Northern Telecom Limited

Canadian Patents & Development Ltd.

Brytech Inc.

H. K. Eyecan Ltd.

David A Kahn

Jan Heynen

Jaroslav M Hvezda

Jack F Dalgleish

John C B Davey

A hand-held colorimetric device () suitable for use by blind or color-blind individuals to determine the color of a surface-under-test (SUT), for example of a fabric, has an aperture () which, in use, is covered by the SUT () whose color is to be determined. Six LEDs (A,B,B,A andB) arranged in pairs (A/B,A/B,a/B) emitting red/orange, green, and blue light illuminate the SUT and diffuse reflections therefrom containing red/orange, green, and blue spectrum sample values are used to determine the luminous reflectivity and chromaticity values for the color of the SUT. The measured values are compared with colorimetric values of reference surfaces to determine the color of the SUT. The colorimetric device may output the name of the color aurally.

Colorimetric device and colour determination process

In an eye-directed communications device which displays characters, for example symbols or letters, and determines a user's selection by monitoring eye position to determine which of the characters is being observed, difficulties in providing for selection of the usual characters and functions of a conventional 101 key computer keyboard are overcome by dividing the required characters/functions into three sets, designated as lower case, upper case and 'command' case. In order to select a particular character, the user first selects the case and then selects the character. Only one set need be displayed to the user, the characters in the other sets having spatial correspondence with those in displayed set. The system may also, or alternatively, display the characters in groups and define position selection fields corresponding to the positions of the characters in each group. The user then determines the position of the desired character in its group and makes a character selection by first selecting the corresponding position field. The apparatus then limits subsequent character selection by the user to the subset of characters in the corresponding positions in their groups. Limitation to the subset allows subsequent detection of the selected character to use a larger area than that occupied by the character in the display.

Visual communications apparatus employing eye-position monitoring

The optical receiver includes a photodiode, a preamplifier and a length of transmission line. The photodiode may be connected to the preamplifier, either via the transmission line, or directly between the preamplifier and the transmission line, that is, the transmission line is connected as an open circuit. The transmission line 14 may comprise a coaxial cable, stripline, or any other suitable form of transmission line. The input impedance of the preamplifier should be designed to match the characteristic impedance of the transmission line. The noise of the preamplifier associated with the transmission line has a periodic spectrum dependent upon the length of the line with peaks at odd multiples of f' and minima at even multiples of f'. The value of f' is related to the length of the transmission line in accordance with: f'=v/4L where v is the propagation velocity, typically 2/3 the speed of light, and L is the length of the transmission line.

Optical receiver for subcarrier frequency division multiplexing signals

An optical receiver includes a reverse biassed photodiode whose output is coupled to a transimpedance amplifier. A load impedance for the photodiode comprises a forward biassed semiconductor diode, enabling the photodiode to be biassed using a low voltage supply. A signal compressing arrangement can be provided between the transimpedance amplifier output and the semiconductor diode on the side thereof remote from the photodiode. The transimpedance amplifier can have a capacitive transimpedance element; a filter, including an open circuit transmission line, is described which is coupled to the output of such an optical receiver to provide a desirable form of optical receiver arrangement. The capacitive transimpedance element can be constituted by a capacitance of the photodiode.

Optical receivers

An optical communications system comprises a pluarality of optical transmitters coupled by a common channel or bus to an optical receiver. The optical transmitters are operated using time division multiplexing (TDM), each TDM period being word or message length. The optical transmitters each comprise a least one current source to drive the light source, for example a laser, in response to the data signal, to vary its output power about a steady level which is the average of the maximum and minimum values. Therefore each current source may be controlled as to increase its output gradually (preferably sinusoidally) to reach the aforesaid mean level at the beginning of a TDM period and to decrease it in the converse way after the period ends. Such an arrangement avoids the need for guard time before and after the TDM time period, thereby increasing channel efficiency, and improves receiver sensitivity by reducing quantum shot noise due to steady light from inactive transmitters.

Optical communication system

A microphone arrangement, suitable for a telephone handset, comprises an array of microphone transducers, conveniently pressure transducers arranged at the vertices of a cube. Signal processing circuitry derives from the transducer outputs signals representing the magnitude and direction of the pressure gradient of the sound field at the array. In response to these signals, the microphone transducer outputs are weighted so as to direct the directional sensitivity lobe of the microphone towards the source of the maximum sound detected thereby.

Microphone arrangement

A crossover arrangement for optical conductors, each in the form of a rod of light-transmissive material, includes a multifaceted, e.g. polyhedral member having pairs of mutually parallel opposed facets. Each pair of facets extend in a direction transverse, preferably perpendicular, to that in which a second pair of facets extend. The end face of each optical conductor is abutted against one of the facets of the polyhedron. Each facet has a coating of a material having a lower refractive index than that of the polyhedron or the optical conductors. Light entering the polyhedron from one conductor passes across the polyhedron and into the opposite conductor, being constrained to stay within the polyhedron by the coatings on the side facets. Preferably the polyhedron member is a cube and the optical conductors are of square cross-sectional shape.

Crossover arrangement for optical conductors

A mounting arrangement for mounting an optical conductor on a 'photonic' backplane provides for simple, accurate positioning during installation and easy access to, and removal of, the optical conductor when in service. The optical conductor constitutes a 'busbar' in that it has a series of reflector surfaces spaced along its length to permit distribution or aggregation of several light signals. In one embodiment, an individual support is provided at each reflector/circuit card location. Each support is a seating member which houses a lens to couple light between the optical conductor and the circuit card. In another, preferred, embodiment the optical conductor is housed in a channel in a guide rail mounted upon the backplane. Separate cover members are releasably mounted upon the guide rail adjacent each circuit card. Each cover member has an aperture and lens to couple light between the reflector and the circuit card. The aperture and lens may be in a boss which couples in spigot-and-socket fashion with a tubular lens-carrying coupled mounted on the circuit card.

Mounting optical busbars on backplanes

An eye-position sensor for use in an eye-activated optical transducer in which a spatial filter is used to modify light reflected from the eye to form a substantially rectangular pattern on a quadrantal array of contiguous sensors. This arrangement provides a substantially linear change in the output signal from the sensors in response to an equivalent movement of the eye.

Eye-position sensor

Light is diverted from one optical conductor to another optical conductor by a suitably oriented non-planar reflecting surface at the junction of the two optical conductors. The non-planar surface comprises facets arranged so that light incident on one facet from one optical conductor will be reflected at that facet onto an adjacent facet, and at the adjacent facet to the other optical conductor. The arrangement of facets is such that the Snell's Law condition for total internal reflection at each facet can be satisfied for a wider range of ray directions than is possible for a single planar reflecting surface. The arrangement is useful for optical backplanes now being proposed for use in computers and telecommunications equipment.

Arrangement for diverting light

At a fiberoptic tap used for monitoring purposes, one fiber, having a certain mode volume is spliced to a second fiber having a relatively lower mode volume. Consequently, in passing from the first fiber to a second fiber, some light is radiated away from the splice. This radiated light is directed to a photodetector. The tap is particularly advantageous for transmitter power monitoring since the radiated optical power is superfluous to that light which is capable of transmission by the line fiber.

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Nepean, Canada

David A Kahn