JPH02154205A - Polarizing element - Google Patents

Abstract

PURPOSE:To obtain the bright, compact and inexpensive polarizing element which has substantially no absorption by arranging units each consisting of a birefringerant lens contacting an isotropic medium and a rotary polarizing layer having opening parts selectively in the vicinity of one focal line of the birefringerant lens on the same plane. CONSTITUTION:The units each consisting of the birefringerant lens 101 which has negative curvature in a plane perpendicular to the optical main axis of the surface of an optical uniaxial material, has a larger refractive index than that of the optical uniaxial material to ordinary light, and contacts the isotropic medium and the rotary polarizing layer 105 which has opening parts 104 selectively in the vicinity of one focal line of the birefringerant lens 101 are arranged on the same plane. Consequently, the same brightness is obtained by a light source whose light quantity is a half as large as before and the compact, large- area polarizing element which is small in heat generation due to absorption is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to the structure of a polarizing element with high light transmittance useful for displays, photodetectors, etc.

[Prior Art] Conventional polarizing elements are used, for example, in optical measurements (Osamu Iida et al.
As described in Vol. A, Asakura Shoten) P414, typical examples include a combination of birefringent crystal prisms such as a Glan-Thompson prism, or a stretched oriented film that utilizes the dichroism of light absorption.

[Problems to be Solved by the Invention] However, since the above-mentioned oriented film type essentially utilizes dichroism of light absorption, those with a high degree of polarization have a low absolute passing vehicle, making it difficult to use for high-definition liquid crystal display. When used in displays or highly sensitive polarization detectors, 1. A high output light source is required; 2. There were issues such as polarizing elements breaking down due to heat generation. 3. The cross-crystal prism type requires a depth that is approximately equal to or greater than the size of the light-receiving surface. It had problems such as being difficult to handle in terms of layout, the system incorporating 40° being heavy, and 5° being expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bright, compact, and inexpensive polarizing element that is essentially free from absorption in order to solve this problem.

[Means for Solving the Problems] The polarizing element of the present invention has a surface of an optically uniaxial material having a concave curved surface in a plane perpendicular to its principal optical axis, so that the ordinary light of the optically uniaxial material is A unit consisting of a birefringent lens configured to be in contact with an isotropic medium having a refractive index larger than the refractive index of , is characterized in that a plurality of them are arranged in the same plane.

[Operation] Light from an incoherent light source such as a lamp is naturally polarized light having an arbitrary plane of polarization, and can be equivalently divided into two orthogonal components (for example, Px and Py).

When using the Px acid component, it is necessary to remove Py by absorption or separate it from the optical path using a polarizing beam splitter, etc., and if this is done, the light intensity will be reduced to 1/2.
It becomes 2 or less. Therefore, a polarizing element with essentially less light attenuation separates the -degree luminous flux using a birefringent lens, and then selectively imparts a phase difference to only one side and rotates it by 90 degrees.
It can be obtained by spatially combining the two again. that time,
By arranging a plurality of units of the birefringent lens and optical rotation layer, a compact system with good uniformity can be obtained.

Fig. 1 is a principle diagram for explaining the present invention in detail, and is equivalent to the present invention, and is a birefringent lens with a convex curved surface placed in a medium having a refractive index smaller than the refractive index of the extraordinary light. I will explain based on. Natural light 102 incident in the Z direction on a birefringent lens 101 uniaxially aligned in the ), Py (solid line).

In the above-mentioned birefringent lens, different refractive indices nx and ny exist, and the lenses undergo different refraction due to the interface 103. When the birefringent lens is a convex lens, if the medium outside the lens has a smaller refractive index than the lens medium, such as air, and ny<nx, Px will undergo greater refraction. In general, the effective focal length on the image side of the lens H1
: f” is Optronics 1983.No,
10. For example, the refractive index n
For a plano-convex lens placed in a medium, it is given by the following equation.

f”=r2/ (1-n/n”) (1)
(However, r2 is the radius of curvature of the lens surface, and n is g! of the lens.
In the vicinity of the focal point Fx of Px (showing a folding wheel), an optical rotation layer 105 made of a half-wave plate having a minute opening 104 has its optical principal axis aligned with the X (or Y) axis in the XY plane. It is installed at an angle of 45 degrees. The plane of polarization is maintained because the light is focused on the Px acid component aperture, but most of the py components, except for a small amount that passes through the aperture, are rotated by 90° due to a phase difference of 1/2 wavelength. The Px acid component is converted by When the lens shape is cylindrical, assuming a lens diameter of 2d and an aperture (12a), the intensity ratios Qx and Qy of both the Px and Py acid components behind the optical rotation layer 105 are given by the following equations.

Qy=50* (a/d) (2) Qx=5
0* (2-a/d) (3) For example, a/d=
0. 1, Qx has a large value of 95.

On the other hand, Fig. 2 shows the lens 101 and optical rotation layer 1 shown in Fig. 1.
The overall configuration is shown when a large number of 05 units are arranged in an array. The luminous flux from each unit overlaps and almost -like P
x deflection is obtained. In order to increase the luminous intensity by 1, it is effective to install a normal polarizing plate or polarizing element 201 that transmits Px polarized light at the rear. The above principle can be equivalently applied to the birefringent lens of the present invention having a concave curved surface in a medium having a refractive index greater than the refractive index of ordinary light.

