JPH03226701A - Polarizing prism - Google Patents

Abstract

PURPOSE:To simultaneously satisfy wide angles of view and to obtain nearly symmetrical angles of view in any of wavelength regions by filling the joint part of the prism formed by joining two triangular prisms consisting of refractive materials with oil having the refractive index smaller than the refractive indices of either of the ordinary rays and extraordinary rays of a double refractive material. CONSTITUTION:The polarizing prism is usually formed by joining the two triangular prisms made of calcite with an adhesive or providing an air layer and joining these prisms. The main refractive indices nomega, nepsilon to the ordinary rays and extraordinary rays of the calcite attain the values of about 1.7 and about 1.5, respectively, in a wavelength region from UV to IR rays. The joint part is then filled with such oil which has the refractive index nc of (1<)nc<nomega, nepsilon and allows the transmission of light from the UV to IR light. The prism is usable from the UV region to the IR region in this way and in addition, the always symmetrical angles of view of >=25 deg. are obtd. The prism has excellent versatility and can exhibit sufficient performance with one piece without changing over of the prism even when the prism is used in a spectrophotometer, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polarizing prism for a wide wavelength range used in spectrometers and the like.

[Prior art]

With a fractional degree needle that determines overforce or reflection force illumination, the deviation of the incident likelihood becomes a problem, especially when measuring at oblique incidence. The light that is separated by the diffraction grating becomes circularly polarized light, which varies depending on the wavelength. However, as a measured quantity, the social S wave and P
The key point is to have a transmittance of 8 reflectance for the wave, so for such measurements, a polarizing prism is inserted after the diffraction grating, and the prism is rotated to irradiate the sample with S radiation light or P radiation. Create radiation light. Since the spectrometer and the meter are used to measure ft' in a wide wavelength range from ultraviolet to infrared, such a polarizing prism must have a wide transmission-A wavelength range5 and must also function as a polarizer. In addition, the intensity of the light that has been weakened after being separated by one diffraction grating [In order to use it efficiently without dropping it, it is preferable to have a wide viewing angle. Regarding the viewing angle, as shown in Figure 0, which will be explained according to No. 71m,
Let tβ be the angle formed by the orthogonal coordinate axis t of the dimension, and the angle formed by the X axis and the optical axis. Assuming that the principal refraction for the beam is $t, nω, nB, the apex angle of the prism is 1rs, and the refractive index of the junction is 1rn,
The critical incidence angle Io at which the ordinary nine lines and the abnormal nine lines are totally reflected at the junction
−”e#i is given by the following equation.

5tn1e = cos SW -nsiHaS For the Glan-Thompson prism, which is a representative polarizing prism, β; 90
．． In the Frank Ritter prism, β is 45.

When the refractive index n of the adhesive is 1.43 in a Glan-Thompson prism made of calcite, the wavelength is 589.23. In ■Io==
Adding all terms of the wedge angle S so that it becomes Ie, 8 = 2
3.53K. FIG. 6 shows the wavelength dependence of the viewing angle IO+Ie of this prism. As is clear from this graph, the Glan-Thompson prism has a wavelength of 1
Wide viewing angle of over 20'k over 400 mwm
You can protect your ai. but.

Due to absorption by the adhesive, it has the disadvantage that it does not transmit light at wavelengths of 300 m or less.

A prism that allows light to pass through 9' of 300 mm or less is a Grand-Foucault prism whose joint portion is an air layer. In the Grand-Foucault prism, if we set 3 = 1, the wavelength is 5.
B9.23 am so that Io = I (calculating the rust angle, S = 50.46.

A complete diagram of the wavelength dependence of the viewing angle of this prism is shown in Figure 5. Since the Glan-Foucault prism has no original absorption by the adhesive layer, it can be conveniently used even at wavelengths of 300° or less, but the viewing angle is accordingly narrower than that of the Glantomon prism, at around 8.

In the Glan-Thompson prism as well as in the Glan-Foucault prism, the magnitude of the critical incidence angle of the 4fK line and the extraordinary ray, IO,1, changes with improvement. It becomes an unbalanced asymmetrical shape where it is thick and Ie is small.
are the two principal refractive indices nω and n of calcite that compose the prism
ε summerizes as the wavelength changes, whereas the refractive index of the bonding layer remains constant12) [b due to Ik.

