Optical: systems and elements – Polarization without modulation
Reexamination Certificate
1998-11-23
2001-07-17
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Polarization without modulation
C359S485050, C359S487030, C359S490020, C359S490020, C353S020000
Reexamination Certificate
active
06262841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus for image formation, and in particular to image forming apparatus for projecting real holographic images in space.
2. Description of the Prior Art
Systems capable of forming images from an illuminated object where one or a plurality of optically superimposed objects are projected into space find numerous and important applications in areas such as advertising and marketing, product exhibition, aircraft flight training and spacecraft simulation, as well as a host or other imaging applications.
One such system described in U.S. Pat. No. 3,940,203 issued Feb. 24, 1976, to LaRussa, which employs a reflection-type holographic analog of a spherical mirror and a birefringent array of optical elements. In this patent, the primary image source is linearly polarized and made incident upon the holographic mirror analog. The light from the primary image passing through the analog is provided a circular polarization by a first quarter wave plate. A fraction of this light is reflected by a beamsplitter where it is collimated and transmitted through the first quarter wave plate, beamsplitter, second quarter wave plate, and second polarizer. The result is then viewed by an observer.
This and other prior art relies upon the inclusion of two beam splitting surfaces within the system. Since the prior art's beam splitting surfaces are not preferential to any polarization state, a large portion of that light is indiscriminately lost within the system. Thus, the prior art requires either an extremely bright source image or, conversely, very dim ambient viewing conditions.
Other prior art relies upon an obliquely placed beamsplitter and concave reflector to produce floating images. Significant efficiency problems also exist as the source light is made incident upon beamsplitting surfaces. Additionally, the field of view characteristic of this art is constrained by the necessity to project the image beyond the obliquely place beamsplitter. Prior art of this configuration is also inherently large due to the basic geometry of the elements. Additionally, that prior art allows an observer to “look into” the device from certain vantage points and discern a “direct view” of the source of the real image.
BRIEF SUMMARY OF THE INVENTION
The object of projecting a bright real image in space (as opposed to a “virtual” or “infinity” image) and the elimination of unwanted “ghost” images is achieved by providing a series of linear polarizers, quarter wave plate retarders, reflector/mirror elements, louvre film elements and optical lenses in combination with a dual brightness enhancement film (hereinafter referred to as “DBEF”) in alignment with a target to provide a real image at a predetermined location with respect to the observer.
An advantage of the present invention is the inclusion of the DBEF material. Unlike a standard beamsplitter, DBEF is a birefringent material, and as such, has the ability to reflect or transmit specific polarization states with high efficiency. Whereas previous systems' beamsplitting elements reflected or transmitted a polarized state of light with low efficiency and indiscriminately with respect to that polarization state, DBEF is not encumbered by this characteristic. Thus, a DBEF-based system has greater overall throughput and greater image brightness.
Another advantage of the use of DBEF and other birefringent materials is the prevention of a “direct view” of the source of a real image which is being projected, in conjunction with the attenuation of reflected, ambient light sources.
REFERENCES:
patent: 3443858 (1969-05-01), La Russa
patent: 3610729 (1971-10-01), Rogers
patent: 3785715 (1974-01-01), Mecklenborg
patent: 3940203 (1976-02-01), La Russa
patent: 4007979 (1977-02-01), Coblitz
patent: 4093347 (1978-06-01), La Russa
patent: 4163542 (1979-08-01), La Russa
patent: 4383740 (1983-05-01), Bordovsky
patent: 4653875 (1987-03-01), Hines
patent: 5305124 (1994-04-01), Chern et al.
patent: 5477385 (1995-12-01), Freeman
patent: 5526184 (1996-06-01), Tokuhashi et al.
patent: 5585946 (1996-12-01), Chern
patent: 5629806 (1997-05-01), Fergason
patent: 5654828 (1997-08-01), Togino et al.
patent: 5673151 (1997-09-01), Rallison
patent: 5715023 (1998-02-01), Hoppe
patent: 5768039 (1998-06-01), Togino
Curtis Craig
Spyrou Cassandra
Steinberg & Raskin, P.C.
LandOfFree
Apparatus for projecting a real image in space does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for projecting a real image in space, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for projecting a real image in space will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2501751