray light is prevented by forming a non-reflection film on the surface of the parallel plane plate, and an optical axis detector for confirming the optical axis position,
Since a mechanism that can be inserted into or removed from the optical path is provided, it is possible to easily confirm the coincidence of the optical axes.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram illustrating a first embodiment of an optical path length adjusting device according to the present invention, FIG. 2 is a diagram illustrating a second embodiment of the present invention,
FIG. 3 is a diagram for explaining the third embodiment of the present invention. In FIG. 1 showing a first embodiment of the present invention, 101 is an optical axis, 10
2 is a light ray traveling along the optical axis 101, 103 and 104 are plane-parallel plates made of a substance that is optically isotropic and transparent or highly transparent to the wavelength of the light ray, and 105 is a plane perpendicular to the optical axis 101. The parallel plane plates 103 and 104
Are installed so as to be plane-symmetric with respect to a plane 105 perpendicular to the optical axis 101, and the plane 105 perpendicular to the optical axis is the plane of symmetry of the parallel plane plates 103 and 104. Note that 106a, 106b, 106c, and 106d indicate dielectric multilayer films, respectively.

In the present apparatus constructed as described above, the light beam 102 along the optical axis 101 has one parallel plane plate 103.
The optical axis 101 deviates from the optical axis 101 at the time of passing, but the original optical axis 10 becomes
Go up one. That is, no deviation of the optical axis occurs before and after this device. Further, since the plane-parallel plates 103 and 104 are made of an optically isotropic material, the light beam 102 does not need to be linearly polarized. The optical path length can be adjusted by adjusting the angle formed by the planes of parallelism 103 and 104 with the plane of symmetry 105 or the angle formed with the optical axis 101 while maintaining the symmetry with respect to the plane of symmetry 105. Further, the surface reflected light of the parallel plane plates 103 and 104, which becomes stray light that must be eliminated in the optical device, is the dielectric multilayer films 106a to 106d.
The non-reflective film prevents the occurrence.

The second embodiment of the present invention shown in FIG. 2 is an apparatus considering the convenience of checking the optical axis when actually adjusting the optical path length. 201 is an optical axis, 202 is a light ray traveling on the optical axis 201,
Reference numerals 203 and 204 denote parallel plane plates having a dielectric multilayer film formed on the surface thereof, 205 is a scattering glass flat glass plate, 206 is a mark such as a pattern provided on the surface of the glass slide plate 205, and 20.
7 is a drawer rod connected to the glass slide 205,
Reference numerals a and 208b are fixing pieces fixed to the drawer rod 207, and reference numerals 209a and 209b are fixing pins. The optical path length adjusting function of the parallel plane plates 203 and 204 is the same as that described in the first embodiment.

The optical axis position confirming operation, which is an important function of this embodiment, will be described below. First, the pull-out rod 207 is pushed in until the fixing piece 208a hits the fixing pin 209a. As a result, the glass slide plate 205 comes to be positioned in the optical path. First, the position of the light beam 202 on the glass slide 205 is confirmed using the mark 206 in the state where the two parallel plane plates 203 and 204 are not provided. Next,
The parallel plane plates 203 and 204 are installed by adjusting the angle formed with the optical axis 201 so that a predetermined optical path length can be obtained. At this time, if the plane-parallel plates 203 and 204 are not plane-symmetric with respect to the plane perpendicular to the optical axis 201 as described in the first embodiment, the light beam 2 on the glass slide 205 will be described.
The position 02 is displaced from the initial position. If there is no such displacement, the plane-parallel plates 203 and 204 are correctly installed. After confirming the optical axis position, the pull-out rod 20 is pushed until the fixing piece 208b hits the fixing pin 209b.
Pull out 7. The sliding glass plate 205 connected to the pull-out rod 207 is excluded from the optical path and does not hinder the travel of the light beam 202.

In this embodiment, the frosted glass plate 205 is used as the optical axis position confirmation plate in the optical axis position detection means. However, the position confirmation plate is not limited to the frosted glass plate, and a paper plate having fine irregularities on the surface is used. Any object such as a metal plate or the like that reflects scattered light may be used. Further, when the wavelength of the light ray 202 is in the ultraviolet region, an object that emits fluorescence, for example, a paper plate containing a fluorescent dye, or a metal plate coated with a fluorescent substance such as salicylic acid may be used.

