JP2000284224A - Stereoscopic image display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the visibility of a stereoscopic display image. SOLUTION: A left-eye and a right-eye liquid crystal shutter are so switched among three states wherein the liquid crystal molecules are aligned in a 1st direction 1 when a negative voltage is applied, in a 2nd direction 2 when a positive voltage is applied, and in a 3rd direction 3 between the 1st direction 1 and 2nd direction 2 when no voltage is applied. Consequently, the shutters are so driven that they are shielded from light alternately in synchronism with left-eye and right-eye images displayed alternately by frame periods, a simultaneous light shield period is provided for each frame, and the time mean value of the applied voltages is substantially zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for displaying an image for the left eye and an image for the right eye, which are given parallax alternately, in a time-division manner. The present invention relates to a technique for displaying a stereoscopic image in a pseudo manner by selectively recognizing the stereoscopic image with the right eye.

[0002]

2. Description of the Related Art The amount of information handled by individuals has increased dramatically in recent years due to the development of information terminals centered on personal computers and the development of information networks represented by the Internet. In particular, with respect to image information, as the amount of information that can be handled by individuals increases due to improvements in compression technology and transfer technology, there is an increasing demand for a display device that can express the content more precisely and more realistically.

[0003] Of these demands, in order to express image information more precisely, a liquid crystal display (LCD), an electroluminescent element (EL), and an electron beam tube (CRT) have been developed in order to increase the definition of the screen. ) And various display elements such as a plasma display panel (PDP) are being vigorously studied for improvement.

[0004] On the other hand, in response to a demand for more realistic representation of image information, it is conceivable to display an image in three dimensions. Potential demands for stereoscopic image display are strong, for example, for industrial use, commercial use such as virtual malls, or amusement such as games.

However, for example, in order to realize a three-dimensional image display using a liquid crystal optical shutter system, the eyeglasses of the observer must be provided with a shutter function due to the limitation of the size of the liquid crystal cell used for the optical shutter. Absent. In addition, it is still difficult to achieve sufficient visibility of a stereoscopic image, and it is hard to say that stereoscopic image display has been sufficiently widespread due to uncomfortable feeling due to low visibility.

[0006] An example of a conventional stereoscopic image display system is disclosed as "stereoscopic television" in Document 1: "Japanese Patent Laid-Open No. 61-227498". According to the technique disclosed in this document, the optical shutters provided for the left and right eyes of the stereoscopic glasses are constituted by two twisted nematic liquid crystal cells.

By supplying an AC voltage synchronized with the switching of the image to the liquid crystal cell, the switching cycle of the left image and the right image of the subject displayed on the television screen is switched every field or every field. In synchronization, the left and right optical shutters are alternately opened and closed. As a result, the observer wearing the glasses can three-dimensionally recognize the image of the subject.

Another example of a conventional stereoscopic image display system is disclosed as a “stereoscopic image display device” in Document 2: “JP-A-8-327961”. According to the technique disclosed in this document, the device is provided with a polarizing plate on the front of the display, and the shutter glasses are provided with a single liquid crystal cell having a region for the right eye and a region for the left eye, a polarizing plate for the right eye, and a left polarizing plate. And an eye polarizing plate. And with such a configuration, the structure of the shutter glasses is simplified, and further,
The system for driving the liquid crystal cell can be one system.
Therefore, according to this technique, the cost of the apparatus can be reduced.

In the technique disclosed in the above-mentioned Document 1, since the twisted nematic liquid crystal cell is used as the shutter, the response is slow, so that the display flickers and the left and right images are displayed twice. There was a point.

In the technique disclosed in the above-mentioned document 2, when the display has a long afterglow like a CRT, the left (right) eye shutter is left (right) when the left (right) eye shutter is in a transmissive state.
The afterglow of the right (left) eye image is captured by the left (right) eye together with the eye image. For this reason, there is a problem that the contrast is substantially reduced and the left and right images are double reflected.

Therefore, the inventor according to the present invention is disclosed in Japanese Patent Application No. Hei.
No. 0-17218, a liquid crystal capable of high-speed response, for example, a smectic liquid crystal, and a solution for preventing double reflection due to afterglow of an image display device, use a smectic liquid crystal capable of high-speed response as a liquid crystal. There has been proposed a technique for providing a simultaneous light-shielding period in which an eye shutter and a right-eye shutter are simultaneously in a light-shielding state.

[0012]

The technique of providing the simultaneous light-shielding period described above is excellent in that the amount of residual light that can be visually recognized can be reduced, so that flicker due to an afterimage can be suppressed. However, when a liquid crystal which has, for example, a chiral smectic C phase as a smectic liquid crystal capable of high-speed response and switches between two states is used, the transmission / shielding state of the liquid crystal shutter is controlled by inverting the polarity of the applied voltage. I have. Therefore, if a simultaneous light-blocking period is provided for the left eye and the right eye, positive and negative asymmetric voltages are applied to the liquid crystal cell.

For this reason, when the time average value of the voltage applied to the liquid crystal cell is taken, it is biased to either positive or negative, so that the liquid crystal cell tends to deteriorate with time, as will be described in a comparative example described later. As a result, there is a possibility that a situation may occur in which the visibility is reduced, so there is room for improvement.

[0014] Further, the left and right eyes of the observer who views the stereoscopic image see the image every other frame period. For this reason, when the frame period is long, the image may be visually recognized as flickering. On the other hand, it is desired to shorten the frame period.

However, in the conventional liquid crystal cell, the orientation of the liquid crystal molecules is switched between the two states by inverting the polarity of the applied voltage. For this reason, the improvement of the frame switching frequency for switching between the left and right images has been practically restricted by the response characteristics of the liquid crystal cell.

The present invention has been made in view of the above circumstances, and has as its object to provide a three-dimensional image display system in which the visibility of three-dimensional image display is improved.

