Abstract: An apparatus for determining the position of an object having one or more magnetic elements. The apparatus includes magnetostrictive optical sensors, each arranged to produce a signal which is indicative of a proximity of the sensor to the one or more magnetic elements. The apparatus is arranged to determine the position of the object based on a plurality of such proximity signals.

Abstract: In some implementations, scene depth is extracted from dual frequency of a cross-correlation signal. A camera may illuminate a scene with amplitude-modulated light, sweeping the modulation frequency. For each modulation frequency in the sweep, each camera pixel may measure a cross-correlation of incident light and of a reference electrical signal. Each pixel may output a vector of cross-correlation measurements acquired by the pixel during a sweep. A computer may perform an FFT on this vector, identify a dual frequency at the second largest peak in the resulting power spectrum, and calculate scene depth as equal to a fraction, where the numerator is the speed of light times this dual frequency and the denominator is four times pi. In some cases, the two signals being cross-correlated have the same phase as each other during each cross-correlation measurement.

Abstract: A sensing system that includes an optical fiber disposed helically around an outer surface of a structure along a longitudinal axis of the structure is provided. The optical fiber is disposed such that at least one complete helical turn of the optical fiber covers the length of the structure. Further, the sensing system also includes a fiber Bragg grating (FBG) set comprising a plurality of FBGs in the optical fiber. Each FBG in the set is configured to generate reflected light that is indicative of strain values at a location of each respective FBG on the optical fiber. Furthermore, the system also includes a processing system coupled to the optical fiber. The processing system is configured to determine location coordinates of each FBG and values of one or more of bending moment, tensile force, and torsional moment acting at each FBG location on the optical fiber.

Abstract: A pressure-sensing touch system for recognition of a touch event caused by a pressure applied at a touch position is disclosed which includes a light guide plate, a light output plate, a light source subsystem, a plurality of interference plates, a plurality of detectors and a controller. Upon application of the pressure at the touch position, a change in an intensity distribution of output light exiting from two through-openings of the interference plate occurs. The plurality of detectors are configured to detect the change. The controller is configured to recognize the touch event based on the detecting by the plurality of detectors. Also disclosed are a pressure-sensing touch method and a display system.

Abstract: An optical unit includes an optical element serving as a light guide path, which includes an incident entrance, an emitter, a light coupler which is arranged in the case where a plurality of incident entrances are arranged, and which couples a primary light, and a light separator which is arranged in the case where a plurality of emitters are arranged, and which separates the primary light to each of the emitters. The optical unit further includes a detector which directly or indirectly detects a leakage light leaking outside of the light guide path from the light guide path.

Abstract: The invention relates to an optical fiber mounted photonic integrated circuit device where the tolerance in the positioning of the coupling between a single mode optical fiber and an optical waveguide provided in the photonic integrated circuit device is increased. A second optical waveguide of which the cross-section of the core is in the form of a slab having a width that is greater than the mode diameter of the single mode optical fiber, and which is tapered in such a manner that the thickness of the core is reduced as the location is closer to the connection portion with the single mode optical fiber, is provided on the input/output end side of the first optical waveguide through which light propagates in such a manner that the inclined connection end surface of the single mode optical fiber is coupled to the upper surface of the second optical waveguide.

Abstract: A load and stress of a tensioner may be determined from the change in the strain of the tensioner. The strain of the tensioner may be detected by an optical device having a Fiber Bragg Grating (FBG) that is attached to the tensioner. An electrical signal may be generated in response to the detected change in the mechanical strain of the tensioner by processing the light reflected from an optical fiber coupled to the optical device. The electrical signal may be processed to calculate a load on the tensioner. The calculated load may be stored and analyzed, along with previously-stored values for the load, to determine the condition of the tensioner system, and whether the tensioner system requires maintenance.

Abstract: Embodiments of present invention provide a digital dispersion compensation module. The digital dispersion compensation module includes a multi-port optical circulator; and a plurality of dispersion compensation units connected to the multi-port optical circulator, wherein at least one of the plurality of dispersion compensation units includes a fiber-bragg grating (FBG) having a first port and a second port; and an optical switch being capable of selectively connecting to one of the first port and the second port of the FBG, wherein the at least one of the plurality of dispersion compensation units is adapted to provide a positive dispersion to an optical signal, from the multi-port optical circulator, when the optical switch connects to the first port of the FBG and is adapted to provide a negative dispersion to the optical signal when the optical switch connects to the second port of the FBG.

