JPH10268249A - Polarization rotating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization rotating element capable of controlling the polarization direction of an incident light at high speed and also variously even in a simple device constitution. SOLUTION: This element is provided with the polarization rotating part 3 which is constituted by laminating plural twisted nematic liquid crystal cells 61 -6i in which nematic liquid crystal having twisted orientation or choloesteric liquid crystal is held in between transparent electrodes and which emits light while rotating the polarization plane of an incident light 2 and a polarized light selecting part 4 on which the outgoing light of the polarization rotating part 3 is made incident and which selects the polarized light having a constant direction and which rotates by itself and controls the polarization direction of a linearly polarized light to be emitted from the polarized light selecting part 4 by voltages to be impressed on the twisted nematic liquid crystal cells 61 -6i and the rotation of the polarized light selection part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization rotating element capable of freely rotating the polarization direction of linearly polarized light, and more particularly to a linear rotation element for optical communication, optical information processing, optical recording, or various optical measurements. The present invention relates to a polarization rotator that can be widely applied to a technique that needs to freely rotate the polarization direction of polarized light.

[Summary of the Invention] The present invention relates to a polarization rotating element capable of freely rotating the polarization direction of linearly polarized light, and comprises a plurality of twisted nematic liquid crystal cells for rotating the plane of polarization of incident light. A rotation unit, and a polarization selection unit that selects polarization in a certain direction and rotates by itself.By combining voltage driving of individual twisted nematic liquid crystal cells with rotation of the polarization selection unit, an arbitrary direction can be obtained. To form linearly polarized light.

[0003]

2. Description of the Related Art Hitherto, as a polarization rotator capable of controlling the polarization direction of an element, those shown in FIGS. 11 to 13 are known.

The polarization rotator 100 shown in FIG.
A four-wavelength plate 101 and a polarizing plate 102 are arranged, and the incident light 103, which is linearly polarized light, passes through the quarter-wavelength plate 101, is converted into circularly polarized light 104, and is incident on the polarizing plate 102. In this example, the incident circularly polarized light 102 is rotated at an arbitrary angle, and the output light 105 linearly polarized in an arbitrary direction is output.

However, the polarization rotator 100
Not only has the basic disadvantage that 50% or more of the circularly polarized light 104 is lost by the polarizing plate 102, but also changes the polarization direction of light having different wavelengths due to the wavelength dependence of the 波長 wavelength plate 101. There are problems such as difficulty in rotating simultaneously. For this reason, the polarization rotator 100 cannot be used in many fields in which a large loss of light intensity is suppressed.

A polarization rotator 110 shown in FIG. 12 allows a transparent material 111 having optical activity to pass incident light 103 which is linearly polarized light. By changing the optical path length of the transparent material, the incident light 105 linearly polarized in a direction different from the direction of the incident light 103 is extracted.

However, the polarization rotator 110
It is difficult to change the length of the optically active material 111 freely and at high speed, so that the polarization rotator 110 cannot be used in many applications requiring real-time control.

A polarization rotator 120 shown in FIG. 13 is a so-called Faraday rotator, and applies a static magnetic field 1 to a transparent material 121 having a Faraday effect in a direction parallel to the traveling direction of light.
22, the intensity of the static magnetic field 122 is changed, and linearly polarized light polarized in a direction different from that of the incident light 103, which is linearly polarized light incident on the transparent material, is output as the outgoing light 105.

However, the polarization rotator 120
Although they have the great advantage that they can be controlled at high speed, they have the drawback that it is difficult to simultaneously change the polarization directions of light of different wavelengths because of their extremely strong wavelength dependence. In addition, not only is it not easy to enlarge the cross-section where light enters and exits, but there is also a disadvantage that peripheral devices become larger than the cross-sectional area of light, such as the need for a static magnetic field applying device. I have.