Due to this asymmetry in the viewing angle, even if the viewing angle itself is large, it is not always possible to effectively use the expanded incident ik even if the viewing angle itself is large.

[Problem that the invention seeks to solve]

Polarizing prisms used in spectrometers, etc. are required to have two performances: a wide transmission wavelength range and a wide viewing angle, but there is no conventional polarizing prism that satisfies both of these requirements at the same time. Ta. Grant-Thompson prism with the widest viewing angle! It cannot be used in the wavelength range below 300 iam, and the ability of Glan-2-Cope prisms with a wide transmission wavelength range to widen the viewing angle has a negative impact on the effective use of incident light.

This asymmetry is particularly noticeable in the short wavelength region.

An object of the present invention is to provide a polarizing prism 84# that simultaneously satisfies a wide transmission range and a wide viewing angle, and also has a viewing angle that is almost symmetrical in any wavelength range.

[Means to solve the problem]

One of the present invention O(I prism has a refractive index nc1 of (1() nc(n(ai, nt) in the 7th FllJ)
Fill the joint with an oil that is durable and transparent from ultraviolet to infrared light.

Another uninvented polarizing prism is shown in FIG. 7 as two sets of triangular prisms A and Bl scales.

The joint portion C is made of synthetic quartz.

Between calcite and synthetic quartz, #'i is chemically joined.

[For production]

Polarizing prisms are usually made by joining two triangular calcite prisms with adhesive or by creating an air space. In the wavelength range from ultraviolet to infrared, the principal refractive indices nω and nε of the ordinary ray and the hetero'7i elemental ray of calcite are 1 after fLl and 71tl, respectively.
．． Take a value t around 5.

If the critical angle of incidence that induces total reflection of the ordinary 'yt, S* and extraordinary rays at the interface of the joint is ψ0゜φe as shown in Figure 4, it becomes 51ntpe; - 06, where 11e is the extraordinary ray. The refractive index of n is normally dependent on the angle of incidence, but for Glan-Thompson type prisms n
It may be set as e=n@, nω=1.7. n@81.5, and the refractive index n k of the medium at the junction is 0.1 to 1.5.
The graph of ψ0, ψe, and ψe-ψ0 when changed to ψ0 is shown in the third example.

ψe−ψθ is the angle corresponding to the viewing angle, but i31! ic
1, it can be seen that the larger the refractive index of the joint, the larger the viewing angle. Therefore, Fig. 145.

As is clear from the comparison in Figure 6, the refractive index of the junction nkf
The viewing angle fl when l=1.43 always takes a value t larger than the viewing angle when rl=1.0.

Therefore, if you want to use it in the ultraviolet range, but also want a wide viewing angle, instead of using an adhesive that absorbs in the ultraviolet range above the joint, or a whole air layer with a small refractive index,
Q1: Just like the present invention, the joint can be filled with oil that transmits from ultraviolet light to infrared light and has a refractive index nck such that n(<nω, nt).

On the other hand, in a polarizing prism made of calcite, the refractive index of the junction medium and the wedge angle of the prism are selected so that the extraordinary rays are transmitted because nω>n, and the ordinary rays are totally reflected at the junction and not transmitted.

'x Nine rays In order to cause total reflection at the junction surface, nω〉n must be present, but if the refractive index n of the junction medium approaches the refractive index ne of the heterogeneous ray, it will cause an aggravating polarizing prism. Become. In other words, when n=ne, the polarizing prism becomes a mere uniform medium for extraordinary rays, but for ordinary rays it acts as a polarizing prism with a total reflection surface.

However, the refractive index nk that satisfies KooKFinω>ne=nr
Since there is no adhesive, select the refractive index of the adhesive so that nω>ne (e) n. However, as the value of n, a value as close as possible to n6 was selected, but as shown in No. 31 JK, it is preferable to widen the viewing angle.

Now, the two king refraction y$nω and nε of calcite have wavelength dependence r as shown in the second section. On the other hand, for example, in an air layer, the refractive index is constant at 1.0 at any wavelength.

For this reason, for example, in a Glan-Coe prism, the viewing angle changes depending on the wavelength, and nω, nε and n (= 1.0
The difference with 7 is significant, and the symmetry of the viewing angle becomes extremely distorted in the ultraviolet region.

