JPH01186902A - Four-beam splitter prism - Google Patents

Abstract

PURPOSE:To simplify and miniaturize the constitution of an optical device by providing a multi-image prism so that it allows only the light, where ordinary and extraordinary rays are synthesized, emitted from a Wollaston prism to pass through and emits polarized light components having oscillation directions which are shifted from oscillation directions of respective rays by pi/8 and are orthogonal to each other. CONSTITUTION:Incident rays as the linear polarized light is separated to extraordinary rays E in the direction of the optical axis of a first crystal body 1 and ordinary rays O orthogonal to rays E when being emitted from the first crystal body 1, and these rays E and O are separated to three components of rays 6-8 when being emitted from a second crystal body 2. Only rays 8 where ordinary rays and extraordinary rays are synthesized out of rays obtained by a Wollaston prism 3 are made incident on a multi-image prism 5 in the succeeding stage to emit ordinary rays 9 and extraordinary rays 10 which are orthogonal to each other and are inclined at 45 deg. to the Y axis, and therefore, four kinds of linearly polarized light whose oscillation directions are shifted from polarization directions by pi/8 are obtained. Since a mobile part to obtain linearly polarity light different in angles is not required, the device is inexpensively constituted.

Description

Detailed Description of the Invention (Industrial Application Field) The valve double-image prism of the present invention, in particular, the double-image prism of the present invention, which emits four linearly polarized lights whose vibration directions differ by π/8 from each other when light is incident on the prism. Regarding beam splitter prisms.

(Prior Art) Conventionally, in an optical device 9 that uses polarized light, such as a polarization interferometer, an optical wavelength meter 1, and a phase difference meter, a birefringent plate or a double-image prism such as a Wallaston prism is used to extract polarized light components. Furthermore, among the above measurement devices, most of the optical wavelength meters and phase difference meters detect and measure linearly polarized light with at least two or more different vibration directions. The number of different linearly polarized lights is increased, and the common method for this purpose is to rotate a birefringent plate using a step motor or the like.

However, the step motor is expensive, and not only does it increase the cost of the device, but it also makes the entire device large, and even if a method that does not require the step motor is used, a birefringent plate is not required. It had the disadvantage that it had to be rotated by an angle of 100 degrees, which required equipment for that purpose.

(Object of the Invention) The present invention was made in view of the increase in size and complexity of measuring instruments as described above, and the accompanying high costs. It is an object of the present invention to simplify and downsize the configuration of the optical device by providing four beam splitter prisms that perform four linear polarization 5[K conversions, each with a different vibration direction.

(Summary of the Invention) In order to achieve the above-mentioned object, the four-beam splitter prism according to the present invention has a predetermined angle in which the main cross section of one crystal body and the main cross section of at least one other crystal body are non-perpendicular. on the rear incident optical axis of a Wallaston prism having
Only the combined light ray of the ordinary ray and extraordinary ray emitted from the Wollaston prism passes through, and the vibration directions of the ordinary ray and the extraordinary ray emitted from the Wollaston prism each move by π/8 and are orthogonal to each other. Phase difference measurement or optical wavelength measurement is performed using a four-beam splitter prism in which a double-image prism is joined or arranged so as to emit a polarized light component having a vibration direction.

(Example) The present invention will be described in detail below based on an example shown in one drawing.

FIG. 1 is a perspective view showing a four-beam splitter prism according to the present invention.

In the same figure, there are two crystals constituting a Wollaston prism 3 having a 1, 2ti, and 3 beam blitz function, and the relative relationship of their optical axes is the ray axis of linearly polarized incident light 4. The plane containing the optical axis of one crystal prism 1 is non-perpendicular to the plane containing the optical axis and the optical axis of the other crystal prism 2, and a double-image prism is arranged after the Wallaston prism 2. 5 are joined or arranged.

The relative relationship between the Wollaston prism and the 'jIi image prism is shown in FIG. 2, where the linearly polarized light 4 incident on the Wollaston prism 3 becomes an ordinary ray 6. extraordinary ray 7
The ordinary ray and the extraordinary ray are separated into a combined light ray 8, but only this ray 8 is set to enter the next stage double-image prism 9, and the other light rays 6 and 7 are set not to enter the double-image prism.

Further, as is clear from FIGS. 1 and 3, the double-image prism is tilted at VC45° in the Y direction about two axes in the X, Y, and Z axes orthogonal coordinate system.