[0017]

In order to achieve this object, according to the stereoscopic image display system of the present invention, the left-eye image and the right-eye image are time-divided for each frame period. , A liquid crystal shutter glasses mechanism including a left-eye liquid crystal shutter and a right-eye liquid crystal shutter, and a driving unit that applies a driving voltage to the left-eye liquid crystal shutter and the right-eye liquid crystal shutter. By alternately setting the left-eye liquid crystal shutter and the right-eye liquid crystal shutter in a light-shielding state for each frame period,
A stereoscopic image display system for selectively recognizing an image for the left eye with the left eye and an image for the right eye with the right eye, wherein the liquid crystal shutters for the left and right eyes are configured by smectic liquid crystal cells. In the liquid crystal cell, the alignment direction of the liquid crystal molecules when a negative voltage is applied is set to the first direction, the alignment direction of the liquid crystal molecules when the positive voltage is applied is set to the second direction, and the alignment direction of the liquid crystal molecules when no voltage is applied is substantially changed. And a direction intermediate between the first direction and the second direction.

As described above, according to the stereoscopic image display system of the present invention, it is a smectic liquid crystal capable of high-speed response, and the orientation of liquid crystal molecules is changed in three directions, that is, in one of three states, depending on the applied voltage. A liquid crystal cell which can be selectively held in a liquid crystal is used. Therefore, since the three states of the liquid crystal cell can be used as the liquid crystal shutter, the opening and closing of the liquid crystal shutter can be controlled by applying and not applying a voltage.

Therefore, according to the present invention, higher-speed response is possible as compared with opening and closing of the shutter by polarity reversal. As a result, by improving the frame frequency, it is possible to suppress flickering and double occurrence of display and improve visibility. It is desirable that the intermediate direction of the alignment direction of the liquid crystal molecules is substantially the direction of an isometric bisector of the first direction and the second direction.

In the stereoscopic image display system of the present invention, preferably, the liquid crystal shutters for the left eye and the right eye are provided with a polarizer having an absorption axis parallel or perpendicular to the intermediate direction on the incident side of the liquid crystal cell. It is desirable to provide an analyzer having an absorption axis orthogonal to the polarizer on the emission side of the liquid crystal cell. With such a configuration, the liquid crystal shutters for the left eye and the right eye are in a transmission state when the liquid crystal molecules are aligned in the first direction and the second direction, and when the liquid crystal molecules are aligned in the intermediate direction. Then, a light shielding state is set.

In the stereoscopic image display system according to the present invention, preferably, the liquid crystal shutters for the left and right eyes have an absorption axis parallel or orthogonal to the first direction or the second direction on the incident side of the liquid crystal cell. A first analyzer having an absorption axis that is orthogonal to the polarizer with respect to the polarizer on the emission side of one of the left-eye and right-eye liquid crystal shutters. A second analyzer having an absorption axis parallel to the direction of the absorption axis of the polarizer is provided on the emission side of the other liquid crystal cell of the liquid crystal shutters for the eye and the right eye.

With such a configuration, in the liquid crystal shutters for the left eye and the right eye, when the liquid crystal molecules are oriented in the first direction or the second direction, one of the liquid crystal shutters is in a transmission state. At the same time, the other liquid crystal shutter is in a light blocking state, and is in a non-transmission state when the liquid crystal molecules are aligned in the intermediate direction. When the absorption axes of the polarizer and the analyzer are arranged with respect to the alignment direction of the liquid crystal molecules, the left and right transmission spectra may be different depending on the retardation of the liquid crystal cell. In such a case, it is preferable to perform compensation by inserting a phase difference plate on the incident side of the analyzer for either the right eye or the left eye.

Further, it is preferable that the liquid crystal cell constituting the liquid crystal shutter for the left eye and the liquid crystal cell constituting the liquid crystal shutter for the right eye be one liquid crystal cell. As described above, if the liquid crystal cell is shared, the cost of the stereoscopic image display system can be reduced.

In the stereoscopic image display system of the present invention, preferably, the driving section alternates between a positive voltage and a negative voltage so that a time average value of a voltage applied to the liquid crystal cell becomes substantially zero. Is desirably applied.

When the driving voltage is applied such that the time average value becomes substantially zero, the DC component is eliminated in the time average. As a result, it is possible to suppress deterioration of the liquid crystal cell with time. That is, it is possible to suppress the impurity ions in the liquid crystal layer from gradually causing polarization in the liquid crystal cell. Further, since the surface of the liquid crystal driving electrode due to the direct current can suppress the occurrence of the oxidation-reduction reaction, the increase in the surface resistance value of the liquid crystal cell can be suppressed. As a result, it is possible to suppress the occurrence of double projection and flickering of a three-dimensional image shoji due to deterioration of the threshold characteristics of the liquid crystal cell and deterioration of the response of the liquid crystal cell.

Even if the afterglow time of the image display device is short, the response characteristics of the liquid crystal cell are poor, and if the switching of the left and right images by the liquid crystal shutter is delayed, the left and right images appear double, and the image is visually recognized. This leads to a decrease in the performance.

Therefore, in the stereoscopic image display system of the present invention, it is preferable that the driving unit switches between the left-eye liquid crystal shutter and the right-eye liquid crystal shutter immediately before the switching time of the frame period. As described above, if the liquid crystal shutter is switched earlier than the switching of the frame period, it is possible to suppress the occurrence of double reflection due to the delayed response of the liquid crystal, thereby improving the visibility. Can be.

When the afterglow time of the image display device is long, the afterglow due to light emission in the immediately preceding frame period is as follows.
It will remain even after entering the next frame period. Moreover,
Parallax is given to display images in adjacent frame periods for stereoscopic image display. For this reason,
The afterimage of the immediately preceding frame period does not match the display image in the next frame period. As a result, the image may look double or flicker due to the afterimage.

Therefore, in the stereoscopic image display system of the present invention, it is preferable that a simultaneous non-transmissive period in which the liquid crystal shutter for the left eye and the liquid crystal shutter for the right eye are simultaneously in a non-transmissive state is provided in a part of each frame period. Is desirable. As described above, by setting the non-transmission state at the same time for only a part of each frame period, a part of the afterglow can be effectively shielded. As a result, the amount of remaining light that can be visually recognized can be reduced. For this reason, it is possible to suppress the occurrence of double reflection and flicker due to an afterimage.