[0010]

As described above, according to the above-described conventional polarization rotators, the polarization rotator 100 in which the quarter-wave plate 101 and the polarization plate 102 are combined has a circular polarization. In addition to the loss of 50% or more in the polarizing plate 102, the wavelength dependency of the 波長 wavelength plate 101 causes
Since it is difficult to rotate the polarization directions of light having different wavelengths at the same time, there is a problem that it cannot be used in many fields where a large loss of light intensity is required. Further, in the case of the polarization rotator 110 that allows linearly polarized light to pass through the transparent material 111 having optical activity, it is difficult to change the length of the transparent material 111 freely and at high speed. There is a problem that it cannot be used for many application fields. Furthermore, in the Faraday rotator 120, it is difficult to simultaneously change the polarization directions of light having different wavelengths because the wavelength dependency is very strong, and it is not easy to increase the cross section where light enters and exits. Further, since a static magnetic field applying device is required, there is a problem that the peripheral device becomes large as compared with the cross-sectional area of light passage.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polarization rotating element which can control the polarization direction of incident light at high speed and variously even with a simple device configuration. It is in.

[0012]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 is characterized by laminating a plurality of twisted nematic liquid crystal cells in which a twisted nematic liquid crystal or a cholesteric liquid crystal is sandwiched between transparent electrodes. A polarization rotating unit configured to rotate the plane of polarization of the incident light and emit the light,
A polarization selection unit having a polarization plate that receives the light emitted from the polarization rotation unit and selects linear polarization in a certain direction, and the polarization rotation unit and the polarization selection unit are arranged in a plane perpendicular to the optical axis of the incident light. Rotate to a desired angle, and drive the individual twisted nematic liquid crystal cells by voltage to maximize the output light intensity from the polarization selector, and emit linearly polarized light at the desired angle. Is what you do.

According to a second aspect of the present invention, in the polarization rotator of the first aspect, the molecular arrangement direction of the substrate surface of the twisted nematic liquid crystal cell is in the molecular arrangement direction of the substrate surface of the adjacent twisted nematic liquid crystal cell. It is characterized by being parallel or vertical.

According to a third aspect of the present invention, in the polarization rotator of the first or second aspect, light passing through the twisted nematic liquid crystal cell passes through the polarization selector.

According to a fourth aspect of the present invention, in the polarization rotator of the first, second, or third aspect, a light detector for photoelectrically converting a part of the linearly polarized light emitted from the polarization selector, and the twisted element. The voltage applied to the nematic liquid crystal cell is controlled, the magnitude of the electric signal output from the photodetector is compared according to the applied voltage, and the intensity of the linearly polarized light emitted from the polarization selector is adjusted. And a signal control unit for selecting an applied voltage so as to have the largest value, and holding the selected voltage, thereby maximizing the output light intensity of the polarization selecting unit. .

According to a fifth aspect of the present invention, in the polarization rotator of the first, second, third, or fourth aspect, the polarization selector comprises a Nicol prism, a Glan-Thomson.
Thompson) prism, Rochon prism, Wollaston prism, Gran Foucault (G
(lan-Foucault) It is characterized by comprising one of a prism, a polarizing film, and a guest-host liquid crystal cell.

According to each invention having the above configuration, the polarization direction of incident light can be controlled at high speed and variously even with a simple device configuration.

[0018]

FIG. 1 shows the structure of a polarization rotator according to the present invention. The polarization rotator 1 is provided with an incident light 2
A polarization rotator 3 for rotating the polarization plane of
And a polarization selector 4 that absorbs a certain amount of polarized light. The incident light 2 incident from the polarization rotator 3 is polarized by the polarization selector 4 and then transmitted. 5 is emitted. The polarization rotator 3 is formed by stacking a plurality of twisted nematic liquid crystal cells 6 ₁ , 6 ₂ ,..., 6 _i-1 , 6 _i having different twist angles. The above configuration is a basic configuration of the present invention, and a specific configuration will be described in the following embodiments, prototypes thereof, and modifications thereof.

<First Embodiment><< Structure of First Embodiment >> FIG. 2 shows the structure of the first embodiment. Polarization rotating element 1 of this embodiment
Reference numeral 0 denotes a configuration in which two twisted nematic liquid crystal cells 6A and 6B are used as the polarization rotation unit 3 and a polarization film 16 is used as the polarization selection unit 4.

Twisted nematic liquid crystal cell 6A
Are a first transparent substrate 11A, a first transparent electrode 12A, a liquid crystal 13A, a second transparent electrode 14A, and a second transparent substrate 15A.
And A in order. Similarly, the twisted nematic liquid crystal cell 6B also includes a first transparent substrate 11B, a first transparent electrode 12B, a liquid crystal 13B, and a second
The transparent electrode 14B and the second transparent substrate 15B are sequentially laminated.

