JPH0578017B2 - - Google Patents

Description

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

<Prior art> Attempts to reproduce three-dimensional images or three-dimensional images have a very long history, and the methods used are laser and
If holograms and the like are included, there will be an extremely wide variety of types. However, there are two successful stereoscopic image display systems that can display moving images in full three primary colors, and both display images for the right eye and left eye individually, making it easier for the viewer to view the image. The basic method is to display a three-dimensional image by giving the viewer the illusion that there is three-dimensional parallax based on the shift of individual images synthesized on the retina.

(1) Images for the left and right eyes are made into linearly polarized light whose polarization directions are at an angle of 90° 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) Display images for both the left and right eyes alternately in a time-sharing manner,
Three-dimensional image display is performed by alternately opening and closing glasses with an electronic light valve function in synchronization with the display cycle.

The three-dimensional images obtained by method (1) above are close to ideal, with no noticeable flicker, and the glasses with polarizing plates worn by viewers 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 method (2) above, the number of frames per second entering both the left and right eyes is halved, so flickering is felt, but it is realistic in that it is possible to create three-dimensional images with one television. However, there is a problem in that glasses with an electronic light valve function must be worn. 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 that is suitable for viewing by a large number of people such as at home or in a classroom. This method incorporates the advantages of each of the above two methods.

<Example> The present invention arranges a ferroelectric smectic liquid crystal in front of a television screen, and alternately switches the polarization direction of the light passing through it in a time-sharing manner. It is characterized by performing stereoscopic image display by viewing the images separately.

Hereinafter, it will be explained in detail according to examples. FIG. 1 is a block diagram 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. Further, in front of the polarizing plate 12, a liquid crystal cell 13 is arranged.
The liquid crystal cell 13 is made by homogeneously aligning ferroelectric smectic 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 whose optical axis can be rotated in the plane of the cell by reversing the polarity of the applied voltage. The drive circuit 14 for the liquid crystal cell 13 is used to create a voltage waveform to be applied to the liquid crystal cell 13, and alternately drives the optical axis of the liquid crystal cell 13 in synchronization with the frame signal of the television signal sent from the television 11 that displays images. Switch to 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 of the TV image and viewing the TV image separately on a time-sharing basis with the left and right eyes using glasses with polarizing plates, the left and right eyes can view the TV image separately. Images are observed with the left and right eyes with a stereoscopic field of view. Next, a method for implementing the basic configuration as described above will be described. This method uses a circularly polarizing plate for the glasses 15 in the configuration shown in FIG. The liquid crystal cell 13
It 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°. Since the liquid crystal cell 13 acts as a quarter-wave plate,
Particularly suitable is one with a retardation of 0.13 microns and an optical axis rotation angle of 90°. liquid crystal cell 13
The arrangement of the polarizing plate 12 is set so that the center line of the two possible optical axes 32, 33 of the liquid crystal cell 13 and the polarizing axis 31 of the polarizing plate 12 are aligned or approximately aligned, as shown in FIG. do. 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.

Ferroelectric smectic liquid crystal cells can sufficiently withstand high-speed responses of tens to hundreds of microseconds, the direction of the optical axis moves only within the plane of the liquid crystal cell 13, and the switching state has a memory effect, resulting in low power consumption. Since it has various excellent properties that other liquid crystal cells do not have, such as being able to be powered and making the liquid crystal cell very thin, it is very suitable for implementing the present invention.

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

This optical switching device uses a chiral smectic liquid crystal that exhibits ferroelectricity, and is based on NAClark.
By STLagarwall, Applied Physics Letters (Volume 36, Page 899, Published 1980)
It was announced and named Surf Eight Stabilized Ferroelectric Liquid Crystal. FIG. 3A 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 diagram. In response to this electric field, the dipoles of the liquid crystal molecules 3 are arranged as shown by the arrows. FIG. 3B is a view of the molecular orientation in this state viewed from a direction perpendicular to the cell plane, and the liquid crystal molecules 3 are tilted by an angle θ from the perpendicular to the lattice plane of alignment. Next, when the polarity of the applied electric field is reversed, the dipole of the liquid crystal molecule 3 is reversed as shown by the arrow as shown in FIG. 4A, and the dipole of the liquid crystal molecule 3 is reversed as shown in FIG. 4B.
changes its azimuth in the direction of an angle -θ.

The crystal optical properties of this liquid crystal cell may be considered as a uniaxial crystal whose optical axis is in the orientation direction of the long axes 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 2θ by reversing the polarity of the applied voltage. The rotation of the optical axis is symmetrical about the normal to the smectic layer, and the retardation of the liquid crystal cell is expressed as the product Δn·d of the birefringence Δn of the liquid crystal and the cell thickness d.

The tilt angle θ of the liquid crystal molecules varies depending on the liquid crystal material, but in order to apply this method, it is desirable that 2θ is 90°, so a material with θ of 45° 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 on-off switching states. That is, as shown in FIG. 5, even if the voltage is set to 0 V after switching by a positive and negative pulsed electric field, each molecular orientation state is approximately maintained. According to the above-mentioned literature, the response time τ of this liquid crystal cell is τ∝η/(Ps·E) (where η, Ps, and E represent the viscosity, spontaneous polarization, and electric field strength of the liquid crystal material, respectively). ), and the stronger the electric field is, the more advantageous it is to achieve 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 can be controlled so that the screen is sent correctly to the left and right eyes, and various waveforms are possible. 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. 6 may be used. This waveform performs high-speed switching at a voltage with a high peak value in periods t ₇₁ and t ₇₃ , and in subsequent periods t ₇₂ and t ₇₄ , it is necessary to maintain the molecular orientation in that state by utilizing the memory effect. It applies voltage. 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> According to the pseudo-stereoscopic display system of the present invention, flicker that occurs when switching between left and right images can be prevented with a simple device configuration, and the system can be easily used in general homes, classrooms, etc. by reducing power consumption and reducing the thickness. This makes it possible to provide an inexpensive and highly practical system that can be used for

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a display system showing one embodiment of the present invention. FIG. 2 is an explanatory diagram showing the angle settings of the optical axis and polarization axis of the optical system shown in FIG. FIGS. 3 and 4 are explanatory diagrams illustrating the operating principle of a liquid crystal cell used in one embodiment of the present invention. FIG. 5 is an explanatory diagram showing the memory effect of a liquid crystal cell used in one embodiment of the present invention. FIG. 6 is an example of a voltage waveform applied to a liquid crystal cell. 11... Television, 12... Polarizing plate, 13... Liquid crystal cell, 14... Drive circuit, 15... Glasses, 31
...Polarization axis of the polarizing plate 12, 32, 33... Possible optical axes of the liquid crystal cell.

Claims (1)

[Claims] 1. A polarizing plate is arranged in front of a display screen, a liquid crystal cell is arranged in front of the polarizing plate, and an alternating current voltage synchronized with a frame signal of an image on the display screen is applied to the liquid crystal cell. A drive circuit for time-divisionally switching the polarization direction of display light traveling from the display screen through the polarizing plate and the liquid crystal cell is connected to the liquid crystal cell, and a drive circuit for the left eye and right eye for visually recognizing the display light is connected to the liquid crystal cell. In a pseudo-stereoscopic display system comprising polarized glasses with different polarization directions, 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 μm. ° to 110°, the center line of the two possible optical axes and the polarizing axis of the polarizing plate roughly match, and the polarizing plate of polarized glasses is an ellipse that has circularly polarized light or polarizing ability close to circularly polarized light. A pseudo-stereoscopic display system characterized by a polarizing plate.