JPH02253127A - Method and device for measuring polarized light - Google Patents

Abstract

PURPOSE:To shorten a measuring time and to simplify the constitution of a measuring device itself by almost radially reflecting light made incident from the top side of a cone at a specified incident angle and detecting the intensity of the reflected light at plural specified spots. CONSTITUTION:The light is made incident from the top side of the circular cone 3 at the incident angle 80 deg. and light made incident on each incident surface is reflected corresponding to the incident surface. As a result, the light made incident on the circular one 3 is almost radially reflected. An (xy) plane is irradiated with the reflected light and a part irradiated with the light on the (xy) plane becomes nearly circumferential. When the intensity of the light on the (xy) plane is comparatively low, a thermosensitive paper is used as a light intensity detection member 5 and when the intensity of the light is comparatively high, an acrylic plate is used as the member 5, so that the intensity of the light which irradiates the (xy) plane is detected and the polarized state of the light is measured. Thus, the polarized state is measured in a comparatively short time and the constitution of the polarized light measuring device 1 is comparatively simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a polarization measuring method and a polarization measuring method capable of measuring the polarization state of light.

(Prior art) The polarization state of light can be broadly classified into linear polarization, circular polarization, and elliptical polarization. Conventionally, devices for measuring the polarization state only measure incident light that is vibrating in a predetermined direction. In addition to providing a transmitting polarizer, a light intensity detection device was also provided to detect the intensity of the light that passed through the polarizer. The above polarizer can be rotated 360° via a rotation device.

Therefore, the polarization state of the light can be measured by appropriately operating the rotation device to rotate the polarizer appropriately, and detecting the intensity of the light transmitted through the polarizer at an appropriate rotation angle using a light intensity detection device. It is something that can be done. That is, for example, when the polarizer is rotated by a predetermined angle, or when it is rotated by 180 degrees from the predetermined angle, the highest intensity of light is detected, and 9002700
If the intensity of the light becomes approximately O when it rotates, we know that the light is linearly polarized, and for example, if the intensity of the light remains approximately constant even when the polarizer rotates, then the light is circular. All it takes is that the light is polarized.

(Problem to be Solved by the Invention) However, since the polarization state of the light is measured by rotating the polarizer and detecting the intensity of the light transmitted through the polarizer at each rotation angle, it is difficult to measure the polarization state. There was a problem that it was time consuming and labor intensive.

Furthermore, it is necessary to use a rotation device to rotate the polarizer, which poses a problem in that the configuration of the polarization measuring device itself becomes complicated.

Therefore, in order to solve the above problems, the present invention can measure the polarization state of light in a relatively short time, and
It is an object of the present invention to provide a polarization measurement method and a polarization measurement device that have a relatively simple configuration.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the conventional problems as described above, the present invention provides a polarization measurement method that measures the polarization state of light, and The polarization state of the light is measured by entering the light from the top side of the cone at the corner, reflecting the incident light almost radially, and detecting the intensity of the almost radially reflected light at multiple predetermined locations. It is something.

In addition, the polarization measuring device measures the polarization state of light, and the light is incident at a predetermined angle of incidence, and a cone is provided to reflect the incident light almost radially. A light intensity detection means is provided for detecting the intensity of light reflected by the light.

(Function) In the above configuration, light is made to enter from the top side of the cone at a predetermined angle of incidence. Reflects incident light almost radially. Then, the intensity of the light reflected at the plurality of predetermined locations is detected by the light intensity detection means, and the measurement state of the light is measured from the state of the intensity of the light detected at the plurality of predetermined locations.

(Example) When a cone made of metal such as pure iron is irradiated with light, the P component (the component of the amplitude of the light parallel to the plane of incidence) of the light that is incident at an angle of incidence θ with respect to the plane of incidence is calculated. Let Ap, the S component (the component perpendicular to the plane of incidence of the light amplitude) be As, the P component of the reflected light be Rp, and the S component be Rs, then the formula for the P component is as follows. .

... (1) ... (2) Here, n2 is the birefringence, and the wavelength of light is ]-071m
This is an old calculation.

Then, the relationship between the incident angle θ, the reflectance of the P component, and the reflectance of the S component is graphed based on the formula 1 (+> (2)) as shown in FIG. 3. In this case, the reflectance of the S component is α, the reflectance of the P component is β, and there is a relationship of αβ−025 between the reflectances α and β.

In this example, in order to take advantage of the fact that the difference between the reflectance α of the S component and the reflectance β of the P component is approximately 0.25 when the incident angle is 80', the polarization measuring device]
2] is provided, and the optical axis of the light is made to coincide with the Z axis.

The bipedal cone 3 is made of metal such as pure iron, and the center of the bottom surface of the cone 3 is located at a common origin position on the X, y, and Z axes.

With the above configuration, light is made to enter the cone 3 from the top side at an incident angle of 80'. At this time, perpendicular to the xy plane and Z
Light is incident on a countless number of incident surfaces radially around the axis, and the light incident on each incident surface is reflected according to the incident surface, resulting in the light incident on the cone 3 being almost radial. It can be reflected. The radially reflected light is irradiated onto the xy plane, and the irradiated portion of the light on the xy plane is approximately circumferential.

