JPH03284706A - Device for canceling polarization - Google Patents

Abstract

PURPOSE:To make it possible to cancel polarization over a wide wavelength range by providing the polarization canceling device with a polarizer and a total reflection utilizing type 1/4 wavelength element arranged in the 45 deg. azimuth direction from the outgoing light of the polarizer. CONSTITUTION:Four beam splitter type polarizers constitute one block, one straight polarized beam is totally reflected on the slant faces of the insides of cubes constituting the polarizers and straight polarized light rectangular to the totally reflected light transmits the slant faces. The oscillating directions of electric fields of two straight polarized beams are shown by an arrow (a) and double circles. A polarized component oscillated in the direction (a) out of incident light L is straight transmitted through a aggregate block of the beam splitters 1 and a polarized component oscillated in the double-circle mark direction is reflected by the slant faces of respective polarizers 1 and converged upon the straight polarized light of the (a) direction on a common projected optical path L'. An optical path difference of 1/4 wavelength is formed between two polarized components intersecting with each other at right angles by a 1/4 wavelength element 2 in accordance with the difference of phase changes based upon the oscillating direction of totally reflected polarized light on the oblique faces, the element 2 is arranged at an azimuth angle so that the optical axis forms 45 deg. angle with each of the two straight polarized beams on the optical path L' and circularly polarized light is projected from the element 2 in the extended direction of the optical path.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a depolarizer for converting polarized light into normal light (circularly polarized light).

(Prior Art) Some optical measurement devices, such as spectrophotometers using a diffraction grating, have polarized measurement light, that is, the component distribution in the direction of vibration of the light is biased. Light phenomena generally exhibit different behavior depending on the vibration direction of the light, so if the measurement light is polarized, the measurement effect will vary depending on the method of irradiating the sample to be measured or the measurement device, which is extremely inconvenient. It is necessary to keep it. Conventional elements that eliminate polarization include
There were types that utilized the non-polarization properties of diffuse reflection, and types that utilized the polarization properties of crystals such as Cornu-Pseudo depolarizers and Lyot depolarizers.

However, the above-mentioned type that uses diffuse reflection has the disadvantage of very low efficiency, and the Lyot type depolarizer is less effective for light with good wavelength purity.
Pseudo-type depolarizers have the disadvantage that their performance may deteriorate depending on the conditions of use, making them difficult to use.

(Problems to be Solved by the Invention) The present invention aims to provide a depolarization device that is efficient, has good wavelength characteristics, and is easy to use.

(Means for Solving the Problems) A depolarization device was constructed by a polarizer and a quarter-wavelength element utilizing total internal reflection disposed at an azimuth angle of 45° with respect to the light emitted from the polarizer.

Furthermore, as the polarizer, a plurality of beam splitter type polarizers and a reflecting surface are arranged so that two linearly polarized emitted lights whose polarization planes are orthogonal to each other meet on the same optical path;
A depolarizer was constituted by a total reflection type 1/4 wavelength element into which the emitted light was incident at an azimuth angle of 45 degrees.

(Function) If the azimuth of the 1/4 wavelength element is set so that the optical axis of linearly polarized light is 45° with respect to the polarization direction, the linearly polarized light incident on the 1/4 wavelength element becomes circularly polarized light and is transmitted. I'll come. Circularly polarized light has the same effect on various optical devices as ordinary light, which is a mixture of light with various polarization directions, and is effectively depolarized.

A beam splitter type polarizer splits incident light into two linearly polarized lights whose polarization planes are orthogonal to each other, and emits these linearly polarized lights in different directions. By appropriately arranging such polarizers and reflective surfaces, two lights whose polarization planes are orthogonal to each other can be brought together on the same optical path. When light polarized in any direction is incident on a combination of a polarizer and a reflective surface arranged in this way, the output light becomes two polarized lights whose planes of polarization are orthogonal to each other as described above, and each polarized light is The direction of the plane is determined by the polarizer. In other words, it converts light in an arbitrary polarization direction into polarization in two predetermined orthogonal directions, and in this conversion, unlike a normal polarizer, the light in one polarization direction is not thrown away, so there is no loss of light quantity.

