Abstract: A series of frames is captured by a rolling-shutter camera, each frame capturing an image of a light source which has a periodic message embedded in its light. With a rolling-shutter camera, each line captures a respective sample of the message and each frame captures a respective fragment of the message made up of a respective subsequence of the samples, wherein the message can be reconstructed from the fragments captured over multiple frames. Further, the frame rate of the rolling-shutter camera is dependent on a region of interest (ROI), and the method further comprises evaluating a metric indicative of how long will be required to accumulate enough fragments to reconstruct the message at the current frame rate, and adapting the ROI in dependence on this metric in order to change the frame rate and thereby reduce the number of subsequent frames required to complete the reconstruction of the message.

Abstract: An apparatus, method and program for receiving a coded light signal comprising a periodically repeating message repeating with a message period. A portion of the message is received in each of a plurality of frames captured by a rolling-shutter camera, with different portions being received in different frames. Using each of a discrete group of trial values of the message period, the respective trial value is used to reconstruct a respective first version of the message from the portions received in a first subset of said frames, and to reconstruct a respective second version of the message from the portions received in a second subset of said frames. For each of the trial values, there is generate a respective value of a measure of similarity between the respective reconstructed first and second versions of the message. An estimate of the message period is determined based on this.

Abstract: A coded visible light receiver comprises: a sensor, a transform module, and an interference cancelling module. The sensor receives light comprising data modulated into the light according to a coding scheme. The transform module is configured to transform the data into a frequency domain representation, representing a band of a spectrum resulting from the data being modulated into the light according to the coding scheme. The interference cancelling module is configured to cancel interference occurring in the band of the data, by determining one or more components in the band that exceed a threshold signal strength and cancelling those components.

Abstract: A device comprising: an input for receiving a signal from a rolling-shutter camera which captures frames by exposing a lines of each frame in sequence, the signal comprising a coded light signal; and a signal processing module arranged to obtain a respective sample of the coded light signal from each of a number of said lines, being a substantially smaller number of the lines than exposed by the camera in each frame. The coded light signal comprises a message having a duration longer than this number of lines, and the message is repeated multiple times with a timing such that a different part of the message is seen by the camera in each of a plurality of different ones of said frames. The signal processing module is configured to time align the different parts of the message from the plurality of different frames, and reassemble the message from the time-aligned parts.

Abstract: A Wiener filter for equalizing an effect of a first filter on an input signal which is subject to the first filter and to noise and/or interference, wherein: the first filter is dependent on at least one unknown quantity; and the Wiener filter is configured based on an averaged representation of the first filter averaged over the at least one unknown quantity, in place of a representation of the first filter being assumed to be known.

Abstract: The present invention relates to a device for detecting muscle seizure of a subject in a comfortable, non-invasive manner and user-friendly manner. The device comprises an activity input configured to obtain activity information related to a subject's activity when using a user device; a gaze input configured to obtain gaze information related to the subject's gaze when using the user device; a detection unit configured to detect a muscle seizure of the subject when using the user device by determining if the activity information indicates a reduction in the subject's activity using a user device and if the gaze information indicates that the subject's gaze is directed to the user device; and a control unit configured to generate a control signal, if the detection unit detects a muscle seizure of the subject configured to control a vibration unit attached to the subject and/or the user device to vibrate.

Abstract: An apparatus, method and program for receiving a coded light signal comprising a periodically repeating message repeating with a message period. A portion of the message is received in each of a plurality of frames captured by a rolling-shutter camera, with different portions being received in different frames. Using each of a discrete group of trial values of the message period, the respective trial value is used to reconstruct a respective first version of the message from the portions received in a first subset of said frames, and to reconstruct a respective second version of the message from the portions received in a second subset of said frames. For each of the trial values, there is generate a respective value of a measure of similarity between the respective reconstructed first and second versions of the message. An estimate of the message period is determined based on this.

Abstract: A coded light signal is embedded into visible light emitted from the light source, to be received by a rolling-shutter camera which captures frames (16) by exposing a plurality of lines (18, 24) of each frame in sequence, the camera having an exposure time with each line being exposed for the exposure time. The coded light signal is formatted according to a format whereby the coded light signal comprises at least one message and the message is repeated multiple times with a timing such that, when samples of the coded light signal are obtained from a substantially smaller number of lines (24) than exposed by the camera in each frame and the message is longer than this number of lines, a different part of the message is seen by the camera in each of a plurality of different ones said frames.

Abstract: The invention relates to an apparatus, a system and a method of locating a location of a portable device using coded light, the portable device comprising an image sensor and an inertial measurement unit, the method comprising: obtaining a first image comprising the coded light source from the image sensor and substantially simultaneously obtaining orientation information indicative of the orientation of the portable device or the image sensor from the inertial measurement unit; obtaining light source specific information in the form of: an identifier that allows retrieval of a three-dimensional location of the coded light source or a three-dimensional location of the coded light source; and computing the location of the portable device or image sensor based on the orientation information, a predetermined height estimate of the portable device or image sensor and the light source specific information.

Abstract: A circuit comprising a controller (2) for controlling a pulse width modulated input signal, and a driver (4) configured to supply current to a load (6) based on the input signal, wherein over the on time of each pulse width modulation period the driver (4) supplies current to the load (6) with a second frequency that is greater than the first frequency. The controller (2) is configured to control the duty cycle to set the output of the load (6) to a desired output level, and to dither the duty cycle about a point corresponding to the desired output level.