In particular, in the present invention, by using a liquid crystal cell which switches between the three states, the duty ratio of the positive and negative applied voltages can be easily made one to one even if a simultaneous non-transmission period is provided. As a result, the time average value of the voltage applied to the liquid crystal cell can be made substantially zero. For this reason, it is possible to suppress the occurrence of deterioration with time of the liquid crystal cell and to suppress a decrease in visibility.

In implementing the stereoscopic image display system of the present invention, preferably, the liquid crystal cell is preferably a ferroelectric liquid crystal cell in which liquid crystal molecules are oriented in an intermediate direction when no voltage is applied.

Since the ferroelectric liquid crystal has a memory property,
Normally, the liquid crystal molecules are switched between two orientation directions (between two states) by reversing the polarity of the applied voltage. However, even in the case of a ferroelectric liquid crystal, in the case of a liquid crystal having a helical pitch extremely short with respect to the thickness of the liquid crystal cell, there is a liquid crystal molecule in which the orientation of the liquid crystal molecules naturally returns to a helical structure when no voltage is applied. . The average of the alignment directions of the liquid crystal molecules when returning to the helical structure is intermediate between the alignment directions when the positive and negative voltages are respectively applied. Therefore, if such a ferroelectric liquid crystal is used, switching can be performed between three states.

Here, the characteristics of the ferroelectric liquid crystal which can be switched between the three states will be described with reference to FIG.
FIG. 1A is a schematic diagram illustrating a configuration example of a liquid crystal shutter, and FIG. 1B is a graph illustrating a relationship between a voltage applied to a liquid crystal cell and transmittance.

As shown in FIG. 1A, this liquid crystal shutter has a ferroelectric liquid crystal cell (FLC) 21 interposed therebetween.
It has a configuration in which a polarizer 22 and an analyzer 23 are arranged. The absorption axis A of the polarizer 22 and the absorption axis B of the analyzer 23 are orthogonal to Nicol. Further, in this configuration example, the direction of the absorption axis A of the polarizer 22 is orthogonal to the orientation direction of the liquid crystal molecules when no voltage is applied (third direction 3).

When a negative voltage (-V) is applied to the liquid crystal cell 22, the liquid crystal molecules are oriented in the first direction 1. on the other hand,
When a positive voltage (+ V) is applied to the liquid crystal cell 22, the liquid crystal molecules are aligned in the second direction 2. Furthermore, when no voltage is applied,
The liquid crystal molecules are helically aligned, and the average direction is the third direction 3
Becomes Note that the angles of the first direction 1 and the second direction 2 with respect to the third direction 3 are substantially the tilt angles of the liquid crystal material.

As shown in FIG. 1B, when the polarizer 22 is oriented in the first direction 1 and the second direction 2,
Is converted into, for example, elliptically polarized light by the birefringence effect of the liquid crystal cell 21, and a part of the linearly polarized light is transmitted through the analyzer 23. Therefore, when a positive or negative voltage is applied,
This liquid crystal shutter is in a transmission state.

On the other hand, as shown in FIG. 1B, when the light is oriented in the third direction 3, the linearly polarized light transmitted through the polarizer 22 passes through the liquid crystal cell 21 in the same polarization direction. The light is absorbed by the analyzer 23. Therefore, when no voltage is applied, the liquid crystal shutter is in a light shielding state.

Further, even for a ferroelectric liquid crystal that has two-state switching (SSFLC) with a normal cell thickness, switching between three states can be performed by changing the switching threshold characteristics. For example, it is preferable to add a small amount of a polymer liquid crystal having poor response to an applied voltage to the liquid crystal and to substantially fix the alignment direction. In this case, since many liquid crystal molecules tend to be constrained in the alignment direction of the polymer liquid crystal, the liquid crystal cell can be switched between three states. in this case,
The polymer liquid crystal having poor response may be added to the liquid crystal later, or may be added in a monomer state in advance and polymerized after alignment.

Here, when a liquid crystal cell shown in FIG. 1A is constructed using a liquid crystal cell to which a polymer liquid crystal is added as shown in FIG. 1C, switching between three states is possible. The characteristics of the ferroelectric liquid crystal will be described. FIG. 1C is a graph showing the relationship between the voltage applied to the liquid crystal cell and the transmittance.

As shown in FIG. 1C, when the liquid crystal is oriented in the first direction 1 and the second direction 2, the linearly polarized light transmitted through the polarizer 22 becomes, for example, elliptical due to the birefringence effect of the liquid crystal cell 21. It becomes polarized light and a part of the light passes through the analyzer 23.
Therefore, when a positive or negative voltage is applied, the liquid crystal shutter is in a transmission state.

On the other hand, as shown in FIG. 1C, when the light is oriented in the third direction 3, the linearly polarized light transmitted through the polarizer 22 passes through the liquid crystal cell 21 in the same polarization direction. The light is absorbed by the analyzer 23. Therefore, when no voltage is applied, the liquid crystal shutter is in a light shielding state.

In this case, the threshold value of the applied voltage is not clear with respect to the orientation direction of the liquid crystal molecules, and the orientation direction of the liquid crystal molecules changes continuously according to the applied voltage. As a result, as shown in FIG. 1C, the light transmittance also changes continuously and gradually according to the applied voltage.

In implementing the stereoscopic image display system of the present invention, it is preferable that the liquid crystal cell is an antiferroelectric liquid crystal cell. It is considered that the antiferroelectric liquid crystal has a structure in which, when the applied voltage is zero, liquid crystal molecules are alternately inclined in opposite directions between adjacent smectic layers. As a result, the average of the molecular orientation directions in this state can be considered to be intermediate between the orientation directions when the positive and negative voltages are applied. Therefore, the antiferroelectric liquid crystal cell can be used by switching between the three states.

In implementing the stereoscopic image display system of the present invention, the liquid crystal cell is preferably a chiral smectic A liquid crystal cell (SmA ^* liquid crystal cell) exhibiting electric field induced tilt. In the case of a liquid crystal material containing an optically active substance, a phenomenon in which liquid crystal molecules are inclined and aligned when a voltage is applied even at a temperature at which a smectic A phase is exhibited is known as an “electroclinic effect”. The orientation direction depends on the sign of the applied voltage, and the magnitude of the inclination is substantially proportional to the magnitude of the applied voltage. Therefore, the SmA ^* liquid crystal cell can also be used as a cell that can switch between three states.

