JPH06289353A - Liquid crystal spatial optical modulator and amplitude phase modulator - Google Patents

Abstract

PURPOSE:To obtain high performance with simple means by incorporating dichromatic dyestuff into a liquid crystal layer and intersecting the transmission axis of the polarizing plate on a light incident side nearly orthogonally with the direction of the liquid crystal directors on the light incident side. CONSTITUTION:The dichromatic dyestuff 107 is added to the liquid crystal layer 105 of the liquid crystal spatial optical modulator of a TN mode. The dyestuff added to this liquid crystal is oriented along the liquid crystal directors 106. The transmission axis 110 of the polarizing plate 103 on the incident side is intersected orthogonally with the orientation direction on the incident light of the liquid crystal spatial optical modulator of the TN mode. The polarizing plate 109 of axis side is arranged so as to arrange incident side polarizing late in parallel with transmission axis. The liquid crystal directors 106 are perpendicular to the polarization direction of the incident light at the time of voltage impression and, therefore, the incident light senses only the ordinary refractive index. The dichromatic dyestuff 107 orients together with the liquid crystal at this time but there are neither change of the phases nor absorption of the light. The extraordinary light is absorbed by the dichromatic dyestuff at the time of the non impression of the voltage and is emitted with the same phase as the phase at the time of the voltage impression. Namely, only the amplitude of the light is changed without entailing the phase change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal spatial light modulator for modulating the amplitude of light and an amplitude phase modulator for independently modulating the amplitude and phase of light.

[0002]

2. Description of the Related Art A conventional liquid crystal spatial light modulator changes the phase of light when modulating the amplitude of light.

[0003]

However, the conventional liquid crystal spatial light modulator has a problem that it cannot be used well due to phase distortion even if it is applied to wavefront control or an optical shutter. Further, the conventional amplitude / phase modulator using the conventional liquid crystal spatial light modulator has a problem that the amplitude and phase cannot be completely modulated independently of the amplitude and phase of light. The present invention solves such a problem, and an object thereof is to provide a high-performance liquid crystal spatial light modulator and amplitude / phase modulator by a simple means.

[0004]

A first liquid crystal spatial light modulator of the present invention is at least a twisted nematic mode liquid crystal spatial light modulator, wherein a liquid crystal layer contains a dichroic dye.
It is characterized in that the transmission axis of the polarizing plate on the light incident side is substantially orthogonal to the direction of the liquid crystal director on the light incident side.

The first amplitude-phase modulator of the present invention is characterized in that the phase modulation type spatial light modulator and the first liquid crystal spatial light modulator are connected with the pixels aligned.

A second amplitude / phase modulator of the present invention is the liquid crystal spatial light modulator of the electric field control birefringence mode in which the phase modulation type spatial light modulator in the first amplitude / phase modulator is a homogeneous alignment. It is characterized by

A third amplitude / phase modulator of the present invention is the same as the second amplitude / phase modulator, in which the direction of the liquid crystal director of the electric field control birefringence mode liquid crystal spatial light modulator of the homogeneous alignment and the first amplitude phase modulator. The liquid crystal spatial light modulator is characterized in that it is substantially orthogonal to the direction of the liquid crystal director on the light incident side.

A fourth amplitude-phase modulator of the present invention is the same as the third amplitude-phase modulator, wherein the polarization plate on the incident side of the first liquid crystal spatial light modulator has the homogeneous alignment in the electric field control birefringence mode. The liquid crystal spatial light modulator is located on the light incident side.

[0009]

The details of the present invention will be described below with reference to Examples.

(Embodiment 1) FIG. 1 shows the structure of a liquid crystal spatial light modulator of the present invention.

Liquid crystal layer 1 of TN mode liquid crystal spatial light modulator
05 was added with dichroic dye 107. The dye added to the liquid crystal is aligned along the liquid crystal director 106.

The transmission axis 110 of the incident side polarizing plate 103 is set to T
The N-mode liquid crystal spatial light modulator was made orthogonal to the alignment direction on the incident side.

In this embodiment, the outgoing side polarizing plate 109 is arranged so that the transmission axis is parallel to the incident polarizing plate.

In the conventional TN mode liquid crystal spatial light modulator, when the applied voltage is changed, not only the transmittance but also the phase of light is changed. This will be explained.

When a voltage is applied, the liquid crystal director 204 becomes perpendicular to the polarization direction 202 of the incident light as shown in FIG. 2, so that any polarized light feels only the ordinary refractive index and the phase of the emitted light is constant.

However, when no voltage is applied, the phase of any polarized light deviates from that when a voltage is applied.

FIG. 3 shows the principle of phase change in a conventional TN mode liquid crystal spatial light modulator. The light 302 transmitted through the polarizing plate is polarized in a direction perpendicular to the liquid crystal director 301 on the incident surface of the TN mode liquid crystal spatial light modulator as shown in FIG. That is, this light is an ordinary light.

