JPH0713004A - Two-wavelength separating element - Google Patents

Abstract

PURPOSE:To obtain the two-wavelength separating element which separates two wavelength lights at a large angle and completely separates them without any light leak. CONSTITUTION:The two-wavelength separating element 1 consists of a triangular prism having a 1st surface S1 on which an incident light consisting of two different wavelength lights lambda1 and lambda2 is made incident, a 2nd surface S2 which projects the light lambda1 having longer wavelength between the two wavelength light made incident from the 1st surface S1 and also totally reflects the light lambda2 having shorter wavelength, and a 3rd surface Ss which projects the shorter- wavelength light lambda2 reflected by the 2nd surface S2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-wavelength separating element for completely separating a light flux composed of light of two different wavelengths at a large angle which has never been seen before.

[0002]

2. Description of the Related Art In the measurement using a two-wavelength interferometer,
Finally, a means for separating the two-wavelength light into single-wavelength light is required. Conventionally, as such a two-wavelength separating means,
A dichroic mirror or a dispersion prism that utilizes the interference of light by an optical thin film has been used. Figure 3
FIG. 3 shows a case where two wavelength lights (λ _a > λ _b ) of wavelength λ _a and wavelength λ _b are separated using a conventional dispersion prism made of heavy flint glass.

Λ _a = 1014 nm, λ _b = 546.1 n
m, the refractive index for each wavelength is n _a = 1.
70338, n _b = 1.73432. Incident angle θ ₀
= 60.13 °, when two-wavelength light enters the dispersion prism, the deviation angles of the wavelength lights λ _a and λ _b at the time of exit are δ _a = 5
6.86 °, δ _b = 60.26 °, and the separation angle Δ is Δ
= 3.4 °.

[0004]

However, in the prior art as described above, the dispersive prism can separate the two wavelength lights at a small angle. Therefore, there is a problem that the entire apparatus becomes large in size, for example, by providing an optical system to guide each detection system after separation.

Further, since the dichroic mirror reflects light in a specific wavelength region and transmits other light, it can be separated at a large angle. However, one light must be mixed with the other and leaked. Therefore, it was not possible to completely separate the two-wavelength light.

It is an object of the present invention to solve the above problems and to obtain a two-wavelength separation element which can separate two-wavelength light at a large angle and can completely separate light without leakage of light.

[0007]

In order to achieve the above object, in the two-wavelength separation element according to the invention described in claim 1,
A first prism that separates one wavelength light from the other wavelength light with respect to incident light composed of two different wavelength lights is provided. The triangular prism is configured such that the two-wavelength light enters the prism. Surface, a second surface that emits the longer wavelength one of the two wavelength light incident from the first surface and totally reflects the shorter wavelength light, and the second surface that is totally reflected by the second surface. And a third surface for emitting light of shorter wavelength.

[0008]

In the present invention, it is a two-wavelength separation element composed of a triangular prism, and one of the two-wavelength light entering the prism on the first surface of the triangular prism is the one having the longer wavelength on the second surface. The light having the shorter wavelength is totally reflected, and the light having the shorter wavelength, which is totally reflected by the second surface on the third surface, is emitted.

Since there is dispersion in the refractive index of the prism, the shorter wavelength of the two wavelength light incident from the first surface is more refracted. Therefore, even if the short-wavelength light is set to be totally reflected by the second surface, the incident angle of the long-wavelength light on the second surface is equal to or less than the total reflection angle, and the light is emitted outside the prism. It will be done.

Therefore, the long-wavelength light emitted from the second surface and the short-wavelength light totally reflected from the second surface and emitted from the third surface form a large angle. Thus, according to the two-wavelength separation element of the present invention, two-wavelength light can be separated at a large angle and completely.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention is shown below in FIG. In the present embodiment, the apex angles α = 60 ° and β = which are two wavelength separation elements
Triangular prism 1 made of 90 ° heavy flint glass
Two-wave dimming with wavelength λ ₁ and wavelength λ ₂ (λ ₁ > λ ₂ )
It shows the case of separating.

First, the total reflection angle θ _c is _{calculated as} follows: na · sin θ = n _b
= 1 (n _a: the refractive index of the prism, n _b: refractive index of air)
Therefore, it is given by the following formula. ^{_{θ c = sin -1 (1 /}} n a) where lambda ₁ = 1014 nm, when the lambda ₂ = 546.1 nm, the total reflection angle for each wavelength, θ _c1 = 3
5.95 °, θ _c2 = 35.21 °, and the incident angle on the first surface S ₁ for the short wavelength light of wavelength λ ₂ to be totally reflected by the second surface S ₂ of the prism 1 is θ. ₀ = 46.65 °.