[0045]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] First, a first embodiment of a stereoscopic image display system will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining the outline of the configuration of the stereoscopic image display system according to the first embodiment. As shown in FIG. 2, the stereoscopic image display system according to the first embodiment includes an image display device 10, an eyeglass mechanism 20, and a driving unit 30.

(Image Display Device) As the image display device 10, any suitable device such as a CRT, an LCD, a PDP, an EL, an LD, and a projector can be used. Then, the image display device 10 alternately displays the left-eye image and the right-eye image for each frame period by time division.

Since the image display device 10 displays the left and right images alternately, it is desirable that the image display device 10 can rewrite the screen at a high speed. Also, CRTs and PDPs have a relatively long afterglow characteristic of 1-2 ms or more. On the other hand, LCD, EL and LED
Has a short afterglow characteristic of 1 ms or less. According to the present invention, a similar high-contrast image can be enjoyed regardless of the length of the afterglow characteristic of the image display device used.

(Eyeglass mechanism) The eyeglass mechanism 20 includes a liquid crystal shutter 20L for the left eye and a liquid crystal shutter 20R for the right eye.
It is composed of

Here, the eyeglass mechanism 20 in the stereoscopic image system of the first embodiment will be described in more detail with reference to FIG. FIG. 3 is a schematic diagram for explaining the configuration of the eyeglass mechanism 20 in the stereoscopic image display system according to the first embodiment. As shown in FIG. 3, in the glasses mechanism 20, the liquid crystal shutter 20L for the left eye and the liquid crystal shutter 20R for the right eye include liquid crystal cells 21L for the right eye and the left eye.
And 21R are sandwiched between a polarizer 22 and an analyzer 23.

In the first embodiment, the polarizer 22 and the analyzer 23 have a single configuration common to the left eye and the right eye by matching the left and right polarization axes. Then, the polarizer and the analyzer may be individually provided.

Each of the liquid crystal cells 21L and 21R has a structure in which a liquid crystal layer is sandwiched between two transparent substrates provided with transparent electrodes such as ITO. The lower substrate of these transparent electrode substrates is grounded (Gnd) via a lead wire. On the other hand, the upper substrate is connected to the drive unit 30 via a lead wire.

As the material of the substrate, those usually used for liquid crystal, such as glass and plastic, can be used. As a plastic, polycarbonate, polyethersulfone, or the like having a small optical anisotropy is preferably used. Furthermore, on the transparent electrode surface,
An insulating film for preventing short circuit between the upper and lower substrates and an alignment film for liquid crystal alignment may be provided.

This liquid crystal cell is constituted by an antiferroelectric liquid crystal cell. In this liquid crystal cell,
When a negative voltage is applied, the liquid crystal molecules are oriented in the first direction 1 shown in FIG. When a positive voltage is applied, the liquid crystal molecules are aligned in the second direction 2 shown in FIG. Then, when no voltage is applied, the average orientation direction of the liquid crystal molecules is an intermediate direction (third direction 3) between the first direction and the second direction, as shown in FIG. The angles of the first direction 1 and the second direction 3 with respect to the third direction 3 are
For example, it becomes 22.5 °.

As a liquid crystal cell capable of switching between the three states, a ferroelectric liquid crystal cell in which liquid crystal molecules are oriented in an intermediate direction when no voltage is applied is preferably used. Further, as a ferroelectric liquid crystal cell capable of switching between three states, for example,
A small amount of a polymer liquid crystal represented by the formula (2) having a poor response to an applied voltage is added to liquid crystal molecules represented by the following formula (1),
Preferably, the orientation direction is substantially fixed. In this case, since many liquid crystal molecules tend to be constrained in the alignment direction of the polymer liquid crystal, the liquid crystal cell can be switched between three states. In addition, for example, those having a molecular structure represented by the following chemical formula may be used.

[0055]

Embedded image

In the embodiment, as the antiferroelectric liquid crystal molecules constituting the antiferroelectric liquid crystal cell capable of switching between three states, for example, those having a molecular structure represented by the following chemical formula may be used.

[0057]

Embedded image

As a liquid crystal cell capable of switching between three states, a chiral smectic A liquid crystal cell (SmA ^* liquid crystal cell) exhibiting electric field induced tilt may be used.

The polarizer 22 and the analyzer 23 may be, for example, neutral polarizers or films that absorb light in the entire visible light region other than the polarization axis. Further, for example, the polarizing plate may be configured by supporting a polyvinyl alcohol (PVA) film in which an element or a dichroic dye is contained and oriented by a transparent film such as a triacetyl cellulose (TAC) film or a polyester film.

Then, the polarizer 22 is set so that its absorption axis is orthogonal to the third direction 3, so that the liquid crystal cells 21L and 21L are
It is provided on the incident side of R. The analyzer 23 is provided on the emission sides of the liquid crystal cells 21L and 21R such that the absorption axis thereof is orthogonal to the absorption axis of the polarizer 22.

By disposing the polarizer 22 and the analyzer 23 in this manner, both the left-eye and right-eye liquid crystal shutters 20L and 20R apply a negative voltage (-V) to the liquid crystal cell 21L or 21R. When the liquid crystal molecules are oriented in the first direction 1, the liquid crystal enters a transmission state (ON). In addition, the positive voltage (+
When V) is applied to orient in the second direction 2, the transmission state (ON) is obtained.

When no voltage is applied, the liquid crystal molecules are substantially oriented in the third direction 3 and are in a light-shielded state (OFF). The relationship between the applied voltage and the transmission characteristics is summarized in Table 1 below.

[0063]

[Table 1]

The value of the absolute value of the positive or negative applied voltage V when the liquid crystal material is aligned in the first direction 1 or the second direction 2 depends on the threshold characteristics of the liquid crystal material used and the cell thickness.
It is good to be in the range of 0V to 50V.

