Abstract: Method of controlling an LED fixture comprising a plurality of LEDs, the plurality of LED comprising at least four LEDs, configured to emit light of different colors, the method comprising: receiving a set point representing a desired color and intensity for the light to be generated by the LED fixture; determining, based on available color characteristics of the plurality of LEDs, at least two different subsets of the plurality of LEDs and a set of intensity set points for each of the at least two different subsets, wherein each set of intensity set points results in obtaining or approximating the desired color and intensity by the LED fixture; selecting the subsets of the plurality of LEDs with the corresponding sets of intensity set points which meet a predetermined criterion; use a selected subset to drive the plurality of LEDs with the corresponding set of intensity set points.

Abstract: The present invention pertains to a system and method for operating at least one LED unit of lighting grid comprising a plurality of LED units, wherein the LED units are configured to transmit a VLC signal including a code word. A plurality of user equipment devices captures the light transmitted by the LED unit and determines parameters related to the light, such as a VLC quality parameter, flicker value, light intensity parameter and light colour parameter. Based on these parameters, a controller determines control parameters for the LED unit. As such, a feedback loop is created wherein the LED unit is controlled based on measurements with the user equipment devices.

Abstract: An LED driver measures a voltage across the LED and a temperature associated with the LED. The LED driver drives the LED to operate below a knee in the voltage/current curve of the LED and derives an expected voltage across the LED from the temperature of the LED, the LED driving current, and a predetermined relation between the expected LED voltage and at least one of LED temperature and LED driving current. The LED driver determines if the measured voltage across the LED exceeds the expected voltage across the LED, and establishes, based on the determination, if an LED approaching end of life warning is to be generated. Thus, an approaching end of life may be determined by the LED driver while the LED is still operational.

Abstract: A visual light communication (VLC) method for a lighting system comprising an LED driver and a plurality of LEDs or LED groups includes the steps of: receiving a set-point representing a desired illumination characteristic, comprising an intensity set-point, a color set-point or a combination thereof, and data that is to be transmitted using VLC; determining a current profile for each LED or LED group of the plurality of LEDs or LED groups based on the desired illumination characteristic represented by the set-point, whereby an envelope of a combined current profile is modulated for a corresponding intensity variation as perceived by a sensor to represent a variable length VLC code comprising one or more code words; and generating one or more control signals to drive the plurality of LEDs or LED groups in accordance with the current profiles for the plurality of LEDs or LED groups to transmit the VLC code.

Abstract: Disclosed is a method of capturing an image of a scene using a user device having a rolling shutter camera. The scene is subjected to an illumination by an LED light source. The method includes providing, by the user device, a notification signal to the LED light source, the notification signal being indicative of a capturing or imminent capturing of an image; adjusting, by the LED light source, an operating characteristic of the LED light source, based on the notification signal; and capturing, by the rolling shutter camera, the image of the scene, while the LED light source is operating at the adjusted operating characteristic.

Abstract: The present invention pertains to a system and method for operating at least one LED unit of lighting grid comprising a plurality of LED units, wherein the LED units are configured to transmit a VLC signal including a code word. A plurality of user equipment devices captures the light transmitted by the LED unit and determines parameters related to the light, such as a VLC quality parameter, flicker value, light intensity parameter and light colour parameter. Based on these parameters, a controller determines control parameters for the LED unit. As such, a feedback loop is created wherein the LED unit is controlled based on measurements with the user equipment devices.

Abstract: An LED light unit comprises an LED assembly and a light sensor to measure light emitted by the LED assembly and having a measurement range; a current source to drive the LED assembly at an LED current A control device is configured to: pre-heat the LED assembly by driving the current source to operate the LED assembly at an operating current; the LED assembly thereby illuminating the light sensor at a light level above the measurement range; interrupt operating the LED assembly during a stray light measurement time; and read an output signal of the light sensor; operate the LED assembly at a measurement current, to emit light at a measurement level; subtract the output signal of the light sensor during the stray light measurement time from the output signal of the light sensor during the light measurement time to obtain a stray light corrected light measurement signal; scale the stray light corrected light measurement signal by a scaling factor based on a ratio of the operating LED current and the measurem

Abstract: The present invention pertains to a system and method for operating at least one LED unit of lighting grid comprising a plurality of LED units, wherein the LED units are configured to transmit a VLC signal including a code word. A plurality of user equipment devices captures the light transmitted by the LED unit and determines parameters related to the light, such as a VLC quality parameter, flicker value, light intensity parameter and light colour parameter. Based on these parameters, a controller determines control parameters for the LED unit. As such, a feedback loop is created wherein the LED unit is controlled based on measurements with the user equipment devices.

Abstract: An LED driver configured to power a plurality of LEDs having a different colour or colour spectrum is described, the LED driver comprising: a power converter configured to supply power to the plurality of LEDs and a control unit, the control unit comprising: an input terminal configured to receive an input signal representing a desired colour set-point; a processing unit configured to: determine a MacAdam ellipse for the desired colour set-point; determine a required intensity or current for each of the plurality of LEDs so as to achieve the desired colour set-point; determine a colour shift direction for the colour set-point, based on the determined required intensities or currents; select a modified colour set-point based on the colour shift direction and the MacAdam ellipse; determine a required supply current for each of the plurality of LEDs so as to achieve the modified colour set-point; determine a control signal for the power converter so as to generate the required supply currents; and wherein

Abstract: Method of controlling an LED fixture comprising a plurality of LEDs, the plurality of LED comprising at least four LEDs, configured to emit light of different colors, the method comprising: receiving a set point representing a desired color and intensity for the light to be generated by the LED fixture; determining, based on available color characteristics of the plurality of LEDs, at least two different subsets of the plurality of LEDs and a set of intensity set points for each of the at least two different subsets, wherein each set of intensity set points results in obtaining or approximating the desired color and intensity by the LED fixture; selecting the subsets of the plurality of LEDs with the corresponding sets of intensity set points which meet a predetermined criterion; use a selected subset to drive the plurality of LEDs with the corresponding set of intensity set points.

