Optical: systems and elements – Optical modulator – Light wave directional modulation
Reexamination Certificate
2000-09-18
2002-05-28
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave directional modulation
C359S316000, C359S319000, C359S721000, C359S742000, C349S057000
Reexamination Certificate
active
06396622
ABSTRACT:
BACKGROUND—FIELD OF INVENTION
This invention relates to electro-optic lenses, such as are used for variably bending light. Such lenses have broad applications including directing and switching light within fiber optics applications, focusing light as with optical lenses, and coherent imaging as with windows that are mounted in a building or on a vehicle, or a television or computer monitor screen. Specifically this invention couples electro-optic components (such as liquid crystals) in series such that a first liquid crystal comprising a first apex angle and a second liquid crystal comprising a second apex angle refract light of at least two frequencies simultaneously with minimal spectral dispersion. Moreover, said first and second liquid crystals so configured produce a first net refractive exiting beam angle with minimal dispersion when in a first state and a second net refractive exiting beam angle with minimal dispersion when in a second state. The invention enables switching between at least two net refractive states each with minimal spectral dispersion upon at least two exiting beam frequencies.
BACKGROUND—DESCRIPTION OF PRIOR ART
The optical properties of liquid crystals have been studied since at least 1888. Particularly since the late 1970's scientific investigation and applications of them has resulted in prolific, widely accepted and profoundly significant uses for their multi-state optical properties.
The dual refractive states associated with liquid crystals referred to as no and ne have been widely studied and applied to provide significant objects and advantages. U.S. Pat. No. 4,037,929 for example utilizes the no and ne states to operate a liquid crystal variable lens to provide a range of focal points. Similarly, U.S. Pat. No. 4,958,914 utilizes the no and ne refractive states to operate an array of liquid crystal variable prisms. U.S. Pat. No. 5,648,859 discloses liquid crystal variable prisms in series to achieve the object of fiber optic communications optical switching. It too relies upon the no and ne refractive states and the resulting range of refractive indices possible in one material.
The prior art contains a large body of information and applications which utilize the no and ne states of liquid crystals. But, it has not anticipated nor addressed the minimization of dispersion caused by different refractive indices for different frequencies of electromagnetic radiation passing through the variable liquid crystal. Particularly as it relates to the challenges posed by dispersion in multiple states (and concomitant multiple refractive indices for any given electromagnetic frequency).
It is well known that any given optical medium (including liquid crystals in the full range between the no and ne states) commonly has differing refractive indices for each frequency of electromagnetic radiation passing therethrough resulting in dispersion of exiting beams that had entered parallel to one another. For over a hundred years, in lens making, this resultant dispersion and symptomatic chromatic distortion have been addressed using crown an flint glasses with complementary spectral dispersion curves. This combination of glasses produces net refraction with minimal dispersion and chromatic distortion. Such glasses nearly always operate only in one state and have only one refractive index for each frequency at any given temperature. By contrast, the problem resolved in the present invention relates to a more complex medium that operates within at least two refractive states for each frequency of electromagnetic radiation.
The complexity of minimizing dispersion in multi-state refractive materials may not have been addressed heretofore because dispersion has not been an issue in the vast majority of applications. Nearly all applications to date have used single frequency electromagnetic radiation or very close frequencies whereby dispersion is not an issue. This is true in most laser and communications applications to date. Also, many of the applications to date are interfacing with photo cells that can retain the information in divergent rays just as efficiently as in parallel rays. Of course, as anyone who has tried to look at the world through a prism knows, the human eye can not efficiently use divergent rays. Such rays, when the eye is close to the dispersing optic, appear as blue and red shading on either side of an object, and as the eye moves away from the dispersing optical element, divergent rays from the same object quickly become an unintelligible blur at just a short distance away. Close-up is where the vast majority of liquid crystal multi-frequency multi-state refraction is utilized (such as with laptop computers). This is another reason why multi-frequency multi-state dispersion has not previously been addressed. The vast majority of applications heretofore involve close up use of exiting divergent rays by either the human eye such as with a laptop or the next in a series of optical components such as in fiber optic switching. Short distances keep dispersion from causing problems. For the previous reasons, multi-frequency multi-state dispersion has not been previously resolved. Solving this problem requires much effort in determining precise prism angles that are required for a minimum of eight refractive indices to cause beams to exit at precise trajectories. Computer software required to establish the precise refractive angles in multi-state materials and to match complementary refractive indices across multiple frequencies is disclosed herein. Also disclosed is software to operate the two materials.
The problem of minimizing the dispersion of at least two parallel beams of differing electromagnetic frequencies caused by liquid crystals operated between at least two states is addressed and resolved herein. It has been heretofore unrecognized that the refractive variability of liquid crystals could be used for additional significant applications if the associated dispersion is eliminated. The present invention retains the refractive variability of liquid crystals while simultaneously providing a reliable and cost effective means to minimize dispersion over an operating range of two materials each have a controllable range of refractive properties and between at least two frequencies of electromagnetic radiation.
SUMMARY
The preferred embodiment of the invention described herein incorporates a series of two variable electro-optic components such as liquid crystal prisms (referred to herein as a couplet) with at least two frequencies of electromagnetic radiation in beams entering parallel to one another and then passing therethrough. The first prism with a first apex angle operating between a first refractive state no and second refractive state ne and the second prism with a second apex angle operating between a first refractive state no and second refractive state ne. In said first state, the couplet producing a first net refracted angle in the beams with minimal dispersion and in said second state, the couplet producing a second net refracted angle in the beams with minimal dispersion. This novel construction has broad applications including directing and switching multi-frequency light within fiber optics applications, producing variable focal length multi-frequency light focus as with optical lenses, and coherent multi-frequency imaging as with windows that are mounted in a building or on a vehicle through which a user can view multiple views with minimal chromatic distortion, or a television or computer monitor screen.
OBJECTS AND ADVANTAGES
Accordingly, several objects and advantages of my invention are apparent. The invention enables multiple frequencies of electromagnetic radiation traveling parallel to be accurately and reliably refracted and exit traveling parallel (within a controllable tolerance). Moreover, utilizing a first prism with a first apex angle operating in a range between a first refractive state no and second refractive state ne and the second prism with a second apex angle operating in a range between a first refracti
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