Each of the first transparent substrates 11A and 11B and the second transparent substrates 15A and 15B is composed of a flat glass substrate or the like. Also, the first transparent electrodes 12A, 12B
And the second transparent electrodes 14A and 14B are, for example,
Thickness formed by adding 5% of Sn to In ₂ O ₃ .
It is composed of an ITO transparent electrode film of about 07 μm.

Twisted nematic liquid crystal cell 6
As the liquid crystals 13A and 13B constituting the liquid crystal elements A and 6B, a liquid crystal material having a low viscosity such as a nematic liquid crystal or a cholesteric liquid crystal having a material itself having a twisted orientation is used in order to realize a polarization rotator having a high-speed response. Is preferred. A nematic liquid crystal may be mixed with a chiral agent that induces a twist in molecular alignment.

The twisted nematic liquid crystal cell 6A has a 45 ° twist orientation, and the twisted nematic liquid crystal cell 6B has a 90 ° twist orientation. In these twisted nematic liquid crystals 6A and 6B, liquid crystal molecules 17, 18, 19 and 20 near the transparent electrode are:
As shown in FIG. 3, the transmitted light 5 output from the polarization selector 4
Assuming that the direction (hereinafter, referred to as the light transmission direction) is 0 °, they are oriented in directions of 45 ° and 90 °, respectively. In addition, the liquid crystal molecules 17, 18, and 19, 20h have the same twist rotation direction. As shown in FIG. 3, the incident light 2 entering the twisted nematic liquid crystal cell 6A travels from the top to the bottom of the paper.

The polarization direction of the incident light 2 of the polarization rotation unit 3 depends on the direction of rotation of the plane of polarization by the polarization rotation unit 4.
Therefore, the twisted nematic liquid crystal cell 6A,
The twist angle of 6B is not limited, and various polarization rotation functions can be obtained by using a twist angle other than 45 ° or 90 °. Therefore, as will be described in a modified example described later, if a twisted nematic liquid crystal cell having a small twist angle is further inserted into the polarization rotation unit 3, a more precise rotation operation of the polarization plane can be obtained.

Twisted nematic liquid crystal cell 6
The optical rotatory power of A and 6B becomes remarkable when the plane of polarization of light is parallel or perpendicular to the liquid crystal molecular arrangement on the substrate surface on the incident side. Therefore, in order to efficiently rotate the polarization plane of the incident light 2 using two or more twisted nematic liquid crystal cells, the twisted nematic liquid crystal cells 6 adjacent to each other are required.
A, 6B substrate surface molecules (liquid crystal molecules 17, 18, 19,
It is desirable that the arrangement direction of 20) is parallel or vertical. In the configuration of FIG. 2, as shown in FIG. 3, the arrangement direction of the liquid crystal molecules 17 on the substrate surface is parallel to the arrangement direction of the liquid crystal molecules 18. However, even when the molecular arrangement directions are not parallel or perpendicular to each other, the polarization plane can be rotated though the polarization intensity is reduced.

Further, the liquid crystal molecules 17, on the substrate surface of the liquid crystal molecules,
In order to control the arrangement directions of 18, 19 and 20, the first
Between the transparent electrode 12A and the liquid crystal 13A, the liquid crystal 13A and the second
Between the transparent electrode 14A, the first transparent electrode 12B and the liquid crystal 13
B, and between the liquid crystal 13B and the second transparent electrode 14B, as an alignment film, a polymer thin film made of a synthetic resin such as polyimide or polyvinyl alcohol, or SiO, SiO ₂
It is also possible to form an inorganic thin film made of such as.

The first transparent electrode 12A and the second transparent electrode 1
AC power supply 23A is connected between the first transparent electrode 12B and the second transparent electrode 14B via a switch 21A and a lead wire 22B. Power supply 23B is connected.

The polarizing film 16 constituting the polarization selecting section 3 in this embodiment is made of a polyvinyl alcohol resin containing iodine molecules absorbing light. Further, in the polarizing film 16, it is desirable that the optical direction in which light is absorbed the most is arranged parallel or perpendicular to the molecular arrangement direction of the substrate surface of the adjacent twisted nematic liquid crystal cell 6B. In the configuration of FIG. 2, as shown in FIG. 3, the adjacent twisted nematic liquid crystal cell 6B
And the absorption axis of the polarization selector 4 are parallel to each other.