Abstract: The present invention relates, generally, to controlling a steerable instrument having an elongate body. More particularly, the present invention relates to a system and method for sensing the shape of a steerable instrument and controlling the steerable instrument in response to a control signal from a user input device and a shape signal corresponding to the sensed shape of at least a portion of the steerable instrument. The present invention also relates to a system for sensing the shape of a flexible instrument with an optical shape sensor.

Abstract: Embodiments of present invention provide a digital dispersion compensation module. The digital dispersion compensation module includes a multi-port optical circulator; and a plurality of dispersion compensation units connected to the multi-port optical circulator, wherein at least one of the plurality of dispersion compensation units includes a fiber-bragg grating (FBG) having a first port and a second port; and an optical switch being capable of selectively connecting to one of the first port and the second port of the FBG, wherein the at least one of the plurality of dispersion compensation units is adapted to provide a positive dispersion to an optical signal, from the multi-port optical circulator, when the optical switch connects to the first port of the FBG and is adapted to provide a negative dispersion to the optical signal when the optical switch connects to the second port of the FBG.

Abstract: Various particular embodiments include a primary waveguide including an end section; cantilevered waveguides, each cantilevered waveguide including an end section disposed adjacent the end section of the primary waveguide; and control pins for applying an electrical bias to the cantilevered waveguides to selectively displace the end sections of the cantilevered waveguides away from the end section of the primary waveguide.

Abstract: Embodiments of present invention provide a digital dispersion compensation module. The digital dispersion compensation module includes a multi-port optical circulator; and a plurality of dispersion compensation units connected to the multi-port optical circulator, wherein at least one of the plurality of dispersion compensation units includes a fiber-bragg grating (FBG) having a first port and a second port; and an optical switch being capable of selectively connecting to one of the first port and the second port of the FBG, wherein the at least one of the plurality of dispersion compensation units is adapted to provide a positive dispersion to an optical signal, from the multi-port optical circulator, when the optical switch connects to the first port of the FBG and is adapted to provide a negative dispersion to the optical signal when the optical switch connects to the second port of the FBG.

Abstract: An optical fiber sensor (100) can be used to measure pressure with high sensitivity and fine resolution. As a (108) at the end of the sensor expands or contracts, the spectrum of a beam reflected from the end of fiber shifts, producing a change linked to pressure exerted on the sensor. Novel aspects of the present inventive sensor include the direct bonding of a silica thin film diaphragm (110) to the optical fiber with localized or confined heating and a uniform thickness of the diaphragm. The resulting sensor has a diameter that matches the diameter of the optical fiber. Because the sensor is all silica, it does not from temperature-induced error. In addition, the sensor can be very sensitive because the diaphragm can be very thin; it can also make highly repeatable measurements due to its very uniform thickness.

Abstract: Disclosed herein is a method for sensing one or more selected parameters related to a structure of interest, for example, the shape of an isolated structure. A cable is attached to the structure of interest at one or more attachment points. The cable contains one or more optical fibers. One or more light signals are transmitted into the one or more optical fibers and then detected to form a data set. The data set is compared with information known about the one or more attachment points to determine error values. The error values are then combined with the data set to determine the selected parameters associated with the structure.

Abstract: The invention relates to a high voltage transformer (6) having a sensor system (30) for monitoring physical characteristic variables. In particular, said sensor system has at least one sensor (1) that comprises a glass fiber (3) with a sensor head (2). Said sensor head supports a plurality of Bragg gratings (7, 8, 9). An evaluation unit (10) is associated with the sensor system and is connected to the at least one sensor head via said glass fiber. The invention is based on the general inventive concept of arranging the sensors of the sensor system between successive windings (4, 5) of the high voltage transformer using spacers. In addition, the use of a plurality of Bragg gratings in the sensor head ensures that at least one of the Bragg gratings determines the actual physical characteristic variables such as temperature or contact force (A).

Abstract: The present disclosure provides an optical sensing apparatus for measuring a change in a first property. The optical sensing apparatus comprises first and second optical fibre portions and a sensing region for exposing both the first and second optical fibre portions to a change in an applied force. The force is, or is related to, the first property and has a component that is transversal to the optical fibre portions. The apparatus further comprises a holder for holding the first and second optical fibre portions in the sensing region. The first and second optical fibre portions are arranged relative to each other such that the change in the force results in a first change of an optical property of the first optical fibre portion and in a second change of the optical property of the second optical fibre portion and wherein the first change differs from the second change.

