Abstract: A multi-pass Fabry-Perot etalon, or bandpass, filter, has a Fabry-Perot cavity defined by two partially reflective mirrors with a gap therebetween and a third reflecting mirror positioned adjacent said two mirrors and arranged to reflect substantially any light eliting said cavity back into it. The filter can replace two single-pass Fabry-Perot etalon filters and can provide lower signal loss and simpler wavelength control.

Abstract: A returnable container suitable to be assembled to contain products, and to be disassembled for return shipping, comprises a molded base having a container bottom plate surrounded by an upstanding flange, a molded top closure having a container top plate surrounded by a depending flange, and a sleeve part suitable for providing sidewalls surrounding a space between the base and the top closure and having upper and lower margins suitable for being received within in the flanges. The sidewalls are each formed from plastic material having an outer sheet and an inner sheet held in spaced relation by a plurality of vertically orientated webs, and the sidewalls are connected by hinge sections comprising flexible continuations of the outer sheets of adjacent sidewalls which extend across gaps between inner sheets of adjacent sidewalls. The hinge sections are capable of forming rounded corners of the container when the container is erected and the hinge sections are also capable of forming 180.degree.

Abstract: An optical tap/coupler consists essentially of a two graded index lenses having a holographic beam splitter (HBS) in between. The HBS independent of polarization state and wavelength of an input light beam splits an incoming beam into at least two beams. The two beams are directed to two separate locations or ports at an end face of one of the graded index lenses thereby providing a main beam and a tap beam at an output of the device. The device is compact and can accommodate other optical components between the two graded index lenses.

Abstract: An apparatus and method are provided for remotely detecting ice on a polarization preserving surface. A target location on the surface is irradiated with two cross-polarized beams of coherent light. A determination is then made as to whether the speckle patterns from each of the two beams interfere with one another. If interference of the speckle patterns from the two beams is detected, ice or some other birefringent material is said to be present on the surface.

Abstract: A method and an apparatus are disclosed for remotely determining the thickness of a transparent or semi-transparent suspended sheet or solid or liquid layer, e.g. ice, on a solid surface which is either light-absorbent or highly reflective. The invention proposes directing a coherent beam of light onto a location on the layer such that the beam undergoes partial reflection from the top of the layer and partial reflection from the bottom of the layer or the underlying surface. Due to the coherency of the beam, two overlapping speckle patterns are produced which give rise to an interference pattern having interference fringes. The pattern can be caused to shift across the field of view and the shift, determined by a number of the passing interference fringes can be interpreted in terms of the thickness of the layer.

Abstract: A quantum well intersubband infrared (IR) photodetector has a spectral response tunable by an external voltage. The photodetector consists of multiple doped quantum wells with different well widths and barrier heights. The preferred embodiment is made by repeating the whole structure of the active region of a multiple quantum well intersubband IR photodetector. Differences between repeats or groups of well widths and barrier heights result in differences in the spectral IR response of the different repeats. The device resistance of a given group is designed to be very different from those for all the other groups. As a function of an applied voltage, the repeat with the highest resistance will be turned on to detect IR with the response peak at a wavelength .lambda..sub.1. Subsequently, the next highest resistance repeat will turn on when increasing voltage with its response peaked at .lambda..sub.2, and so on. Since .lambda..sub.1, .lambda..sub.

Abstract: An optical switch has a stepping motor with a fiber faceplate on which are mounted end portions of output optical fibers terminating in GRIN lenses. The end portions are arranged along a pitch circle. The faceplate is spaced from the stepping motor and the diameter of the pitch circle is smaller than the diameter of the stepping motor, the output fibers diverging from the faceplate towards the motor and beyond in a space-saving arrangement. The stepping motor drives a movable arm with attached end portion of an input optical fiber, also with a GRIN lens, into one of a plurality switching positions. The connection between the fibers and the lenses and also the relative axial arrangement of the paired lenses in the switching positions is offset to reduce or minimize the reflection of light transmitted from the input fiber to the output fiber, back to the input fiber.

