Abstract: A system and method are disclosed for demulitplexing closely spaced channels carrying optically encoded data. A composite optical signal having data channels corresponding to center wavelengths .lambda.1, .lambda.2, .lambda.3, .lambda.4, . . . .lambda.n are separated into two composite optical signals of first of which comprises data channels corresponding to center wavelengths .lambda.1, .lambda.3, . . . .lambda.n and a second which comprises data channels corresponding to center wavelengths .lambda.2, .lambda.4, . . . .lambda.n-1, wherein adjacent channels center wavelengths are separated from one another by a distance "d". A periodic multi-cavity Fabry-Perot etalon having a free spectral range of "2d" is coupled to a circulator for launching an input beam. The first of the two composite optical signals carrying channels 1, 3, . . . n is reflected from the input port of the etalon and the second of the of the two optical signals carrying channels 2, 4, . . . n-1 is transmitted through the etalon.

Abstract: A method for infrared (IR) imaging using a panel made of integrated GaAs quantum well infrared photodetector (QWIP) and near-infrared (NIR) or visible light emitting diode (LED). The panel is a large area diode with an optical window for top illumination or without the window for backside illumination. The integrated device acts as a photon energy up-converter which converts infrared light of wavelength longer than about 1.1 .mu.m to near infrared or visible light which falls into the silicon detector spectral range. Using this device, an IR image is up-converted and the resulting NIR or visible image is then detected by an off-the-shelf silicon charge-coupled-device (CCD) camera The image detected on the CCD camera represents the original infrared image. A specific device embodiment for converting 9 .mu.m IR to 870 nm NIR is given.

Abstract: A new method is presented for efficient and reliable object recognition within noisy, cluttered, and occluded range images. An image is captured and quantized into cells having characteristics. A tree data structure is provided wherein each node of the tree is associated with a cell. The tree is traversed according to the characteristics of each associated cell using a best-first algorithm. When a leaf node is reached, potential object poses, types and locations associated with the leaf node are stored. Once sufficient information is stored, each potential recognized object is verified using a more reliable algorithm.

Abstract: A method and an apparatus for monitoring and controlling a characteristic of process waters or effluents from wood pulp bleaching, pulping and paper making processes utilizing a bleaching agent such as hydrogen peroxide (H.sub.2 O.sub.2), Na.sub.2 S.sub.2 O.sub.4, ClO.sub.2, Cl.sub.2 or O.sub.3 or a pulp delignification process utilizing a delignification agent such as NaOH, Na.sub.2 S, O.sub.2, Na.sub.2 SO.sub.3, and enzymes including ligninase, xylanase, mannanase, laccase, and peroxidase are disclosed. This is done by obtaining at least three measurements of ultraviolet-visible light from the effluent by taking a first measurement measured at a first wavelength, a second measurement measured at a second wavelength, and a third measurement at a third wavelength, formulating two ratios from the three measurements and using the ratios for computing an empirical value of the characteristic of the effluent.

Abstract: A device capable of demultiplexing or multiplexing optical signals includes a wavelength dependent element for separating an input beam into sub-beams of light in accordance with their wavelength. Precisely spaced optical fibers are disposed to receive at least some of the sub-beams of light; a focusing lens is disposed between the wavelength dependent element and the optical fibers for focusing the sub-beams at ends of the optical fibers. A rod-like GRIN lens for correcting for an offset in the focal length of the focusing lens is placed between the focusing lens and the optical fibers. The GRIN lens can be polished to change its length in order to correct for the offset in focal length of the focusing lens.

Abstract: A novel design for producing bandpass filters with essentially square shapes with little or no ripple in the passband zone. Filters are of the all-dielectric type consist of multiple cavities of bandpasses. Quarter wave thick layers of low index material separate all of the cavities from each other. Multiple half-waves may be added to the outer cavity quarter-wave stacks in particular. This invention provides the addition of half wave to some of the inner cavity stacks to remove ripple that would otherwise be present. Together, these additional half wave layers added to the outer and inner cavities sharpen the transition from low transmission to high transmission without unduly adding ripple to the high transmission zone.

Abstract: Light is coupled out of a first mono-mode optical waveguide such as an optical fiber an into another single mode waveguide through a substantially planar slab waveguide. The first mono-mode optical waveguide has a grating impressed within which has refractive index perturbations that reflect predetermined wavelengths of incident light out of a portion of a side of the optical waveguide adjacent the grating; The slab planar waveguide has an end optically coupled to the portion of the first mono-mode optical waveguide, for guiding light coupled out of the side of the waveguide, and for maintaining a uni-phase wavefront of said light by having a response that confines the light to a single mode in one dimension, and multi-mode in another dimension and allows at least a portion of the light to converge.

Abstract: In the past, databases containing three dimensional images were searched by keywords and indexes. For such functionality, a set of keywords must be associated with each image. This is usually performed by a person and is prone to errors. It has now been found that searching of three-dimensional images stored electronically can be performed in dependence upon a variety of criteria such as colour, shape, size, etc. A method is disclosed for searching three dimensional images of objects in dependence upon the above criteria, other images, or other criteria. This obviates the need for keyword indexing of image databases.

Abstract: An optical fiber having a small numerical aperture (NA) is optically coupled with a short birefringent crystal to provide a polarization beam splitter. This arrangement obviates the use of a GRIN lens coupled between an input optical fiber and the birefringent crystal and provides significant cost savings by allowing a short crystal to be used. In this invention, the birefringent crystal has a beam-shifting angle that is larger than the numerical aperture at the output end of the optical fiber.