In this embodiment, as shown in FIG. 4, the polarization rotation unit 3 and the polarization selection unit 4 are attached to a rotation mechanism 25. This rotating mechanism 25 is manually or electrically rotated, and one of the components constituting the polarization rotator 3;
Alternatively, the configuration is such that the maximum light intensity is obtained from the polarization selector 4 by turning on / off the applied voltage to a plurality of twisted nematic liquid crystal cells 6A and 6B having different twist angles. The rotation mechanism 25 can be easily configured by processing a normal rotation holder that holds a polarization plate or a wavelength plate so that the liquid crystal cells 6A and 6B of the polarization rotation unit 3 can be attached in addition to the polarization plate. This can be easily realized by manually rotating it to an arbitrary angle or by attaching a pulse motor to this and electrically rotating it by applying a pulse voltage.

<< Operation of the First Embodiment >> In the polarization rotator 10 having the configuration shown in FIG. 2, the incident light 2 incident on the polarization rotator 3 is a 45 ° or 90 ° twisted nematic liquid crystal cell 6A, 6B. Then, the light passes through the polarizing film 16 of the polarization selector 4 and is emitted as transmitted light 5.
Since the two twisted nematic liquid crystal cells 6A and 6B of the polarization rotator 3 are arranged so that liquid crystal molecules are continuously twisted, the plane of polarization of the incident light 2 is rotated by 135 ° at the maximum. On the other hand, the optical rotation power of each twisted nematic liquid crystal cell 6A, 6B depends on the first transparent electrodes 12A, 12A.
This is canceled by applying a voltage between B and the second transparent electrodes 14A and 14B. The polarization angle of the polarization rotation element 10 is controlled by the voltage-controlled twisted nematic liquid crystal cells 6A and 6B.
Is the sum of the optical rotation angles of Therefore, when the polarization direction of the incident light 2 is parallel or orthogonal to the arrangement of the liquid crystal molecules 17, the linearly polarized light incident on the liquid crystal cells 6A and 6B changes its polarization direction by switching the switches 21A and 21B. 0
Rotate to four angles of {180}, 45 °, 90 °, 135 °. Here, as shown in FIG. 4, the polarization rotation unit 3 and the polarization selection unit 4 are incorporated in a rotation mechanism 25, and the rotation mechanism is rotated to a desired angle to select four types of applied voltage values applied to the liquid crystal cell. If the output of the polarization selector 4 is maximized, the polarization direction of the incident light can be changed with a very small loss.

If the polarization direction of the incident light 2 does not match the arrangement direction of the liquid crystal molecules 17, the optical rotation power of the liquid crystal changes depending on the angle between the polarization direction of the incident light and the arrangement direction of the liquid crystal molecules. However, in the configuration of FIG. 2, since the maximum value of the angle is at most 45 °, the effect of the optical rotatory power of the liquid crystal is large, and as shown in the result of FIG. Thus, the polarization plane of the incident light can be rotated, and the loss can be significantly reduced as compared with the conventional polarization rotation element.

<Second Embodiment><< Structure of Second Embodiment >> FIG. 5 shows a structure of a second embodiment. Polarization rotating element 3 of this embodiment
0 is 2 as the polarization rotator 3 as in the first embodiment.
In this embodiment, two twisted nematic liquid crystal cells 6A and 6B are used, and a guest-host liquid crystal cell 36 is used as the polarization selector 4 instead of the polarizing film 16.
The same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The guest host liquid crystal cell 36 constituting the polarization selector 4 includes a first transparent substrate 31 and a first transparent electrode 32.
, A guest-host liquid crystal 33, a second transparent electrode 34, and a second transparent substrate 35 in that order. First and second transparent substrates 31 and 35 and first and second transparent electrodes 3
Reference numerals 2 and 34 denote the same thickness of the same material as the first and second transparent substrates 11A and 15A and the first and second transparent electrodes 12A and 14A of the twisted nematic liquid crystal cell 6A. Can be configured.

An AC power supply 42 is connected between the first transparent electrode 32 and the second transparent electrode 34 via a switch 40 and a lead wire 41 to drive and control the guest-host liquid crystal 33. I have.

The guest-host liquid crystal 33 is a liquid crystal in which a dichroic dye 37 having light absorption anisotropy is mixed in a nematic liquid crystal 38. Various colors can be used as the dichroic dye 37, but it is desirable that the guest-host liquid crystal 33 be made black by adding one or more dichroic dyes.

