Minnesota Mining and Manufacturing Company

Other

Trevor W MacDougall

Dale R Lutz

Bryon J Cronk

William L Taylor

James Robert Onstott

Wayne Francis Varner

Robert A Wandmacher

Jay W Dawson

Ted F Hutchinson

Jay Walter Dawson

Leonard A Johnson

Yi Yang

An interoperative light therapy apparatus and method are disclosed. The apparatus includes an excitation light source, a plurality of light emitting devices and a plurality of light detecting fibers, wherein the plurality of light emitting devices produce a fluorescence light in cancerous cells of a patient treated with a photosensitizing medication. The fluorescence light is collected by the plurality of detector fibers and a digital spatial image of the cancerous cells is produced. The digital spatial image is useful for targeting the cancerous cells in a subsequent resection procedure. An interoperative light therapy apparatus is disclosed that further include a therapy light source that can deliver therapy light to the cancerous cells using the digital spatial image in the subsequent resection procedure.

Direct in-vivo tumor imaging using optical applicator

A fiber optic, Faraday-effect current sensor (optical current transducer) which has improved temperature sensitivity due to compensation for temperature-induced variations of the Verdet constant. Fiber optic sensing coils can exhibit shifts in their bias angle due to a number of reasons, including physical rotation of the fibers, an apparent circular birefringence attributable to the sensing coil shape (Berry's phase), circular birefringence in the sensing fiber, or a DC magnetic field or current. The present invention takes advantage of the change in bias angle by identifying a preferred channel from the two sensing axes of the output fiber, based on the manner in which these axes respond to the change in bias angle. One of the axes will exhibit a change in sensitivity that exacerbates the change in sensitivity due to the Verdet constant, while the other channel will exhibit a change that complements, or compensates for, the change in sensitivity due to the Verdet constant. Once the preferred channel is identified, a polarizing fiber is attached to the output of the sensing coil, aligned to transmit the preferred channel to the optical detector.

Verdet constant temperature-compensated current sensor

A Faraday effect current sensor uses a plurality of concatenated field sensors, with a single light source and a single detector. At least two Faraday effect sensing elements (single mode sensing fibers) are used, preferably at least three, the sensing elements being interconnected by fusion spliced, polarizing fibers. The sensing fibers may be oriented generally straight, and arranged to form a regular polygon, e.g., an equilateral triangle for a three-element sensor. The locations of the splices between the sensing fibers and the polarizing fibers may further be advantageously arranged such that the sensing fibers form a substantially closed path which may be placed about the current-carrying conductor. The linearity of the sensor response may be improved by selecting an appropriate value of the bias angle of each sensing element, optimally equal to arctan�1/.sqroot.(2n-1)! where n is the number of sensing elements. The present invention may also be adapted for use as a differential current sensor wherein each sensing element is housed in a separate package allowing the elements to be placed about different conductors at a Y-branch, or about a single conductor at different locations.

Concatenated magneto-optic field sensors

A fiber optic subassembly for a Faraday-effect current sensor has an optical sensing fiber supported by a tubular holder in a square or rectangular configuration, with the three of the four corners thereof designed with bends which have a net zero bend-induced birefringence. The bends are formed by providing two loops which have effective angles of about 90.degree., the two loops lying in orthogonal planes, such that the fast axis of birefringence in the first loop is parallel to the slow axis of birefringence in the second loop, and the slow axis of birefringence in the first loop is parallel to the fast axis of birefringence in the second loop. In this manner, retardance accumulated in the first loop is offset by retardance accumulated in the second loop. If the loops are substantially identical, the offsetting of the retardance is effectively complete such that the bend exhibits negligible bend-induced birefringence.

Fiber optic current sensor with bend birefringence compensation

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.

Method of annealing a fiber within a coiled tube to thereby make a fiber

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.

Holder for annealing fiber optic coils

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.

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Cedar Park, TX, United States of America

Trevor W MacDougall