The direction of the absorption axis of the polarizer 22 can be set to any direction, but if it is provided perpendicular to the third direction 3, the driving waveform of the liquid crystal cell can be simplified as described later. Can be. Further, the absorption axis of the analyzer 23 can be set in any direction. However, if the analyzer is arranged so as to be orthogonal to the polarizer 22, the contrast ratio can be maximized.

In FIG. 3, the polarizer 22 and the analyzer 23 are connected to the liquid crystal cells 21L and 21L for easy understanding of the configuration.
Although shown separated from 1R, they are actually stacked and integrated. In addition, the polarizer 22 and the analyzer 23
Is adhered to the liquid crystal cells 21L and 21R, the polarizer 22 and the analyzer 23 are required to be in contact with the liquid crystal cells 21L and 21R.
It is preferable to apply an adhesive made of a polymer such as an acrylic resin in a thickness of several μm to several tens μm on the surface to be adhered.

(Drive Unit) The drive unit 30 applies a drive voltage to the liquid crystal shutter 20L for the left eye and the liquid crystal shutter for the right eye, and independently controls opening and closing of the left and right liquid crystal shutters by the applied voltage. Then, the driving unit 30
The liquid crystal shutter for the left eye and the liquid crystal shutter for the right eye are alternately set to the light-shielding state for each frame period, so that the image for the left eye can be selectively viewed by the left eye and the image for the right eye can be selectively visually recognized by the right eye. The driving unit 30 may be provided independently of the eyeglass mechanism 20 and the image display device 10 or may be built therein.

The drive section 30 supplies a voltage waveform to the liquid crystal cells 21L and 21R so that the left-eye and right-eye alternately repeat the light shielding / transmitting state in synchronization with the image switching of the image display device. As the voltage waveform, for example, it is preferable that the time average value of the applied voltage is substantially zero from the viewpoint of the durability of the liquid crystal material and the drive electrode. Further, for example, it is preferable to supply a voltage waveform that provides a simultaneous light-shielding period in which the left-eye and right-eye are simultaneously in a light-shielded state, from the viewpoint of reducing the double reflection of the left and right images.

(First Operation Example) Next, referring to FIG. 4, as a first operation example of the stereoscopic image display system of the first embodiment, an operation suitable for a case where the afterglow time of the image display device 10 is short. An example will be described. Image display device 1 with short afterglow time
Examples of 0 include LCD and EL.

FIG. 4 is a timing chart for explaining the first operation example. As shown by the curves I and II in FIG. 4, the driving unit 30 controls the positive voltage (+ V) and the negative voltage (−V) such that the time average value of the voltage applied to each liquid crystal cell becomes substantially zero. V) are applied alternately.

That is, in the first operation example, the positive voltage (+ V) is applied for the same length of time as the light emission time Tf of the left image frame L and the right image frame R, and subsequently, no voltage is applied (0). State, then apply a negative voltage (-V), and then apply the voltage waveform of the cycle of applying no voltage (0). When the drive voltage is applied such that the time average value becomes substantially zero, the DC component is removed in the time average. As a result, it is possible to suppress the occurrence of deterioration over time of the liquid crystal cell as described in a comparative example described later.

In this operation example, a waveform whose phase is shifted by the time Tf is applied to the liquid crystal shutter 20R for the right eye and the liquid crystal shutter 20R for the left eye. As a result, as shown by curves III and IV in FIG. 4, the left and right liquid crystal shutters alternately turn on and off.

Further, in the first operation example, the driving unit 30
Immediately before the switching time of the frame period, the liquid crystal shutters for the left eye and the right eye are switched. That is, the drive waveform is applied at a timing faster by Td than the light emission timing of the image display device in accordance with the response time of the liquid crystal cell to be used.

As described above, by advancing by Td,
Even if the afterglow time of the image display device is short, the occurrence of double reflection due to delayed response can be suppressed, and as a result, the visibility can be improved. The shorter the time Td, the larger the amount of light transmitted through the liquid crystal shutter.
When the image display device is observed through glasses, the user feels bright. Therefore, it is desirable to use, for example, an antiferroelectric liquid crystal having a fast response time in the liquid crystal cell.

(Second Operation Example) Next, referring to FIG. 5, as a second operation example of the stereoscopic image display system of the first embodiment, an operation suitable for a case where the afterglow time of the image display device 10 is long. An example will be described. Image display device 1 with long afterglow time
Examples of 0 include a CRT and a PDP.

FIG. 5 is a timing chart for explaining the second operation example. As shown by the curves I and II in FIG. 5, the driving unit 30 controls the positive voltage so that the time average value of the voltage applied to each liquid crystal cell becomes substantially zero, as in the first operation example. (+ V) and a negative voltage (−V) are alternately applied.

Then, in the second operation example, as in the first operation example, a waveform whose phase is shifted by time Tf is applied to the right-eye liquid crystal shutter 20R with respect to the left-eye liquid crystal shutter 20L. This results in curves III and I of FIG.
As shown in V, the left and right liquid crystal shutters are turned on alternately,
Repeat OFF.

Further, in the second operation example, the driving unit 30
Liquid crystal shutter for left eye 20L and liquid crystal shutter for right eye 2
A simultaneous non-transmissive period (simultaneous light-shielding period) in which OR is simultaneously set to a non-transmissive state (ie, a simultaneous light-shielding state in the first embodiment) is provided in a part of each frame period. In other words, the simultaneous light-shielding period extends from the last time Td to the first time Tz of each frame period. Note that the time Tz may be adjusted so that a decrease in luminance does not cause a problem in visual perception.

By providing the simultaneous light-blocking time in this manner, the afterglow portion in the period of Tz can be blocked. Further, by setting the time Td to be the simultaneous light-shielding period, it is possible to avoid the influence of the liquid crystal response as in the first operation example. Therefore, in the second operation example, it is possible to suppress the occurrence of double reflection and flicker due to an afterimage.

Also in the second operation example, the duty ratio of the positive and negative applied voltages can be easily set to one-to-one even when the simultaneous non-transmission period is provided by using the liquid crystal cell which switches between the three states. . As a result, the time average value of the voltage applied to the liquid crystal cell can be made substantially zero. For this reason, it is possible to suppress the occurrence of deterioration with time of the liquid crystal cell and to suppress a decrease in visibility.