The theory of the four-beam splitter prism constructed in this way will be explained in detail below.

FIG. 4 (at shows the separation state of the light beam when exiting the first crystal body 1 of the Wallaston prism 3, and FIG. 4 (b)
) is a diagram illustrating the emission of light from the second crystal body 2.

That is, when an incident ray of linearly polarized light exits the first crystal body IY, it is separated into an extraordinary ray E in the direction of its optical axis and an ordinary ray 0 perpendicular to this, and when it exits the second crystal body 2, the same As shown in Figure (c), the beam is separated into three components.

Furthermore, when only the light ray 8, which is a combination of the ordinary ray and the extraordinary ray obtained by the Wallaston prism, is incident on the subsequent double-image prism, the light rays are perpendicular to each other and relative to the X-axis direction, as shown in Since the ordinary ray 9 and the extraordinary ray 10 tilted by 45 degrees are emitted, the polarization direction as seen from the right side (A) of FIG. Obtainable.

Next, an optical device using the above-mentioned four-beam splitter prism will be explained.

First, before explaining the optical device of the present invention, the principle of the present invention w4
The 7th phase difference measurement device, which was conventionally used to help
This will be explained briefly using figures.

In the figure, 1 is a light source, 2 is a polarizer, and the light source 11
The emitted light passes through the polarizer and becomes linearly polarized light, and the direction of the vibration vector of the linearly polarized light is the X-axis direction of the x, y, and z-axis orthogonal coordinate system, and the traveling direction of the linearly polarized light is the Z-axis direction. The light source 11 and polarizer 12 are arranged so that A phase plate 13 is disposed on the exit surface side of the polarizer so as to be orthogonal to the kZ axis, and the linearly polarized light incident on the phase plate 13 is output as circularly or elliptically polarized light, and is emitted to the sample 14 at the primary stage. The circularly or elliptically polarized light incident on the sample is transmitted and reflected by the sample, and the transmitted elliptically polarized light is detected by the analyzer 1.
5 and enters the photodetector 16 to measure the intensity of the light.

In the above configuration, the relationship between the light intensity incident on the photodetector 16 and the optical phase difference δ of the sample 14 is determined by the rotation angle θ9 of the phase plate 13 with respect to the two axes of the analyzer 15. The deviation angle fj of the optical axis in the X-axis direction with respect to the X-axis! :
A, the reflectance of the sample for P-polarized light and S-polarized light is r, , r
5.

Furthermore, the phase difference due to reflection from the sample is δ2, and the phase difference of the phase plate is Δ
Then, the intensity of the light incident on the photodetector 16 is determined by the analysis method of the jeans vector as I(θ, A)=rp(X
LS θ-(rp cos θ-rs 5i
ll θ)Sill 2A・5lIIΔ/2ju35in2θ(sin 4 As1nΔ/2ωSδ+si
n 2 A e sinΔ−5inδ) −・−・
...It is expressed as (1). Now, assuming that the deviation angle A of the optical axis of the 9 phase plate is 45°, the equation (1) is ■(θ)=rpCO3(j-(rp cos θ-r
s 811! θ) sin tJ2+ ”” sin 2
θ” 51flΔ” 3141δ ・−・−・(21
becomes.

Furthermore, the rotation angle θ of the analyzer 5 is set to 01=π/2. θ2=π/
4. θ8=0. By setting θ4=-π/4 and substituting them into equation 2), the light intensities It and I obtained at each rotation are obtained.
2. Is, I4 is 11=I(θx)=rs stnΔ/2 −・・・・
・−(3)I 2 = I (θ2)=1/2rp −
1/2(rp-rs)su 7￥/2+ ”'si
nΔ・sinδ ・・・・・・・・・(4) l5=I(
0g ) = r p cos Δ/2 − (5)
I a = I (θ4) = 1/2rp -1/2(r
p-rs) sin A/2-2 sinΔ* sin
δ ・・・・・・・・・(6), so (31, f4
), (51, (From equation 61, the phase difference δ of the sample is expressed as.

That is, the rotation angle θ with respect to the analyzer 5'kZ axis is π
/2. Light intensity obtained by rotating the trap with π/4, O, -π/4 11. It is possible to calculate the phase difference δ of the sample without knowing the phase difference Δ of the phase plate by performing the arithmetic processing in Equation 7) to detect It, Is, and In. As mentioned above, the υ device, which requires a motor etc. to rotate, has the disadvantage of being large and expensive.

