JPS62191824A - Pseudo stereoscopic display system - Google Patents

Abstract

PURPOSE:To permit easy observation of stereoscopic images with light and inexpensive spectacles by disposing a liquid crystal cell on the front surface of a television screen, alternately and time-dividedly changing the polarizing direction of the light passed the cell and viewing the images with the spectacles having polarizing plates. CONSTITUTION:The polarizing plate 12 and the ferroelectric smectic liquid crystal cell 13 are disposed on the front face of the screen of a television 11. The liquid crystal 13 is so provided that the optical axis of the cell is alternately changed over in synchronization with the frame signal of the television by a driving circuit 14. An observer views the images with the spectacles 15 having the polarizing plates which are respectively opposite in the polarizing directions on the right and left. The right and left eyes, therefore, recognize the images separately and observe the television images by having the stereoscopic parallax between the right and left eyes. The stereoscopic images are thus easily observed by using the light and inexpensive polarizing spectacles.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image display system such as a stereoscopic television that utilizes the parallax between left and right eyes.

<Prior Art> Attempts to realize three-dimensional images or three-dimensional images have a very long history, and there are many different methods including lasers, holograms, etc. However, 3
The following three systems have been successful as three-dimensional image display systems that can display moving images in full primary colors.In each case, images for the right eye and left eye are displayed individually, and the images are combined on the viewer's retina. The basic method is to display a three-dimensional image by giving the viewer the illusion that there is a three-dimensional parallax based on the displacement of individual images.

(1) Images for both the left and right eyes are made into linearly polarized light whose polarization directions make an angle of 90 degrees to each other, and the images are separated and viewed using glasses with polarizing plates. This is the mainstream method for theatrical 3D movies.

(2) Three-dimensional images are displayed by alternately displaying images for the left and right eyes in a time-sharing manner, and by alternately opening and closing glasses with an electronic light valve function in synchronization with the display cycle.

The three-dimensional image obtained by the method (1) above is nearly ideal, with no visible flicker, and the glasses with polarizing plates worn by the viewer are light and inexpensive. However, in order to always display two images with different polarization axes at the same time, two display devices and projection devices are required, which increases the number of devices and makes operation complicated, making it unsuitable for general home use. .

In the method (2) above, the number of frames per second entering both the left and right eyes is halved, so flicker is felt, but it is realistic in that it is possible to create a stereoscopic image with one television. However, there is a problem in that the user must wear glasses with electronic optical pulp function.

In other words, such glasses are heavy and cause fatigue when used for a long time. Moreover, glasses with such a light valve function are expensive, and each person needs one pair, so the cost of purchasing them for the number of viewers is quite high.

<Purpose of the Invention> The present invention has been made for the purpose of providing a stereoscopic image display system using a time-sharing two-image method, which is suitable for viewing by a large number of people such as at home or in a classroom. This method incorporates the advantages of the two methods described above.

<Embodiment> The present invention arranges a liquid crystal cell in front of a television screen and alternately switches the polarization direction of light passing through the cell in a time-division manner.
It is characterized by displaying stereoscopic images by viewing the left and right eyes separately using glasses with polarizing plates.

Hereinafter, a detailed explanation will be given according to examples. , Fig. 1 and Fig. 2 are respectively configuration diagrams of a display system showing one embodiment of the present invention. In the figure, 11 is a television, and a polarizing plate 12 is provided in front of the screen. Furthermore, the polarizing plate 1
In front of 2, a liquid crystal cell/L'13 is arranged. The liquid crystal cell 13 is made by homogeneously aligning ferroelectric numectic liquid crystal, and a transparent electrode is provided inside the substrate of the liquid crystal cell 13. In this system, the liquid crystal cell 13 acts as an optical compensator that can rotate multiple optical axes in the plane of the cell by reversing the polarity of the applied voltage. The drive circuit 14 of the liquid crystal cell 13
The optical axis of the liquid crystal cell 13 is alternately switched in synchronization with the frame signal of the television signal sent from the television 11 that displays images. Glasses 15 worn by the viewer are provided with polarizing plates having opposite polarization directions on the left and right sides. By alternately switching the polarization direction of the light from the TV image and viewing it separately in time between the left and right eyes using glasses with polarizing plates, the left and right eyes will be able to view the TV image separately. TV images are observed with stereoscopic parallax between the left and right eyes.