The optical direction in which the dichroic dye 37 of the guest-host liquid crystal 33 absorbs the most light is parallel to the molecular arrangement direction of the substrate surface (liquid crystal molecules 20) of the adjacent twisted nematic liquid crystal cell 6B. Or it is desirable to be arranged vertically.

The polarization selecting section 4 includes a guest-host liquid crystal cell 36, a Nicol prism, a Glan-Thompson prism, and a Rochon (Roc) prism.
hon) prism, Wollaston prism,
A Glan-Foucault prism or the like can also be used.

<< Configuration of the Second Embodiment >> In the polarization rotator 30 having the configuration of FIG.
Unnecessary polarization components in the incident light 2 rotated by the polarization rotation unit 3 are changed only when no voltage is applied to the dichroic dye 3.
7 to be absorbed. On the other hand, the guest host liquid crystal cell 36
When an AC voltage from an AC power supply 42 is applied between the first transparent electrode 32 and the second transparent electrode 34 via the switch 40 and the lead wire 41, the dichroic dye 37 in the guest host liquid crystal 32 Each molecule of the nematic liquid crystal 38 is oriented in the voltage application direction, the light absorption of the guest-host liquid crystal 32 decreases, and the polarization intensity decreases.

That is, when a sufficient voltage is applied to the guest-host liquid crystal cell 36, the polarization rotator 30 does not exhibit a polarization operation. As described above, by controlling the voltage applied to the guest-host liquid crystal cell 36, the polarization intensity can be controlled.

Therefore, when the polarization function is no longer necessary in the photographing apparatus equipped with the polarization rotation element 30,
A voltage may be applied to the guest host liquid crystal cell 36, and it is not necessary to remove the polarization rotator 30.

<Third Embodiment><< Structure of Third Embodiment >> FIGS. 6 and 7 show the structure of the third embodiment. In the first and second embodiments described above, four types of polarization rotation angles are created by turning on and off the switches 21A and 21B. These four
Out of the three states, the maximum output light is one or two. Therefore, in the third embodiment, the condition for maximizing the output light intensity is automatically selected.

That is, as shown in FIG. 6, a beam splitter 51 that transmits a part of the transmitted light 5 emitted from the polarization selector 4 and reflects the other part,
In a light detector 52 for detecting the intensity of reflected light, switches 21 _1, 21 ₂ based on the electric signal 53 representing the intensity of light output from the light detector 52, ..., 21 _i-1, 21
a signal control unit 54 for generating a switch control signal for controlling the _i on / off, comprising a twisted nematic liquid crystal cell 6 _1, 6 _2, ..., a drive control of the 6 _i-1, 6 _i automatically It is intended to be performed.

As shown in FIG. 6, the signal control unit 54 converts the electric signal 53 output from the light detection unit 52 into an A / D signal.
An A / D converter 55 for conversion and a microcomputer, which have the largest value by comparing the magnitude of a digital signal (electric signal 53 corresponding to light intensity) output from the A / D converter 55 Switch status (switch 21 ₁ ,
21 ₂ ,..., 21 _i−1 , 21 _i ).
_1, 21 _2, ..., and a 21 _i-1, 21 _i on / off generated by the switch control signal 58 of 2 ⁱ as to control the output switch controller 57.

<< Operation of Third Embodiment >> FIGS. 6 and 7
In the switch control unit 57 of the signal control unit 54,
Switch _{21 1, 21 2, ...,} 21 i-1, 21 i on / off is generated switch control signal 58 of 2 ⁱ as to control the switches _{21 1, 21 2, ...,} 21 i-1, 21
_i is on / off controlled. The light intensity of the transmitted light 5 in the 2 ⁱ states is equal to the beam splitter 51.
Is detected by the light detection unit 52 via the. In the light detecting section 52, photoelectric conversion is performed, and an electric signal 53 corresponding to the light intensity is obtained.
Is supplied to the signal control unit 54. The signal comparing / holding unit 56 of the signal control unit 54 compares the magnitudes of the 2 ⁱ electric signals, selects the switch state having the largest value, and holds the selected switch state. Thereafter, the switch control unit 57 executes control based on the switch state having the largest value.