Abstract: A strain measurement device is provided. The strain measurement device includes at least one filiform strain sensor and a support of longilinear shape on which the filiform strain sensor is positioned. The strain measurement device also includes a stiffener.

Abstract: A monitoring device is provided that is used for the monitoring of an area of building or land, including an optical strand used as a sensor, one optical source for emitting an optical emission signal transmitted in the optical strand, and one optical analogue detector for detecting an intensity of an optical return signal corresponding to the optical emission signal returning from the optical strand. The monitoring device is arranged as a compact unit and includes a controller for alternately activating and deactivating the emission of the optical source so that a ratio between the non-emission duration and the emission duration is greater than 5000. A monitoring system is also provided including such a monitoring device, and a monitoring method carried out in the monitoring device.

Abstract: A pressure sensing system includes a pressure sensor, an optical fiber in operable communication with the pressure sensor, and a body having a diaphragm integrally formed therein and separated a distance from the optical fiber.

Abstract: Methods for fabricating ultra-sharp nanoprobes can include the steps of providing a wafer, and patterning a silicon layer on the wafer with a plurality of geometric structures. The geometric structures can be patterned using electron-beam lithography or photolithography, and can have circular, triangular or other geometric shapes when viewed in top plan. The methods can further include the step of depositing a non-uniform cladding on the geometric structures using plasma enhanced chemical vapor deposition (PECVD) techniques, and then wet-etching the wafer. The non-uniform nature of the cladding can result in more complete etching in the areas where the cladding has lower density and incomplete etching in the areas of higher density of the non-uniform cladding. The different etching rates in the proximity of at least adjacent two geometric structures can result in the formation of ultra-sharp nanoprobes.

Abstract: A measurement apparatus includes a body suit for a body that includes an appendage having a pivotable joint, the body suit comprising a sleeve to cover the appendage, wherein a first portion of the sleeve is configured to cover the pivotable joint. One or more multi-core optical fiber sensors is/are within or on the sleeve in a routing pattern that is substantially aligned with a longitudinal axis of the sleeve except within the first portion and that is at least partially transverse to the longitudinal axis within the first portion. An optical shape sensing system coupled to the one or more multi-core optical fiber sensors sends light into the one or more multi-core optical fiber sensors and determines a position of each of the multiple appendages based on reflected optical signal measurements detected from one or more multi-core optical fiber sensors.

Abstract: A method and device for the detection of impact events on a security barrier. A hollow rebar is farmed within a security barrier, whereby the hollow rebar is completely surrounded by the security barrier. An optical fiber passes through the interior of the hollow rebar. An optical transmitter and an optical receiver are both optically connected to the optical fiber and connected to optical electronics. The optical electronics are configured to provide notification upon the detection of an impact event at the security barrier based on the detection of disturbances within the optical fiber.

Abstract: A photonic apparatus comprises an integrated waveguide, an integrated resonator in the form of a microtoroid and a thermally reflowable film. The reflowable film comprises a first film area and a second film area. The reflowable film is one of a thin film and a stack of thin films. The first film area is thermally reflown, the microtoroid is formed in the thermally reflown first film area. The second film area is not reflown in the immediate vicinity of the microtoroid. The microtoroid is optically coupled to the integrated waveguide located on or located within one of or both of the first or second film areas. The first and second film areas are directly connected to each other. The microtoroid has an edge extending along a circumference. The microtoroid can be a non-inverted or an inverted microtoroid, wherein the second film area is inside or outside of the circumference.

Abstract: A wireless headset capable of receiving audio signals transmitted wirelessly and compatible for use in an MRI scanner is disclosed. The headset includes a first wireless module connected to the first earphone and a second wireless module connected to the second earphone. Each wireless module is electrically connected to a speaker in the respective earphone. The first wireless module receives the audio signal from a remote source and coordinates transmission of the audio signal to each of the speakers. The compact nature of each earphone minimizes the length of wire runs. In addition, the headset is made of materials having low magnetic susceptibility such that they will not be affected by the magnetic field from the MRI scanner.