Abstract: A wavelength filter for use with optical fibers comprises a plurality of filter units, each unit comprising first and second collimating lenses separated by a filter element, the filter elements of the two units being capable of passing first and second wavelengths respectively, and each unit being such as to reflect light transmitted by the filter element of each of the other units. A first of the units has its first lens connected to an input optical fiber and also connected to a first connecting optical fiber positioned so that one of these optical fibers is capable of receiving light from the other fiber reflected off the filter element of the first unit. The first unit has its second lens connected to a second connecting optical fiber carrying light of a first wavelength transmited from the input optical fiber through the first filter unit.

Abstract: The invention relates to a method of measuring the wavelength of an optical signal such as a light beam. The optical signal is directed toward a detector where its intensity is detected and stored. Several optical elements each having a different wavelength dependence are moved into the path of the optical beam one at a time and for each intensity is detected and stored. The wavelength of the optical signal is then approximately determined based upon the ratio of the detected intensity of the optical signal in the absence of any optical elements and the detected intensities of the optical signal in the presence of each optical element.

Abstract: A semiconductor device comprises a plurality of colored deformable mirrors controllable by electrical circuitry. Groups of mirrors, responsive to the electronic signals, are selectably operable to reflect incident light. The deformable mirrors are coated with an optical thin film interference color coating having at least a layer that is substantially transparent to the visible light. As well the optical thin film interference color coating includes at least one further layer that is partially absorbing with respect to the visible light. The spectral reflectance and absorptance of the deformable mirror is modified in order to obtain a desired reflected color by the process of optical interference enhanced absorption in the optical thin film interference color coating. The optical thin film interference color coating has predetermined layer thicknesses and materials; the substantially transparent layer substantially determines the desired reflected color.

Abstract: The invention relates to a method of determining prefocused pulses with sufficiently low power and short duration to allow multi-slice in-vivo spectroscopic imaging of humans. The method has two main stages, analytic and numerical. In the analytic stage a magnetization response is selected with certain desired characteristics such as prefocused time. During the numerical stage, the response is then transformed into an RF pulse for use in magnetic resonance imaging. The theoretical response to the RF pulse is evaluated and characteristics such as duration and amplitude may be altered to meet further requirements. The theoretical response is then transformed into an RF pulse for use in magnetic resonance imaging or for further application of the numerical stage.

Abstract: A semi-automatic method is provided for finding an equation for a geometric surface patch that closely approximates a geometric surface within a digitized scene. By finding equations for patches within a scene, equations representing the entire scene can be found by stepwise sequential processing or alternatively by a system capable of parallel processing. Initially an operator using a mouse or pointing device selects a region from the digitized scene, and then selects one of a plurality of geometric surface types to represent a predominant geometric surface covered by the region. The process is based on randomly choosing the minimal number of data points from the selected region. Based on this information an equation of a surface on which the randomly selected points lie is determined. The process is repeated a predetermined number of times and the equation of the surface with the maximum number of associated data points is selected.

Abstract: A bandpass optical filter is provided that is formed within an optical fiber in the form of a Bragg grating. The grating includes multiple Fabry Perot cavities disposed along the waveguide. Each of the cavities includes a pair of reflectors. Each reflector comprises alternating high-low index regions within the waveguide, each region having a thickness of one quarter-wave at a bandpass wavelength, each alternate region being of a different index of refraction than an adjacent region. A multiple odd quarter-wave or quarter-wave high or low index region is sandwiched between each pair of reflectors. The number of high/low regions within a reflector is selected in accordance with the refractive index difference between two alternate adjacent regions.

Abstract: A system is provided for collecting subjective data from a user of a computer or computer terminals. A user performing a task on his or her computer or terminal is polled, by: interrupting the task being performed; a banner appears on the screen of the display terminal with the selectable option of continuing with the interruption or returning immediately to the interrupted task. If a user selects to continue with the interruption, one or more questions, having selectable responses is presented to the user. After responding to the questions, the responses are stored on disk, and the user returns to the task that was interrupted. In real-time or after a period of days, weeks or months, the data is collected from the hard disk or system memory and is analyzed. The analyzed data is then used to control a process. In one example, the questions asked relate to a user's thermal comfort, and the data collected and analyzed is used to control a heating and cooling system.