As described above, according to the third embodiment, the twisted nematic liquid crystal cells 6 ₁ , 6 ₂ ,..., 6 _i−1 , 6 _i that maximize the light intensity of the transmitted light 4.
Can be automatically controlled.

<Trial Production Example><< Trial Production Example 1 >> In order to confirm the operation and effect of the above-described first embodiment shown in FIG. 2, the polarization rotator 1 shown in FIG.
0 was prototyped as follows.

First, 0.07 of In ₂ O ₃ : Sn is used.
A polyimide film (AL-1254, manufactured by Nippon Synthetic Rubber Co., Ltd., having a thickness of 0.05 μm) is applied on a transparent substrate made of soda glass having a thickness of 1.1 mm to which a transparent electrode having a thickness of μm is adhered. By rubbing, a so-called rubbing treatment was performed to prepare an alignment film.

Next, the transparent electrode 12 coated with the alignment film is
Nematic liquid crystals 13A and 13B (Chisso Corporation, JB-4002LA, refractive index anisotropy Δn =
0.137). By changing the rubbing direction of the alignment film, twisted nematic liquid crystal cells 6A and 6B having twist angles of 45 ° and 90 ° were prototyped.
The fabricated twisted nematic liquid crystal cell 6A,
The area of 6B is 10 cm × 10 cm. here,
The thickness d of the twisted nematic liquid crystal cells 6A and 6B and the wavelength λ of the incident light satisfy the Morgan condition (Δn · d> 2).
λ) so that sufficient optical rotation can be obtained.
Was set to 10 μm.

The light transmission direction of the polarizing film 16 of the polarization rotating element 10 in which the two twisted nematic liquid crystal cells 6A and 6B and the polarizing film 16 (manufactured by Luceo) are combined is fixed at an arbitrary rotation angle, and various rotation angles are set. He of polarization angle
-Ne laser light is incident as incident light 2 and its transmitted light 5
FIG. 8 shows the result of measuring the strength of the sample. In FIG. 8, the polarization angle of 0 ° corresponds to the case where the polarization direction of the He—Ne laser beam and the light transmission direction of the polarizing film 16 match. The following can be understood from FIG.

0 ° to 22.5 °, 157.5 ° to 1
In the range of 80 °, the highest transmitted light intensity is obtained when both the switches 21A and 21B are turned on.

In the range of 22.5 ° to 67.5 °,
The highest transmitted light intensity is obtained when both the switches 21A and 21B are turned off.

In the range of 67.5 ° to 112.5 °, the highest transmitted light intensity is obtained when the switch 21A is turned on and the switch 21B is turned off.

In the range of 112.5 ° to 157.5 °, the highest transmitted light intensity is obtained when the switch 21A is turned off and the switch 21B is turned on.

22.5 °, 67.5 °, 112.5
１５ and 157.5 ゜, the four types of switch states are 2
Degenerate into types. There are two switch states showing the maximum transmitted light intensity. Any of the 22.5 か の states,
Either one of the states at 67.5 °, one of the states at 112.5 °, and one of the states at 157.5 ° may be selected.

The above results indicate that “this prototype device is
It has the ability to rotate more than 85% of the power of linearly polarized light with any polarization angle to any given angle. "

Here, the liquid crystal molecules 17,
AC voltage sources 23A, 23B of 10 V or more so that 18, 19, 20 are oriented perpendicular to the substrate and leave no optical rotation.
(Frequency 1 kHz), the twisted nematic liquid crystals 6A and 6B were driven. In FIG. 8, in order to further reduce the loss of light in all polarizations, a twisted nematic liquid crystal cell having a twist angle smaller than 45 ° (for example, 22.5 ° which is half of 45 °) is used as the polarization rotator 2.
Should be added to

Next, a linearly polarized white light (λ = 400n)
FIG. 9 shows the relationship between the intensity of light emitted from the polarization rotator 10 and the angle of polarization of the incident light when (m-680 nm) is incident on the polarization rotator 10. As can be understood by comparing FIGS. 9 and 8, almost the same characteristics were exhibited except that the maximum value and the minimum value were slightly different from those in the case where the laser beam was incident as shown in FIG.