The two mutually orthogonal linearly polarized lights obtained as described above are both turned into circularly polarized lights by a quarter-wavelength element arranged so that the azimuth angle is 45° with respect to both of the polarized lights, so that various optical devices can be used. It has the same effect as non-polarized light, and the polarized light is cancelled.

In this case, the 1/4 wavelength element that utilizes total internal reflection is used because it utilizes the change in phase during total internal reflection1,/
4 Compared to wavelength elements that utilize the birefringence of crystals,
This is because it has almost no wavelength characteristics.

(Example) FIG. 1 shows an example of the present invention. In the figure, 1 is a beam splitter type polarizer, and four of them are combined to form a block. In a beam splitter type polarizer, one linearly polarized light is totally reflected by the slopes inside the cube, and the linearly polarized light perpendicular to that is transmitted through the slopes.

The vibration directions of the electric fields of these two M-ray scratches are shown in the figure by arrows a and circles with midpoints. The polarized light component of the incident light that vibrates in the direction of arrow a is transmitted straight through the collective block of beam splitter 1, and the polarized light component in the vibration direction indicated by nine points is reflected by the slope of each polarizer and is reflected in a straight line in the direction of arrow a. It meets the polarized light on a common exit optical path L. Two linearly polarized lights that are orthogonal to each other coexist on the optical path L'. 2 is a Fresnel rhomb (Fresnel rhomb), in which 1. This is a 1/'4 wavelength element that provides an optical path difference of /4 wavelength. This Fresnel ROM is placed at an azimuth angle such that its leading axis forms an angle of 45" with both of the two linearly polarized lights on the optical path L" (see Figure 2). The two linearly polarized lights become circularly polarized lights that rotate in opposite directions, and are emitted from the 7-lens ROM 2 in the direction in which the optical path L° extends.

In the embodiment shown in FIG. 3, the beam splitter type polarizer 1 shown in FIG. 1 has only two blocks in the upper half, and the polarizer in the lower half is replaced with a mirror or total reflection prism 11 having two perpendicular surfaces. The operation is the same as the embodiment shown in FIG.

In the above embodiment, the incident light is divided into two mutually orthogonal polarization components, and then both are used. Therefore, no matter which direction the polarization direction of the incident light is, the intensity of the output light is However, since the reason for using a depolarizer is that the incident light is polarized, if you want to match the azimuth of the depolarizer to the direction of polarization of the incident light, use the embodiment shown in Figure 4. Even if the configuration is such that only one polarized component is passed through a single polarizer 1, that polarized component is made into circularly polarized light by a quarter-wavelength element 2, and the other polarized component is discarded. In reality, the loss of light is small. In this case, polarizers l′ and 1
/4 wavelength element 2 are rotated integrally around the optical axis of the incident light, and used by setting the direction in which the amount of output light is maximized.

(Effects of the Invention) According to the present invention, since an element that utilizes phase change during total reflection is used as a 1/4 wavelength element, it is possible to depolarize light over a wide wavelength range, compared to a device that utilizes diffuse reflection. and is highly efficient.

Note that in a quarter-wavelength element that utilizes total reflection, the effective wavelength range can be further widened by coating the total reflection surface with a thin film to an appropriate thickness.

[Brief explanation of drawings]

FIG. 1 is a side view of an apparatus according to one embodiment of the present invention, FIG. 2 is a perspective view of the same, FIG. 3 is a side view of another embodiment, and FIG. 4 is a side view of still another embodiment. 1...Beam splitter type polarizer, 2...1/4 wavelength element utilizing total reflection, '11...Mirror or total reflection prism.

Claims (2)

[Claims] (1) A depolarization device comprising a polarizer and a quarter-wavelength element using total internal reflection disposed at an azimuth angle of 45 degrees with respect to the light emitted from the polarizer. (2) A beam splitter type polarizer and a reflecting surface arranged so that two linearly polarized light beams whose polarization planes are orthogonal to each other meet on the same optical path, and which of the two linearly polarized light beams that meet on the same optical path. 1. A depolarization device comprising a total internal reflection type 1/4 wavelength element arranged so as to form an azimuth angle of 45°.