Embedding data into light

1. A system comprising:

a non-light-emitting element disposed so as to transmit and/or reflect light from a light-emitting element, the non-light-emitting element having a variable transmission or reflectance respectively, and the non-light-emitting element being separate from the light-emitting element at least in that the non-light-emitting element and the light-emitting element are not controlled by a same device, wherein the light-emitting element is selected from natural light, display device or a household luminaire; and

a controller configured to control the transmission or reflectance of the non-light-emitting element in order to temporally modulate the light, wherein the non-light-emitting element uses an electrophoretic or suspended particle technology selected from e-INK or smart glass, to thereby embed data into the transmitted and/or reflected light in a manner imperceptible to human vision;

wherein the non-light-emitting element is arranged to transmit or reflect the light towards a mobile detecting apparatus housed in a unit separate from the light-emitting element and non-light-emitting element, in order for the embedded data to be detected by the detecting apparatus;

wherein the transmission or reflectivity of the non-light-emitting element is variable in that across an area of the non-light-emitting element the transmission or reflectance can be varied only uniformly, such that said modulation is performed by temporally varying the transmission or reflectance uniformly across said area.

2. The system of claim 1 , wherein the light has a primary function that is perceivable to a human user, and the embedding of said data is a secondary function not perceivable to the user.

3. The system of claim 1 , wherein the light emitting element does not embed data in the light it emits, such that the only modulation for purpose of embedding data in the light is by said modulation of the transmission or reflectance of the non-light-emitting element.

4. The system of claim 1 , wherein the light is ambient light illuminating an environment occupied by a user.

5. The system of claim 4 , wherein the light-emitting element is a luminaire.

6. The system of claim 1 , wherein the light-emitting element is a manmade light source.

7. The system of claim 6 , wherein the light-emitting element is a display screen and the non-light emitting element is a retrofitted layer retrofitted over the display screen.

8. The system of claim 1 , wherein the light emitting element is separated from the non-light emitting element by no less than 10 cm of air or free space between any two respective points on the light-emitting element and non-light emitting elements, such that the light propagates through the air or free space before being transmitted or reflected by the non-light-emitting element.

9. The system of claim 1 , wherein the non-light-emitting element is one of, or a retrofitted layer retrofitted over one of:

a window;

a surface of a user terminal, kitchen appliance, item of furniture, building, vehicle, or item of clothing or other wearable item; or

a signpost, billboard or other signage.

10. The system of claim 1 , wherein the modulation consists only of temporally varying the transmission or reflectance uniformly across the entirety of said area.

11. The system of claim 1 , wherein the light is in the visible spectrum, and the controller is configured to perform said modulation at a frequency beyond human visual perception.

12. The system of claim 11 , wherein the data comprises a sequence of symbols, said frequency being a symbol frequency of the symbols, and wherein the symbol frequency is greater than or equal to 100 Hz.

13. The system of claim 1 , wherein the mobile detecting apparatus is selected from a smartphone, tablet and laptop.

14. A system comprising:

a non-light-emitting element disposed so as to transmit and/or reflect light from a light-emitting element, the non-light-emitting element having a variable transmission or reflectance respectively, and wherein the non-light-emitting element is applied to a surface receiving light from the light-emitting element wherein the light-emitting element is selected from natural light, display device or a household luminaire; and

a controller configured to control the transmission or reflectance of the non-light-emitting element in order to temporally modulate the light, wherein the non-light-emitting element uses an electrophoretic or suspended particle technology selected from e-INK or smart glass, to thereby embed data into the transmitted and/or reflected light in a manner imperceptible to human vision;

wherein the non-light-emitting element is arranged to transmit or reflect the light towards a mobile user apparatus, wherein the mobile user apparatus is selected from a smartphone, tablet and laptop, in order for the embedded data to be detected by the mobile user apparatus;

wherein the transmission or reflectivity of the non-light-emitting element is variable in that across an area of the non-light-emitting element the transmission or reflectance can be varied only uniformly, such that said modulation is performed by temporally varying the transmission or reflectance uniformly across said area.

15. The system of claim 14 , wherein the surface is selected from a window a user terminal, TV, kitchen appliance, item of furniture, building, vehicle, item of clothing, signpost or billboard.

16. A signaling method comprising:

using a non-light-emitting element to transmit and/or reflect visible light emitted from a light-emitting element, wherein the light-emitting element is selected from natural light, user terminal or a household luminaire, the non-light-emitting element having a variable transmission or reflectance respectively, and the non-light-emitting element being separate from the light-emitting element at least in that the non-light-emitting element and the light-emitting element are not controlled by a same unit, wherein the transmission or reflectivity of the non-light-emitting element is variable in that across an area of the non-light-emitting element the transmission or reflectance can be varied only uniformly, such that said modulation is performed by temporally varying the transmission or reflectance uniformly across said area;

controlling the transmission or reflectance of the non-light-emitting element in order to modulate the light, wherein the non-light-emitting element uses an electrophoretic or suspended particle technology selected from e-INK or smart glass, at a frequency beyond human visual perception, and to thereby imperceptibly embed data into the light in a manner imperceptible to human vision;

directing the transmitted or reflected the light towards a mobile detecting apparatus housed in a unit separate from the light-emitting element and non-light emitting element, such that the embedded data is detected by the detecting apparatus.