U.S. Philips Corporation

U.S. Phillips Corporation

Coen T Liedenbaum

John J Reid

Adriaan Valster

Lukas Frederik Tiemeijer

Ronald Reindert Drenten

Michiel Johannes Jongerius

Raymond Van Roijen

Engelbertus C Pennings

Jeroen J Vleggaar

Bastiaan H Verbeek

Adrianus J Berntsen

Giok D Khoe

Bernardus A Jacobs

Sel Brian Colak

Aemilianus G Staring

Hermannus F Schoo

Robert J Demandt

Jeroen J Horikx

Henri M Boots

Martinus B Van Der Mark

Johannes J Schleipen

Hermanus F Schoo

Arnoldus L Severens

Electroluminescent device having an active layer of an electroluminescent material situated between two patterns of electrodes at least one of which is transparent to light emitted by the active layer, one of the patterns comprising a material for injecting charge carriers for emission a control for supplying bias voltage across a part of the active layer or setting bias current through the part of the active layer, means for applying a voltage in the reverse direction across part of the active layer, for measuring current associated with voltage applied in the reverse direction and for varying bias voltage or current depending on the measured current value.

Organic electroluminescent device

An organic electroluminescent device (1) has an organic emitter layer (5) disposed between, on the one side, a common electrode (6) and, on the other side, a first and second electrode (3A, 3B) which are mutually interlaced and independently driveable. When driven by means of, respectively, the first and second electrode (3A, 3B), respectively, a first and second pattern-wise light-emitting surface emerges. Using different light-emitting patterns, optionally in combination with light-absorbing patterns, a group of icons differing in color and/or shape can be displayed selectively using the same part of a display area.

The illumination system (1) has a substrate (2) and an active layer (3) comprising an electroluminescent material, in which the active layer (3) is present between a first, optically transparent electrode layer (5) and a second electrode layer (7). The illumination system (1) is characterized in that a light-scattering layer (28) comprising a medium having light-scattering properties is present in a forward direction (29) with respect to the active layer (3), in which the non-scattered fraction of a (collimated) light beam, when passed through the light-scattering layer (8) in the forward direction (29), is in the range between 0.05 and 0.8, preferably in the range between 0.1 and 0.5. The light-scattering properties of the medium are preferably stronger as the light is more obliquely incident, as is achieved by using birefringent particles and/or media. A very suitable light-scattering layer (28) is a (half) monolayer of TiO.sub.2 particles provided on the substrate (2), with an average size of the (spherical) particles of 0.1-1 .mu.m. The light output of the illumination system (1) is further improved by providing the edges of the substrate (2) with a reflective coating (26).

Electroluminescent illumination system with an active layer of a medium

The invention relates to an optical unit (17) for synchronizing clock signals. The unit (17) comprises at least two ring lasers (1', 1'), each ring laser (1', 1') generating a repetitive optical pattern at a different repetition frequency f.sub.i. The repetition frequency of at least one of the ring lasers (1', 1') is variable. The unit (17) comprises detection means (19) adapted to simultaneously receive the optical patterns from two ring lasers (1', 1') to be synchronized with each other and to compare these patterns. The ring laser, whose repetition frequency is variable, is controllable on the basis of a signal from the detection means, by which the optical path length of this laser is changed. The invention also relates to a high-frequency carrier transmission system comprising an optical unit as described hereinbefore.

Optical unit for synchronizing clock signals

A description is given of a method of providing an electroluminescent device (20) comprising an active layer (5) of conjugated 2,5-alkyl- or alkoxy-substituted poly(p-phenylene vinylene) with inactive regions (51) and emissive regions (52) by means of patterned irradiation with UV light. Both regions (51) and (52) of the active layer (5) show a clear difference in electroluminescence, electrical resistance and solubility. By means of the above-described effects, displays can be manufactured without making use of structured electrode layers (3) and (11).

Electroluminescent device

An optical unit for multiplying the frequency of a clock signal includes at least two series-arranged ring lasers. Each ring laser has a different resonance frequency f.sub.i. The unit has an input for receiving a signal, for example, a low-frequency electric signal for modulating one of the ring lasers. The repetition frequency of at least one of the ring lasers is variable by adapting the optical path length of the resonator.

Optical unit for multiplying the frequency of a clock signal

An optical unit for restoring a pulse pattern is described. The unit has an input for receiving a signal pulse series at a modulation period T and wavelength .lambda.hd p and comprises a pulsed laser for supplying a pulse series whose distance between two consecutive pulses is equal to n.T, in which n is an integer and is variable throughout the pulse series. Pulses of the signal pulse series can be injected into the pulsed laser. Moreover, the unit comprises at least a detection system arranged in the path of the radiation emitted by the pulsed laser, which system detects on the basis of a variation of a feedback-sensitive parameter of the laser.

