PATENT ABSTRACT
A method for communicating with a vehicle has a generator for producing a data stream that can indicate, street sign information, house number, lead vehicle information, traffic information, oncoming vehicle information, juxtaposed vehicle information, a voice channel, etc. vehicle information can indicate braking, low beam requests, direct or indirect traffic flow information, adjacency, partial adjacency, or presence of nearby vehicles, etc. This signal is generated by at least one of: the sign, house number, oncoming vehicle, lead vehicle, operator of the lead vehicle, operator of the oncoming vehicle, operator of the juxtaposed vehicle, a traffic control system. A device for generating such data streams is discussed, as well as, a device for receiving such data streams. Information pertinent to the people in the vehicles or operation of the vehicle can be modulated on the link.

PATENT DESCRIPTION
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application, Ser. No. 60/792,525, filed 17 Apr. 2006, the contents of which are hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to communications systems, and in particular, to systems communicating to or from vehicles using modulated electromagnetic radiation in the visible, infrared or other nearby spectra. 
         [0004]    2. Description of Related Art 
         [0005]    Driving a motor vehicle involves sending and receiving messages and signals of various types. Stoplights, flashing warning lights, detour signs and the like give the driver immediate driving information and instructions. Brake lights and turn signals are illuminated to alert nearby drivers of actions that are being taken or are about to be taken by a driver. 
         [0006]    Brake lights and turn signals on many motor vehicles are implemented as LED arrays. Referring to  FIG. 1  a schematic representation of an LED array  12  and power supply  18  are illustrated. LED array  12  is connected to the positive potential +V of supply  18  and ground. LED array  12  is an array of serially connected LEDs connected anode to cathode. The positive potential of supply  18  connects to the anode of the first LED of array  12  while the last one has its cathode connected to ground. The LEDs  12  are arranged to provide a voltage drop across the entire LED array  12  equal to the system voltage of the application in which the LED array  12  is installed. In typical vehicle applications the system voltage is commonly 6, 12, 24, or 50 volts. When the proper voltage is applied to the LED array  12 , it will illuminate. LED arrays such as this are used in automotive applications typically for marker, brake, and turn signal lamps. 
         [0007]    The information that can be conveyed by these traffic signals and vehicle signals is relatively limited. On the one hand, the media is limited to the visual. Also, the information content is relatively small and the sender does not have the opportunity to send more complicated messages. 
         [0008]    In some cases a driver may want to receive more complex information. For example, if a detour is necessary the driver may want to know more about the appropriate detour route. If traffic congestion lies ahead, a driver would like to know about such difficulties in advance and receive sufficient information to plot a course avoiding such congestion. The driver may use a radio to get traffic reports, but these are often not comprehensive and current, are not available continuously, and may report only the most serious congestion. 
         [0009]    Drivers can receive information from various wireless devices such as cell phones, wirelessly connected PDAs, CB radios, walkie-talkies, etc. These devices are not however well adapted to provide information about the driver&#39;s immediate surroundings. Also, such devices may require a driver to operate a keyboard or control panel, which may not be feasible or safe while driving. 
         [0010]    See also, U.S. Pat. Nos. 3,601,792; 3,604,805; 3,790,780; 3,941,201; 4,670,845; 5,295,551; 5,568,136; 5,635,920; 5,708,415; 5,736,935; 5,914,652; 5,986,575; 6,243,026; 6,369,720; 6,654,681; 6,850,170; 6,885,282; and 6,943,677. 
       SUMMARY OF THE INVENTION 
       [0011]    In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a communications arrangement for transmitting a message from a vehicle. The vehicle has an operator controllable assembly operable by a vehicle occupant for selectively energizing a plurality of electrical connectors that connect to operator controllable vehicle lights including one or more of turn signals, brake lights, headlights, and parking lights. The arrangement has a processor with a modulator and is coupled to the operator controllable assembly. The modulator is adapted to be connected to one or more of the plurality of connectors to affect the one or more of turn signals, brake lights, headlights, and parking lights. The modulator has an input adapted to receive an occupant-initiated control signal and produce in response an encoded main signal selectively modulated at or above a critical flashing frequency or with a pulse duration that is human imperceptible 
         [0012]    In accordance with yet another aspect of the invention, there is provided a communications arrangement for transmitting a message from a vehicle having one or more externally detectable signalers. The arrangement has a processor with a vehicle sensitive apparatus for producing a dynamic signal signifying traveling information associated with dynamic operation of the vehicle. The processor includes a modulator coupled to the vehicle sensitive apparatus and adapted to be coupled to the one or more signalers for sending thereto in response to the dynamic signal a main signal modulated and encoded to indicate at least some of the traveling information. This modulation is conducted at or above a critical flashing frequency or with an inter-pulse blanking that is human imperceptible. 
         [0013]    In accordance with still yet another aspect of the invention, there is provided a communications method for transmitting a message from a vehicle having one or more externally detectable signalers. The method includes the step of producing a dynamic signal signifying traveling information associated with dynamic operation of the vehicle. Another step is sending to the one or more signalers in response to the dynamic signal a main signal modulated and encoded to indicate at least some of the traveling information. This modulation is conducted at or above a critical flashing frequency or with an inter-pulse blanking that is human imperceptible. 
