Optical: systems and elements – Single channel simultaneously to or from plural channels
Reexamination Certificate
2000-11-20
2001-11-27
Dang, Hung Xuan (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
C359S629000
Reexamination Certificate
active
06324007
ABSTRACT:
TECHNICAL FIELD
The present invention relates to optical imaging systems and, more particularly, to systems employing scanning inputs or outputs.
BACKGROUND OF THE INVENTION
A variety of techniques are available for providing visual displays of graphical, textual or video images to a user. For example, cathode ray tube displays (“CRTs”), such as televisions and computer monitors, are very common. Such devices suffer from several limitations. For example, CRTs are typically bulky, consume substantial amounts of power and require high voltages, making them undesirable for portable or head-mounted applications.
Flat panel displays, such as liquid crystal displays, plasma displays, and field emission displays, may be less bulky and consume less power. However, typical flat panel displays utilize screens that are several inches across. Such screens have limited use in head mounted applications or in applications where the display is intended to occupy only a small portion of a user's field of view.
More recently, very small displays have been developed for partial or augmented view applications and for various head-mounted applications. In augmented view applications, a portion of the display is positioned in the user's field of view and presents an image that occupies a small region
42
of the user's field of view
44
, as shown in FIG.
1
. The user can thus see both a displayed image
46
and background information
48
.
One approach to providing a small display is a scanned beam display such as that described in U.S. Pat. No. 5,596,339 to Furness, et. al., entitled “VIRTUAL RETINAL DISPLAY WITH FIBER OPTIC POINT SOURCE,” which is incorporated herein by reference. In such displays, a modulated beam of light is scanned through a periodic two-dimensional pattern. The scanned light is then received by a viewer's eye. The light strikes the viewer's retina and the viewer perceives an image in response.
SUMMARY OF THE INVENTION
In an optical imaging apparatus, light from an optical source is divided into two separately polarized beams that are separately modulated and simultaneously transmitted to a scanning assembly. In one embodiment of the invention, each of the beams is modulated with respective image information. The modulated beams are then coupled into a polarization maintaining optical fiber and transmitted to a scanning assembly. The scanning assembly scans the beams through a predetermined pattern, such as a raster pattern. Then, a birefringent crystal separates the beams into their polarized components. The separated components are then transmitted to a viewer's eye or eyes along different paths. Each of the beams thus forms a separately modulated pixel of a scanned image.
In one embodiment, the optical source is a laser that emits polarized light. The polarized light is split by a beam splitter into two separate beams. Each of the beams is modulated by a respective modulator. Then, a polarization rotator rotates one of the beams so that the two beams are orthogonally polarized. The orthogonally polarized beams are then coupled into the fiber for transmission to the scanning assembly.
In one embodiment, the optical source includes three separate optical emitters that emit beams of red, green and blue light, respectively. Each of the beams is then separated by a respective beam splitter and all six of the beams are separately modulated. One of each of the red, green, and blue beams are then rotated to orthogonal polarizations relative to their unrotated counterparts. The six beams are then coupled to the fiber and transmitted to the scanning assembly, where they are separated into the orthogonally polarized components. The unrotated components are then directed along a first optical path to the viewer's eye and form a first set of color pixels. The rotated components are directed along a second optical path to the viewer's eye and form a second set of color pixels. Because both of the components can be modulated separately and transmitted simultaneously, the information represented by the two modulated components is effectively multiplexed.
REFERENCES:
patent: 5596339 (1997-01-01), Furness, III et al.
Dang Hung Xuan
Microvision Inc.
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