CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application of PCT/GB2018/052200, filed on Aug. 1, 2018, which claims priority to GB Application No. 1713092.3, filed on Aug. 15, 2017, which are hereby incorporated by reference in their entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates to eye safety techniques for optical wireless communication devices.

BACKGROUND

Eye-safety constraints may impose restrictions on the power per solid angle of the light that light emitting devices radiate. Higher communication rates in optical wireless communications require more optical radiation to reach the optical detector, which translate into higher energy levels being emitted on the transmitter side for the same area coverage. At the same time, integration of communication interfaces into smaller devices leads to the requirement for smaller detectors, which further increases the required optical energy per unit of coverage area as the light collection area of the detector is reduced.

Eye-safety constraints may be defined in terms of overall light intensity that enters the human eye and, hence, in terms of the power per unit area (also referred to as irradiance) of the light at the human pupil. Hence, for any device that emits dispersed light, there is a minimum distance at which the light source is eye-safe, which is the distance at which the light intensity is within the allowed limits.

FIG. 1(a)presents an example where the power per unit area of the light reaching the human eye is too high. In this example, a transmitter20of the device emits optical signals22, for example comprising infrared light. In this example, the intensity of light that enters the human eye24(e.g. the power per unit area at the human pupil) is too high and thus the device is not eye-safe at close proximity.

In an alternative configuration, as shown inFIG. 1(b), the same light is dispersed with a different design of transmitter optics26, such that the light exiting the device is sufficiently dispersed to be eye-safe at close proximity.FIG. 1(b)shows a similar arrangement as inFIG. 1(a)with a transmitter20emitting optical signals22, for example comprising infrared light, which reach a human eye24. However, in this case the transmissive optics26disperse the light and reduce its intensity such that eye-safety constraints may be met. However, the use of dispersive optics can reduce the range and/or maximum data rate of optical wireless communications.

SUMMARY

In a first aspect, there is provided an optical wireless communication device for transmitting data comprising:

a transmitter comprising a light source; a controller configured to control operation of the light source to produce modulated light comprising an optical wireless communication signal representative of said data; at least one proximity determining component configured to determine a proximity of an object; and a processing resource configured to determine whether the determined proximity is within a threshold distance, wherein the controller is configured to control operation of the transmitter and/or of at least one other component of the optical wireless communication device in dependence on whether the determined proximity is within the threshold distance.

The controlling of operation of the transmitter may comprise reducing an intensity of the light in response to the determined proximity being within the threshold distance.

The processing resource and controller may be provided as separate components or as a single component. The processing resource may form part of the controller or vice versa.

The controlling of operation of the transmitter may comprise, in response to the determined proximity being within the threshold distance, at least one of halting generation by the light source of the light, or at least partially blocking or redirecting the light.

The device may comprise at least one further transmitter. The controller may be configured to transmit said data by producing modulated light comprising the optical wireless communication signal representative of said data using one or both of the transmitter and the at least one further transmitter. The controller may be configured to selectively control operation of the at least one further transmitter in dependence on whether the determined proximity of the object is within the threshold distance.

The optical wireless communication signal, or at least part of the optical wireless communication signal, may be transmitted simultaneously or successively by the transmitter and the further transmitter. The data may be transmitted as a data stream during a transmission time. At least part of the data stream may be transmitted by the transmitter and a further at least part of the data stream may be transmitted by the further transmitter, for example in dependence on a proximity of one or more objects to the transmitter and/or the further transmitter during the transmission time.

The at least one proximity determining component may be configured to determine a proximity of an object from the transmitter and to determine a further proximity of an object from the further transmitter. The controller may be configured to control operation of the transmitter and the at least one further transmitter in dependence on whether the determined proximity is within the threshold distance and in dependence on whether the further proximity is within the or a threshold distance.

The further transmitter may comprise a further light source or the light may be selectively directed to one or other, or both of the transmitter and the further transmitter from the same light source. The transmitter and the further transmitter may each comprise a respective output, for example a respective output aperture and, optionally, the device may comprise a guide and/or switch arrangement for guiding light from the light source to a selected or other, or both of the transmitter and the further transmitter.

The controller may be configured to selectively control operation of the transmitter and the further transmitter such that the total power or irradiance from the transmitter and the further transmitter is maintained at a desired value or within a desired range, optionally subject to there being at least one of the transmitters for which determined object proximity is not within the threshold distance.

The controlling of operation of the at least one further component of the optical wireless communication device may comprise controlling said at least one further component such as to encourage a user to increase a distance between their eye or eyes and the wireless communication device.

The at least one further component may comprise a further light source, and the further light source is configured to emit visible light.