Abstract: An LED driver for driving a plurality of LEDs or LED groups to transmit light in a VLC mode is described, wherein the LED driver comprises a control unit that is configured to: receive, at an input terminal, a set-point representing a desired illumination characteristic and data that is to be transmitted using VLC; determine a current profile for each of the plurality of LEDs or LED groups to generate the desired illumination characteristic, whereby an envelope of the combined current profile comprises a modulation in order for a corresponding intensity modulation as perceived by a sensor to represent a variable length VLC code representing the data, the VLC code comprising code words, a code word comprising a plurality of symbols; generate one or more control signals to drive the plurality of LEDs in accordance with the current profiles in order for the plurality of LEDs or LED groups to transmit the VLC code; and upon receipt of a further set-point representing a different illumination characteristic dur

Abstract: Disclosed is a method of capturing an image of a scene using a user device having a rolling shutter camera. The scene is subjected to an illumination by an LED light source. The method includes providing, by the user device, a notification signal to the LED light source, the notification signal being indicative of a capturing or imminent capturing of an image; adjusting, by the LED light source, an operating characteristic of the LED light source, based on the notification signal; and capturing, by the rolling shutter camera, the image of the scene, while the LED light source is operating at the adjusted operating characteristic.

Abstract: An LED driver configured to power a plurality of LEDs having a different colour or colour spectrum is described, the LED driver comprising: a power converter configured to supply power to the plurality of LEDs and a control unit, the control unit comprising: an input terminal configured to receive an input signal representing a desired colour set-point; a processing unit configured to: determine a MacAdam ellipse for the desired colour set-point; determine a required intensity or current for each of the plurality of LEDs so as to achieve the desired colour set-point; determine a colour shift direction for the colour set-point, based on the determined required intensities or currents; select a modified colour set-point based on the colour shift direction and the MacAdam ellipse; determine a required supply current for each of the plurality of LEDs so as to achieve the modified colour set-point; determine a control signal for the power converter so as to generate the required supply currents; and wherein

Abstract: Method of controlling an LED fixture comprising a plurality of LEDs, the plurality of LED comprising at least four LEDs, configured to emit light of different colors, the method comprising: receiving a set point representing a desired color and intensity for the light to be generated by the LED fixture; determining, based on available color characteristics of the plurality of LEDs, at least two different subsets of the plurality of LEDs and a set of intensity set points for each of the at least two different subsets, wherein each set of intensity set points results in obtaining or approximating the desired color and intensity by the LED fixture; selecting the subsets of the plurality of LEDs with the corresponding sets of intensity set points which meet a predetermined criterion; use a selected subset to drive the plurality of LEDs with the corresponding set of intensity set points.

Abstract: An LED light unit comprises an LED assembly and a light sensor to measure light emitted by the LED assembly and having a measurement range; a current source to drive the LED assembly at an LED current A control device is configured to: pre-heat the LED assembly by driving the current source to operate the LED assembly at an operating current; the LED assembly thereby illuminating the light sensor at a light level above the measurement range; interrupt operating the LED assembly during a stray light measurement time; and read an output signal of the light sensor; operate the LED assembly at a measurement current, to emit light at a measurement level; subtract the output signal of the light sensor during the stray light measurement time from the output signal of the light sensor during the light measurement time to obtain a stray light corrected light measurement signal; scale the stray light corrected light measurement signal by a scaling factor based on a ratio of the operating LED current and the measurem

Abstract: The present invention pertains to a system and method for operating at least one LED unit of lighting grid comprising a plurality of LED units, wherein the LED units are configured to transmit a VLC signal including a code word. A plurality of user equipment devices captures the light transmitted by the LED unit and determines parameters related to the light, such as a VLC quality parameter, flicker value, light intensity parameter and light colour parameter. Based on these parameters, a controller determines control parameters for the LED unit. As such, a feedback loop is created wherein the LED unit is controlled based on measurements with the user equipment devices.

Abstract: An LED driver for driving a plurality of LEDs or LED groups to transmit light in a VLC mode is described, wherein the LED driver comprises a control unit that is configured to: receive, at an input terminal, a set-point representing a desired illumination characteristic and data that is to be transmitted using VLC; determine a current profile for each of the plurality of LEDs or LED groups to generate the desired illumination characteristic, whereby an envelope of the combined current profile comprises a modulation in order for a corresponding intensity modulation as perceived by a sensor to represent a variable length VLC code representing the data, the VLC code comprising code words, a code word comprising a plurality of symbols; generate one or more control signals to drive the plurality of LEDs in accordance with the current profiles in order for the plurality of LEDs or LED groups to transmit the VLC code; and upon receipt of a further set-point representing a different illumination characteristic dur