Patent Application
20060067707
This invention relates to visual light communication systems and more particularly to systems and methods for increasing data communication bandwidth.
The use of infrared (IR) signals has become commonplace for transmitting line of sight information from one place to another. Such IR signaling is employed, for example, in hand-held controls used for turning television sets and other electronic devices on-off and for changing channels, volume control, etc. These devices are specially designed for communications there between and such communications, since they are in the IR band, are not meant for general purpose communications.
Light in the visual range is now being investigated for communication purposes. Such systems, known as visual light communication (VLC) systems, use commonly available light sources, such as LED and LCD displays for communication purposes. Thus, a device that serves the purpose of displaying information (or even simply providing illumination) can also be simultaneously used to transmit information to one or more light receptacles. In a VLC system data is modulated onto the visible light coming from the light source and any detector (demodulator) that is in the path of the visible light can receive that data.
As with most communication systems, the bandwidth soon fills thus limiting the data transfer rate between the light source and the light detector. If VLC systems are to become a source for data transfer to and from mobile devices, such as PDA's, computers, and the like, it is important that the data transfer bandwidth be as high as possible.
In one embodiment, color sensors allow multiple data transfer channels to occur between a light source and a light detector. Light of differing wavelengths can be detected simultaneously and the modulated data on each wavelength delivered can be independently and simultaneously processed, and, if desired, selectively to an end-user.
In another embodiment, different colors can be used for different directions of communication thereby allowing for simultaneous bi-directional communication.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized that such equivalent constructions do not depart from the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
The outputs of the modulators modulate the light of each driver independently such that red driver 22R is modulated by data on input DATA 1, green driver 22G is modulated by data on input DATA 2, while blue driver 22B is modulated by data on input DATA 3. The outputs of the drivers then drive the three light sources 23B, 23G and 23R of light source 23. Note that in the embodiment shown each light source 23B, 23G, 23R is shown as a single source, but in reality each source can be a plurality of individual light sources, such as LEDs, LCDs, etc.
Broken lines 24B represent the modulated light from light source 23B while broken lines 24G represent the modulated light from source 23G and likewise broken lines 24R represent the modulated light from light source 23R. This light is in the visual range and is detected, in one embodiment, by color sensor 26 which is a sensor utilizing filters.
The output of color sensor 26, which sensor could be on a color-by-color basis, or integrated for several colors, is separated with respect to the various light frequencies. Accordingly, blue modulated light is provided to demodulator 27B, green modulated light is provided to demodulator 27G, while red modulated light is provided to demodulator 27R. The outputs of these three demodulators then recover the data from input DATA 1, input DATA 2, input DATA 3. Note that device 13 can be a mobile device coming into proximity of light source 11 from time to time, or it can be stationary with respect to light source 11.
Assuming one channel is selected in demodulator, that channel is provided to display input/output 18 for communal (or private) display to a user. The user could then input information via input/output 18 which data then is provided to modulator 31 and LED driver 32. LED driver 32 then drives light source 33 having a specific color 34 which color is different from the colors currently being used for the direction from device 16 to device 17. These selected colors can be on a permanent bases, such that, for example, yellow is always used from device 17 to device 16, while red is always used from device 16 to device 17.
The system could also be set so that selector 302 determines which color is coming in the direction towards device 17 and then controls light source 33 so that a different color is used in the reverse direction. In any event, the color going from device 17 to device 16 is a different color than is used from device 16 to device 17 thereby allowing simultaneously transmitted bi-directional modulation. Color sensor 36 provides the proper color modulated light to modulator 37 which in turn provides the data from input/output 18 to high speed data network 302. Note that high speed data network 301 is only necessary if, in fact, the information is to go beyond device 16. In some situations, the information goes back and forth between device 16 and device 17 without need for delivery to any further destination.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
