JPS6215518A - Polarizing converter - Google Patents

Abstract

PURPOSE:To convert unpolarized light into linear polarized light with small loss by discriminating the unpolarized light from an LED by a polarizing prism, passing the discriminated P or S polarized light through a dedicated liquid crystal cell, and multiplexing it by a mirror system which uses two mirrors and a wedgelike mirror. CONSTITUTION:When a changeover switch 10 is placed at a side A, a voltage is impressed to a liquid crystal cell 4b and not impressed to a liquid crystal cell 4a. Similarly, when the changeover switch 10 is placed at a side B, the voltage is impressed to the liquid crystal cell 4a and not impressed to the liquid crystal cell 4b. Namely, when the changeover switch 10 is at the side A, the polarization of the light passing through the liquid crystal cell 4a is converted from S polarization to P polarization, light passing through the liquid crystal cell 4b passes as P polarized light as it is, and multiplexed light is P polarized light. Similarly, when the changeover switch 10 is at the side B, the light passing through the liquid crystal cell 4a passes as S polarized light as it is, the light passing through the liquid crystal cell 4b is converted from P polarized wave to the S polarized light, and multiplexed light is S polarized light.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to various optical measuring instruments that use LEDs as light sources.

This invention relates to polarization converters used in optical devices and the like.

[Prior art]

First, regarding this type of conventional polarization converter, Fig. 2 (a
), (1=) will now be explained. In the figure, (heavy) is a grating, and (2) is a polarizing prism. The light emitted from the LHiD is so-called non-polarized light that does not have a specific polarization, and is a mixture of linearly polarized P-polarized light and 8-polarized light. Therefore, using LmD as a light source,
In various optical devices that perform signal processing using linearly polarized light, an element called a polarizer is generally inserted into the optical path in order to obtain the required linearly polarized light. The grating (1) in Figure 2 (a) is a substrate with excellent light transmittance, on which metal strips (IJ) are deposited at intervals finer than the wavelength of the light, and it emits non-polarized light in the E-axis direction. When it is incident, the transmitted light becomes S polarized light and P
The polarized light component is reflected and travels in the negative direction of the two axes. The polarizing prism (2) in FIG. 2(b) is made by depositing a polarizing film at an angle of 45 degrees within a glass base material. However, if unpolarized light is incident in the z-axis direction, the transmitted light will be P-polarized light.

The S-polarized light component is reflected and travels in the y-axis direction.

[Problem that the invention seeks to solve]

The conventional polarization converter described above separates unpolarized light into a P-polarized light component and an S-polarized light component), and one component is discarded and becomes 1, so the conversion efficiency is a little less than 3. It was more efficient than 'aB'. It's a trench.

Only one polarization component can be used.

This invention was developed in order to solve the problems that existed on the one hand, and the purpose is to convert unpolarized light into [alpha]-polarized light with little loss.

[Means for solving problems]

The polarization converter according to the present invention focuses on the fact that polarized light can be rotated by applying a voltage to the liquid crystal, and distinguishes different linearly polarized light components using polarization beams.
There are 7 types of liquid crystal cells arranged in one line.

[Effect]

In this invention, by switching the voltage applied to the two liquid crystal cells, unpolarized light can also be produced. 〈 can be converted into only the S-polarized component.

〔Example〕

FIG. 1 shows an embodiment of the polarization converter of the present invention. In FIG. 1, (2) is a polarization prism, and +31i is a polarization converter.

(4) is a liquid crystal cell, (5) is a mirror, (6) wedge-shaped mi → -1 (7) is a rod lens, C81 is an LED, (9
One power supply, aI is a changeover switch. Polarization converter (3
) is LEDlB+.

Rod lens (7), polarizing prism +21. 2 h
LJ? , a power source (9) that applies voltage to the cells (4a), (4b) and the kneading device.

Changeover switch ON, 'i-Yo, Mirror (5a),
(5'b).

It consists of a mirror system consisting of a wedge-shaped mirror (6).