Abstract: A compiler 134 for compiling a first computer program 110 written in a first computer programming language into a second computer program written in a machine language, the compiler comprises a code generator to generate the second computer program by generating tables 142 and machine language code 144, the generated tables and the generated machine language code together forming the second computer program, wherein the generated machine language code references the tables and the generated machine language code does not contain arithmetic or logic machine instructions, the tables comprising pre-computed results of arithmetic and/or logic machine instructions.

Abstract: A drive signal is generated, describing a waveform having discrete levels used to represent packets of data interspersed with idle periods, the data being encoded according to an at least three-level code, which is DC-free in that, at least when the data is substantially random, the symbol values average to the value of the zero symbol. The drive signal is used to drive a light source, and thereby transmit the encoded signal embedded in the emitted visible light. At least when the data is substantially random, the levels of the drive signal have a predetermined average DC level during the packets; and the modulation comprises representing the idle periods using a DC-free modulation alternating between a plurality of levels comprising at least a first and a second level, such that over each idle period the levels average to said predetermined DC level of the packets.

Abstract: A coded visible light receiver comprises: a sensor, a transform module, and an interference cancelling module. The sensor receives light comprising data modulated into the light according to a coding scheme. The transform module is configured to transform the data into a frequency domain representation, representing a band of a spectrum resulting from the data being modulated into the light according to the coding scheme. The interference cancelling module is configured to cancel interference occurring in the band of the data, by determining one or more components in the band that exceed a threshold signal strength and cancelling those components.

Abstract: A coded visible light receiver comprises: a sensor, a transform module, and an interference cancelling module. The sensor receives light comprising data modulated into the light according to a coding scheme. The transform module is configured to transform the data into a frequency domain representation, representing a band of a spectrum resulting from the data being modulated into the light according to the coding scheme. The interference cancelling module is configured to cancel interference occurring in the band of the data, by determining one or more components in the band that exceed a threshold signal strength and cancelling those components.

Abstract: A coded light receiver comprising a sensor for receiving coded light, a filter, and a timing and data recovery module. The coded light comprises a signal whereby data and timing are modulated into the light according to a self-clocking coding scheme. The filter is arranged to match a template waveform of the coding scheme against the received signal, thereby generating a pattern of filtered waveforms each corresponding to a respective portion of the data, and the timing and data recovery module recovers the timing from the signal based on characteristic points of the filtered waveforms. The timing and data recovery module is configured to do this by separating the filtered waveforms into different sub-patterns in dependence on the data, and to recover the timing by processing each of the sub-patterns individually based on the characteristic points of each sub-pattern.

Abstract: The invention relates to an apparatus, a system and a method of locating a location of a portable device using coded light, the portable device comprising an image sensor and an inertial measurement unit, the method comprising: obtaining a first image comprising the coded light source from the image sensor and substantially simultaneously obtaining orientation information indicative of the orientation of the portable device or the image sensor from the inertial measurement unit; obtaining light source specific information in the form of: an identifier that allows retrieval of a three-dimensional location of the coded light source or a three-dimensional location of the coded light source; and computing the location of the portable device or image sensor based on the orientation information, a predetermined height estimate of the portable device or image sensor and the light source specific information.

Abstract: A circuit comprising a controller (2) for controlling a pulse width modulated input signal, and a driver (4) configured to supply current to a load (6) based on the input signal, wherein over the on time of each pulse width modulation period the driver (4) supplies current to the load (6) with a second frequency that is greater than the first frequency. The controller (2) is configured to control the duty cycle to set the output of the load (6) to a desired output level, and to dither the duty cycle about a point corresponding to the desired output level.

Abstract: A device comprising: an input for receiving a signal from a rolling-shutter camera which captures frames by exposing a lines of each frame in sequence, the signal comprising a coded light signal; and a signal processing module arranged to obtain a respective sample of the coded light signal from each of a number of said lines, being a substantially smaller number of the lines than exposed by the camera in each frame. The coded light signal comprises a message having a duration longer than this number of lines, and the message is repeated multiple times with a timing such that a different part of the message is seen by the camera in each of a plurality of different ones of said frames. The signal processing module is configured to time align the different parts of the message from the plurality of different frames, and reassemble the message from the time-aligned parts.

Abstract: A coded light signal is embedded into visible light emitted from the light source, to be received by a rolling-shutter camera which captures frames (16) by exposing a plurality of lines (18, 24) of each frame in sequence, the camera having an exposure time with each line being exposed for the exposure time. The coded light signal is formatted according to a format whereby the coded light signal comprises at least one message and the message is repeated multiple times with a timing such that, when samples of the coded light signal are obtained from a substantially smaller number of lines (24) than exposed by the camera in each frame and the message is longer than this number of lines, a different part of the message is seen by the camera in each of a plurality of different ones said frames.

Abstract: A Wiener filter for equalizing an effect of a first filter on an input signal which is subject to the first filter and to noise and/or interference, wherein: the first filter is dependent on at least one unknown quantity; and the Wiener filter is configured based on an averaged representation of the first filter averaged over the at least one unknown quantity, in place of a representation of the first filter being assumed to be known.