Patent Description:
Light Fidelity (LiFi), which uses light within certain wavelength ranges for the local area wireless communications, represents one alternative wireless technology that may replace or complement WiFi. LiFi systems rely on visible, infrared, and/or near ultraviolet spectrum waves. By modulating a light source, e.g., a light emitting diode, a LiFi transmitter transmits high speed signals detectable by a photodetector. The photodetector converts the detected light to electrical current, which is further processed by the receiver to interpret the detected light.

The visible light spectrum is ~<NUM>,<NUM> times larger than the radio frequency spectrum. LiFi is therefore expected to increase the bandwidth achievable by WiFi alone by a factor of <NUM>. Further, LiFi tends to be more suitable in high density and/or high interference environments, e.g., airplanes, office buildings, hospitals, power plants, etc. Thus, considerable focus has recently been given to improving LiFi technology and/or adapting LiFi technology for specific applications and/or devices. Publication <CIT> discloses diffusers for coupling light in and out in a bi-directional fashion in a light guide configuration that is tapped n times in series. Of the optical signals propagating in the optical signal line, a portion is extracted by light diffusion, namely, in a direction running substantially perpendicular to the direction of propagation. The shape and size of the plurality of diffusers are preferably tuned to one another such that, in the guiding of electromagnetic radiation in the optical signal line, the absolute value of the extracted radiation power is substantially constant for each optical access along the main direction of the line. A plurality of receivers that are provided in series along the light guide configuration can then be supplied with respective optical signals of equal intensity.

Publication <CIT> discloses a three layer waveguide structure. Incident light is coupled to the waveguide at a specific wavelength and incident angle by a grating coupler at a coupling region, providing a spectral/angular filtering function. The light is then out-coupled from the waveguide downstream from the coupling region at an out-coupling grating located at junction region to a photodetector fabricated in an underlying silicon substrate.

The solution presented herein uses waveguides to efficiently collect light used for light communications, particularly wavelength-specific light, and propagates the collected light to a sensor to implement wavelength-specific detection. Such wavelength-specific light collection may involve filtering light at a waveguide entrance to channel wavelength-specific light to a sensor, channeling collected light to wavelength-specific sensor(s), and/or filtering the light at the sensor so that the sensor only detects the desired wavelength(s). As used herein, "wavelength-specific" refers to one or more peak wavelengths that have the largest amplitude of a range of wavelengths. Thus, it will be appreciated that references to "wavelength-specific" generally include some number of wavelengths, e.g., surrounding each peak wavelength, in addition to the peak wavelength(s).

The solution presented herein increases the amount of light available for light communications, and particular for wavelength-specific light communications, even when the light associated with the light communications enters the device at an angle. Further, because multiple waveguides may channel light from multiple collection points to a single sensor, the solution presented herein reduces the number of sensors needed for the light communications. The waveguide solution presented herein may be implemented inside a device and/or along an exterior surface, e.g., housing or casing, of a device. As such, the solution presented herein also enables the implementation of light communications for a wide variety of devices (e.g., cellular telephones, tablets, smartphones, smart watches, smart glasses, etc.) and/or in a wide variety of scenarios.

The invention provides a detection system for light communications according to independent claim <NUM> and a method of detecting light according to independent claim <NUM>. Further embodiments are provided by the dependent claims.

According to exemplary embodiments, the detected light is processed according to any known means to determine the information transmitted in the light collected by the detection system, and to convey that information (when appropriate) to a user.

The use of light communications, e.g., LiFi, with WiFi or as a replacement for WiFi, has expanded the capabilities of local area wireless communications. However, the devices typically preferable for such communications are small, and have limited space available for the detectors/receivers used for such communications. Further, the space available in these devices continues to decrease due to the continual reduction in size of these devices and/or the continual addition of new features and/or hardware into these devices. For example, wearable devices (e.g., glasses, watches, etc.) are designed to have a minimal size to improve their wearability (e.g., make them lighter, more comfortable, etc.). The limited physical size of many devices, especially when combined with all the functionality intended to be included in such devices, places limitations on the location and/or size and/or number of light sensors that may be included in the device for light communications.