[0013] The first incidence angle to the surface S ₁ of the prism 1 theta ₀ =
The two-wavelength light incident at 46.65 ° is transmitted through the prism 1, but due to the dispersion of the prism 1, the short-wavelength light having the wavelength λ ₂ is refracted more. The short-wavelength light is incident on the second surface S ₂ at a total reflection angle θ _c2 and is totally reflected here, but the long-wavelength light is incident on the second surface S _{2 at} an angle smaller than the total reflection angle θ _c1. Then, it is ejected to the outside of the prism 1 from here.

Further, the short-wavelength light reflected by the second surface S ₁ is incident on the third surface S ₃ of the prism 1 at an angle of total reflection or less and is emitted from here. ₂ of these wavelengths λ ₁ wavelength λ 2
The deviation angles of the wavelength light are δ ₁ = 62.68 ° and δ ₂ = 12, respectively.
7,58 °, and the separation angle δ becomes δ = 64.9 °. This separation angle is much larger than the separation angle of the conventional dispersion prism.

Next, FIG. 2 shows a case where the prism 1 is used in a two-wavelength interferometer. In FIG. 2, the two-wavelength input beam emitted from the two-wavelength light source 10 is transmitted and reflected by the polarization coating surface 4 of the polarization beam splitter 3 to be separated into a two-wavelength measuring beam 5 and a two-wavelength reference beam 6, respectively. It

The two-wavelength measuring beam 5 enters the movable corner cube prism 7, is reflected, is returned to the polarization beam splitter 3, and is transmitted through the polarization coating surface 4. On the other hand, the two-wavelength reference beam 6 enters the fixed corner cube prism 8, is reflected and returned to the polarization beam splitter 3, is reflected by the polarization coating surface 4, and is combined with the previous two-wavelength measurement beam to form two wavelengths. It becomes the output beam 9.

The two-wavelength output beam is separated into each wavelength light by the triangular prism 1 which is a two-wavelength separation element, and is incident on the measuring instrument 11 and the measuring instrument 12, respectively. In each of the measuring instruments 11 and 12, the phase difference between the reference light component and the length measuring light component, which are linearly polarized light components orthogonal to each other, is measured for each wavelength, and the displacement amount of the movable corner cube prism 7 is obtained. The amount of displacement obtained at each wavelength is input to the two-wavelength calculator 13, where the amount of displacement corrected for air fluctuations is calculated and output.

As described above, when the two-wavelength separating element according to this embodiment is used, the two-wavelength light can be completely separated at a sufficiently large separation angle, and the arrangement of the detection system for each wavelength becomes simple.

In the above embodiment, the case where the two-wavelength separation element according to the present invention is used in the two-wavelength interferometer is shown, but the present invention is not limited to this, and means for separating the two-wavelength light. Needless to say, it can be widely used for optical systems that require the.

[0020]

As described above, the present invention is capable of completely separating two-wavelength light at a large angle. Therefore, unlike the conventional case, the light of one wavelength is not mixed with the light of the other wavelength, and the arrangement of the detection system is not complicated due to the small separation angle of the two-wavelength light. The arrangement is simple, and the entire device can be simplified.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing two-wavelength separation by a two-wavelength separation element (triangular prism) which is an embodiment of the present invention.

FIG. 2 is a schematic optical path diagram illustrating a case where the triangular prism 1 of FIG. 1 is used in a two-wavelength interferometer.

FIG. 3 is an explanatory diagram showing two-wavelength separation by a conventional two-wavelength separation element.

[Explanation of symbols]

 1: Trigonal prism (2 wavelength separation element) 10: 2 wavelength light source 3: Polarizing beam splitter 7: Movable corner cube prism 8: Fixed corner cube prism 11, 12: Phase difference measuring device 13: 2 wavelength calculator

Claims (1)

[Claims] 1. A triangular prism that separates light of one wavelength from light of the other wavelength with respect to incident light of two different wavelength lights, wherein the triangular prism is such that the two-wavelength light is inside the prism. The first surface which is incident on the first surface, the second surface which emits the longer wavelength one of the two wavelength light incident from the first surface and totally reflects the shorter wavelength light, and the second surface And a third surface which emits the totally reflected light of the shorter wavelength.