Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2000-12-13
2002-03-19
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S629000, C359S631000, C359S277000
Reexamination Certificate
active
06359723
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to image generating systems, and more particularly to optics arrangements and light source arrangements especially suitable for miniaturized image generating systems such as the miniaturized image generator disclosed in copending U.S. patent application Ser. No. 08/362,234, now U.S. Pat. No. 5,808,800, entitled ACTIVE MATRIX LIQUID CRYSTAL IMAGE GENERATOR and copending U.S. patent application Ser. No. 08/361,775 entitled DC FIELD-BALANCING TECHNIQUE FOR AN ACTIVE MATRIX LIQUID CRYSTAL IMAGE GENERATOR filed cotemperaneously herewith, which applications are incorporated herein by reference.
One of the ongoing challenges facing the manufacture of miniature image generating systems is providing smaller and smaller systems. Miniature image generating systems which are small enough to be mounted onto a helmet or small enough to be supported by a pair of eyeglasses will find a wide variety of uses if they can provide adequate resolution and brightness in a small, low-power package at a low cost. Conventional technologies such as CRTs are difficult to miniaturize and therefore do not hold much promise in this field. Alternatively, new systems based on VLSI integrated circuits are currently being developed which provide much smaller spatial light modulators for use in a miniaturized image generating systems. However, one of the problems in this field is providing optics and illuminating arrangements which may be scaled down in coordination with the miniaturized spatial light modulator in order to provide an overall image generating system which is practical and compact enough to be mounted onto a helmet or supported by a pair of glasses. Another problem in this field is providing an illuminating arrangement which requires as little power as possible in order to make the overall system more portable.
Referring to
FIG. 1
, a prior art miniature image generator system generally designated by reference numeral
10
will be described. System
10
includes a transmissive spatial light modulator
12
which modulates light from a light source
14
positioned immediately adjacent to spatial light modulator
12
by selectively changing the polarization of light passing through the spatial light modulator. A polarizer
16
is positioned between light source
14
and spatial light modulator
12
which allows light of one polarization from light source
14
to enter spatial light modulator
12
. An analyzer
18
is positioned adjacent to the opposite side of spatial light
12
which allows light of a particular polarization to pass through analyzer
18
. An eyepiece lens
20
having a focal length F
1
is positioned approximately one focal length F
1
from spatial light modulator
12
such that a viewer may see a virtual image of the pattern of modulated light formed by spatial light modulator
12
when the viewer's eye is positioned in an appropriate location. As shown in
FIG. 1
, this arrangement results in a viewing region indicated by reference numeral
22
from which a viewer may view the entire virtual image of the pattern at modulated light produced by the spatial light modulator display.
In the above described arrangement, since light source
14
is positioned adjacent to spatial light modulator
12
, light source
14
must have a light emitting surface with essentially the same surface area as spatial light modulator
12
. Also, in order for the optics to perform properly, the light source is a diffuse light source. However, these requirements causes two major problems. First, a large diffuse light source as described above is substantially more expensive than other types of light sources. Second, because light source
14
is diffuse, a large percentage of the light generated by light source
14
, indicated by lines
24
, is directed to areas which are not within viewing region
22
including areas in which the light does not pass through eyepiece lens
20
. This wastes a large percentage of the light produced by light source
14
and requires much more light to be produced than would be necessary if substantially all of the available light were directed into viewing region
22
. This wastage of light significantly increases the power requirements of the overall system. As will be seen hereinafter, the present invention provides a variety of novel optics arrangements including novel light source arrangements which, when combined with miniaturized spatial light modulators, are capable of providing low power, compact miniaturized image generating systems that may be used to produce a direct view miniature display.
SUMMARY OF THE INVENTION
As will be described in more detail hereinafter, a system for producing modulated light is disclosed. The system comprises a spatial light modulator including a light modulating medium switchable between different states so as to act on light in ways which form overall patterns of modulated light. The system also includes means for switching the modulating medium between the different states in a controlled way and illumination means for producing a source of light. The system further includes optics means for directing light from the source of light into the spatial light modulator and for directing light from the spatial light modulator through a predetermined source imaging area. The optics means cooperates with the illumination means and the spatial light modulator so as to produce a real image of the source of light within the source imaging area such that an individual is able to view a virtual image of the overall patterns of modulated light from the source imaging area.
In one preferred embodiment of the present invention the spatial light modulator is a reflective type spatial light modulator and the optics means cooperate with said illumination means and said spatial light modulator such that some of the light passing from the illumination means to the spatial light modulator overlaps with some of the light passing from the spatial light modulator to the source imaging area.
In another embodiment of the present invention, the light source is provided by means of an array of light emitting sources such as LEDs (light emitting diodes) spaced apart by a predetermined distance. These spaced apart light sources, in combination with the optical components, produce an equal plurality of images at the source imaging area which are spaced apart from one another by a predetermined distance. The optical components of this embodiment may include a single collimating lens disposed optically between the light sources and the spatial light modulator, or alternatively, may include a plurality of collimating lenses, each of which is disposed optically between an associated one of the light sources and the spatial light modulator so as to direct light from its associated light source to a corresponding portion of the spatial light modulator.
In the case of a plurality of collimating lenses, the optical components also include a single eyepiece lens which is disposed optically between the spatial light modulator and the source imaging area and which defines a much greater focal length than the focal length of each of the individual collimating lenses. Also, the light sources may be disposed optically approximately a focal length away from their associated collimating lens, such that the plurality of images produced at the source imaging area a substantially larger than their respective light sources. Alternatively, in this arrangement, the light sources are disposed optically slightly closer to their associated collimating lens than one focal length so as to cause each collimating lens to direct light from its associated light source to the spatial light modulator in a slightly diverging manner. The spatial relationship between the light sources and the divergence of the light from the collimating lenses are such that the plurality of images produced at the source imaging area overlap one another in a predetermined way.
The plurality of light sources may be provided in a variety of arrangeme
Chase Holden
Handschy Mark A.
Meadows Michael R.
Crouch Robert
Displaytech, Inc.
Epps Georgia
Thompson Tim
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