Conventional solutions require a sensor for every light capturing/entrance location of a device. For example, a device that implements light communications may include three openings in a housing of the device, where such openings are intended to, or could be used to, receive external light associated with light communications. In a conventional solution, such a device necessarily includes three sensors, one sensor disposed beneath each of the three openings, to capture the light entering each opening. Because many devices have limited space available for such sensors, such conventional solutions severely limit the number of sensors available for light communications, and thus limit the amount of light that can be collected for light communications and/or the effectiveness of light communications. Further, conventional solutions generally have challenging mechanical requirements regarding the location of the sensor and/or alignment of a sensor with the corresponding opening in order to enable the sensor to capture as much of the light entering the opening as possible. These mechanical limitations may severely limit the location options for the openings.

The solution presented herein solves many problems associated with conventional solutions by using waveguides to channel light from one or more openings to a sensor to facilitate wavelength-specific light communications. In so doing, the solution presented herein reduces the number of sensors used for light communications, enables each sensor to capture more light associated with the light communications, and/or enables flexibility regarding the sensor size, the sensor location in the device, and/or the alignment of the sensor with any particular opening. In particular, the solution presented herein enables any number of openings to be placed anywhere on the device, while also enabling one or more sensors to be placed at any suitable location within the device, which improves the signal quality and reduces the mechanical constraints associated with LiFi.

<FIG> shows one exemplary light detection system <NUM> for light communications according to embodiments of the solution presented herein, where the light used for the light communications comprises a plurality of peak wavelengths, e.g., λ<NUM> - λN, e.g., as shown in <FIG>. The light detection system <NUM> comprises a waveguide <NUM> and one or more light sensors <NUM>. The waveguide <NUM> comprises a Total Internal Reflection (TIR) structure <NUM> through which light propagates, a diffusive element <NUM>, and one or more waveguide entrances <NUM>. The TIR structure <NUM> has a first index of refraction n<NUM>, where indices of refraction, e.g., n<NUM> and/or n<NUM>, surrounding/adjacent to the TIR structure <NUM> is/are less than the first index of refraction n<NUM> such that light input to the waveguide <NUM> propagates along the waveguide <NUM> within the TIR structure <NUM>. Diffusive element <NUM> is disposed along an internal edge of the TIR structure <NUM> at a predetermined location of the waveguide <NUM> to disrupt the propagation of the light along the TIR structure <NUM>. Each of the waveguide entrance(s) <NUM> is at a location laterally offset along the waveguide <NUM> from the location of the diffusive element <NUM>, where each waveguide entrance <NUM> collects light <NUM> associated with the light communications and inputs the collected light <NUM> to the TIR structure <NUM> at the corresponding input location. Each of the one or more light sensors <NUM> detects a subset λm - λM of the plurality of wavelengths λ<NUM> - λN, where ((M - m) + <NUM>) < N. To that end, the light sensor(s) <NUM> is/are disposed adjacent to an internal edge of the TIR structure <NUM> opposite the location of the diffusive element <NUM> and generally spaced from the diffusive element <NUM> by a thickness t of the TIR structure <NUM> so that the light sensor(s) <NUM> detect wavelength-specific light disrupted by the diffusive element <NUM>. For example, each of the one or more light sensors <NUM> may comprise a Photo Sensitive Receptor (PSR) configured to detect the wavelength-specific light disrupted by the diffusive element <NUM>.

The propagation of the light through TIR structure <NUM> is at least partially controlled by the index of refraction n<NUM> of the TIR structure <NUM> relative to the surrounding index/indices of refraction. When material(s) surrounding TIR structure <NUM> have a lower refractive index than the TIR structure <NUM>, TIR structure <NUM> functions as a TIR layer, which enables the light entering the TIR structure <NUM> at a TIR angle to propagate along the TIR structure <NUM> with total internal reflection, and thus with minimal to no loss. While in some embodiments the indices of refraction surrounding TIR structure <NUM> are all the same, the solution presented herein does not require the index/indices of refraction surrounding the TIR structure <NUM> to be equal. Instead the solution presented herein only requires that the index of refraction n<NUM> of the TIR structure <NUM> be greater than each index of refraction of the surrounding material so that light input into TIR structure <NUM> propagates along the TIR structure <NUM> with total internal reflection.

