Modulation of light emitted by a lighting device, using plurality of different modulation periods

摘要

The possibility to emit and detect coded light, whereby data is modulated into the light, is known. According to one aspect of the present disclosure, to reduce the risk of the modulation going undetected due to possible frequency blind spots in the detection spectrum, the lighting device (2a, 2b, 2c) is arranged such that the frequency of its emitted modulated light (3a, 3b, 3c) shivers around a base, or center, frequency. For example the modulated light (3a, 3b, 3c) may be transmitted using pulse-width-modulation, and the resulting pulse-width-modulation light signal (3a, 3b, 3c) may thus have a period that fluctuates around the base period (T). The parameters determining the shivering of the modulated light (3a, 3b, 3c) may be chosen such that visible flicker in the emitted modulated light (3a, 3b, 3c) is avoided. According to another aspect, the lighting device (2a, 2b, 2c) emits with a plurality of different modulation frequencies simultaneously.

主权项

1. A lighting device comprising:
a light emitter arranged to emit light with a periodic modulation which embeds information into the light; and a light driver arranged to drive the light emitter by providing an indicator to the light emitter, the indicator relating to the modulation of the light to be emitted by the light emitter and the light emitter being arranged to emit the light modulated according to said indicator; wherein the light driver is arranged to drive the light emitter to emit the light with said information being embedded at a plurality of different modulation periods; wherein the light emitter is arranged to emit light to be detected by an image capturing unit; and the light driver is arranged to drive the light emitter to avoid at least one of the modulation periods that corresponds to a frequency blind spot produced by an acquisition process of the image capturing unit.