In order to maintain a wide viewing angle at any wavelength without significantly disturbing the symmetry of the viewing angle, it is desirable that the refractive index of the coupling medium changes depending on the wavelength while satisfying the at, 4no relationship.

Furthermore, it is preferable that the coupling medium transmits % of ultraviolet light.

Therefore, in another aspect of the present invention, synthetic quartz is used as a uniform dispersion medium that satisfies the above conditions. As is clear from Figure 2, the refraction of synthetic quartz "4ns" is always VCn
It changes depending on the wavelength while satisfying the relationship ε_n5(Z). In addition, the transmission wavelength range of synthetic quartz is 160 to 2500 nm.
It extends to. The air layer also has a large refractive index, and unlike adhesives, it also allows ultraviolet light to pass through, so synthetic quartz is suitable as a bonding medium for calcite-based polarized light filters.

[Example 1] A Glan-Thompson prism made of calcite has an adhesive layer with a refractive index n(
The wavelength dependence of the field of view when filled with oil = 1.45 is 1s (shown in AJ, wavelength 589.23-
Wedge angle S'k so that l0==Ie at -
21.32.

In the Glan-Thompson prism, β=90, but the direction of the optical axis is not limited to this.

[Example 2] When the optic axis direction of the calcite nine-sided prism is Glan-Thompson type and the joint part is made of synthetic quartz, the workpiece is 0. I
The wavelength dependence of e and viewing angle ■o+Ie is shown in the first section (B).

Engineering at tIl length 589.23 m-. The wedge angle S is set to 20.26 so that =18.

In the Glan-Thompson type, the direction β of the optical axis is 90, but the direction of the optical axis is not limited to n.
.

[Invention (iD9jJ*) The Glan-Thompson prism has a large viewing angle but does not miss ultraviolet light, and the Grand-Foucault prism allows ultraviolet light to escape but has a small viewing angle. Furthermore, in both cases, the asymmetry of the viewing angle at a wavelength different from the design wavelength cannot be achieved.
Namely.

There has been no conventional polarizing prism that can be used in a wide wavelength range from ultraviolet light to ultraviolet light, and that also has a wide and symmetrical viewing angle.

Therefore, when trying to use a polarizing prism over a wide wavelength range with a nine-dimensional meter, etc., it is necessary to use a polarizing prism according to the wavelength range, such as using a Glan-Foucault prism in the ultraviolet region and a Glan-Thompson prism in the visible to infrared region. It was inevitable.

However, there is also the problem of absorption in the ultraviolet region due to the biased prism invented by X! It is possible to solve the problem of narrow viewing angles caused by two gas layers and the problem of poor viewing angle symmetry all at once.

The polarizing prism of the present invention can be used from the ultraviolet region to the infrared region, and has a symmetrical viewing angle of VC25'' or more, making it more versatile than conventional polarizing prisms.
Even when used in a spectroscopic fimeter, etc., one prism can be used without changing the prism.

[Brief explanation of drawings]

Figure 1) (B) is a graph showing the wavelength dependence of the viewing angle of the polarizing prism of the present invention, Figure 2 is a graph showing the wavelength dependence of the refractive index of calcite, synthetic quartz, etc., and Figure 3 is a graph showing the total reflection. Figure 4 is a graph showing the relationship between the critical incident angle and the refractive index of the junction, Figure 4 is a diagram that fully explains the state of total reflection at the junction surface of the prism, and Figure 5 shows the wavelength dependence of the viewing angle of the Hagelan Phu-Coe prism. Figure 6 is a graph showing the wavelength dependence of the viewing angle of a Glan-Thompson prism, and Figure 7 is a diagram illustrating a polarizing prism in which the optical axis is in a plane perpendicular to the cross section of the prism. Manufactured by Shimazu Co., Ltd. Patent attorney Hatahiko Takeishi. Branch length (4m) Concave 48th layer Tsukuku J 斤Mu Figure 3 Fuki 7 Concave

Claims (2)

[Claims] (1) A prism made by joining two triangular prisms made of birefringent materials, and the joint portion is filled with oil having a refractive index smaller than the refractive index of both the ordinary and extraordinary rays of the birefringent materials. A polarizing prism characterized by: (2) A polarizing prism that is made by optically joining two triangular prisms made of calcite, and characterized in that the joint portion is made of synthetic quartz.