Abstract: This application describes methods and apparatus for fiber optic distributed acoustic sensing (DAS) where microstructured fiber (202), such as holey fiber or photonic crystal fiber is used as the sensing fiber (104). The microstructured fiber is configured so to provide at least one of enhanced sensitivity to a given incident acoustic signal; an enhanced non-linear optical power threshold and directional sensitivity. By configuring the microstructured fiber to be more compliant than an equivalent solid fiber and/or provide a large refractive index variation in response to applied strain, the response to a given acoustic stimulus may be larger than for the equivalent fiber, Providing a hollow core may allow higher optical powers and by providing a directionality to microstructured (304) allows the fiber to be used in a DAS system with a directional response.

Abstract: An instrument system that includes an elongate instrument body and an optical fiber sensor is provided. The optical fiber sensor includes an elongate optical fiber that is coupled to the elongate instrument body, wherein a portion of the optical fiber is coupled to the elongate instrument body in a manner to provide slack in the fiber to allow for axial extension of the elongate instrument body relative to the optical fiber.

Abstract: An optical fiber attenuation sensor that includes a first protrusion movable between a first position and a second position, a second protrusion movable between a third position to a fourth position, and an elastic object coupled to the first protrusion that causes the first protrusion to move from the first position to the second position. When the first protrusion moves from the first position to the second position, the second protrusion moves from the third position to the fourth position. The second protrusion is configured and positioned to cause an event in a signal in an optical fiber when the second protrusion moves from the third position to the fourth position.

Abstract: Optical fiber sensors adapted to measure strain or pressure are disclosed. The optical fiber sensor has a lead-in optical fiber having an end surface at a forward end, and a first optical element having a body with an outer dimension, Do, a front end surface coupled to the lead-in optical fiber, a pedestal including a retracted surface that is spaced from the front end surface, the retracted surface at least partially defining an optical cavity, a gutter surrounding the pedestal, the gutter having a gutter depth defining an active region of length, L, the first optical element further exhibiting L/Do?0.5. Also provided are systems including the optical fiber sensor, and methods for manufacturing and using the optical fiber sensor. Numerous other aspects are provided.

Abstract: A light hood for a fiber identifier tool that includes a head portion having interior photo detectors, a slot for receiving an optical fiber to be tested, and a clamp mechanism for urging the fiber to bend in the vicinity of the photo detectors when the mechanism is operated. The hood has a generally T-shaped body that defines a lower hood portion arranged to engage the clamp mechanism and operate the mechanism when the lower hood portion is pulled downward by a user. An upper hood portion of the body is configured so that when the lower hood portion is engaged with the clamp mechanism and pulled downward, the upper hood portion descends to cover the head portion of the tool including the slot. Outside light is then blocked from entering the slot and reaching the photo detectors whenever a fiber is tested by the tool, thus preventing false indications.

Abstract: The spatial resolution of a fiber optical Distributed Acoustic Sensing (DAS) assembly is enhanced by: arranging an optical DAS fiber with a series of contiguous channels that are sensitive to vibration in a U-shaped loop such that substantially parallel fiber sections include pairs of channels that are arranged at least partially side by side; transmitting a series of light pulses through the optical fiber and receiving back reflections of said light pulses by a light transmission and receiving assembly; and processing the received back reflections such that back reflections stemming from at least one pair of channels that are arranged at least partially side by side are correlated to each other.

Abstract: A method, apparatus and computer-readable medium for determining deformation of a plurality of coupled members. A distributed strain sensor string on a first member is coupled to a distributed strain sensor string on a second member. Signals are obtained from the sensor strings. A subset of strain data relating to sensor strain on the first member and the second member is created. A virtual sensor string is created having a plurality of virtual sensors placed on the first and second members including a joint therebetween. Strain data of sensors in the distributed stain sensor strings is mapped to sensors in the virtual sensor string. The deformation of the plurality of coupled members is determined using the strain data of the virtual sensors.

Abstract: The present invention relates to a laser apparatus for inducing a photo-mechanical effect. More particularly, the present invention relates to a laser apparatus for outputting a pulsed laser beam and inducing a photo-mechanical effect by controlling pulse energy of the pulsed laser beam.

Abstract: A tubular insertion device includes a tubular insertion portion including a flexible portion in a predetermined part, bending sensors distributed and arranged in the flexible portion, and an operation support information calculating unit. The operation support information calculating unit extracts operation support information including at least first external force information regarding an external force applied to the tubular insertion portion by a combinational calculation based on detection information from the bending sensors.