(Third Operation Example) Next, a third operation example of the stereoscopic image display system of the first embodiment will be described with reference to FIG.

FIG. 6 is a timing chart for explaining the third operation example. As shown by the curves I to IV in FIG. 6, in the third operation example, the driving unit 30 controls the simultaneous light-shielding period Tz.
Is driven in the same manner as in the above-described second operation example, except that it is provided at the center of the frame period separately from the time Td. Also in the third operation example, visibility can be improved by suppressing the occurrence of double reflection and flicker due to an afterimage.

[Second Embodiment] Next, referring to FIG.
A second embodiment of the stereoscopic image display system will be described. In the stereoscopic image display system of the second embodiment, the configuration other than the eyeglass mechanism 20 is the same as the configuration of the above-described first embodiment, and a detailed description thereof will be omitted.

FIG. 7 is a schematic diagram for explaining the configuration of the glasses mechanism 20 in the stereoscopic image display system according to the second embodiment. As shown in FIG. 7, in the eyeglass mechanism 20, the liquid crystal shutter 20L for the left eye and the liquid crystal shutter 20R for the right eye use one left and right common liquid crystal cell 24, and the right and left common polarizer 25 and the left eye And analyzer 26 for the right eye
L and 26R. in this way,
Not only can the cost be reduced by using a common liquid crystal cell, but also the waveform of the voltage applied from the drive unit 30 can be made common to the left and right to form one voltage waveform. As a result, drive control becomes easy.

In the second embodiment, the liquid crystal cell 24 and the polarizer 25 have a single structure common to the left eye and the right eye, but in the present invention, the liquid crystal cell and the polarizer are: They may be provided individually.

The polarizer 25 is provided on the incident side of the liquid crystal cell 24 so that its absorption axis is parallel to the first direction. The analyzer 26R for the right eye is provided on the exit side of the liquid crystal cell 24 so that the absorption axis thereof is orthogonal to the absorption axis of the polarizer 25. On the other hand, the left-eye analyzer 26L is provided on the emission side of the liquid crystal cell 24 such that the absorption axis thereof is parallel to the absorption axis of the polarizer 25.

In the second embodiment, the analyzers 26L and 26R have different polarization axes. As a result, the left and right transmission spectra may be different depending on the retardation of the liquid crystal cell. For this reason, in the second embodiment, the liquid crystal cell 24 is placed on the liquid crystal cell 24 side of the analyzer 23L for the left eye.
A retardation film (retardation plate) 27 having the same retardation as that of the above is bonded so that its optical axis is orthogonal to the liquid crystal molecule direction 2. Thereby, the contrast ratio of the left and right eyes and the hue of the transmitted light can be corrected to the same degree.

By disposing the polarizer 22 and the analyzer 23 in this manner, when a negative voltage (−V) is applied to the liquid crystal cell 24 and the liquid crystal molecules of the liquid crystal cell 24 are oriented in the first direction 1, Next, the liquid crystal shutter 20L for the left eye is in the transmissive state (O
N), and the liquid crystal shutter 20R for the right eye is in the light blocking state (OFF).

When a positive voltage (+ V) is applied to orient the liquid crystal molecules in the second direction 2, the right-eye liquid crystal shutter 20R enters a light-shielding state (OFF), and the left-eye liquid crystal shutter 20R. 20L is in the transmission state (ON).

When no voltage is applied, when the liquid crystal molecules are substantially oriented in the third direction 3, both the left and right liquid crystal shutters 20L and 20R enter a non-transmission state. However, the non-transmissive state in the second embodiment refers to an intermediate state showing a transmissivity between the transmissivity in the transmissive state and the transmissivity in the light-shielded state. Table 2 below summarizes the relationship between the applied voltage and the transmission characteristics.

[0091]

[Table 2]

(First Operation Example) Next, referring to FIG. 8, as a first operation example of the stereoscopic image display system of the second embodiment, an operation suitable for a case where the afterglow time of the image display device 10 is short. An example will be described.

FIG. 8 is a timing chart for explaining the second operation example. As shown by the curve I in FIG. 8, the driving unit 30 controls the positive voltage (+ V) so that the time average value of the voltage applied to each liquid crystal cell becomes substantially zero.
And a negative voltage (-V) are alternately applied.

Further, in the first operation example, the driving unit 30
Immediately before the switching time of the frame period, the liquid crystal shutters for the left eye and the right eye are switched. That is, the drive waveform is applied at a timing faster by Td than the light emission timing of the image display device in accordance with the response time of the liquid crystal cell to be used. In this way, by advancing by Td, even if the afterglow time of the image display device is short, the occurrence of double reflection due to delayed response can be suppressed, and as a result, the visibility can be improved. Can be planned.

(Second Operation Example) Next, referring to FIG. 9, as a second operation example of the stereoscopic image display system of the second embodiment, an operation suitable for a case where the afterglow time of the image display device 10 is long. An example will be described.

FIG. 9 is a timing chart for explaining the second operation example. As shown by the curves I and II in FIG. 9, the driving unit 30 controls the positive voltage so that the time average value of the voltage applied to each liquid crystal cell becomes substantially zero, as in the first operation example. (+ V) and a negative voltage (−V) are alternately applied.

Further, in the second operation example, the driving unit 30
Liquid crystal shutter for left eye 20L and liquid crystal shutter for right eye 2
A simultaneous non-transmissive period in which 0R is simultaneously in a non-transmissive state (that is, an intermediate state in the second embodiment) is provided in a part of each frame period. That is, a simultaneous non-transmissive period extends from the last time Td to the first time Tz of each frame period. Note that the time Tz may be adjusted so that a decrease in luminance does not cause a problem in visual perception.

By providing the simultaneous non-transmission period as described above, the afterglow portion in the period of Tz can be substantially shielded. Also, by setting the time Td to the simultaneous non-transmission period, the effect of the liquid crystal response can be avoided as in the first operation example. Therefore, in the second operation example, it is possible to suppress the occurrence of double reflection and flicker due to an afterimage.