The unpolarized light from LP' D +s'+ is converted into P-polarized light as well as linearly polarized light of 1(ke S(-). The conversion process is as shown below. Generally, the emission from T4 K Di81 is Since it spreads out in a diffused manner, it is converted into parallel light using a rod lens (7) and is made incident on the polarizing film of the polarizing prism (2). The P-polarized light component, which is the transmitted light, passes through the liquid crystal cell (4b) and is reflected at Mi → -(5b) and heads toward the wedge-shaped Mi →-(6).On the other hand, the S-polarized light component, which is the transmitted light, passes through the liquid crystal cell (4b) and is reflected from Mi → -(5b) to the wedge-shaped Mi →-(6). The component changes its optical path in the right-angle prism part that is part of the polarizing prism (2), undergoes liquid crystal aging (4a), is reflected by the mirror (5a), and heads toward the wedge-shaped mirror (6). Wedge-shaped mirror +61 Vi, 2 mentioned above
Combine the book's light beams. 2. Figure 3 is a diagram for explaining the entire operation of the liquid crystal cell (4). In Figure 1, (9) is the power supply, and (II) is the switch.

There are various types of liquid crystal cells (4), but in this case, T, , N (
Tw! ,,s,tea,,Nemat,iq I will explain using types and things. ,・The liquid crystal cell (4) has liquid crystal sealed between seven glass plates, and when voltage from the power supply (9) is applied to both sides of the cell, the molecular arrangement of the liquid crystal changes.1. Polarized light rotates. For TN type, when no voltage is applied.

In other words, when the switch OI is set to py1t', if S-polarized light is input, the transmitted light is converted to P-polarized light. , the transmitted light is S-polarized and remains as light.

In other words, 2, voltage ON10. , FF can convert linearly polarized light from P to S or from Sl to P.

Returning to Figure 1, the two liquid crystal cells (,4a1゜(4
The opening force n of the voltage to b) will be explained. One end of the power supply (9) is connected to two liquid crystal cells (4a) and ' (4b).

The other end is connected to the midpoint of the changeover switch θl.

Therefore, when the selector switch is on the A side.

A voltage is applied to the liquid crystal cell (4b), and the liquid crystal cell (4a)
is not applied. Similarly, the changeover switch al is
11, a voltage is applied to the liquid crystal cell (4a).

No voltage is applied to the liquid crystal cell (4b). Namely.

When the switch 61 is in the upright position, the polarization of the light passing through the liquid crystal cell (4a) is converted from S polarization to P polarization, and the polarization of the light passing through the liquid crystal cell (4b) passes as P polarization. Therefore, the two combined lights become P-polarized light.

Similarly, if the selector switch tJI is on the mouth side, the liquid crystal cell (
The polarized light of the light passing through 4a) passes through the S-polarized light trench, and the polarized light of the light passing through the liquid crystal cell (4b) is converted from 1P polarized light to 8-polarized light, so that the two combined lights become S-polarized light.

〔Effect of the invention〕

As explained above, according to the polarization converter of the present invention, non-polarized light from LE and I) is discriminated by a polarizing prism, and the discriminated P-polarized light or S-polarized light is passed through a specialized liquid crystal cell. Since the structure is configured so that the two me y- and wedge-shaped mi →- are synthesized using a mirror system, it is possible to obtain 1 ffl linear polarization of P polarization, I〈, and S polarization with low loss.
, By switching the voltage applied to the liquid crystal cell, the polarization can be switched instantaneously.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the polarization converter of the present invention, FIGS. 2(a) and 2(b) show an embodiment of an optical component corresponding to a conventional polarization converter, and FIG. 3 shows an embodiment of the polarization converter of the present invention. FIG. 2 is a diagram illustrating the operation of a liquid crystal cell, which is a main component of the present invention. In the figure, (1) is a grating and (2) is a polarizing prism. (3) is a polarization converter, (4) is a liquid crystal cell, (5) is a mirror, (6) is a wedge-shaped mirror, -1C71 is a rod 1 / lens, (81 is an LED, 191 is a power supply, and an OI switch) In the drawings, the same or corresponding parts are indicated by the same reference numerals.

Claims (1)

[Claims] A polarization converter that converts light from a non-polarized light source such as a light emitting diode into linearly polarized light such as P-polarized light or S-polarized light consists of a polarizing prism, a rod lens, two liquid crystal cells, and a mirror system. The P-polarized or S-polarized light discriminated by the prism is converted into predetermined linearly polarized light by the two liquid crystal cells, and these two light beams are combined by a mirror system and connected to the power source. 1. A polarization converter characterized in that the polarization converter is configured such that P-polarized light and S-polarized light can be arbitrarily selected by switching a single-pole double-throw changeover switch.