Abstract: An optical filter is provided having first and second graded index (GRIN) lenses preferably disposed in a coaxial relationship so that they have a common optical axis. Each of the GRIN lenses have an endface providing a port at predetermined location. The ports are disposed on opposite sides of the optical axis and each of the ports are substantially equidistant from the optical axis, so as to be oppositely offset from the optical axis by a same amount. The filter also includes an optical interference filter disposed between other endfaces of the first and second graded index lenses. By changing the location of the ports by a same small amount, the center wavelength of the filter changes by a small amount, thus in manufacture, the filter is tunable. After tuning the filter to a desired wavelength, the locations of the ports are fixed.

Abstract: A multi-wavelength optical filtering device for optical signal transmission, capable for functioning as a multiplexer or a demultiplexer. The device has at least one (first) optical circulator having at least four ports including an input port and a plurality of sequential ports, the last of said sequential ports being an output port, and an in-fiber Bragg grating (wavelength selective means) coupled to each of said sequential ports except said output port. The circulator may be branched off to a number of other circulators, the number depending on the number of the sequential ports of the first circulator, through the Bragg grating rather than through the output port of the first circulator. The other circulators, which are preferably also at least four-port circulators with wavelength selective means at the sequential ports, can also be branched off in an analogous manner as the first circulator.

Abstract: A method and apparatus for generating and detecting ultrasound on a workpiece utilizing a long pulse laser. A modulated pulsed laser beam is directed at the workpiece. The pulse duration is defined to be the time of propagation of ultrasound from a generation location to a flaw or discontinuity to be detected within the workpiece and then to a detection location, or, the time of propagation of ultrasound directly from the generation location to the detection location. A second pulsed laser beam, having a pulse duration longer than the ultrasonic propagation time, is also directed at the workpiece. After receiving phase modulated light from second pulsed laser beam reflected or scattered by the workpiece, phase modulated light is demodulated to obtain a demodulation signal representative of the ultrasonic motion at the surface of the workpiece. The demodulation signal is then electronically processed.

Abstract: An optical connector ferrule is provided having an standard single mode optical fiber therein whose mode field diameter is approximately 10 .mu.m along its length. An end portion and the end face of the optical fiber are heated to thermally expanded the mode field diameter to approximately 20 .mu.m or greater for reducing power density at the end face. By providing an expanded mode field diameter at the end face of the fiber, the power density is lessened, thereby lessening the probability that any dirt or debris at the end face will become heated sufficiently to damage the optical fiber.

Abstract: An integrated optical isolator arrangement is described that is capable of isolating an input optical signal and coupling a pump signal. The coupler includes a pair of lenses with an isolator disposed therebetween. The isolator is sandwiched between a splitter/filter and a wavelength selective device. An end face of each lens has an input and an output port for receiving and transmitting optical signals. The splitter/filter is selected to transmit some of the input signal on a first input port and to reflect the remaining untransmitted portion of the input optical signal to a first output port proximate to the first input port. The wavelength selective device allows the input signal from the first input port to pass through it to a second output port, and in addition, reflects a pump signal transmitted on the second input port to the second output port for combination with the input optical signal.

Abstract: An optical wavelength selective device is provided that is particularly useful as a demultiplexer. The device is made from a planar slab optical waveguide material transmissive to light. Perturbations in the form of holes are etched into the slab waveguide cladding or preferably into the core of the waveguide thereby changing the effective refractive index of regions within the core. The holes are very closely spaced and form a transmissive optical grating, having dimensions suitable for operating in the Raman-Nath regime. Mirrors or lenses are formed within the device for guiding an input beam into the waveguide as a parallel light source.