In the second operation example, by using a liquid crystal cell that switches between three states, liquid crystal molecules are substantially oriented in the third direction 3 with no voltage applied, and a simultaneous non-transmission period is provided. ing. For this reason, the duty ratio of the positive and negative applied voltages during the simultaneous non-transmission period can be easily set to one-to-one. As a result, the time average value of the voltage applied to the liquid crystal cell can be made substantially zero. For this reason, it is possible to suppress the occurrence of deterioration with time of the liquid crystal cell and to suppress a decrease in visibility.

[Comparative Example] Next, with reference to FIG. 10, a description will be given of a comparative example in which a liquid crystal cell is constituted by a ferroelectric liquid crystal cell 28 which performs switching between two states. FIG.
FIG. 4 is a schematic diagram for explaining a configuration of an eyeglass mechanism of a stereoscopic image display system of a comparative example.

This liquid crystal cell is a ferroelectric liquid crystal cell 28 that performs switching between two states. The liquid crystal molecules are oriented in the first direction 1 when a negative voltage is applied, and the liquid crystal molecules are oriented in the third direction 3 when a positive voltage is applied. Orientation. Since the ferroelectric liquid crystal cell 28 has a memory property, when no voltage is applied,
The alignment direction at the time of immediately preceding voltage application remains.

The left and right liquid crystal shutters constituting the eyeglass mechanism of the comparative example are configured such that the liquid crystal cell 28 is sandwiched between the polarizer 22 and the analyzer 23 in the orthogonal Nicol state. . Further, the polarizer 22 is arranged such that its absorption axis is orthogonal to the third direction 3 of the liquid crystal cell 28.

When the polarizer 22 and the analyzer 23 are arranged as described above, the liquid crystal shutters 20L and 20R for the left eye and the right eye both apply a negative voltage (-V) to apply a negative voltage (-V) to the liquid crystal cell 28L or 28R. When the liquid crystal molecules are oriented in the first direction 1, the liquid crystal enters a transmission state (ON). In addition, the positive voltage (+
When V) is applied to orient in the third direction 3, a light-shielded state (OFF) is set. Table 3 below shows the relationship between the applied voltage and the transmission characteristics.

[0104]

[Table 3]

Next, an operation example in the comparative example will be described with reference to FIG. FIG. 11 is a timing chart for explaining the second operation example. Curve I in FIG.
And II, the positive voltage (+ V) and the negative voltage (-V)
Are applied alternately. In addition, the left-eye liquid crystal shutter 2
In contrast to 0L, a waveform whose phase is shifted is applied to the right-eye liquid crystal shutter 20R. This results in curve II in FIG.
As shown by I and IV, the left and right liquid crystal shutters alternately turn on and off.

Further, a simultaneous non-transmission period in which the left-eye liquid crystal shutter 20L and the right-eye liquid crystal shutter 20R are simultaneously shielded from light is provided in a part of each frame period. That is, the last time Td of each frame period
From the first time Tz to the simultaneous light blocking period.

However, in the comparative example, since the liquid crystal cell of the two-state switching is used, when the simultaneous light-shielding period is provided, the voltage waveform applied to the liquid crystal cell is longer than the time during which -V is applied. Become longer and asymmetric.

As a result, impurity ions in the liquid crystal layer are gradually polarized in the liquid crystal cell, and a bias is applied to the drive voltage. Therefore, the threshold voltage characteristics of the cell change with time, and desired response characteristics cannot be obtained.
In addition, when viewed on a time average, this is equivalent to applying a DC voltage to the liquid crystal cell. Since the liquid crystal layer has a finite resistance value, a small amount of current flows, and the current causes the surface of the liquid crystal driving electrode to undergo an oxidation-reduction reaction, thereby increasing the surface resistance value.

Here, with reference to FIG. 12, deterioration of characteristics after driving the liquid crystal shutter of the comparative example for a long time will be described. FIG. 12 is a timing chart for explaining operation characteristics after long-time driving.

When this system was continuously driven, as shown by curves I and II in FIG. 12, an offset voltage of -kV was constantly applied due to, for example, polarization of impurity ions in the liquid crystal layer in the liquid crystal layer. State, and the difference between the rise time and the fall time of the transmitted light gradually occurs. As a result, as shown by curves III and IV in FIG. 12, the time during which the transmitted light changes from ON to OFF becomes longer, the substantial simultaneous light-shielding period becomes shorter, and the left and right images are more likely to be double-projected. Problems arise.

Note that the value of k depends on the amount of impurity ions in the liquid crystal layer and the duration of continuous driving, but is usually about 0.1. This can be easily obtained by preparing a second DC power supply separately from the driving unit, applying an offset voltage to the liquid crystal cell, and obtaining a voltage at which the rise time and the fall time are symmetrical.

When the system of the comparative example is continuously driven, a DC voltage is always applied, the resistance value of the liquid crystal driving electrode gradually increases, and the response time of the liquid crystal increases. Although it depends on the amount of organic impurities in the liquid crystal and the electrode insulating film and the initial state of the electrode, the resistance value is approximately doubled by continuous driving for 1000 hours.

Therefore, if the response of the liquid crystal cell deteriorates with time, problems such as double reflection and flickering of the screen are liable to occur, and the visibility is reduced. In order to solve the problem of the deterioration over time while keeping the positive and negative applied voltage periods asymmetric, for example, it is necessary to purify the liquid crystal material, which leads to an increase in cost.

In the above-described embodiment, an example in which the present invention is configured under specific conditions has been described. However, the present invention can be variously modified. For example, in the above-described embodiment, an example in which a polarizer is closely attached to the incident side of a liquid crystal cell has been described.
The polarizer may be provided on the screen of the image display device.

In the above-described embodiment, an example was described in which an analyzer was provided as a component of the liquid crystal shutter. However, in the present invention, an analyzer is not necessarily required.
For example, when a dichroic dye is added to a liquid crystal cell to form a guest-host type liquid crystal shutter, an analyzer is not necessary.

[0116]

As described above in detail, according to the present invention, among the smectic liquid crystal cells capable of high-speed response,
A liquid crystal cell capable of switching between three states by an applied voltage is used. As a result, it is possible to increase the frame frequency, reduce the flicker, and improve the visibility.