The desired index of refraction relationship between the TIR structure <NUM> and the surrounding structure(s)/material(s) may be achieved in any number of ways. For example, when the TIR structure <NUM> is a cylindrical tube having a first index of refraction n<NUM>, having a second index of refraction n<NUM> surrounding the tube less than the first index of refraction (n<NUM> < n<NUM>) causes the desired total internal reflection in the TIR structure <NUM>. In another example, when the TIR structure <NUM> is a right rectangular prism having the first index of refraction n<NUM>, having a second index of refraction n<NUM> on one side of the TIR structure <NUM> that is less than the first index of refraction (n<NUM> < n<NUM>), and a third index of refraction n<NUM> on an opposing side of the TIR structure <NUM> that is also less than the first index of refraction (n<NUM> < n<NUM>), as shown in <FIG>, causes total internal reflection in the TIR structure <NUM>. In another example, waveguide <NUM> may be realized using a set of coatings or layers, where each layer/coating represents a different part of the waveguide <NUM>. In this example, one layer may represent a TIR layer (i.e., the TIR structure <NUM>), while one or more layers surrounding the TIR layer has a lower index of refraction than that of the TIR layer, and thus represents a "reflective" layer. Such a reflective layer may also serve as a protective layer that protects the TIR structure <NUM> from scratches, debris, and/or other foreign objects. Alternatively, a protective layer separate from the reflective layer may be applied between the TIR structure <NUM> and the reflective layer, where the protective layer has the same or lower index of refraction as the reflective layer. The protective layer may also be used to add print (e.g., text, images, etc.) that when visible to a user of the device <NUM> identify any desired information related to or about the device <NUM>, e.g., brand name, model name/number, team affiliations, school affiliations, etc..

The diffusive element <NUM> comprises any material or structure that disrupts the propagation of the light within the TIR structure <NUM>. In some embodiments, the diffusive element <NUM> may direct the disrupted light to the sensor <NUM>. In other embodiments, the diffusive element <NUM> may scatter the light such that at least some of the originally propagating light is captured by the sensor <NUM>. In one exemplary embodiment, the diffusive element <NUM> comprises white or colored paint applied to the inner edge of the TIR structure <NUM> above the sensor <NUM>. In another exemplary embodiment, the diffusive element <NUM> is constructed by altering the material at the location of diffusive element <NUM> so that this location of the TIR structure <NUM> is no longer flat and/or smooth. For example, machined dots may be placed at the location of the diffusive area <NUM> or the location of the diffusive area <NUM> may be etched or roughened.

As noted above, each of the one or more light sensors <NUM> detects a subset λm - λM of the plurality of wavelengths λ<NUM> - λN, where ((M - m) + <NUM>) < N. The plurality of wavelengths comprises a plurality of peak wavelengths suitable for light communications, e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, as shown in <FIG>. In some embodiments, each subset λm - λM of the plurality of wavelengths λ<NUM> - λN may comprise one of the plurality of peak wavelengths or multiple ones of the plurality of peak wavelengths. For example, a first subset may include <NUM>, a second subset may include <NUM> and <NUM>, etc. It will further be appreciated that some subsets may overlap such that a particular peak wavelength is part of two or more subsets. Further, it will be appreciated that the subset may include additional non-peak wavelengths, e.g., surrounding the peak wavelength(s), and that the solution presented herein is described in terms of subsets of one or more peak wavelengths and/or as wavelength-specific, where wavelength-specific refers to the one or more peak wavelengths of a particular subset but does not exclude the existence of other surrounding, non-peak wavelengths.

