Optical waveguides – Miscellaneous
Reexamination Certificate
1999-06-08
2002-03-12
Schuberg, Darren (Department: 2872)
Optical waveguides
Miscellaneous
C385S901000, C385S031000, C362S297000, C362S298000, C362S302000, C362S346000, C359S859000
Reexamination Certificate
active
06356700
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to highly efficient, radiant power transferring, light engines and, in particular, to projection display systems, fiber-optic illumination systems, and to the design optimization of related components.
Many applications of light, or more broadly, coherent and incoherent electromagnetic energy, require a physical separation between the locations of light generation and the locations of its use, i.e. target locations. Together all light usage locations of interest form a target T. In the same manner, all energy emission locations of interest form a source S. Such electromagnetic energy radiating sources can be operated continuously or pulsed, can be incoherent, coherent or partially coherent and/or a combination thereof. They can be energized by AC or DC currents, by microwave heating, by electromagnetic radiation means using energy in similar and/or different wavelength regions, by chemical means, and by many other sources of energy. Depending on the distributions of the respective location of interest they can be characterized either as surface, volume, as surface and volume type source S and target T.
A given target T usually has some associated formatting requirements on the light beam used to illuminate it. Further, the spectral, spatial and angular emission energy density function of a source S, is in general different from the spectral, spatial and angular light acceptance function of a given target T. Therefore, for best energy coupling between a given source S and a given target T, the associated target illumination beam has typically to be reformatted to increase the delivery efficiency of collectable light that is also usable by the target. Examples of common formatting requirements for a target illumination beam are restrictions for DE its cross sectional shape and size near the respective collection aperture, its spatial intensity distribution, its minimum and maximum intensity level, its maximum incident angle dependent on a preferred azimuth direction, its local energy propagation direction, its spectral energy content and spectral intensity distribution, etc. Further, in many types of illumination systems, selected internal optical components choices (for example, a Color Wheel (CW), a Light Valve (LV), a Light Guide (LG), a Polarization Conversion System (PCS), a color cube combiner (CQC), an Anamorphic Beam Converter (ABC), etc.) and/or component layout constraint (input and output coupling of a LV, maximum height of a component, etc) effect the maximum light delivery efficiency. These design constraint and/or throughput limiting components can effectively also be interpreted as effective or intermediate targets T′.
Only those light rays that fulfill the formatting requirements of a given target T are useful for the illumination of the target T. The rest of the light rays, incident either on the target T itself or its neighborhood, are typically wasted. Often these non-usable rays have to be stopped with masks and or spectral filters from reaching the target T or its surrounding space to prevent them from interfering with a particular target illumination application: for example, by causing an undesired overheating of the target object itself or reducing the image contrast in a projection display system. Often also selected color bands and/or polarization directions have to be attenuated to create a particular color balanced system with a chosen white point and color gamut and/or a well defined polarization state.
Thus, it is in general preferred that light (i.e., for the purpose of this invention, electromagnetic radiation of any wavelength) is captured from a source S and delivered to a target T be reformatted in such a manner that as much as possible of the light delivered to a given target is also useable by the target T.
A Light Engine (LE) is an apparatus that accomplishes the above described electromagnetic radiation power transfer and beam-formatting task. It is typically made up of multiple optical components that together have at least two or three major tasks. The first task is to collect light from a source S. The second task is to deliver some of the collected light to the target T. The third, and often optional, task is to reformat the light beam to enhance the usable content of the light delivered to the target T.
To facilitate an understanding of this invention, three subclasses of LE's are defined: a Minimal Light Engine (MLE), a Light Guide Light Engine (LGLE) and an Anamorphic Beam Transformer Light Engine (ABTLE). A MLE is a special LE (or a portion of a more complex LE) that collects light emitted from the emission surface ES
s
or emission volume EV
S
of a source S and concentrates it inside a volume EV
S
′. This volume EV
S
′ can be interpreted as the emission volume of a secondary source S′, also called emission source S′, that illuminates either a target T directly or the collection aperture CA of a beam reformatting and/or remote transmission system of a related LE. A LGLE is another special LE where a MLE couples energy into at least one LG (for example for beam reformatting and/or remote energy transmission purposes) and where the input port of the respective LG collects light from the emission volume EV
S
′ of the respective MLE. The respective illumination target T is the exit port of the respective LG optionally combined with constraint for the spatial and/or angular extend of the exiting beam. An ABTLE is similar to a LGLE and uses at least one ABT for beam reformatting purposes. If the LG is also an ABT then a LE can be both a LGLE and an ABTLE.
The optical parameters called étendue E, étendue efficiency EE, throughput efficiency TE and delivery efficiency DE are important in better understanding this invention and are defined and discussed below. The étendue E is a measure of both the spatial and angular confinement of a light beam. The throughput TE and étendue efficiency EE are related parameters and measure in different ways how efficiently a given optical system reformats a given input beam compared to an ideal performing optical system. The delivery efficiency DE parameter measures both the fulfillment of the target formatting requirements and the throughput efficiency of a LE for a given target T, i.e. measured the amount of both collectable and usable light by a given target T.
This invention relates to both high efficient MLE, LGLE and ABTLE and where the respective input and output ports of the respective LG's and/or ABT's are preferably customized to the respective MLE and Target T to optimize the delivery efficiency of a given and constrained LE design.
The below referenced invention discloses embodiments that are satisfactory for the purposes for which they were intended and are in their entireties hereby expressly incorporated by reference into the present application for purposes including, but not limited to, indicating the background of this invention and illustrating the state of the prior art.
U.S. Pat. No. 5,491,765 to Matsumoto (1996) describes a typical LGLE design where a parabolic, sealed short arc reflector lamp, in combination with a focusing lens, is used to deliver collected energy to the entrance surface of a round fiber optic LG. Another related common, on-axis, prior art LGLE design uses an ellipsoidal mirror as Collection and Concentration System (CCS) of a lamp with a separate envelope. Both design families are of a non-imaging type and therefore result typically a low étendue efficiency EE. Thus, they achieve a high delivery efficiency DE only for large diameter fiber bundles having an input area A
L
in
>>A
S
with A
S
being the respective effective cross sectional area of the emission region of the source S.
U.S. Pat. No. 4,460,939 to Marakami et. all (1984) shows a LGLE which has a double concave reflector system as MLE and a sheet LG, thus creating spatial high output intensity uniformity, high delivery efficiency, but also low étendue efficiency since the collection étendu
Boutsikaris Leo
Cohen Jerry
Erlich Jacob N.
Perkins, Smiith & Cohen, LLP
Schuberg Darren
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