However, in the TN cell, since the liquid crystal is twisted and aligned, the liquid crystal director tilts with respect to the light 302. Therefore, as shown in FIG.
In addition to 04, an extraordinary light component 305 appears. This extraordinary light is out of phase with the ordinary light.

When the light further advances, the liquid crystal director further tilts, and the ordinary light component 307 and the extraordinary light component 308 from the ordinary light component 304 as shown in FIG. 3C, and the abnormal light component 305 as shown in FIG. 3D. From the ordinary light component 309 and the extraordinary light component 31
0 appears.

Originally, the extraordinary light component 305 is the ordinary light component 30.
4, the ordinary light components 307 and 309 are also out of phase.

In this way, the lights whose phases are shifted one after another overlap each other, so that the phase of the emitted light is shifted as compared with the case where only the ordinary refractive index is sensed.

The above is the case where ordinary light is incident, but it will be apparent from the above description that the phase changes if an extraordinary light component is included from the beginning.

In the conventional TN cell, this phase change is from 1/8 wavelength to about the wavelength.

On the other hand, in the liquid crystal spatial light modulator of the present invention, the phase of light is not changed even if the applied voltage is changed.

First, when a voltage is applied, the liquid crystal director 404 becomes perpendicular to the polarization direction of the incident light as shown in FIG. 4, so that the incident light feels only the ordinary refractive index. At this time, the dichroic dye 407 is also aligned with the liquid crystal, but it does not change the phase and does not absorb light.

When no voltage is applied, the extraordinary light that has appeared through the liquid crystal is immediately absorbed by the dichroic dye. Therefore, unlike the conventional TN-mode liquid crystal spatial light modulator, there is no overlap of the phase-shifted component with the ordinary light, and the emitted light has the same phase as when the ordinary refractive index is felt (when voltage is applied). Is emitted at.

That is, in the TN mode liquid crystal spatial light modulator of the present invention, only the amplitude of light can be changed without changing the phase.

In this embodiment, the polarizing plates are arranged in parallel Nicols (normally black which is in the extinction state when no voltage is applied).
Therefore, the absorption ratio of the dye also improves the contrast ratio. Even in the case of crossed Nicols, the phase of light does not change if the polarizing plate on the incident side is arranged according to the present invention.

In this example, S-344 manufactured by Mitsui Toatsu Dye Co., Ltd. was used as the dichroic dye.

If the TN-mode liquid crystal spatial light modulator of the present invention is used for recording an amplitude hologram such as a Lohmann type or a Lee type, a good reproduced image without phase distortion can be obtained.

Further, by using the TN mode liquid crystal spatial light modulator of the present invention, a liquid crystal shutter which does not disturb the wavefront can be realized. This can be applied to various information processing and image processing.

(Embodiment 2) FIG. 5 shows the configuration of the amplitude / phase modulator of the present invention.

The amplitude / phase modulator of the present invention is the TN of the first embodiment.
Mode liquid crystal spatial light modulator 503 and homogeneous alignment type ECB (electric field control birefringence) mode liquid crystal spatial light modulator 5
02 is a combination of the pixels with the pixels aligned.

The ECB mode liquid crystal spatial light modulator can ideally modulate the phase without changing the amplitude of the light.
However, actually, there are cases where the transmittance changes as shown in FIG.

The amplitude / phase modulator of the present invention has such an EC
Even if a B-mode liquid crystal spatial light modulator is used, the amplitude and phase of light can be independently modulated.

FIG. 7 shows the arrangement of the liquid crystal director and the polarizing plate of the amplitude / phase modulator of the present invention. In the amplitude phase modulator of the present invention, an ECB mode liquid crystal spatial light modulator is arranged on the light incident side. The polarizing plate 703 on the incident side has a transmission axis 710 parallel to the liquid crystal director 704 of the ECB mode liquid crystal spatial light modulator. The incident light undergoes phase modulation by an ECB mode liquid crystal spatial light modulator. At this time, the polarization state does not change. Therefore, even when the light is incident on the TN-mode liquid crystal spatial light modulator, it remains linearly polarized.

The liquid crystal director 106 on the incident side of the TN mode liquid crystal spatial light modulator has this polarization direction (that is, ECB).
Direction of the director of the liquid crystal spatial light modulator of the mode). Therefore, as in the case of the first embodiment, the incident light is amplitude-modulated without being phase-modulated.

In order to independently modulate the amplitude and phase of light, the data input to the amplitude / phase modulator is modified.

The driving device of the liquid crystal spatial light modulator stores the change in the transmittance and the phase of the liquid crystal spatial light modulator in the ECB mode, which is obtained in advance.

When the driving device receives the phase data,
Based on the stored contents, a transmittance correction amount is obtained, and a drive signal corresponding to this transmittance is input to the TN mode liquid crystal spatial light modulator.