Each of the sensor(s) <NUM> of the solution presented herein may detect a particular subset of the plurality of wavelengths in any number of ways. In one exemplary solution, each sensor <NUM> may be wavelength-specific such that each sensor <NUM> is configured to detect a particular subset of the plurality of wavelengths. For example, as shown in the top view of <FIG>, one sensor for each subset of the plurality of wavelengths may be disposed opposite the diffusive element <NUM> such that each sensor <NUM> only detects the corresponding peak wavelength(s). In the example of <FIG> each sensor detects one of the peak wavelengths of <FIG>, e.g., sensor <NUM>, detects <NUM>, sensor <NUM><NUM> detects <NUM>, sensor <NUM><NUM> detects <NUM>, sensor <NUM><NUM> detects <NUM>, sensor <NUM><NUM> detects <NUM>, sensor <NUM><NUM> detects <NUM>, and sensor <NUM><NUM> detects <NUM>. It will be appreciated that more sensors <NUM> may be used if there are more peak wavelengths or fewer sensors <NUM> may be used if there are fewer peak wavelengths to detect or if each subset includes multiple peak wavelengths. For example, <FIG> shows one exemplary embodiment comprising four sensors, where each of the four sensors is arranged opposite diffusive element <NUM>, and where sensor <NUM><NUM> detects <NUM>, sensor <NUM><NUM> detects <NUM> and <NUM>, sensor <NUM><NUM> detects <NUM> and <NUM>, and sensor <NUM><NUM> detects <NUM> and <NUM>. Thus, it will be appreciated that the solution presented herein allows for more or fewer sensors, depending on the number of wavelength subsets.

While the figures used to illustrate embodiments of the solution presented herein show hexagonal-shaped sensors <NUM>, it will be appreciated that the sensors <NUM> are not limited to a hexagonal shape. Each sensor <NUM> may be any shape and/or size, where the shape and/or size is generally defined based on space constraints and/or manufacturer parameters. Further, the sensors <NUM> used for the solution presented herein are not required to all be the same size or shape. Further still, it will be appreciated that the solution presented herein does not require that each sensor <NUM> abut one or more of the other sensors <NUM>, as shown in <FIG>; the sensors <NUM> may be arranged opposite the diffusive element <NUM> in any suitable way such that the each sensor <NUM> detects its corresponding subset of the plurality of wavelengths.

In another exemplary embodiment, light destined for each sensor <NUM> may first pass through a wavelength-specific element <NUM>, e.g., at the waveguide entrance <NUM> (as shown in <FIG>) and/or at the location of the sensor <NUM> (as shown in <FIG>) such that the light input to the sensor <NUM> only includes the wavelengths in the corresponding subset. In such exemplary embodiments, the sensor <NUM> used to collect the light disrupted by the diffusive element <NUM> may also be wavelength-specific, or may be capable of detecting any number of wavelengths, including but not limited to the wavelengths in the corresponding subset.

<FIG> shows an exemplary embodiment where the wavelength-specific element <NUM> is a filter <NUM> disposed at the waveguide entrance <NUM>, where the filter <NUM> is configured to pass the peak wavelengths λm - λM in a particular subset of wavelengths, while blocking the remaining peak wavelength(s) in the plurality of wavelengths. In this embodiment, wavelengths λm - λM propagate down the waveguide <NUM> until they are disrupted by the diffusive element <NUM> and detected by the corresponding sensor <NUM>. As shown in <FIG>, the filter <NUM> may alternatively or additionally be disposed proximate the sensor <NUM>, where the wavelengths captured at the waveguide entrance <NUM> propagate down the waveguide <NUM>, but only the subset of wavelengths λm - λM pass to, and are detected by, the sensor <NUM>.

<FIG> shows another exemplary embodiment of the solution presented herein, where the wavelength-specific element <NUM> is a prism <NUM>. Exemplary prisms include, but are not limited to, a dispersive prism (e.g., a refracted prism or a diffraction grating) or a reflective prism. In this embodiment, prism <NUM> separates the input light into individual subsets of wavelengths, where each subset is input to a subset-specific waveguide <NUM>. For example, if the input light has seven peak wavelengths λ<NUM> - λN, the prism <NUM> may separate the input light into seven different directions, where each direction corresponds to one of the peak wavelengths, so that each of the peak wavelengths is input into a separate waveguide <NUM> for detection by a sensor <NUM>. For the example of <FIG>, this would result in λ<NUM> being input into waveguide <NUM><NUM> for detection by sensor <NUM><NUM>, λ<NUM> being input into waveguide <NUM><NUM> for detection by sensor <NUM><NUM>, λ<NUM> being input into waveguide <NUM> for detection by sensor <NUM>, λ<NUM> being input into waveguide <NUM><NUM> for detection by sensor <NUM><NUM>, λ<NUM> being input into waveguide <NUM><NUM> for detection by sensor <NUM><NUM>, λ<NUM> being input into waveguide <NUM><NUM> for detection by sensor <NUM><NUM>, and λ<NUM> being input into waveguide <NUM><NUM> for detection by sensor <NUM><NUM>. It will be appreciated that additional waveguides <NUM> and sensors <NUM> may be used if there are more than seven peak wavelengths, and that fewer waveguides <NUM> and sensors <NUM> may be used if there are fewer than seven peak wavelengths and/or one or more subsets include multiple peak wavelengths. Further, while <FIG> shows a top view of one exemplary prism solution, where the prism <NUM> fans each of the subsets out in one plane, it will be appreciated that the prism <NUM> may be configured to separate the wavelengths in any suitable manner and/or direction, and that the solution presented herein would configure the orientation of the waveguides <NUM> relative to the prism <NUM> and waveguide entrance <NUM> as appropriate so that the waveguide <NUM> receives and directs the corresponding subset of wavelengths to the corresponding sensor <NUM>.