Further, red light (λ = 600 to 680 n)
m), green light (λ = 500 to 590 nm), and blue light (λ = 400 to 490 nm). The figure shows the case where the optical rotatory power of two liquid crystal cells is superimposed and the plane of polarization of the incident light 2 is rotated by 135 ° (the above-mentioned state, that is, the switch 21A is turned off and the switch 21B is turned off). The wavelength dependence is small in all polarization directions. The optical rotation of the twisted nematic liquid crystal cells 6A and 6B is very small in the color of the transmitted light 5 as compared with other materials exhibiting optical rotation.
It has been shown to be very advantageous to simultaneously rotate the polarization angle of light in a wide wavelength range.

<< Trial Production Example 2 >> A polarization rotator 30 according to the second embodiment shown in FIG. 5 was prototyped. Black guest-host liquid crystal 33 (JB-1000XX, manufactured by Chisso Corporation) was homogeneously aligned using the alignment film to form a guest-host liquid crystal cell 36 (area 10 cm × 10 cm) having a thickness of 10 μm. White light having various polarization planes was made incident on the polarization rotating element 30, and the light transmittance was measured. as a result,
By applying a voltage (10 V or more) of an AC voltage source 42 between the first transparent electrode 32 and the second transparent electrode 34 of the guest host liquid crystal cell 36 via the switch 40, the polarization function of the element can be controlled. confirmed.

As described above, according to each of the embodiments, a plurality of twisted nematic liquid crystal cells 6 ₁ to 6 ₁ .
6 _i , a polarization rotating unit 3 and a polarization selecting unit 4 are laminated,
By controlling the voltage, it is possible to provide the polarization rotating elements 10 and 30 that can control the polarization direction of the element in various ways and at high speed. Therefore, these polarization rotating elements 10 and 30
It can be applied to a wide range of optical applications such as optical communication, optical information processing, optical recording, and various optical measurements.

<Modification> In each of the embodiments shown in FIGS. 2 and 5, the polarization rotator 3 is composed of two twisted nematic liquid crystal cells 6A and 6B, but the twisted nematic liquid crystal having a small twist angle is used. One or more cells may be further stacked. With this configuration, it is possible to obtain a more precise rotation of the polarization plane.

In each of the embodiments shown in FIGS. 2 and 5, the twisted nematic liquid crystal cells 6A and 6B having the same twist orientation in the rotation direction are used, but the twist directions in the twist orientation are different. It is also possible to use a nematic liquid crystal cell in combination.

[0063]

As described above, according to the first aspect of the present invention, a twisted nematic liquid crystal having a twisted orientation or a cholesteric liquid crystal is laminated with a plurality of twisted nematic liquid crystal cells sandwiched between transparent electrodes, and is formed by stacking a plurality of twisted nematic liquid crystal cells. A polarization rotator that rotates the polarization plane and emits the light, and a polarization selector that has a polarizing plate that receives the light emitted from the polarization rotator and selects linearly polarized light in a certain direction, and the polarization rotator and the polarization selector. And the individual twisted nematic liquid crystal cells are driven by voltage to maximize the intensity of the output light from the polarization selector, and the desired angle is obtained. Since the linearly polarized light is emitted, the polarization direction of the incident light can be controlled at high speed and variously even with a simple device configuration.

According to the second aspect of the present invention, the molecular arrangement direction of the substrate surface of the twisted nematic liquid crystal cell is parallel or perpendicular to the molecular arrangement direction of the substrate surface of the adjacent twisted nematic liquid crystal cell. Can be efficiently rotated.

According to the third aspect of the present invention, since the light passing through the twisted nematic liquid crystal cell passes through the polarization selecting section, the polarization direction of the incident light can be increased even with a simple device configuration. , And can be variously controlled.

According to the fourth aspect of the present invention, a photodetector for photoelectrically converting a part of the linearly polarized light emitted from the polarization selector,
The voltage applied to the twisted nematic liquid crystal cell is controlled, the magnitude of an electric signal output from the photodetector is compared according to the applied voltage, and the linearly polarized light emitted from the polarization selector is controlled. And a signal control unit that selects an applied voltage so that the intensity of the transmitted light has the largest value and holds the applied voltage. Therefore, a plurality of twisted units that maximize the light intensity of the transmitted light are provided. According to the invention of claim 5, wherein the driving control of the nematic liquid crystal cell can be automatically performed, the polarization selector includes a Nicol prism, a Gran-Thomson prism, a Rochon prism, a Wollaston prism, a Gran Foucault prism, and a polarized light. Since it is composed of either a film or a guest-host liquid crystal cell, the polarization direction of incident light can be increased even with a simple device configuration. And it can be variously controlled.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the basics of a polarization rotation element according to the present invention.

