Optical: systems and elements – Polarization without modulation – Depolarization
Reexamination Certificate
1998-04-06
2001-05-08
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Polarization without modulation
Depolarization
C359S465000, C353S020000, C353S034000
Reexamination Certificate
active
06229648
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to projectors generally and more particularly to video and data projectors.
BACKGROUND OF THE INVENTION
Various types of video and computer generated information projectors are known. These include, for example, the SharpVision product line commercially available from Sharp Corporation of Japan. Conventional projectors of this type have achieved significant market penetration but suffer from various disadvantages and limitations.
One of the significant limitations in liquid crystal panel projectors lies in the relatively limited amount of light that can be projected. It may be appreciated that the amount of light that can be transmitted through a conventional color liquid crystal panel assembly is limited by the amount of light that can be absorbed by the liquid crystal panel without degradation of its performance and permanent damage thereto inter alia mainly due to overheating. Accordingly the brightness of projected images produced by such projectors is correspondingly limited.
SUMMARY OF THE INVENTION
The present invention seeks to provide an improved projector which is highly efficient in light utilization.
There is thus provided in accordance with a preferred embodiment of the present invention a projector including a non-polarized light source, at least one polarizing beam-splitter receiving light from the non-polarized light source, a selectably actuable polarization rotating light valve having impinging thereon light from the polarizing beam splitter and operating in a reflective mode, and a mirror having impinging thereon light from the polarizing beam splitter and reflecting the light via the polarizing beam splitter to the light source.
Preferably the color modulator is associated with the light source.
Further in accordance with a preferred embodiment of the present invention the at least one polarizing beam-splitter directs light of a first polarity to the selectably actuable polarization rotating light valve and directs light of a second polarity to the mirror, the mirror reflects the light of the second polarity to the polarizing beam-splitter which directs it back to the light source, and the light source at least partially depolarizes said light of the second polarity.
Still further in accordance with a preferred embodiment of the present invention the polarizing beam-splitter transmits light of a first polarity to the selectably actuable polarization rotating light valve and reflects light of a second polarity to the mirror and the polarizing beam-splitter reflects light from the mirror to the light source.
Moreover in accordance with a preferred embodiment of the present invention the polarizing beam-splitter reflects light of a first polarity to said selectably actuable polarization rotating light valve and reflects light of a second polarity to said mirror and said polarizing beam-splitter reflects light from said mirror to said light source.
Additionally in accordance with a preferred embodiment of the present invention the polarizing beam-splitter reflects light of a first polarity to the selectably actuable polarization rotating light valve and transmits light of a second polarity to the mirror and the polarizing beam-splitter transmits light from the mirror to the light source.
Further in accordance with a preferred embodiment of the present invention the selectably actuable polarization rotating light valve includes a total internal reflection color splitter/combiner associated with red, green and blue light valves.
Alternatively the selectably actuable polarization rotating light valve comprises a color splitter/combiner associated with red, green and blue light valves.
Additionally in accordance with a preferred embodiment of the present invention the selectably actuable polarization rotating light valve comprises a total internal reflection color splitter/combiner associated with red, green and blue light valves.
Further in accordance with a preferred embodiment of the present invention the selectably actuable polarization rotating light valve comprises a color splitter/combiner associated with red, green and blue light valves.
Still further in accordance with a preferred embodiment of the present invention includes a phase volume grating associated with the light source, and a microlens array associated with the selectably actuable polarization rotating light valve.
Moreover in accordance with a preferred embodiment of the present invention includes a holographic microlens array associated with the light source.
There is also provided in accordance with a preferred embodiment of the present invention a non-polarized light source, at least one polarizing beam-splitter receiving light from the non-polarized light source, at least one selectably actuable polarization rotating light valve having impinging thereon light from the polarizing beam splitter and operating in a reflective mode, and a color modulator associated with the light source.
There is further provided in accordance with a preferred embodiment of the present invention a projector including a non-polarized light source; at least one polarizing beam-splitter receiving light from the non-polarized light source, at least one selectably actuable polarization rotating light valve having impinging thereon light from the polarizing beam splitter and operating in a reflective mode, a phase volume grating associated with said light source, and a microlens array associated with the selectably actuable polarization rotating light valve.
There is yet further provided in accordance with a preferred embodiment of the present invention a projector including a non-polarized light source, at least one polarizing beam-splitter receiving light from the non-polarized light source, at least one selectably actuable polarization rotating light valve having impinging thereon light from the polarizing beam splitter and operating in a reflective mode, and a holographic microlens array associated with said light source.
There is also provided in accordance with a preferred embodiment of the present invention a projector including a non-polarized light source, at least one polarizing beam-splitter receiving light from the non-polarized light source, at least one selectably actuable polarization rotating light valve having impinging thereon light from the polarizing beam splitter and operating in a reflective mode, and a color modulator associated with the light valve.
The present invention, a preferred embodiment of which is described hereinabove, has a number of advantages over the prior art:
It utilizes both polarized components of the light from the light source as well as the full spectrum of the light. Thus, the percentage of the light emitted by the light source that is outputted exceeds that conventionally realized in the prior art.
The use of reflective light valves provides greater efficiency than would be achieved using transmissive light valves since it avoids the obscuration produced by the black matrix of the transistors used therein and shortens the optical path. Also, the utilization of a polarizing beam splitter obviates the need for polarizers usually associated with a liquid crystal light valve.
Operation in a reflective mode enables the beam splitters to be used as beam combiners, thus reducing the number of components and the overall size and weight of the display.
A first light valve may be operative to modulate an image intended for a viewer's left eye, while a second light valve may be operative to modulate an image intended for a viewer's right eye, or vice versa.
A combined image projected via an objective lens appears on a suitable polarization retaining screen as two mutually orthogonally polarized images. A viewer, wearing glasses having left and right lenses having mutually orthogonal polarization, sees a resulting image, in three dimensions, as if it were coming out of the screen.
In an alternative embodiment of the invention wherein time-interlaced stereo projection is provided, the glasses may contain time-interlaced s
Abelman ,Frayne & Schwab
Curtis Craig
Spyrou Cassandra
UNIC View Ltd.
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