         [0014]    In accordance with a further aspect of the invention, there is provided a system for transmitting a message to a vehicle. The system has a traffic signaling device for providing a dynamic traffic information signal relevant to driving the vehicle. The signaling device has a modulator for producing a main signal modulated and encoded according to the dynamic traffic information signal. This modulation is conducted at or above a critical flashing frequency or with a pulse duration that is human imperceptible. Also included is a receiver mounted in the vehicle for receiving the dynamic traffic information signal. The receiver has a luminance sensing device for producing a detection signal. The system also has a utilization device mounted in the vehicle and coupled to the receiver for using the detection signal. 
         [0015]    In accordance with yet another further aspect of the invention, a method is provided employing a traffic signaling device for transmitting a message to a vehicle. The method includes the step of providing a dynamic traffic information signal relevant to driving the vehicle. Another step is producing a main signal modulated and encoded according to the dynamic traffic information signal. This modulation is conducted at or above a critical flashing frequency or with a pulse duration that is human imperceptible. The method also includes the step of receiving in the vehicle the dynamic traffic information signal and producing therefrom a detection signal. Another step is using the detection signal in the vehicle. 
         [0016]    In accordance with still yet another further aspect of the invention, there is provided a system for transmitting a message to a vehicle. The system has a signaling device for providing a travel information signal relevant to driving the vehicle. The signaling device has a modulator for producing a main signal modulated and encoded according to the travel information signal. This modulation is conducted at or above a critical flashing frequency or with a pulse duration that is human imperceptible. Also included is a receiver mounted in the vehicle for receiving the travel information signal. The receiver has a luminance sensing device for producing a detection signal. The system also has a utilization device mounted in the vehicle and coupled to the receiver for using the detection signal. 
         [0017]    In accordance with another aspect of the invention, there is provided a system for exchanging messages among a plurality of vehicles. Each of the vehicles has one or more externally detectable signalers. The system has in each vehicle a transceiver including a processor, a receiver, and a utilization device. The processor has a vehicle sensitive apparatus for producing a dynamic signal signifying traveling information associated with dynamic operation of the vehicle. The processor includes a modulator coupled to the vehicle sensitive apparatus and adapted to be coupled to the one or more signalers for sending thereto in response to the dynamic signal a main signal modulated and encoded to indicate at least some of the traveling information. The transceiver also includes a receiver mounted in the vehicle and having a luminance sensing device for producing a detection signal in response to receipt of the main signal sent from the one or more externally detectable signalers of other ones of the vehicles. The transceiver also includes a utilization device mounted in the vehicle and coupled to the receiver for using the detection signal. 
         [0018]    In accordance with another aspect of the invention, a method is provided for exchanging messages among a plurality of vehicles. Each of the vehicles has a transceiver, a luminance sensing device, and one or more externally detectable signalers. The method includes the step of producing a dynamic signal signifying traveling information associated with dynamic operation of a given one of the vehicles. Another step is sending to the one or more signalers in response to the dynamic signal a main signal modulated and encoded to indicate at least some of the traveling information. The method also includes the step of producing a detection signal from the luminance sensing device in response to receipt thereof of the main signal sent from the one or more externally detectable signalers of other ones of the vehicles. Another step is using the detection signal. 
         [0019]    By employing equipment and methods of the foregoing type improved vehicle communications is achieved. In one embodiment a microcontroller is programmed to produce a modulated main signal when powered. This processor can be used to drive an LED array, for example. In such a case, the LED array provides a predetermined modulated light signal signifying a message such as “stop” or “left turn”, for a processor associated with a stoplight or left turn signal, respectively. The processor can be built into a replaceable vehicle light or can be contained on a separate printed circuit board located at some distance from the vehicle light. Also, the presently disclosed equipment can be used to modulate light from headlamps, tail lamps, fog lamps, running lights, etc. Also, these vehicle lights can emit light in the visible, ultraviolet or infrared range. 
         [0020]    To avoid objectionable flickering, the modulation repetition rate (normally a pulse repetition rate) will be kept higher than 15 Hz, a rate that is referred to herein as a critical flashing frequency. In some cases the repetition rate may be less than the critical flashing frequency but the pulse duration will be kept small enough so as to not be human perceptible. For the purposes of this disclosure a pulse duration of less than 30 ms will be considered human imperceptible. On the other hand, in most embodiments, superior performance is achieved if the pulse repetition rate is kept higher than 150 Hz or the pulse duration is kept less than 3 ms. 
         [0021]    In some embodiments modulation is dictated by a separate data source that is either dedicated to one or more specific lights or is a central source for controlling the modulation of all lights that might be modulated. For cases where more complex messages are desired, the data source can be a PDA or an operator&#39;s panel having certain buttons or a keypad for selecting specific messages that are to be encoded in the modulated signal. In some of these cases the data source can be tied into a central electronic control system similar to that found on conventional vehicles. In still other cases the modulation may be produced by a microphone to implement a walkie-talkie feature. 