Abstract: A bearing comprises a Bragg grated optical fiber to measure one or more parameters of the bearing. The optical fiber is coupled to the bearing in such a way that at least a part of the optical fiber that comprises Bragg grating is curved. The grating which is curved is adapted to the curvature in such a way that the frequency response is well defined and not spread out. This is achieved by arranging the gratings such that even though the fiber is curved the gratings appear to be substantially parallel instead of being influenced by the curvature.

Abstract: A method of correlating physical locations with respective positions along an optical waveguide can include transmitting to the waveguide a signal including an indication of the transmitting location, and the waveguide receiving the signal. A system for correlating a physical location with a position along an optical waveguide can include a transmitter which transmits to the optical waveguide a signal including an indication of the transmitter location, and a computer which correlates the location to the position, based on the signal as received by the waveguide. A method of determining a position along an optical waveguide at which a signal is transmitted can include modulating on the signal an indication of a transmission location, and transmitting the signal to the waveguide, thereby causing vibration of the waveguide.

Abstract: The present invention relates to an optical fiber cable net including: one elongated optical fiber cable having a front end portion repeatedly moved upward and downward from the lower end portion of the left side of a bee hive-like section along a line forming the bee hive-like section, the optical fiber cable being wound by a plurality of times onto pre-disposed portions where it meets the pre-disposed portions and being moved upward or downward, so that if the front end portion of the optical fiber cable reaches the lower end portion of the right side of the bee hive-like section, the front end portion of the optical fiber cable is sequentially passed through the respective net eyes of the right side of the bee hive-like section, the respective net eyes of the upper side thereof and the respective net eyes of the left side thereof.

Abstract: Pressure-sensing touch systems and methods are disclosed for sensing the occurrence of a touch event based on pressure applied at a touch location. The touch system includes a light-source system and a detector system operably adjacent respective input and output edges of a waveguide. Pressure at a touch location on the waveguide gives rise to a touch event causes the waveguide to bend or flex. The waveguide bending causes a change in the optical paths of light traveling by FTIR, causing the light distribution in the output light to change. The changes are detected and are used to determine whether a touch event occurred, as well as the time-evolution of the touch event. The changes in the output light can include polarization changes caused by birefringence induced in the waveguide by the applied pressure applied. Various detector configurations are disclosed for sensing the location and pressure of a touch event.

Abstract: Systems and methods comprise or involve optical fibers having Bragg gratings. The optical fibers can be assembled in a parallel manner into a fiber sensor configuration. Bragg gratings can be written onto different cores of optical fibers. Bragg gratings may be written at a same or nearly same axial position for all optical fibers in the configuration and may be written at the same time and may have a substantially equal index of refraction variation and unequal lengths. Spaced Bragg gratings may also have characteristic sidelobe spectrums for tagging the respective gratings. Gratings can also be written at different wavelengths and over another grating at the same location.

Abstract: The location of one or more fiber optic channels (16) along the length of a fiber optic cable (12) is determined by: a) arranging an electrical conductor and a magnetic source at a known location adjacent to at least one of the channels (16); b) transmitting an electrical current through the electrical conductor, thereby deforming the electrical conductor by Lorenz forces in the vicinity of the magnetic source; c) conveying the deformation of the electrical conductor to deform an adjacent channel (16); d) transmitting light pulses through the fiber optic cable (12) and using variations in the light pulses back reflected by the deformed channel (16) and the known location of the magnetic source to determine the location of the deformed channel (16).

Abstract: A reinforcing cable for a prestressed concrete structure is disclosed. The cable has an optical fiber entwined between the twisted wire ropes that form the cable. The optical fiber facilitates in situ monitoring of cable integrity by comparing optical signal transmission over time.

Abstract: Wind turbine blade comprising a sensor system with an optical path comprising a first optical sensor fiber, a second optical sensor fiber and a patch optical fiber, the first optical sensor fiber including a first core with a first core diameter wherein the first optical sensor fiber extends from a first end to a second end and comprising at least one sensor, the second optical sensor fiber including a second core with a second core diameter, wherein the second optical sensor fiber extends from a first end to a second end and comprising at least one sensor, the patch optical fiber including a patch core with a patch core diameter, wherein the patch optical fiber extends from a first end to a second end and connects the first optical sensor fiber and the second optical sensor fiber, wherein the first core diameter is the same as the patch core diameter.

Abstract: An optical fiber for a sensor that can measure a current or a voltage precisely is provided. The optical fiber for the sensor 10 comprises: an FBG 12 wherein a refractive index of a core changes periodically; a metal layer 13 for sheathing the FBG 12; and a pair of electrodes 14 and 15 provided at the metal layer 13. The electrodes 14 and 15 are connected to an object to be measured in desired positions. Current flowing through the metal layer 13 is calculated based on variation in Bragg wavelength of the FBG 12.

