Abstract: The invention relates to a color-tunable illumination system (10), to a lamp and to a luminaire. The color-tunable illumination system comprises a light source (20) emitting light of a first predefined color (B), and comprises a luminescent material (30) for converting light of the first predefined color into light of a second predefined color (A). The color-tunable illumination system further comprises shielding means (40, 42) arranged for preventing at least part of the light emitted by the light source to impinge on the luminescent material. The light source, the luminescent material and/or the shielding means are changeable from a first situation to a second situation. In the first situation the color-tunable illumination system is arranged for shielding at least part of the luminescent material against impinging light of the first predefined color.

Abstract: The invention provides a tool to select reliable organic LED devices, where the risk for failure before the end of its lifetime is low. This tool comprises the steps of: i) subjecting the device to a high electric field over the electroluminescent layer. This leads to a division of the devices into two, clearly separated, populations, namely one population with a low leakage current (current through the electroluminescent layer in reverse voltage operation) and one population with a high leakage current. In this step, the first population is selected in accordance with a current criterion. ii) detecting instabilities in the leakage current, referred to as noise. It has been established that these instabilities arise in particular at reverse driving voltages between 1 and 10 Volts. These instabilities are a measure of the occurrence of early failures during operation. In this step, the devices are selected in accordance with a noise criterion.

Abstract: The invention provides a tool to select reliable organic LED devices, where the risk for failure before the end of its lifetime is low. This tool comprises the steps of: i) subjecting the device to a high electric field over the electroluminescent layer. This leads to a division of the devices into two, clearly separated, populations, namely one population with a low leakage current (current through the electroluminescent layer in reverse voltage operation) and one population with a high leakage current. In this step, the first population is selected in accordance with a current criterion. ii) detecting instabilities in the leakage current, referred to as noise. It has been established that these instabilities arise in particular at reverse driving voltages between 1 and 10 Volts. These instabilities are a measure of the occurrence of early failures during operation. In this step, the devices are selected in accordance with a noise criterion.

Abstract: The invention provides a tool to select reliable organic LED devices, where the risk for failure before the end of its lifetime is low.

Abstract: The invention provides a tool to select reliable organic LED devices, where the risk for failure before the end of its lifetime is low. This tool comprises the steps of: i) subjecting the device to a high electric field over the electroluminescent layer. This leads to a division of the devices into two, clearly separated, populations, namely one population with a low leakage current (current through the electroluminescent layer in reverse voltage operation) and one population with a high leakage current. In this step, the first population is selected in accordance with a current criterion. ii) detecting instabilities in the leakage current, referred to as noise. It has been established that these instabilities arise in particular at reverse driving voltages between 1 and 10 Volts. These instabilities are a measure of the occurrence of early failures during operation. In this step, the devices are selected in accordance with a noise criterion.

Abstract: An organic electroluminescent device whose electroluminescence efficiency is independent of the work function of the cathode material, and whose service life under ambient conditions is excellent without the necessity of taking additional protective measures. These properties are obtained as a result of the fact that an organic layer of the device comprises mobile ions which are compensated by immobile ions in such a manner that the polarity of all mobile ions is the same.

Abstract: Electroluminescent display device comprising drive circuitry (a number of alternatives is given) to determine the surface area of a pixel (via capacitance, reverse current) and adjust the current density in the pixel accordingly.

Abstract: The invention provides an organic electroluminescent device whose electroluminescence efficiency is independent of the work function of the cathode material, and whose service life under ambient conditions is excellent without the necessity of taking additional protective measures. These properties are obtained as a result of the fact that an organic layer of the device comprises mobile ions which are compensated by immobile ions in such a manner that the polarity of all mobile ions is the same.

Abstract: Integrated voltage level indicator comprising a plurality of polymer LEDs between two contact leads, in which the number of luminescing LEDs and/or the intensity of the light in each LED is determined by the external voltage level.

Abstract: A polymer electroluminescent device (1) comprises an electroluminescent layer (7) of a poly(1,4-phenylenevinylene) having aryl-1,4-phenylene units, where the aryl group is a phenyl, naphthyl or biphenylyl group. Using such a poly(1,4-phenylenevinylene) has the effect that the light emitted by the polymer electroluminescent device has no or at least a reduced tendency to change color when driven the device is and/or kept at an elevated ambient temperature of, for example, 70° C. The poly(1,4-phenylenevinylene)s having aryl-1,4-phenylene units are prepared using aryl-bishalomethylbenzenes as an intermediate compound.

Abstract: An organic electroluminescent device whose electroluminescence efficiency is independent of the work function of the cathode material, and whose service life under ambient conditions is excellent without the necessity of taking additional protective measures. These properties are obtained as a result of the fact that an organic layer of the device comprises mobile ions which are compensated by immobile ions in such a manner than the polarity of all mobile ions is the same.

Abstract: Electroluminescent display screen having a transparent substrate (1), a surface (2) of which is provided with a first, transparent electrode layer (3) on which a metal top layer (12) is formed. The metal top layer is provided with a layer of insulating material (4). Windows (5) in accordance with a pattern (8, 9, 10) to be displayed are formed in the layer of insulating material as well as in the metal top layer. An organic electroluminescent layer (6) is deposited on said layer of insulating material and in said windows. This layer is provided with a second electrode layer (7). Said pattern (8, 9, 10) can be displayed without differences in brightness.

Abstract: Integrated voltage level indicator comprising a plurality of polymer LEDs between two contact leads, in which the number of luminescing LEDs and/or the intensity of the light in each LED is determined by the external voltage level.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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).

Abstract: 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.

Abstract: 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.

Abstract: 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.