Depending on how polarized light is used, a quarter-wave plate 16 may be provided in front of the liquid crystal cell 13, as shown in FIG. 2, to convert the linearly polarized light that has passed through the liquid crystal cell 13 into approximately circularly polarized light. Also good.

In implementing the basic configuration as described above, the following three typical methods can be considered depending on the type of polarization and the retardation of the liquid crystal cell 13.

The first method uses a circularly polarizing plate for the glasses 15 in the configuration shown in FIG. LCD C/L/13: 0.1 to 0.
It has a retardation of 15 microns and the rotation angle of the optical axis is 70° to 110° due to polarity reversal of the applied voltage.
Use what is. In order for the liquid crystal cell 13 to function as a quarter-wave plate, the special nitroreflection is set to 0.
It is preferable that the diameter is 13 microns and the rotation angle of the optical axis is 90°. The arrangement of the liquid crystal panel 1713 and the polarizing plate 12 is shown in Figure 3 (
As shown in A), the optical axis of the liquid crystal center/+713 can be taken 2
The center lines of the two optical axes 32 and 33 are set to coincide or approximately coincide with the polarization axis 31 of the polarizing plate 12. The light of the television image becomes circularly polarized light by the polarizing plate 12 and the liquid crystal cell 13, and the direction of polarization is alternately switched to the right or left by reversing the polarity of the voltage applied to the liquid crystal cell 13.

The second method uses a linear polarizing plate for the glasses 15 in the configuration shown in FIG. The liquid crystal cell 13 is 0.2 L 0.
It has a retardation of 3 microns and the rotation angle of the optical axis due to polarity reversal of the applied voltage is 35° to 55°. The liquid crystal cell 13 has a retardation of 0.25 in order to function as a half-wave plate.
It is preferable that the optical axis has a rotation angle of 45 degrees in microns. LCD-t! The arrangement of the filter 13 and the polarizing plate 12 is shown in Figure 3 CB)
As shown in FIG. 3, one of the two possible optical axes 32 and 33 of the liquid crystal cell 13 is set to coincide or approximately coincide with the polarization axis 31 of the polarizing plate 12. The light of the television image passes through the polarizing plate 12 and the liquid crystal cell 13 as linearly polarized light, and the polarization direction is alternately switched between two orthogonal directions by reversing the polarity of the voltage applied to the liquid crystal cell 13.

Polarization axes 34 of the two linear polarizers attached to the glasses 15.
35, one side is set to coincide with the polarization axis of the polarizing plate 12 on the TV screen side, and the other side is set to an angle perpendicular thereto.

The third method uses a circularly polarizing plate for the glasses 15 in the configuration shown in FIG. The liquid crystal cell 13 is 0.2 to 0.3
It has a micron retardation and the rotation angle of the optical axis due to polarity reversal of the applied voltage is 35° to 55°. The liquid crystal cell 13 preferably has a retardation of 0.25 microns and an optical axis rotation angle of 45° in order to function as a half-wave plate.

The arrangement of the liquid crystal cell 13 and the polarizing plate 12 is such that the optical axis of the liquid crystal cell 13 has two possible optical axes 32, as shown in Figure 3 (C).
．． 33 and the polarization axis 31 of the polarizing plate 12 are set to match or approximately match. The optical axis 36Vi of the quarter-wave plate 16 is installed so as to form an angle of approximately 45° with respect to the polarization axis of the polarizing plate 12. The light of the TV image is transmitted through the polarizing plate 12.
The liquid crystal cell 13 and the quarter-wave plate 16 turn the light into circularly polarized light, and the direction of polarization is alternately switched to the right or left by reversing the polarity of the voltage applied to the liquid crystal cell 13.