FIG. 2 is a configuration diagram showing a first embodiment of the polarization rotation element according to the present invention.

FIG. 3 is an explanatory diagram showing a relationship between optical directions in a polarization rotation element.

FIG. 4 is an explanatory diagram illustrating a configuration of a rotation mechanism that houses a polarization rotation unit and a polarization selection unit.

FIG. 5 is a configuration diagram showing a second embodiment of the polarization rotation element according to the present invention.

FIG. 6 is a configuration diagram showing a third embodiment of the polarization rotation element according to the present invention.

FIG. 7 is a block diagram illustrating a configuration of a signal control unit of a polarization rotation element according to a third embodiment of the present invention.

FIG. 8 is an explanatory diagram showing the relationship between the transmitted light intensity of the polarization rotation element and the polarization angle of incident light when He-Ne laser light is incident.

FIG. 9 is an explanatory diagram showing a relationship between transmitted light intensity of a polarization rotation element and polarization angle of incident light when white light is incident.

FIG. 10 is an explanatory diagram showing a relationship between transmitted light intensity and polarization angle of incident light when three primary colors of incident light are used.

FIG. 11 is a configuration diagram illustrating an example of a conventional polarization rotation element.

FIG. 12 is a configuration diagram showing another example of a conventional polarization rotation element.

FIG. 13 is a configuration diagram showing still another example of a conventional polarization rotation element.

[Explanation of symbols]

1,10,30 polarization rotation element 2 incident light 3 polarization rotating unit 4 polarization selecting unit 5 transmitted light 6 ₁ ~6 _i, 6A, 6B twisted nematic liquid crystal cell 11A, 11B, 31 first transparent substrate 12A, 12B, 32 First transparent electrode 13A, 13B Liquid crystal 14A, 14B, 34 Second transparent electrode 15A, 15B, 35 Second transparent substrate 16 Polarizing film 17, 18, 19, 20 Liquid crystal molecules 21 _{1 to} 21 _i , 21A, 21B, 40 Switch 22A, 22B, 41 lead wire _{23 1 ~23 i, 23A, 23B} , 42 AC power supply 35 guest-host liquid crystal 36 guest-host liquid crystal cell 37 dichroic dye 38 a nematic liquid crystal 51 beam splitter 52 optical detector 54 signals the control unit

Claims (5)

[Claims] 1. A polarization rotator configured by laminating a plurality of twisted nematic liquid crystal cells in which a twisted nematic liquid crystal or a cholesteric liquid crystal is sandwiched between transparent electrodes, and rotating a polarization plane of incident light to emit the light. A polarization selector having a polarizing plate for selecting the linearly polarized light in a certain direction by entering the output light of the polarization rotator, wherein the polarization rotator and the polarization selector are arranged in a plane perpendicular to the optical axis of the incident light. Rotating to a desired angle, and voltage driving individual twisted nematic liquid crystal cells to maximize the output light intensity from the polarization selector, and emits linearly polarized light at the desired angle. Polarization rotation element. 2. The polarization rotator according to claim 1, wherein the molecular arrangement direction of the substrate surface of the twisted nematic liquid crystal cell is parallel or perpendicular to the molecular arrangement direction of the substrate surface of the adjacent twisted nematic liquid crystal cell. A polarization rotation element, comprising: 3. The polarization rotator according to claim 1, wherein the light passing through the twisted nematic liquid crystal cell passes through the polarization selector. 4. The polarization rotator according to claim 1, 2 or 3, further comprising: a photodetector for photoelectrically converting a part of the linearly polarized light emitted from the polarization selector; and a light detector for the twisted nematic liquid crystal cell. Controlling the applied voltage value, comparing the magnitude of the electric signal output from the light detection unit according to the applied voltage value, and the intensity of the linearly polarized light emitted from the polarization selection unit is the largest value. And a signal controller for selecting an applied voltage and holding the voltage, thereby maximizing the output light intensity of the polarization selector. 5. The polarization rotator according to claim 1, wherein the polarization selector comprises a Nicol prism, a Gran-polarizer.
Glan-Thompson Prism, Rochon
A polarization rotator comprising a prism, a Wollaston prism, a Glan-Foucault prism, a polarizing film, or a guest-host liquid crystal cell.