Liquid crystal cells – elements and systems – Liquid crystal system – Stereoscopic
Reexamination Certificate
2000-01-11
2001-04-03
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Stereoscopic
C349S096000, C349S098000, C349S117000, C348S051000, C348S057000, C348S058000, C348S059000, C359S462000, C359S464000, C345S215000
Reexamination Certificate
active
06211927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display unit and a display system thereof which allow a stereoscopic image or different images to be displayed on the same screen.
2. Description of Related Art
Hitherto, there has been known a technology for obtaining stereoscopic images by forming images for right and left eyes by utilizing two projectors and by viewing them by right and left eyes, respectively (see Chihiro Masuda, Three-Dimensional Display, Sangyo Publishing Co., 1990).
There have been also known a front projection method and a rear projection method as methods for displaying stereoscopic images. It has been common so far that the front projection method projecting stereoscopic images on a silver screen is performed to show to many people in events or the like.
On the other hand, the rear projection method of projecting polarized stereoscopic images has been very rare so far. Because the polarization characteristics of the image light degrades in passing through the screen due to scattering and the like, thus failing to give stereoscopic view or causing after-image and dark screen. It has been difficult to let the light pass through the screen while maintaining the polarization characteristics, especially when circularly polarized light is used.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to solve the aforementioned problems of the rear projection method by providing means which allows to transmit image lights using circularly polarized light to observers without degrading the polarization characteristics by an optical system such as lenses and the screen.
According to the present invention, a display unit is provided with first and second liquid crystal panels for displaying images, and linearly polarized image lights output respectively from each of the liquid crystal panels are projected onto the surface of a screen so that their polarization directions differ from each other. Then, the projected linearly polarized lights pass through the screen after transforming into circularly polarized lights by transformation means provided in the screen. Thereby, the circularly polarized image lights may be transmitted to the observers without degrading the polarization characteristics by the optical systems such as lenses and screen.
In the concrete, the transformation means is a quarter wavelength plate and the projecting means projects each of the linearly polarized image lights onto the screen so that the polarization axis of the image lights make an angle of 45° with an optical axis of the quarter wavelength plate. At this time, it is preferable to dispose the quarter wavelength plate on the back of the screen so that the image light which has transmitted from the front (light source side) surface of the screen in the linearly polarized state reaches to an observer after transforming into the circularly polarized light at the back of the screen.
Further, according to the present invention, the observer can enjoy to select various modes by switching them by one display unit from either a first mode which allows images to be displayed stereoscopically, a second mode which allows different observers to observe different images and a third mode for superimposing and displaying the same images.
In the concrete, the display unit of the present invention comprises a first liquid crystal panel for displaying images and a second liquid crystal panel for displaying images disposed adjacent to the first liquid crystal panel. And the linearly polarized image lights outputs are projected from the first and second liquid crystal panels, respectively, on the light source side surface of the screen simultaneously so that their polarization directions differ from each other. Then, transformation means provided in the screen transforms the projected linearly polarized lights into circularly polarized lights.
This transformation means is a quarter wavelength plate and the projecting means projects each of the linearly polarized image lights onto the screen so that the polarization axis of the image lights make an angle of 45° with an optical axis of the quarter wavelength plate. At this time, it is preferable to dispose the quarter wavelength plate on the back of the screen so that the image light which has transmitted from the light source side surface of the screen in the linearly polarized state reaches to an observer after transforming into the circularly polarized light.
In the present invention, the quarter wavelength plate is provided within the screen itself, because the polarization characteristics of the image light in passing through the screen degrade by scattering and the like. Thus failing to view stereoscopic images or causing after-image or darkness if the quarter wavelength plate is separated from the screen and is disposed in front of the screen (on the light source side). It is particularly difficult to let the image light pass through the screen while maintaining the polarization characteristics when circularly polarized light is used. Then, the quarter wavelength plate is provided within the screen itself to allow the circularly polarized image light to be transmitted to the observer without degrading the polarization characteristics by the optical systems such as the lenses and screen.
Further, it is preferable to construct the projecting means described above by combining a plurality of polarization plates. In concrete, the projecting means is constructed by combining a first polarization plate disposed on the light source side of the first liquid crystal panel; a second polarization plate which is disposed on the screen side of the first liquid crystal panel and whose polarization direction makes an angel of 90° with that of the first polarization plate; a third polarization plate disposed on the light source side of the second liquid crystal panel; and a fourth polarization plate which is disposed on the screen side of the second liquid crystal panel and whose polarization direction makes an angle of 90° with that of the third polarization plate. It is noted that the orientation of liquid crystal of the first and second liquid crystal panels is different by 90° from each other.
It is preferable to provide the screen with, besides the quarter wavelength plate, an image-formation film for forming images; a Fresnel lens provided on the light source side toward the image-formation film; and a lenticular lens provided on the observer side with respect to the image-formation film.
Further, in a display system of the present invention, an observer watches images from the back of the screen by wearing special glasses. The glasses have a function of selectively separating the image lights for right and left eyes, respectively from the first and second liquid crystal panels which have passed the screen. Thereby, it allows stereoscopic images to be observed.
In the concrete, circularly polarizing means by which directions of rotation of circularly polarized light differ each other for the right eye and left eye and linearly polarizing means by which polarization directions of linearly polarized lights differ each other for the right eye and left eye are provided respectively in the glasses. The combination of the circularly polarizing means and the linearly polarizing means allows the image which has passed through the screen to be observed.
Further, the inventive display system allows different images to be observed among a first observer and a second observer. In this case, different glasses are allotted to the first and second observers, respectively. In the concrete, first glasses is selectively transmitting the image light of the first liquid crystal panel and second glasses id selectively transmitting the image light of the second liquid crystal panel to the second observer, respectively. Here, in the first and second glasses, circularly polarizing means for different directions of rotation of circularly polarized lights differ each other and linearly polarizing means by which polarizat
Hirakata Yoshiharu
Koyama Jun
Yamazaki Shunpei
Fish & Richardson PC
Ngo Julie
Semiconductor Energy Laboratory Co,. Ltd.
Sikes William L.
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