The polarizing element of the present invention will be described below based on Examples.

[Example] Example 1 Figure 3 shows an example of the present invention in which a nematic liquid crystal layer is used as a birefringent lens, and the liquid crystal layer is used to achieve the effect of the convex birefringent lens explained in [Operation]. FIG. 2 is a perspective view of a configuration in which a convex substrate having a refractive index larger than the refractive index for ordinary light is used on one side and uniaxially aligned. A birefringent lens array in which a nematic liquid crystal 304 is uniaxially aligned in the Y direction is sandwiched between a transparent substrate 301 and a transparent substrate 303 having a cylindrical convex array 302; A half-wave plate 105 made of polycarbonate (PC) is arranged in stripes on a transparent support substrate 305 parallel to the lens array.
It consists of a Qffl optical rotation layer.

The maximum thickness of the liquid crystal layer was about 19 μm, and a cyanobiphenyl fh mixture with high birefringence was used as the liquid crystal. The pitch of the prong-convex array is 0.5 mm, and the radius of curvature of the convex surface is approximately 14 mm.
It is 3mm. For the substrate of the cylindrical array, press-molded lead silicate glass, which has a low softening point and a high refractive index, was used. Figure 4 shows the trajectory of a typical light beam when plane waves Px and Py polarized in the X and Y directions are vertically incident on one unit of the above configuration.Actual tm106,6fP
Px and Py incident on the liquid crystal layer are respectively extraordinary light of the nematic liquid crystal layer,
Feel the refractive index nx, ny of ordinary light. At the convex interface 302, the incident angle θi.

The exit angles θ0 are related to each other according to the 5nell's law, and as a result are affected by the difference in focal length based on equation (1). Here, 589 nm of the material used in this example
Table 1 shows the refractive index values at .

As is clear from Table 1, the following relationship exists for the parameters of equation (1).

ny/n"<nx/n" ~ 1 (4) Therefore, Py107 is focused in the front, and Px and py are spatially separated within the plane where the optical rotation layer 105 is placed. The position of the optical rotation layer is determined according to the py based on the thickness of the element and the like. The selective optical rotation layer 105 has a width of 50 mm after bonding or pressing the PC to the glass substrate.
A stripe shape 104 of .mu. is formed by dry etching, laser processing, or the like. As a result, linear polarizing plate 2.0
When the transmittance for Py and Px was measured at the rear 401 of 1, it was 5% and 70%, respectively. By skillfully controlling the thickness of the liquid crystal layer, a 100 mm size product could be produced relatively easily.

Table 1 Example 2 FIG. 5 shows another example of the present invention, in which a selective optical rotation layer is formed near the focal line. As in Example 1, a stretched film is pressure bonded onto a glass substrate 305 and then dry etched to leave the optical rotation layer only in the focal line vicinity portion 501.

In this case, the py acid component 06 receives a phase difference of 90° after convergence, and most of the Px acid component is rotated, whereas the Py component 107
Most of the light passed through as is, and a polarized component opposite to that of Example 1 was obtained.

In the above example, nematic liquid crystal was used as the optically uniaxial material, but other materials with high orientation properties, such as liquid crystal polymers, which are formed by alignment molding and then coated with a material with a high refractive index, may also be effective. It's self-evident.

[Effects of the Invention] As is clear from the above embodiments, according to the present invention, the surface of an optically uniaxial material is held in a plane perpendicular to its optical principal axis with a negative self-vehicle, and the surface of the optically uniaxial material is A birefringent lens configured to be in contact with an isotropic medium having a refractive index larger than the refractive index of ordinary light of a uniaxial material, and an optical rotation layer having an opening selectively provided near one focal line of the birefringent lens; A unit consisting of
By arranging the number of Pi in the same plane, it is about 1/2 of the conventional
The same brightness can be obtained with a light source with a light amount of , and it is possible to provide a polarizing element that is compact, generates little heat due to absorption, and has a large area. We are confident that this will greatly contribute to the development of liquid crystal displays, which were previously dark and hard to see, and array-type polarization detectors, which had mediocre sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram explaining the operation of the polarizing element of the present invention. FIG. 2 is an overall view of the polarizing element of the present invention. FIG. 3 is a perspective view of a configuration using the liquid crystal of the present invention. FIG. 4 is a trajectory diagram of typical light rays in the polarizing element of the present invention. FIG. 5 is a diagram showing the structure of the present invention in which an optical rotation layer is selectively formed. 101 Birefringent lens 104 Aperture 105 Optical rotation layer 106 X polarized light 107 Y polarized light 201 Linear polarizing plate 303 Cylindrical array substrate 304 Nematic liquid crystal 501 Partial optical rotation layer or above Applicant Seiko Epson Corporation agent Patent attorney Masayoshi Kamiyanagi (1 other person) Figure 3 Figure 4

Claims (1)

[Claims] The surface of an optically uniaxial material is brought into contact with an isotropic medium having a concave curved surface in a plane perpendicular to its principal optical axis and having a refractive index larger than the refractive index of the ordinary light of the optically uniaxial material. What is claimed is: 1. A polarizing element comprising a plurality of units arranged in the same plane, each consisting of a birefringent lens having the above structure and an optical rotation layer selectively provided near one focal line of the birefringent lens.