In order to eliminate the above-mentioned drawbacks, the phase difference measuring device according to the present invention has a rotating analyzer 15 in the above-mentioned phase difference measuring means as shown in FIG.
0, and photodetectors 16 are installed corresponding to the respective lights emitted from the four beam splitter prisms 20. Accordingly, the rotation angle 0 in equation (1) above is O9.
π/8. −π/8. It becomes π/2.

The phase difference measuring device configured in this manner does not require any moving parts, and therefore can measure phase differences with a simple and inexpensive configuration.

Furthermore, sample 14 fj! :, replacing the phase difference with a phase difference generating element whose generated phase difference is wavelength dependent, measuring the phase difference of the phase difference generating element based on the detected light intensity, and measuring the wavelength of the light source based on the phase difference. It can also be applied to optical wavelength measuring devices.

1. Among the four beam splitter prisms of the present invention, the double-image prism provided at the latter stage is manufactured by Wollaston, 0-Si1.
It is clear that a polarizing beam splitter prism made of a glass prism with a vapor-deposited electrical shield may also be used.

(Effects of the Invention) “Since the present invention is constructed and functions as described above, it is possible to convert linearly polarized light into four linearly polarized lights by inputting it into one optical component, and also convert polarized light into four linearly polarized lights. The optical device used does not require moving parts such as step motors that are necessary to obtain linearly polarized light with different angles of vibration direction, so it can be constructed at low cost and can be easily adjusted. It has a remarkable effect.

[Brief explanation of the drawing]

1 to 3 are diagrams showing a four-beam splitter prism according to the present invention, FIG. 4 is a diagram showing a Wollaston prism having a three-beam splitter function according to the present invention, and FIG. Diagram 6 showing the functions of such a double-image prism
The figure shows the polarization direction of the output light of the four-beam splitter prism according to the present invention, FIG. 7 shows a conventional phase difference measuring device, and FIG. 8 shows a phase difference measuring device according to the present invention. be. 1.2...Crystal, 3...
...Wollaston Prism, 4...
...Linearly polarized light. 5......Double image prism, 6,9...
・・・・・・Different rays, 7.10・・・・・・
...Anomalous rays. 8......Light ray that is a combination of ordinary ray and extraordinary ray, 11...Light source, 12
・－・・・・・・Polarizer, 13・・・・・・・・・
...Phase plate. 14... Sample, 15...
...Analyzer. 16......Photodetector, 20...
...4 beam splitter prism.

Claims (1)

[Scope of Claims] The main cross section of one crystal body and the main cross section of at least one other crystal body are on the rear incident optical axis of a Wollaston prism having a predetermined angle such that the main cross section of at least one other crystal body is a non-perpendicular angle, Only the combined light ray of the ordinary ray and extraordinary ray emitted from the Wollaston prism passes through, and the vibration direction of the ordinary ray or extraordinary ray emitted from the Wollaston prism is π/
1. A four-beam splitter prism characterized in that double-image prisms are joined or arranged so as to emit polarized light components whose vibration directions are perpendicular to each other and whose vibration directions are perpendicular to each other. (2) A method for determining the shift (hereinafter referred to as phase difference) between P-polarized light and S-polarized light that occurs when a sample is irradiated with polarized light, the method comprising:
Linearly polarized light that travels in the Z-axis direction in the Y, Z-axis orthogonal coordinate system and whose vibration vector direction is in the X-axis direction is incident on the phase plate installed with respect to the Z-axis, and is obtained by the input. Irradiating a sample with circularly or elliptically polarized light, inputting reflected light or transmitted light from the sample obtained by the irradiation into the four-beam splitter prism, and measuring the light intensity of the light emitted from the four-beam splitter prism. A phase difference measuring device characterized in that the phase difference of the sample is determined by: (3) A method for measuring the wavelength of light, comprising: means for polarizing light from a light source; and irradiating the polarized light obtained by the means onto a phase difference generating element whose generated phase difference is wavelength dependent;
The reflected light or transmitted light from the generating element obtained by the irradiation is made incident on the four beam splitter prism,
An optical wavelength measuring device characterized in that the phase difference of the phase difference generating element is determined based on the light intensity emitted from the beam splitter prism, and the wavelength of the light source is measured from the phase difference.