Furthermore, by providing a simultaneous light-shielding period in which both the left and right eyes are simultaneously shielded from light, a substantial decrease in contrast due to afterglow of the image display device can be reduced. Also,
When the simultaneous light-shielding period is provided, the time average value of the voltage applied to the liquid crystal cell can be made substantially zero, so that the deterioration of the liquid crystal material and the electrode for driving the liquid crystal over time can be prevented.

[Brief description of the drawings]

FIG. 1A is a schematic diagram for explaining a configuration of a liquid crystal shutter using a three-state liquid crystal cell, and FIG.
It is a graph which shows the relationship between the applied voltage and light transmittance of a ferroelectric liquid crystal cell, and (C) is a graph which shows the relationship between the applied voltage and light transmittance of an antiferroelectric liquid crystal cell.

FIG. 2 is a schematic diagram for explaining a schematic configuration of a stereoscopic image display system according to the present invention.

FIG. 3 is a schematic diagram for explaining a configuration of an eyeglass mechanism in the stereoscopic image display system according to the first embodiment.

FIG. 4 is a timing chart for explaining a first operation example of the stereoscopic image display system of the first embodiment.

FIG. 5 is a timing chart for explaining a second operation example of the stereoscopic image display system of the first embodiment.

FIG. 6 is a timing chart for explaining a third operation example of the stereoscopic image display system of the first embodiment.

FIG. 7 is a schematic diagram for explaining a configuration of an eyeglass mechanism in a stereoscopic image display system according to a second embodiment.

FIG. 8 is a timing chart illustrating a first operation example of the stereoscopic image display system according to the second embodiment.

FIG. 9 is a timing chart for explaining a second operation example of the stereoscopic image display system according to the second embodiment.

FIG. 10 is a schematic diagram for explaining a configuration of an eyeglass mechanism of a stereoscopic image display system of a comparative example.

FIG. 11 is a timing chart for explaining the operation of the stereoscopic image display system of the comparative example.

FIG. 12 is a timing chart for explaining a problem of the comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image display apparatus 20 Glasses mechanism 20L Liquid crystal shutter for left eyes 20R Liquid crystal shutter for right eyes 21, 21L, 21R Liquid crystal cell 22, 22L, 22R Polarizer 23, 23L, 23R Analyzer 24L, 24R Liquid crystal cell 25L, 25R Polarizer 26L, 26R Analyzer 27 Compensator 28L, 28R Liquid crystal cell 30 Driver 40 Optical axis

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H059 AA23 AA24 AA26 AA33 2H088 EA07 GA04 GA13 HA06 HA18 JA06 JA17 JA19 JA20 MA01 MA02 MA20 2H091 FA07X FA07Z GA11 HA08 HA12 LA16 LA17 MA01

Claims (10)

[Claims] 1. An image display device for alternately displaying a left-eye image and a right-eye image for each frame period by time division, and liquid crystal shutter glasses including a left-eye liquid crystal shutter and a right-eye liquid crystal shutter. And a driving unit for applying a drive voltage to the liquid crystal shutter for the left eye and the liquid crystal shutter for the right eye, wherein the liquid crystal shutter for the left eye and the liquid crystal shutter for the right eye are alternately shielded in the frame period. A stereoscopic image display system for selectively recognizing the left-eye image with the left eye and the right-eye image with the right eye, respectively, wherein the left-eye and right-eye liquid crystal shutters are A liquid crystal cell comprising a liquid crystal cell, wherein the liquid crystal cell has a first direction in which liquid crystal molecules are aligned when a negative voltage is applied, and a second direction in which the liquid crystal molecules are aligned in a second direction when a positive voltage is applied. Stereo image display system, characterized in that an intermediate direction between substantially the first direction and the second direction alignment direction of liquid crystal molecules upon application. 2. The liquid crystal shutters for the left eye and the right eye are provided with a polarizer having an absorption axis parallel or orthogonal to the intermediate direction on the incident side of the liquid crystal cell, The stereoscopic image display system according to claim 1, further comprising an analyzer having an absorption axis that is orthogonal to the polarizer with respect to the polarizer. 3. The liquid crystal shutter for the left eye and the liquid crystal shutter for the right eye, wherein a polarizer having an absorption axis parallel or orthogonal to the first direction or the second direction is provided on an incident side of the liquid crystal cell; A first analyzer having an absorption axis that is orthogonal to the polarizer with respect to the polarizer is provided on the emission side of one of the liquid crystal shutters for the right eye and the left eye. The three-dimensional image display system according to claim 1, wherein a second analyzer having an absorption axis parallel to a direction of an absorption axis of the polarizer is provided on an emission side of the other one of the liquid crystal cells. 4. The liquid crystal cell constituting the liquid crystal shutter for the left eye and the liquid crystal cell constituting the liquid crystal shutter for the right eye are one liquid crystal cell. The stereoscopic image display system as described. 5. The method according to claim 1, wherein the driving unit alternately applies the positive voltage and the voltage such that a time average value of a voltage applied to the liquid crystal cell becomes substantially zero. A stereoscopic image display system according to any one of claims 1 to 4. 6. The stereoscopic image according to claim 1, wherein the driving unit switches between the left-eye liquid crystal shutter and the right-eye liquid crystal shutter immediately before the switching time of the frame period. Display system. 7. A simultaneous non-transmission period in which the left-eye liquid crystal shutter and the right-eye liquid crystal shutter are simultaneously in a non-transmission state is provided in a part of each of the frame periods. The stereoscopic image display system according to any one of the above. 8. The stereoscopic image display system according to claim 1, wherein the liquid crystal cell is a ferroelectric liquid crystal cell in which liquid crystal molecules are aligned in the intermediate direction when no voltage is applied. 9. The stereoscopic image display system according to claim 1, wherein said liquid crystal cell is an antiferroelectric liquid crystal cell. 10. The stereoscopic image display system according to claim 1, wherein said liquid crystal cell is a chiral smectic A liquid crystal cell exhibiting an electric field induced tilt.