In FIG. 3 showing the third embodiment of the present invention,
301 is an optical axis, 302 is a light ray traveling on the optical axis 301, 303
Reference numerals 304 and 304 denote parallel plane plates having a dielectric multilayer film formed on the surface thereof, and 305 denotes a two-dimensional position sensor as a two-dimensional photoelectric conversion device. The optical path length adjusting function of the plane parallel plates 303 and 304 is the same as that described in the first embodiment.
An important function in this embodiment is to electrically confirm the position of the optical axis, and the two-dimensional position sensor 305 is positioned in the optical path length as described above. Insertion or exclusion in the optical path is performed by the method as shown in the embodiment. Next, the plane parallel plates 303 and 304 are installed by adjusting the angle formed with the optical axis 301 so that a predetermined optical path length can be obtained. At this time, if the parallel plane plates 303 and 304 are not plane-symmetric with respect to the plane perpendicular to the optical axis 301 as described in the first embodiment, the light beam 30 on the two-dimensional position sensor 305 will be described.
The position of 2 is displaced from the initial position. Without this displacement, the plane parallel plates 303 and 304 are correctly positioned. If the two-dimensional position sensor 305 is removed from the optical path by the method shown in the second embodiment after confirming the optical axis position, the traveling of the light beam 302 is not hindered. In this embodiment, the two-dimensional position sensor 305 is used to confirm the optical axis position, but any two-dimensional CCD device or the like that can electrically detect the light spot position may be used.

In each of the above embodiments, a dielectric multilayer film is formed on the surface in order to prevent the reflected light from the surface of the plane-parallel plate.
Not limited to this, it may be a dielectric single layer film.

[0015]

As described above, the optical path length adjusting device according to the present invention is transparent or has high transparency to the wavelength of incident light,
By disposing two parallel plane plates made of an optically isotropic material so that a plane perpendicular to the optical axis of the incident light is a plane of symmetry, the optical axis is not displaced, and ,
Since the plane-parallel plate is an optically isotropic substance, it is not necessary that the light ray traveling along the optical axis be linearly polarized light. Further, it has a simple structure and can be made inexpensive in terms of material and processing. Further, it is possible to confirm the position of the optical axis without hindering the progress of the light beam, and since the surface of the plane-parallel plate is subjected to antireflection treatment, stray light does not occur.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a first embodiment of an optical path length adjusting device according to the present invention.

FIG. 2 is a diagram illustrating a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a third embodiment of the present invention.

FIG. 4 is a diagram showing the simplest example of a conventional optical path length adjusting device.

FIG. 5 is a diagram showing another example of a conventional optical path length adjusting device.

[Explanation of symbols]

101, 201, 301 Optical axes 103, 104, 203, 204, 303, 304
Parallel plane plate 105 Symmetrical plane 106a, 106b, 106c, 106d Dielectric film 205 Object having a scattering or fluorescent plane (frosted glass) 206 Pattern 305 Two-dimensional photoelectric conversion device (two-dimensional position sensor)

Claims (6)

[Claims] 1. A pair of plane-parallel plates, which are transparent or highly transparent to the wavelength of incident light and are made of an optically isotropic material, and a plane perpendicular to the optical axis of the incident light is a plane of symmetry. An optical path length adjustment device installed as follows. 2. The optical path length adjusting device according to claim 1, wherein the parallel plane plate has a single-layer or multi-layer dielectric thin film formed on the surface thereof. 3. The optical path length adjusting device according to claim 1, wherein said optical axis has means for detecting its position. 4. The means for detecting the position of the optical axis has a scattering flat surface when the wavelength of the incident light is in the visible range, and is fluorescent when the wavelength of the incident light is in the ultraviolet range. 4. The optical path length adjusting device according to claim 3, wherein the object has a flat surface, and the flat surface has a mark. 5. The optical path length adjusting device according to claim 3, wherein the means for detecting the position of the optical axis is a two-dimensional photoelectric conversion device provided in the optical path. 6. The optical path length adjusting device according to claim 3, wherein the means for detecting the position of the optical axis has a mechanism for inserting it in the optical path or removing it from the optical path.