As a result, accurate modulation according to the given amplitude / phase data was achieved. Therefore, when the amplitude / phase modulator of the present invention is applied to three-dimensional image reproduction, a good reproduced image with less noise was obtained. Moreover, this amplitude / phase modulator can be applied to various fields such as various information processing, image processing, wavefront measurement, and wavefront correction.

Although the integrated amplitude / phase modulator has been described in the present embodiment, in addition to this, the TN mode liquid crystal spatial light modulator and the ECB mode liquid crystal spatial light modulator are connected by an afocal optical system. Such a configuration is also possible.

Since the amplitude / phase modulator of the present invention enables the amplitude and phase of light to be independently modulated even when an ECB mode liquid crystal spatial light modulator that causes a change in transmittance is used, the degree of freedom in device design is high. Is improved.

Although the embodiments of the present invention have been described above, the present invention can be widely applied to other display devices.

[0045]

According to the liquid crystal spatial light modulator of the present invention, it is possible to realize an amplitude modulator without a phase change. In addition, since the contrast ratio can be made large, the wavefront can be controlled with high accuracy, and the high-performance amplitude hologram and optical shutter can be realized.

According to the amplitude phase modulator of the present invention, since the amplitude and phase of light can be independently modulated, the optical wavefront can be controlled with high accuracy. This made it possible to realize highly accurate hologram reproduction, three-dimensional beam steering, optical correlator, three-dimensional measurement, adaptive optics, and the like.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a liquid crystal spatial light modulator of the present invention.

FIG. 2 is a side view showing a state of a conventional liquid crystal spatial light modulator when a voltage is applied.

FIG. 3 is a diagram showing a principle of causing a phase change in a conventional TN mode liquid crystal spatial light modulator.

FIG. 4 is a side view showing a state when a voltage is applied to the liquid crystal spatial light modulator of the present invention.

FIG. 5 is a side view showing the configuration of the amplitude phase modulator of the present invention.

FIG. 6 is a diagram showing amplitude and phase modulation characteristics of an ECB mode liquid crystal spatial light modulator used in this example.

FIG. 7 is a perspective view showing a configuration of an amplitude / phase modulator of the present invention.

[Explanation of symbols]

 101 Polarization component perpendicular to transmission axis of incident side polarizing plate 102 Polarization component parallel to transmission axis of incident side polarizing plate 103 Polarizing plate on incident side 104 Light transmitted through polarizing plate 105 Liquid crystal layer 106 Liquid crystal director 107 Dichromatic dye 108 Light modulated by liquid crystal 109 Polarizing plate on outgoing side 110 Transmission axis of polarizing plate 201 Polarizing plate 202 Polarizing direction of incident light 203 Electrode 204 Liquid crystal director 205 Electrode 206 Polarizing plate 301 Liquid crystal director on incident plane 302 Transmitted through polarizing plate Light 303 liquid crystal director 304 ordinary light component 305 extraordinary light component 306 liquid crystal director 307 ordinary light component 308 extraordinary light component 309 ordinary light component 310 abnormal light component 401 polarizing plate 402 polarization direction of incident light 403 electrode 404 liquid crystal director 405 electrode 406 polarizing plate 407 two colors Sex dye 501 Polarizer 502 TN mode liquid crystal spatial light modulator 503 ECB mode liquid crystal spatial light modulator 504 Polarizing plate 701 Polarization component perpendicular to transmission axis of incident side polarizing plate 702 Polarization component parallel to transmission axis of incident side polarizing plate 703 Polarizing plate on incident side 704 Liquid crystal director 708 Light modulated by liquid crystal 709 Polarizing plate on outgoing side 710 Transmission axis of polarizing plate

Claims (5)

[Claims] 1. In a twisted nematic mode liquid crystal spatial light modulator, a liquid crystal layer contains a dichroic dye, and a transmission axis of a polarizing plate on the light incident side is substantially orthogonal to a direction of a liquid crystal director on the light incident side. Liquid crystal spatial light modulator characterized in that 2. An amplitude phase modulator, wherein the phase modulation type spatial light modulator and the liquid crystal spatial light modulator according to claim 1 are connected by aligning pixels. 3. The amplitude phase modulator according to claim 2, wherein the phase modulation type spatial light modulator is a liquid crystal spatial light modulator of electric field control birefringence mode of homogeneous alignment. 4. The direction of the liquid crystal director of the liquid crystal spatial light modulator of the electric field control birefringence mode of the homogeneous alignment and the direction of the liquid crystal director on the light incident side of the liquid crystal spatial light modulator of claim 1 are substantially orthogonal to each other. The amplitude-phase modulator according to claim 3, wherein 5. The polarizing plate on the incident side of the liquid crystal spatial light modulator according to claim 1 is on the light incident side of the liquid crystal spatial light modulator of the homogeneously oriented electric field control birefringence mode. The amplitude phase modulator according to claim 4.