Abstract: A method and circuit is provided for more efficiently coupling light between two optical waveguides such as optical fibres. When the two waveguides are coupled to spaced apart collimating lenses such as GRIN lenses, the beam propagating between the spaced part lenses may be shifted. In this instance light can more efficiently be coupled out of the output optical fibre if it is angled with respect to the optical axis of the GRIN lens to which it is coupled. This invention provides an output fibre that is non-parallel with the optical axis of the lens it is coupled thereto.

Abstract: A polarization beam splitter combiner uses a birefringent crystal that is a fraction of the size of conventional crystals used in similar devices. Since the crystal is considerably shorter in length, the beam passing through the crystal can be uncollimated, spreading very little from one end to the other. Launching uncollimated beams through a short small crystal obviates the requirement for lenses at the end face of the crystal having two waveguides coupled thereto. Since lenses are not required the waveguides at the input/output end face can be very closely spaced apart. Conventional lensed devices utilizing a pair of lenses at an input/output end face must be considerably larger in order to accommodate the lenses and resulting collimated beams.

Abstract: The present invention relates to a multi-layer dielectric bandpass filter having a primary and a secondary passband. A secondary passband outside the reflection zone of the primary passband is optimized to reduce ripple achieving a passband of at least 90% transmission. Optimization comprises modifying the thickness of certain quarter wavelength reflector layers of a single passband filter from true quarter wavelength at the primary passband to non-quarter, or non-integer-multiple quarter wave thickness.

Abstract: A fault detection circuit and method of detecting catastrophic faults for example from a total line outage due to a transmission waveguide being inadvertently cut, includes tapping a sample of the amplified transmission multichannel signal light for analysis. The tapped light is then fed to a periodic filter such as a Mach Zehnder interferometer or a Fabry Perot etalon having a free spectral range and phase at one output that coincides with the channel central wavelengths of the transmission system. Another output of the periodic filter provides an output response that is phase shifted by 180 degrees. Two output signals from the two output two output signals are then compared, in one embodiment by using a photodiode bridge. When one output of the periodic filter has a substantially different signal energy than the other, it is assumed that no faults occur. Conversely when the two outputs are substantially similar, it is assumed that a catastrophic fault has occurred.

Abstract: A mobile mapping system is designed to generate a geometrically precise three-dimensional detailed model of an unknown indoor environment. There is no limit on the distance the mobile system may travel, nor on the type of details that can be mapped. The same design is used for environments ranging from simple office hallways to long winding underground mine tunnels. Surfaces and features can be mapped from images acquired by a unique configuration of different types of optical imaging sensors and positioning devices. This configuration ensures that all the information required to reconstruct the three-dimensional environment is included in the collected images. Provided a sufficient overlap between two-dimensional intensity images and combining such with three-dimensional range images, the method reconstructs an environment by adjusting a plurality of images simultaneously.

Abstract: The present invention relates to an optical logical AND gate comprising an erbium doped waveguide which is attenuating at a signal wavelength and responsive to pump light energy to be transmissive at a signal wavelength. A first laser pump excites a portion of the waveguide. A second laser pump excites a remaining portion of the waveguide. The waveguide is only transparent to transmit a signal if both the first and second pumps excite the waveguide together. The optical AND gate of the present invention can be used as the control element of an N.times.N matrix. A number of first ports and a number of second ports are interconnected by erbium waveguide AND gates. Pump light is switched to a selected first port. Pump light from a second pump is switched to a selected second port. Only the erbium waveguide gate interconnecting the selected first and second port is transmissive to switch a signal. All other gates are attenuating and other signals are accordingly blocked.

Abstract: This invention relates to a method and apparatus for switching an optical signal from one or more input ports to one of a plurality of output ports. A beam is launched into the input port. By controllably switching a switching element, such a liquid/air switch selection can be made selecting a plurality of deflections along a first plane to direct a beam along the first plane to one of a plurality of output locations; the beam is received from one of the plurality of locations and is directed along a second plane intersecting the first plane, to direct the beam to one of the output ports. In a preferred embodiment, the switch includes two prisms each having switching elements at end faces of the prisms.

Abstract: An apparatus and method for in situ spectral measurement is disclosed. The apparatus uses a low-resolution grating to disperse light and thereby image a spectrum thereof. The imaged spectrum is converted into a digital electrical signal and is processed in order to enhance the spectral information. The resulting spectral information is analogous to that captured using a higher resolution spectral imager with optical processing of the spectral data.

Abstract: A novel design for producing bandpass filters with essentially square shapes with little or no ripple in the passband zone. Filters are of the all-dielectric type that consist of multiple cavities of bandpasses with the first and last cavities consisting of four less layers than the inner cavities. The inner cavities are all identical. All of the cavities are separated from each other by quarter wave thick layers of low index material. Layers of low index material may be added between the filter and the entrance and exit mediums. The thickness of the first few layers and last few layers may be altered to enhance the transmission of the filter by matching the index structure of the passband to the adjacent mediums.

Abstract: In the design of transcutaneous energy transfer devices variation in spacing between the coils results in energy transfer efficiency changes. These changes may have other causes. It is proposed to use an autotuning circuit and a voltage control circuit in cooperation with feedback from the internal coil in order to better maintain energy transfer levels as desirable. The feedback is typically provided via IR communication; however, when skin is highly pigmented, IR communication is inefficient. A method and system for using RF signals to accomplish the communication is disclosed.