The processing resource may be configured to control the further light source and/or the light source of the transmitter to emit visible light having at least one property such as to provide discomfort and/or a warning signal for a user in response to the device being within the threshold distance of at least one of the user, the face of the user, an eye or eyes of the user.

The at least one property of the visible light may comprise intensity, colour, or colour and/or intensity variation as a function of time. The visible light may be flashing or pulsed light and the at least one property comprises a pulse or flash repetition frequency.

The at least one further component may comprise an alarm.

The alarm may be configured to output an alarm signal in response to the determined proximity being within the threshold distance.

The alarm signal may comprise at least one of an audible, visible, or tactile alarm signal.

The at least one proximity determining component may comprise a camera and the processing resource may be configured to perform an image recognition procedure on image data obtained from the camera in order to determine the proximity and/or at least one property of the object.

The image recognition procedure may comprise determining whether the object comprises a user, a user's face or eye based on the image data obtained from the camera.

The image recognition procedure may further comprise determining the proximity to the device of the user, the user's face or eye based on the size or scale of the user, the user's face or eye in the image data obtained from the camera.

The device may further comprise a camera, wherein the at least one proximity determining component and/or the processing resource may be configured to provide proximity information from the at least one proximity determining component both to the camera and for use by the processing resource in determining whether the determined proximity is within the user safety threshold distance

The device may further comprise at least one sensor for receiving light reflected by the object and configured to provide a sensor signal representative of the received light, and the at least one proximity determining component may be configured to determine the proximity based on the sensor signal, wherein optionally the transmitter is arranged such that light reflected by the object comprises light from the transmitter.

The threshold distance may comprise a user safety threshold distance.

The threshold distance may be a distance at which power per solid angle of light emitted by the transmitter is at or below a predetermined threshold value.

The threshold distance may be in a range 1 cm to 20 cm, optionally in a range 1 cm to 36 cm, optionally in a range 1 cm to 5 cm, optionally less than 20 cm, optionally less than 36 cm, optionally less than 5 cm.

The controlling of the operation of the transmitter and/or of at least one other component of the optical wireless communication device may be in dependence on both the determined proximity being within the threshold distance and at least one further selected condition being satisfied.

The selected condition may comprise a length of time for which the object is at a particular distance or distances. The processing resource may be configured to determine a length of time for which the object is at any particular distance(s). The length of time that an object is at a particular distance from the transmitter, whilst the transmitter is operational, may be referred to as an exposure time at that distance.

The selected condition may comprise a value of a function representing total light energy received by the object from the transmitter. The processing resource may be configured to control operation of the transmitter and/or of at least one other component of the optical wireless communication device in dependence on a value of a function. The processing resource may calculate the value of the function. The function may comprise a function of exposure time and distance between the object and the transmitter and/or power per solid angle of the transmitter. The function may represent total light energy received by the object from the transmitter.

The object may comprise at least one of a user's face or eye.

The processing resource may be configured to: determine at least one property of the object and/or at least one operating parameter or property of the device; determine whether the object comprises a user, a user's face or eye, based on the determined at least one property or operating parameter; and to perform the proximity-dependent controlling of operation of the transmitter and/or of at least one other component of the optical wireless communication device in response to determining that the object comprise a user, a user's face or eye.

The optical wireless communication device may comprise at least one further sensor for detecting at least one property of the object

The at least one proximity determining component may comprise at least one of an infra-red sensor, an ultra-violet sensor, an RF sensor, a camera-based sensor, an imaging device, an inductive and/or capacitive sensor, an acoustic sensor.

The at least one proximity determining component may be configured to generate at least one detection signal and the at least one proximity determining component and/or the processing resource may be configured to determine at least one property of the object based on the at least one detection signal.

The optical wireless communication device may comprise at least one of a mobile and/or hand-held computing device, a smartphone, a mobile phone, a tablet, a computer, a laptop, an access point.

The device may be configured to communicate using a further communication protocol in addition to optical wireless communication.

The further communication protocol may comprise at least one of: a radio-frequency communication protocol, wireless mobile telecommunication, Wi-Fi, global positioning system, short message service, multimedia message service, Ethernet connection.

The modulated light may comprise at least one of infra-red radiation, ultra-violet radiation, visible light.

In a further aspect, which may be provided independently, there is provided a method of controlling operation of an optical wireless communication device comprising: determining a proximity of an object to the device; determining whether the determined proximity is within a user safety threshold distance and controlling operation of a transmitter of the optical wireless communication device and/or of at least one other component of the optical wireless communication device in dependence on whether the determined proximity is within the user safety threshold distance.

Features in one aspect may be applied as features in another aspect. For example, method features may be applied as device features and vice versa.