Optical unit for restoring a pulse pattern, receiver suitable for use in

A radiation beam is generated by a radiation source such as laser. An optical system focuses the radiation beam at a recording layer (in a disc-shaped carrier) of a type in which an optically detectable change is caused to take place if the recording layer is heated to above a write temperature. The recording layer is scanned by the radiation beam by means of a motor. A control circuit feeds the radiation source with electric power which is converted in the radiation source partly into heat and partly into radiation for the radiation beam. The control circuit operates in a read mode in which the power supplied to the radiation source has a value at which the rise in temperature of the recording layer caused by the radiation beam is insufficient to cause an optically detectable change to take place. The control circuit also operates in a write mode in which the radiation source is intermittently fed with power pulses having a strength at which the rise in temperature of the recording layer caused by the radiation beam is sufficiently large to cause an optically detectable change to take place. The power pulses generated in the write mode have a strength and a duration for which the corresponding mean heat dissipation in the radiation source is substantially equal to the mean heat dissipation in the radiation soure in the read mode. As a result, the wavelengths of the generated radiation in the read mode and write mode are equal, thereby avoiding problems with a wavelength dispersion in the optical path of the optical system.

Optical reading and recording device containing a radiation source which

An optical information processing system comprises a coding unit for individually coding a plurality of optical information carrier waves, and a processing unit for processing the plurality of coded waves. The processing unit has a laser for producing laser light through longitudinal laser mode competition among the waves received.

Multimode-laser for an optical information processing system such as a

In a transmitter in a coherence multiplexed transmission system the output signal of a laser is directly applied to a channel and indirectly via a plurality of cascaded circuits of delay elements and modulators. The modulators vary a component of the autocorrelation function of the output signal of the transmitter as a function of an associated modulation signal (m.sub.1, m.sub.2, m.sub.3). In the receiver the autocorrelation functions values of the channel output signal for delays (D.sub.1, D.sub.2, D.sub.3) are determined in the demodulators. These autocorrelation function values from the modulated signal (m.sub.1 ', m.sub.2 ', m.sub.3 '). To reduce the number of periodic components of the autocorrelation function of the signal source, and hence enhance the possible transmission capacity, the transmitter comprises a decorrelation modulator for modulating the signal source with pulses generated by a pulse generator.

Coherence multiplexed transmission system

The invention relates to an optical switch which is switchable by means of light. The switch includes a directional coupler having four gates, the first gate of which forms part of an input of the switch for receiving an optical data pulse series, the second gate forms part of an output of the switch and the third gate and the fourth gate are interconnected by means of a waveguide structure. This waveguide has a non-linear optical portion at an asymmetrical position in the waveguide. A control pulse signal is also introduced into the waveguide via the first gate of the directional coupler. The waveguide is asymmetrical for the data pulse series and symmetrical for the control pulse signal.

Optical fiber switch using four gate directional coupler and control

In a sychronizing arrangement for synchronizing two streams of optical pulses, the problem arises that for pulse frequencies above 10 GHz the operation of the synchronizing arrangement becomes increasingly difficult. To overcome that problem it has been proposed to use a phase locked loop having an optical phase detector, but prior art optical phase detectors have low efficiency and was rather complex. According to the invention an optically controlled optical switch is used as the phase detector.

Optical synchronization arrangement

An optical communication system includes a directly modulated semiconductor laser (10), the output of which results in pulse shortening of light pulses corresponding to high level bits of a high frequency electrical digital modulating signal. A travelling wave laser amplifier (14) coupled to the laser provides an amplified modulated light signal to an optical channel (16), and an optical detector (18) converts a light signal received from the optical channel into an electrical signal. The amplifier has an overshoot characteristic which provides an extended output when overdriven by a high level optical input pulse, and the modulated laser is arranged to provide such high level pulses. The overshoot characteristic of the amplifier thus compensates for pulse shortening produced by the modulated laser in the case of isolated high level bits and the initial bit of a stream of high level bits. The invention also relates to a transmitter and to a repeater for use in such an optical communication system.

Optical communication system

The invention relates to an optical unit for generating an optical data signal in conformity with a data pattern. The unit has an input for receiving the data pattern with a modulation period T, a pulsed laser for supplying an optical pulse series having a pulse period n.T and a pulse duration .tau., in which n is an integer, and a converting unit for converting this pulse series into an optical data signal in conformity with the data pattern. The converting unit is a radiation-controlled optical switch. This switch has a first input for receiving the data pattern in the form of an optical pulse series whose pulses have a pulse width b, a second input for receiving the optical pulse series from the pulsed laser for sampling the data pattern during periods when the switch is open, and an output for supplying a data pulse series having a pulse width .epsilon..b, in which 0 &lt;.epsilon.&lt;1.

Unit for modulating an optical pulse series in conformity with a data

A unit for generating signal pulses. comprises a first, pulsed laser for supplying a pulse series having a pulse period T and a wavelength .lambda..sub.1, and a modulation unit comprising a second laser. The second laser has a wavelength band which is different from .lambda..sub.1 and can be modulated at a modulation period T in accordance with a data signal to be transported. The radiation from the second laser ) can be injected into the first laser at instants for which it holds that E(P.sub.m)&gt;E(LP.sub.i), in which E(P.sub.m) is the radiation energy of the second laser injected into the first laser at the relevant instant and E(LP.sub.i) is the radiation energy built up in the first laser at the relevant instant. Moreover, the unit comprises a wavelength discriminator which selects the pulses of wavelength .lambda..sub.1 from the radiation emitted by the first laser after injection.

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Eindhoven, Netherlands

Coen T Liedenbaum