In order to detect the intensity of the light irradiated on the xy plane,
As shown in FIG. 1, a light intensity detection member 5 such as thermal paper or an acrylic plate is provided on the X37 plane. here,
When the intensity of light is relatively low, thermal paper is used as the light intensity detection member 5, and when the intensity of light is relatively high, an acrylic plate is used as the light intensity detection member 5.

In addition, in order to detect the intensity of the light reflected radially, the optical sensor 7 is rotated freely on the xy plane around the common origin of the y-axis, y-axis, and Z-axis, as shown in FIG. There is no problem even if it is provided in

The operation of this embodiment will be explained based on the above-described configuration.

Light is made to enter the cone 3 from the top side at an incident angle of 80°. The incident light is reflected in a substantially reflective manner, and the reflected light illuminates the xy plane, and the irradiated portion of the light on the xy plane forms a substantially circumferential shape. The polarization state of the light is measured by detecting the intensity of the light irradiating the xy plane with the light intensity detection member 5 or the optical sensor 7.

To specifically explain the measurement of the polarization state of light: (a) The polarization state is linearly polarized light (for example, oscillation in the X direction).
In this case, the light that irradiates on the X-axis is the light that enters the xz plane as the incident plane and is reflected. In other words, the incident light is transmitted to the incident surface (
In this case, it vibrates only in the horizontal direction (X-axis direction) with respect to the xz plane), and the reflectance of the P component is β, so the
The intensity of the light irradiated on the axis is β times the intensity of the incident light.

Similarly, the light that irradiates on the y-axis is light that enters the yz plane as the incident plane and is reflected. In other words, it vibrates only in the direction perpendicular to the incident plane (in this case, the yz plane) (X-axis direction), and the reflectance of the S component is α, so the intensity of the light irradiated on the y-axis is equal to the incident It is α times the intensity of the light.

Therefore, if the intensity of the light irradiated on the y-axis is approximately 0.25 times greater than the intensity of the light irradiated on the X-axis, then the light incident on the cone 3 will be The polarization state can be determined to be linearly polarized light (vibrating in the X-axis direction).

Note that it is not possible to measure only linearly polarized light vibrating in the X-axis direction, but it is also possible to measure linearly polarized light vibrating in a predetermined direction.

(b) When the polarization state is circularly polarized light, consider that circularly polarized light is light that oscillates with the same amplitude in two arbitrary orthogonal directions in a plane perpendicular to the direction in which the light travels. be able to. Therefore, the same S component and P component of light exist on any incident plane, and the intensity of the light irradiating the xy plane is almost equal.

Therefore, if the intensity of the light on the irradiated portion on the xy plane is approximately the same, it can be determined that the light incident on the cone 3 is circularly polarized light.

Note that random polarized light can also be measured in the same way.

(C) When the polarization state is elliptically polarized light, elliptically polarized light is light that vibrates with different amplitudes in two predetermined orthogonal directions in a plane perpendicular to the direction in which the light travels. It can be considered that there is.

Therefore, the S
The component matches the larger amplitude, and the P component matches the smaller amplitude. Then, the light enters the predetermined entrance plane or the entrance plane located at a position rotated 180 degrees around the Z-axis from the predetermined entrance plane, and is reflected, and the intensity of the light that irradiates the xy plane is within the irradiated area on the xy plane. Maximum at .

Further, at the entrance plane located at a position rotated by 90° or 270° around two axes from the above-mentioned predetermined entrance plane, the S component matches the smaller amplitude, and the P component matches the larger amplitude. Then, 9
The intensity of the light incident on the incident surface at a position rotated by 0° or 270° and reflected, and irradiating the Xy plane, is the minimum among the irradiated portions on the xy plane.

Therefore, if the maximum and minimum light intensities are detected at 90° intervals in a substantially circumferential irradiated area on the xy plane, it can be determined that the light incident on the cone 3 is elliptical polarized light. It is something that can be done.

As described above, according to this embodiment, light is incident from the top side of the cone 3 at a predetermined incident angle (for example, 80° in this embodiment), and the intensity of the light irradiated onto the xy plane is Since the polarization state of the light is measured by detecting the intensity of the almost radially reflected light by the light intensity detection member 5 or the optical sensor 7, the conventional polarizer is rotated as appropriate. Therefore, the polarization state can be measured in a relatively short time compared to the case where the polarization state of the light is measured by detecting the intensity of the light transmitted through the polarizer at every predetermined rotation angle.

Furthermore, since the polarization measuring device 1 does not include a polarizer and a rotation device for rotating the polarizer as in the conventional case, the configuration of the polarization measuring device itself is relatively less complicated.

A second embodiment will be described with reference to FIGS. 4 and 5.