The following provides further details about how the light enters the device and is channeled to the sensor(s) <NUM>. It will be appreciated that these details apply to any individual peak wavelength, subset of peak wavelengths, and/or plurality of peak wavelengths that are separated at some point in the detection system <NUM>, e.g., at the waveguide entrance <NUM>, at the sensor <NUM>, etc. As such, the above-described wavelength-specific aspects apply to each of the multiple openings, multiple sensor, multiple directions, light guiding elements, etc., aspects discussed further below.

As noted above, the light enters the waveguide <NUM> after first entering a waveguide entrance <NUM>. Each waveguide entrance <NUM> comprise an opening in the housing of a device <NUM> configured to collect light <NUM>, e.g., associated with light communications, and input the collected light to the TIR structure <NUM> of the waveguide <NUM>. Each waveguide entrance <NUM> is laterally offset from the location of the diffusive element <NUM>/sensor <NUM>, where light <NUM> collected at one entrance propagates along the waveguide <NUM> to get to the sensor <NUM>. In some embodiments, the waveguide entrances <NUM> may comprise just the openings. In other embodiments, the waveguide entrances <NUM> may include a collection element <NUM>, e.g., a lens or lens system (e.g., <FIG>), where the collection element <NUM> is configured to increase the amount of external light <NUM> that is input into the waveguide <NUM>. When the waveguide entrance <NUM> includes a collection element <NUM>, generally the collection element <NUM> will have a wide Field of View (FoV) to increase the amount of collected light. Exemplary lenses include, but are not limited to a Fresnel lens 124a (<FIG>), a plano-convex lens 124b (<FIG>), etc. It will be appreciated that the use of any collection element <NUM> in one or more waveguide entrances <NUM> is optional.

The waveguide <NUM> may further comprise a light guiding element <NUM> opposite a corresponding waveguide entrance <NUM> that is configured to facilitate the propagation of the collected light from the waveguide entrance <NUM> along the TIR structure <NUM>. In one exemplary embodiment, the light guiding element <NUM> comprises a reflector configured to reflect the light collected by the corresponding waveguide entrance <NUM> at a total internal reflection angle to facilitate the propagation of the collected light along the TIR structure <NUM>. One exemplary reflector includes an angled mirror <NUM>, as shown in <FIG>, which reflects the incident light at an angle θ equivalent to the entry angle θ. To implement the total internal reflection, this angle θ may be equivalent to the total internal reflection angle for the waveguide <NUM>. Additional reflectors include, but are not limited to, a plurality of etched surfaces, as shown in <FIG>, mirror print or a material with a lower refractive index so that the angle θ of the light exiting the light guiding element <NUM> is the same as the angle of incidence on the light guiding element <NUM>, etc. In another exemplary embodiment, the light guiding element <NUM> comprises a bend proximate the corresponding waveguide entrance <NUM>, e.g., as shown in <FIG>, where the bend is configured to direct the collected light at the total internal reflection angle to facilitate the propagation of the collected light along the TIR structure <NUM>.

