Abstract: Optical elements, color combiners using the optical elements, and image projectors using the color combiners are described. The optical elements can be configured as color combiners that receive different wavelength spectrums of light and produce a combined light output that includes the different wavelength spectrums of light. In one aspect, the received light inputs are unpolarized, and the combined light output is polarized in a desired state. The optical elements are configured to minimize the passage of light which may be damaging to wavelength-sensitive components in the light combiner. Image projectors using the color combiners can include imaging modules that operate by reflecting or transmitting polarized light.

Abstract: Optical elements, color combiners using the optical elements, and image projectors using the color combiners are described. The optical elements can be configured as color combiners that receive different wavelength spectrums of light and produce a combined light output that includes the different wavelength spectrums of light. In one aspect, the received light inputs are unpolarized, and the combined light output is polarized in a desired state. The optical elements are configured to minimize the passage of light which may be damaging to wavelength-sensitive components in the light combiner. Image projectors using the color combiners can include imaging modules that operate by reflecting or transmitting polarized light.

Abstract: A projection system contains an illumination system having at least a first source of incoherent light capable of generating light in a first wavelength range. The illumination system also includes a body containing a fluorescent material that emits light in a second wavelength range, different from the first wavelength range, when illuminated by light in the first wavelength range. The system further includes at least a second fluorescent material that absorbs light in at least one of the first and second wavelength ranges, and emits light in a third wavelength range. The body has an extraction area, and at least some of the light in either the second or third wavelength ranges is internally reflected within the body to the extraction area. Light from the extraction area illuminates at least one image-forming device. Image light from the image-forming device is projected by a projection lens unit onto a screen.

Abstract: A projection system contains an illumination system having at least a first source of incoherent light capable of generating light in a first wavelength range. The illumination system also includes a body containing a fluorescent material that emits light in a second wavelength range, different from the first wavelength range, when illuminated by light in the first wavelength range. The system further includes at least a second fluorescent material that absorbs light in at least one of the first and second wavelength ranges, and emits light in a third wavelength range. The body has an extraction area, and at least some of the light in either the second or third wavelength ranges is internally reflected within the body to the extraction area. Light from the extraction area illuminates at least one image-forming device. Image light from the image-forming device is projected by a projection lens unit onto a screen.

Abstract: Silica tubes and sleeves are used to protect fusion splices between the ends of the fiber coil and polarizing fibers. Use of silica for most of the subassembly components matches the coefficients of thermal expansion of the subassembly to that of the fiber coil, and also allows the coil to be annealed at extremely high temperatures. Annealing yields fiber coils of lowered birefringence, particularly when used with spun fibers. Ferrules are used to adjust the angular orientation of the fibers with respect to their planes of polarization.

Abstract: A holder for annealing a fiber optic coil uses a silica ring on a silica substrate, or silica tubular coil, either of which may be directly incorporated into a coil subassembly for a Faraday-effect current sensor. The ring may be formed in a silica plate by sandblasting or grinding, or formed separately and adhered to the plate. In the tubular holder embodiment, silica tubes and sleeves are used to protect fusion splices between the ends of the fiber coil and polarizing fibers. Use of silica for most of the subassembly components matches the coefficients of thermal expansion of the subassembly to that of the fiber coil, and also allows the coil to be annealed at extremely high temperatures. Annealing yields fiber coils of lowered birefringence, particularly when used with spun fibers. Ferrules are used to adjust the angular orientation of the fibers with respect to their planes of polarization.

Abstract: A fiber optic, Faraday-effect sensing coil has very low linear and circular birefringence, which remains stable over a wide range of temperatures. The coil is fabricated from a spun fiber having an effective linear beat length of 100 meters or more, and is annealed after being formed into the coil. The coil has improved discrimination for magnetic fields associated with electric current-carrying cables, and may be incorporated into an optical current transducer (OCT), either interferometric or polarimetric.

Abstract: A holder for annealing a fiber optic coil uses a silica ring on a silica substrate, or silica tubular coil, either of which may be directly incorporated into a coil subassembly for a Faraday-effect current sensor. The ring may be formed in a silica plate by sandblasting or grinding, or formed separately and adhered to the plate. In the tubular holder embodiment, silica tubes and sleeves are used to protect fusion splices between the ends of the fiber coil and polarizing fibers. Use of silica for most of the subassembly components matches the coefficients of thermal expansion of the subassembly to that of the fiber coil, and also allows the coil to be annealed at extremely high temperatures. Annealing yields fiber coils of lowered birefringence, particularly when used with spun fibers. Ferrules are used to adjust the angular orientation of the fibers with respect to their planes of polarization.

Abstract: A fiber optic, Faraday-effect sensing coil has very low linear and circular birefringence, which remains stable over a wide range of temperatures. The coil is fabricated from a spun fiber having an effective linear beat length of 100 meters or more, and is annealed after being formed into the coil. The coil has improved discrimination for magnetic fields associated with electric current-carrying cables, and may be incorporated into an optical current transducer (OCT), either interferometric or polarimetric.

Abstract: A depolarizer operates by splitting light traveling along an optical fiber into two sub-beams. One of the sub-beams is inserted into a recirculation loop, where it has its polarization state altered. The light in the recirculation loop is then reinserted into the fiber at a position prior to that at which the splitting occurred.

Abstract: In known Faraday effect current sensors, light is fed into a polarizer, through a coil of field-sensitive optical fiber, and into a polarization measuring device. Such a current sensor can provide greater accuracy of current measurement by using a polarizing optical fiber as its polarizer and splicing the polarizing fiber to the input end of the optical fiber coil. The exit end of the optical fiber coil can be spliced to a second polarizing optical fiber, the other end of which is optically connected to a photodetector. In another embodiment, a mirror at the exit end of the optical fiber coil reflects light back through the coil to second and third polarizing fibers which in turn are optically connected to a pair of photodetectors, thus doubling the Faraday rotation while canceling out reciprocal optical effects.