Abstract: An optical-based sensing apparatus and method are provided. A sensing apparatus (10) may include a tube (30). An optical fiber (12) may be encased in the tube. A buffering layer (14) may be interposed between the optical fiber and the tube. The buffering layer and/or the tube may be selectively configured to form along a length of the apparatus a plurality of optical sensing zones (16, 18, 20) spatially arranged to sense parameters involving different parameter modalities.

Abstract: A transversal load insensitive optical waveguide includes a primary section having a core. The waveguide may further include an outer cladding. The primary section includes a primary section surface and the outer cladding includes an exterior surface mechanically attached to the primary section surface by an interior cladding structure forming a mechanical connection. The cladding structure is such that for at least part of a distance between each two radial corresponding points on the exterior surface and the primary section surface respectively, the mechanical connection deviates from being radial, so that a radially-directed load on an exterior surface of the outer cladding is deflected by the cladding structure.

Abstract: A long-distance fiber optic monitoring system having a sensing unit and an analyzer that is remotely located from the sensing unit is provided. The sensing unit comprises a source of optical energy for injecting optical energy into the fiber optical cable and an optical detector configured to detect an optical return signal from the optical fiber. The detected optical return signal is associated with an acoustic signal impinging on the optical fiber. The analyzer receives a signal from the remote sensing unit via the optical fiber that is representative of the optical return signal, and determines a location of a disturbance based at least on the received signal. The representative signal can be transmitted from the remote sensing unit to the analyzer as an optical signal or via a metallic wired included with the optical fiber.

Abstract: A fuse state indicator for a cascading fuse multiple discharge device including a fiber optic cable having a first end, a second end, and an intermediate segment. The intermediate segment is configured for attachment to a fuse assembly of a fuse panel where the fuse panel is arranged for physically severing the intermediate segment of the fiber optic cable in response to discharge of the fuse assembly.

Abstract: The invention relates to a distributed fiber optic sensor (104, 106) having a first spatial resolution (301, 303) and a second, different, spatial resolution (302, 304). The sensor, which may be a distributed acoustic sensor, has an optical source (112) configured to interrogate an optical fiber (104) with optical radiation and a detector (116) configured to detected optical radiation back-scattered from within the fiber. A processor (108) is configured to process the detected back-scatter radiation to provide a plurality of longitudinal sensing portions of fiber. The optical source and processor are adapted to provide the first and second spatial resolutions, for instance by changing the duration and/or separation of the optical pulses and analysis bins. The first and second spatial resolutions may be provided sequentially or simultaneously and the spatial resolution used may be varied as part of a default pattern or in response to a detection event.

Abstract: Optic fiber sensor characterized in that the sensing fiber is provided with a continuous Bragg grating covering the entire fiber length which is dedicated to sensing and along which spatially resolved measurements are performed.

Abstract: A getting-on/off determination apparatus determines rider's getting-on/off for an inverted two-wheel vehicle that travels while maintaining the inverted state. The getting-on/off determination apparatus includes an optical fiber laid in a step portion that a rider gets on/off, a light emitting unit that emits detection light and is connected to one end of the optical fiber, a light receiving unit that receives the detection light emitted from the light emitting unit and is connected to another end of the optical fiber, at least one transmitted light varying portion that varies an amount of transmitted light of the detection light passing through the optical fiber in conjunction with a vertical displacement of the step portion that occurs when the rider gets on/off the inverted two-wheel vehicle, and a determination unit that determines getting-on/off of the rider based on an amount of the detection light received by the light receiving unit.

Abstract: An input panel for an interactive input system comprises an optical waveguide; a first radiation source directing radiation into said optical waveguide, said radiation undergoing total internal reflection within said optical waveguide; a diffusion layer adjacent to and on one side of the optical waveguide, totally internally reflected light being frustrated and escaping the optical waveguide in response to pointer contacts on the diffusion layer; a second radiation source directing radiation towards another side of the optical waveguide that is opposite the one side; and at least one imaging device having a field of view looking at the optical waveguide and capturing image frames, wherein said first and second radiation sources are turned on and off in succession and wherein said first radiation source is turned off when said second radiation source is on and wherein said first radiation source is turned on when said second radiation source is off.