The exemplary light detection systems <NUM> of <FIG> and <FIG> show a single waveguide entrance <NUM> providing light to a single sensor <NUM>. The solution presented herein, however is not so limited. Alternative embodiments may include multiple waveguide entrances <NUM> that collect light for propagation along one or more corresponding waveguides <NUM> to the sensor <NUM>. In some embodiments, multiple waveguide entrances <NUM> use the same waveguide <NUM> to propagate the light to a single sensor <NUM>. In other embodiments, multiple waveguides <NUM> propagate light from one or more waveguide entrances <NUM> to a single sensor <NUM>. In addition, the location of one or more waveguide entrances <NUM> relative to the sensor may be selected to reduce noise and/or increase the signal strength. For example, the lateral spacing between multiple waveguide entrances <NUM> and the corresponding sensor <NUM> may be configured such that the light entering the sensor <NUM> adds constructively. Alternatively or additionally, the lateral spacing between multiple waveguide entrances <NUM> and the corresponding sensor <NUM> may be configured such that interference present in the collected light adds destructively or neutrally.

<FIG> show exemplary embodiments with multiple waveguide entrances <NUM> channeling light to a single sensor <NUM>. As shown in <FIG>, light sensor <NUM> may detect light originating from multiple waveguide entrances <NUM>, e.g., a first waveguide entrance 116a and a second waveguide entrance 116b located on opposing sides of the TIR waveguide <NUM> from the light sensor <NUM>. In this exemplary embodiment, waveguide entrance 116a and lens 124a collects light 140a, light guiding element 118a establishes the TIR angle for the collected light to propagate 126a the collected light along the TIR structure <NUM> towards the sensor <NUM> in a first direction. Further, waveguide entrance 116b and lens 124b collects light 140b, light guiding element 118b establishes the TIR angle for the collected light to propagate 126b the collected light along the TIR structure <NUM> towards the sensor <NUM> in a second direction opposite the first direction. The diffusive element <NUM> disrupts the propagation 126a, 126b, from both directions, of the light collected by the waveguide entrances 116a, 116b for detection by sensor <NUM>.

In <FIG>, light sensor <NUM> detects light originating from three waveguide entrances: 116a, 116b, 116c. In this exemplary embodiment, TIR waveguide <NUM> comprises multiple legs 110a, 110b, 110c, each of which respective propagate 126a, 126n, 126v light in different directions from the corresponding entrance 116a, 116b, 116a towards the light sensor <NUM>, where the diffusive element <NUM> disrupts the propagating light to enable detection by the light sensor <NUM>. It will be appreciated that the multiple legs 110a, 110b, 110c of <FIG> may represent different waveguides <NUM> that collectively channel collected light to a single sensor <NUM>.

While exemplary detection systems <NUM> are shown as having one to three waveguide entrances <NUM>, it will be appreciated that the detection system <NUM> disclosed herein may include any number of waveguide entrances <NUM>. In general, detection system <NUM> may comprise any number of waveguide entrances <NUM> and/or waveguides <NUM>, where each entrance <NUM> is located at a location of the waveguide <NUM> laterally displaced from the sensor <NUM> and diffusive element <NUM>, such that light communications are implemented using fewer sensors <NUM> than waveguide entrances <NUM> and/or waveguides <NUM>. In so doing, the solution presented herein reduces the number of sensors <NUM> associated with light communications, while simultaneously improving the quality of the light communications, e.g., by increasing the amplitude of the detected light. Further, by using waveguides <NUM> to direct the light from multiple entrances <NUM> to the sensor(s) <NUM>, the solution presented herein relaxes limitations previously placed on the sensor(s) <NUM>, e.g., the size, power, etc., because the sensor(s) <NUM> may now be placed at any suitable location in the device <NUM>.