In the three systems described in detail above, the letter tension of the liquid crystal center/l/13, the rotation angle or setting angle of the optical axis, the letter tsion or setting angle of the optical axis of the quarter-wave plate 16, or the polarization of the glasses 15. Setting the angle of the board, etc.
For optimum design, the conditions may be varied from those mentioned here.

Ferroelectric smectic liquid crystal cells are highly suitable for implementing the present invention. In other words, it can sufficiently withstand high-speed response of tens to hundreds of microseconds, and the liquid crystal cell 13
It has various excellent properties that other liquid crystal cells do not have, such as the ability to move the direction of the optical axis only within the plane of , and the fact that it has a memory effect in the nutching state.

The operating principle of this ferroelectric numectic liquid crystal cell will be explained below.

This optical switching device uses chiral numectic liquid crystal exhibiting ferroelectricity, and consists of N, A, C1ark, S,
It was published by T. Lagerwall in Abrid Physique Letters (vol. 36, p. 899, published in 1980) and named Surface Stabilized Ferroelectric Refided Crystal. FIG. 4(A) shows a cross section of this liquid crystal cell when an electric field is applied, in which 1 is a glass substrate, 2 is a transparent electrode, and 3 is a liquid crystal molecule.

The electric field inside the cell goes from top to bottom in the figure.

In response to this electric field, the dipoles of the liquid crystal molecules 3 are arranged as shown by the arrows. Figure 4 (CB) is a diagram of the molecular orientation in this state viewed from a direction perpendicular to the cell surface, and the liquid crystal molecules 3 are offset by an angle θ from the perpendicular to the lattice plane of arrangement. Next, when the polarity of the applied electric field is reversed, the dipole of the liquid crystal molecule 3 is reversed as shown in the arrow as shown in FIG. 5(A), and as shown in FIG. 5(CB).
As shown in , the liquid crystal molecules 3 change their azimuth in the direction of angle -0.

In practical terms, the crystal optical properties of this liquid crystal cell can be considered to be a uniaxial crystal whose optical axis is the orientation direction of the long axis of the molecules. That is, this liquid crystal cell can be regarded as an optical compensator whose optical axis can be rotated by an angle of 2.theta. by reversing the polarity of the applied voltage. Note that this rotation of the front axis is symmetrical about the normal line of the smectic layer, and the retardation of this liquid crystal cell is expressed by the product Δn - d of the birefringence Δn of the liquid crystal and the cell thickness d.

The tilt angle θ of liquid crystal molecules varies depending on the liquid crystal material, but the first
In order to apply to the second method, it is desirable that 2θ is 90°, so a material with θ of 45° is suitable, and in order to apply to the second and third methods, 2θ is 45°. Therefore, a material with θ of 22.5° is suitable.

However, there is no practical problem even if θ deviates from these conditions within a range of about ±10°.

This liquid crystal cell exhibits a memory effect in its on-off switching states. That is, as shown in FIG. 6, after switching by a positive and negative pulsed electric field, the voltage is
However, each molecular orientation state is approximately maintained. According to the above-mentioned literature, the response time τ of this liquid crystal cell is τlη/(Ps-E) (where η, Ps, and E are the viscosity of the liquid crystal material, respectively;
Hail spontaneous polarization, electric field strength. ), and a strong electric field is advantageous for high-speed switching. The voltage applied to this liquid crystal cell only needs to be faster than the switching speed of the television screen and whose phase is controlled so that the screen is sent correctly to the left and right eyes, and the waveform of Type 4 can be considered. The simplest waveform is a square wave.