In this embodiment, as shown in FIG. 4, a cone 3 made of a material with transmission characteristics, such as zinc selenide, is provided in the xy plane, and light is incident on the cone 3 at Brewster's angle. Therefore, the apex angle of cone 3 is (9
0° - Brewster's angle) x 2.

Now, referring to Figure 5 regarding Brewster's angle,
Figure 5 shows the relationship between the angle of incidence and the reflectance of the S and P components when light with a wavelength of 10 μm is incident on the zinc selenide cone 3.
The reflectance of the component becomes almost 0, and only the reflection of the S component exists. The above-mentioned predetermined angle of incidence is called the Brewster's angle, and in the case of this embodiment, the Brewster's angle is 67.4°. In addition,
In this case, the reflectance of the P component is γ.

Next, the operation of the second embodiment will be explained.

In this embodiment as well, x
The light intensity detection member 5 detects the intensity of the light at the irradiated portion on the y plane.
Alternatively, the polarization state of the light is measured by detecting it with the optical sensor 7.

(a) The polarization state is linearly polarized light (for example, vibration in the X direction)
If , the light irradiating on the X-axis enters the xz plane as the incident plane,
Since it is reflected light and the reflectance of the S component is O,
The light intensity of the irradiated part on the X-axis becomes almost 0, and the light that irradiates on the X-axis enters the yz plane as the incident plane and is reflected light, and the reflectance of the S component is γ, so The intensity of the light irradiating the lens is γ times the intensity of the incident light.

Therefore, the intensity of the light irradiating X-suke'2 is almost 0,
If the intensity of the light irradiating the y-axis 2 is γ times the intensity of the incident light, then the polarization state of the light incident on the cone 3 is linearly polarized (vibrating in the X-axis direction). It is possible to determine the

(b) When the polarization state is circularly polarized light As in the first embodiment, the intensities of the light irradiating the X3' plane in a substantially circumferential manner are substantially equal. Therefore, xy
If the intensity of the light on the irradiated portion on the plane is almost the same, it can be determined whether the polarization state of the light incident on the cone 3 is circularly polarized light. however,
Since the reflection of the P component is almost zero, the intensity of light is smaller than in the first embodiment.

Note that the same applies to the case of randomly polarized light.

(C) Polarization state is elliptical Similar to the first embodiment, the intensity of the light shining on the xy plane substantially circumferentially reaches its maximum and minimum at 90° intervals.

Therefore, the intensity of the light on the irradiated part on the xy plane is 90
If the maximum and minimum light intensity is detected in the °C interval,
It can be determined that the light incident on the cone 3 is elliptically polarized.

As described above, the second embodiment also provides the same effects as the first embodiment.

It should be noted that the present invention is not limited to the description of the above-mentioned embodiments, but can be implemented in various other embodiments by making appropriate changes, such as using an octagonal pyramid, a 10-sided pyramid, etc. instead of the cone 3. It is possible.

[Effects of the Invention] As can be understood from the above description of the embodiments, according to the present invention, light is incident from the top side of a cone at a predetermined angle of incidence, and light is emitted at a plurality of predetermined locations. Since the polarization state of the light is measured by detecting the intensity of the almost radially reflected light through a light intensity detection means, the polarizer is rotated appropriately as in the conventional method, and the polarization state is measured at each predetermined rotation angle. Compared to measuring the polarization state of light by detecting the intensity of light transmitted through a polarizer, the polarization state can be measured in a relatively short time.

Furthermore, since the polarization measuring device does not have a polarizer or a rotation device for rotating the polarizer as in the conventional case, the configuration of the polarization measuring device itself is relatively less complicated.

[Brief explanation of drawings]

The drawings are for explaining embodiments according to the present invention.
The figure is a schematic diagram of a polarization measuring device equipped with a light intensity detection member. FIG. 2 is a schematic diagram of a polarization measuring device equipped with an optical sensor. FIG. 3 is a graph showing the relationship between the incident angle and the reflectance of the P component and the S component. The cone is made of pure iron and the wavelength of the light is 10 μm. FIG. 4 shows a polarization measuring device according to a second embodiment. FIG. 5 is a graph showing the relationship between the incident angle and the reflectance of the P component and the S component. The cone is zinc selenide and the wavelength of light is 10 μm. 1... Polarization measuring device 3... Cone 5... Light intensity detection member 7... Optical sensor agent Patent attorney
Miyoshi Hide Kazushie g! 30°60'80°90' Angle of incidence Figure 3 Figure 4

Claims (2)

[Claims] (1) A polarization measurement method that measures the polarization state of light, in which light is incident from the top side of a cone at a predetermined angle of incidence, and the incident light is reflected almost radially at multiple predetermined points. A polarization measurement method characterized by measuring the polarization state of light by detecting the intensity of light reflected almost radially by the light. (2) A polarization measurement device that measures the polarization state of light, which allows light to enter at a predetermined angle of incidence, and is equipped with a cone to reflect the incident light almost radially, and at multiple predetermined points. 1. A polarization measuring device comprising a light intensity detection means for detecting the intensity of light reflected substantially radially.