<FIG> shows an exemplary method <NUM> of detecting light associated with light communications. The method <NUM> comprises collecting light configured for the light communications via one or more waveguide entrances <NUM> disposed at different first locations along a total internal reflection TIR waveguide <NUM> (block <NUM>), where the light comprises a plurality of wavelengths λ<NUM> - λN. The TIR waveguide <NUM> comprises a TIR structure <NUM> having a first index of refraction n<NUM>, where a second index of refraction n<NUM> and/or n<NUM> adjacent the TIR structure <NUM> is less than the first index of refraction n<NUM> such that light entering the TIR waveguide <NUM> propagates along the TIR structure <NUM>. The method <NUM> further comprises disrupting the propagation of the light along the TIR waveguide <NUM> using a diffusive element <NUM> disposed along an internal edge of the TIR structure <NUM> at a second location of the TIR waveguide <NUM> (block <NUM>). The second location is offset (laterally) along the TIR waveguide <NUM> from each of the one or more first locations. The method <NUM> further comprises detecting the disrupted light using one or more light sensors <NUM> disposed adjacent an edge of the TIR structure <NUM> opposite the second location and spaced from the diffusive element <NUM> by a thickness t of the TIR structure <NUM> (block <NUM>). Each of the light sensor(s) <NUM> detects a subset λm - λM of the plurality of wavelengths λ<NUM> - λN of the disrupted light, where the subset λm - λM of the plurality of wavelengths λ<NUM> - λN comprises one or more wavelengths totaling fewer than the plurality of wavelengths, i.e., ((M - m) + <NUM>) < N.

As mentioned above, the light detection system <NUM> of the solution presented herein may be implemented in and/or as part of any number of wireless devices <NUM> that implement light communications. Exemplary devices <NUM> may be worn and/or carried by a user, where the light detection system <NUM> disclosed herein may be internal to a housing of a device <NUM>, disposed partially internally to the device <NUM> and partially integrated with/disposed on the housing of the device, or implemented on an external surface of the housing of the device <NUM>.

<FIG> show an exemplary smart phone device <NUM>. Smart phone device <NUM> may comprise waveguide entrances <NUM> around the display <NUM> along the perimeter of the housing <NUM>, as shown in <FIG>. Alternatively or additionally, device <NUM> may comprise waveguide entrances on a back of the smart phone device <NUM>, as shown in <FIG>, and/or integrated with the display <NUM>, as shown in <FIG>. It will be appreciated that the integration of waveguide entrance(s) <NUM> with the display <NUM> may include placing the waveguide entrance(s) <NUM> below a transparent type of display <NUM>, e.g., an Active-Matrix Organic Light-Emitting Diode (AMOLED) screen/display. It will further be appreciated that the waveguide solution presented herein enables multiple waveguide entrances <NUM> to be placed at any suitable location on the smart phone device <NUM>, besides those explicitly shown, while simultaneously enabling a single sensor <NUM> (or fewer sensors <NUM> than there are waveguide entrances <NUM>), placed in the device <NUM> at any location suitable for the sensor <NUM>, to detect the light from the multiple entrances <NUM>, and thus enable the light communications.

In another exemplary embodiment, the device <NUM> comprises a watch, as shown in <FIG>. For the watch embodiment, the waveguide entrances <NUM> may be placed at any suitable location, e.g., around the face <NUM> of the watch and/or in a bezel of the watch, integrated with the display of the watch (not shown), as part of the face of the watch (not shown), etc. In yet another exemplary embodiment, shown in <FIG>, the device <NUM> comprises glasses, where the waveguide entrances <NUM> are disposed along a frame <NUM> of the glasses. In addition to the smartphone, watch, and glasses implementations discussed herein, the solution presented herein is also applicable to any wireless devices implementing light communications. For example, other exemplary devices <NUM> include, but are not limited to, hearing aids, fitness monitors, cellular telephones, laptop computers, tablets, etc..

The present invention may, of course, be carried out in other ways than those specifically set forth herein.

Claim 1:
A detection system (<NUM>) for light communications, the detection system comprising:
a total internal reflection, TIR, waveguide (<NUM>) comprising:
a first structure (<NUM>) having a first index of refraction, wherein a second index of refraction adjacent the first structure is less than the first index of refraction such that light for light communications input to the TIR waveguide at one or more waveguide entrances (<NUM>) propagates along the TIR waveguide within the first structure, said light comprising a plurality of wavelengths;
a diffusive element (<NUM>) disposed along an internal edge of the first structure at a first location of the TIR waveguide offset from one or more second locations of the one or more corresponding waveguide entrances; and
a plurality of wavelength specific light sensors (<NUM>) disposed adjacent an edge of the first structure opposite the first location and each spaced from the diffusive element by a thickness of the first structure, wherein each of said plurality of wavelength specific light sensors detects a different subset of the plurality of wavelengths of light disrupted by the diffusive element.