Furthermore, if the memory effect is utilized to save power and extend the life of the liquid crystal cell, a waveform as shown in FIG. 7 may be used. In this waveform, high-speed switching is performed using a voltage with a high peak value in periods t71 and t73, and in subsequent periods t72 and t74, a voltage necessary to maintain the molecular orientation in that state is applied using a memory effect. It is something. Furthermore, a DC offset voltage may be superimposed on the applied voltage waveform for the purpose of equalizing the two switching speeds and improving the retention characteristics of the memory effect.

<Effects of the Invention> The time-sharing two-image power type three-dimensional image display system according to the present invention has a simple device configuration! Since the glasses worn by viewers are light and inexpensive, they can be easily used at home or in classrooms, making them extremely practical.

[Brief explanation of drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are schematic configuration diagrams of a display system showing one embodiment of the present invention. FIG. 3 is an explanatory diagram showing the angle setting of the optical axis and polarization axis of the optical system shown in FIGS. 1 and 2. FIG. FIGS. 4 and 5 are explanatory diagrams illustrating the operating principle of a liquid crystal cell used in one embodiment of the present invention. FIG. 6 is an explanatory diagram showing the memory effect of a liquid crystal cell used in one embodiment of the present invention. FIG. 7 is an example of a voltage waveform applied to a liquid crystal cell. 11...TV, 12...Polarizing plate, 13.
・・Liquid, crystal cell, 14・・Drive circuit, 15・・Glasses, 16・・Quarter wavelength plate, 31・Polarizing plate 12
Polarization axis of 32.33... Possible optical axis of liquid crystal cell,
34... Polarization axis on one side of the glasses, 35... Polarization axis on the other side of the glasses, 36... Optical axis of the quarter-wave plate. Agent Patent attorney Takeshi Sugiyama (1 other person) (A)
CB) (C) Fig. 3 3 Usakiri/ir Chi Fig. 4 1, Fig. 5 Fig. 6 Fig. 7

Claims (1)

[Claims] 1. A polarizing plate is arranged in front of the display screen, a liquid crystal cell in which ferroelectric smectic liquid crystal is aligned is arranged in front of the polarizing plate, and synchronized with the frame signal of the image on the display screen. A drive circuit is connected to the liquid crystal cell to apply an alternating current voltage to the liquid crystal cell to time-divisionally change the polarization direction of display light traveling from the display screen through the polarizing plate and the liquid crystal cell. A pseudo-stereoscopic display system characterized by comprising polarized glasses for the left eye and right eye for viewing light with different polarization directions. 2. The liquid crystal cell has a retardation of 0.1 to 0.15 microns, and the rotation angle of the optical axis due to polarity reversal of the applied voltage is 70° to 110°, and it is one of the two possible optical axis directions. Claim 1, wherein the line and the polarization axis of the polarizing plate roughly match, and the polarizing plate of the polarized glasses is a circularly polarizing plate or an elliptically polarizing plate having a polarizing ability close to that of circularly polarizing light.
Pseudo-stereoscopic display system described in Section 2. 3. The liquid crystal cell has a retardation of 0.2 to 0.3 microns, and the rotation angle of the optical axis due to polarity reversal of the applied voltage is 35° to 55°, one of two possible optical axis directions. 2. The pseudo-stereoscopic display system according to claim 1, wherein the polarizing axis of the polarizing plate and the polarizing plate are substantially coincident with each other, and the polarizing plate of the polarized glasses is a linear polarizing plate. 4. The liquid crystal cell has a retardation of 0.2 to 0.3 microns, and the rotation angle of the optical axis due to polarity reversal of the applied voltage is 35° to 55°, one of two possible optical axis directions. and the polarization axis of the polarizing plate are approximately coincident with each other, and the optical axis on the front side is at an angle of 35° to 5° with the polarization axis of the polarizing plate.
The quarter-wave plate is arranged to form an angle of 5°, and the polarizing plate of the polarized glasses is a circularly polarizing plate or an elliptically polarizing plate having a polarizing ability close to circularly polarized light. Pseudo-stereoscopic display system.