         [0022]    Embodiments are anticipated where the data source can communicate its selection signal by modulating the current on a power line using either an electromagnetic coupler, a current shunt (ohmic coupler), capacitive coupling, switching into the power line (electronic or relay) or the like. In some cases the processor can modulate a power line with troubleshooting or status information. For example a defective vehicle light can produce a failure signal. Alternatively, a functioning light can produce a regular status or heart beat signal that verifies proper operation of the vehicle light. These data signals can be captured by a portable diagnostic device, for example, a device that plugs into a power utility socket (cigarette lighter socket). The portable diagnostic tool may capture these signals in order to drive a simple display indicating the location and nature of a fault. 
         [0023]    In some embodiments the vehicle will have a receiver that may be as simple as a directional light sensor that is sensitive to the spectrum of expected transmitters. The sensor can be designed to capture modulated emissions from other vehicles, traffic signals, roadside signalers, house-mounted devices for indicating house number, etc. The transmitted information can be simple vehicle information (braking, turning left, etc.). Traffic signalers and roadside signs can also include information about the status of the traffic signal or can include more complicated information such as detour information, public service announcements, etc. The received information can be decoded and presented as synthesized speech, a simple visual or audible alarm, or a character display. 
         [0024]    In still other embodiments the sensor may be an image sensing device such as a CCD, video camera, or the like. In such a case, the receiving system can concentrate its attention to certain visual elements in the field of view. For example, the system can notice that modulation of a characteristic type is occurring in certain regions of the field of view. Frame to frame changes covering a significant region can be detected and recorded over time to determine the coding of a modulated signal. In some embodiments objects matching certain templates can be targeted for special attention as likely sources of modulated signals. In some cases the changes are averaged over a predetermined n×m pixel matrix to reduce the effect of spurious noise or the effect produced by an edge moving across a field of view. 
         [0025]    In another embodiment a family of vehicles may have transceivers for exchanging traffic information. For example a vehicle may have a GPS that is used for recording the travel history of a vehicle, which may reveal traffic congestion. This information can be exchanged between vehicles and relayed to still other vehicles to develop a shared database of traffic information. This traffic information can be used to display regions of congestion and allow a driver to map alternate routes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0026]    The above brief description as well as other objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein: 
           [0027]      FIG. 1  is a schematic diagram of an LED array that is part of the prior art; 
           [0028]      FIG. 2  is a schematic block diagram of apparatus in accordance with principles of the present invention; 
           [0029]      FIG. 3  is a perspective view of an LED assembly showing installation in a vehicle; 
           [0030]      FIG. 4  is perspective view of a vehicle fitted with LED assemblies as shown in  FIG. 3 ; 
           [0031]      FIG. 5  is a flow chart associated with the processor of  FIG. 2 ; 
           [0032]      FIGS. 6A and 6B  are perspective views of stand-alone signalers incorporating the apparatus of  FIG. 2 ; 
           [0033]      FIG. 7  is a schematic block diagram of apparatus that is an alternate to that of  FIG. 2  and including a separate data source; 
           [0034]      FIG. 8  is a flowchart associated with the processor of  FIG. 7 ; 
           [0035]      FIG. 9  is a schematic block diagram of apparatus that is an alternate to that previously illustrated; 
           [0036]      FIG. 10  is a schematic block diagram of apparatus that is part of a system that is an alternate to that previously illustrated; 
           [0037]      FIG. 11  is a flowchart showing image processing being performed by the system of  FIG. 10 ; 
           [0038]      FIG. 12A  is an illustration of an image frame captured with the system of  FIG. 10  and being subjected to template matching; 
           [0039]      FIG. 12B  illustrates video production for a scanline traversing the image of  FIG. 12A ; 
           [0040]      FIG. 12C  is an illustration of an image frame being analyzed for matching templates with a process that is an alternate to that of  FIG. 12A ; 
           [0041]      FIG. 12D  is a schematic illustration of the template matching process associated with  FIGS. 12A and 12C ; 
           [0042]      FIG. 12E  is a composite illustration showing the outputs produced with the template of  FIG. 12D  when scanning across the image of  FIG. 12C ; 
           [0043]      FIG. 13  illustrates a blanked image resulting from the template matching of  FIG. 12E ; 
           [0044]      FIG. 14  is a schematic diagram of diagnostic apparatus that cooperates with the processors of  FIG. 2 ,  7 , or  9 ; 
           [0045]      FIG. 15  is a perspective view of a diagnostic tool that may be used in connection with previously illustrated apparatus, including the apparatus of  FIG. 14 ; 
           [0046]      FIG. 16  is a schematic diagram illustrating a signaling device that is part of a system arranged to cooperate with the apparatus of the other Figures; 
           [0047]      FIG. 17  is a cross-sectional view of apparatus employed in the arrangement of  FIG. 16 ; 
           [0048]      FIG. 18  is a schematic block diagram of intervehicle communications system employing apparatus that is an alternate to that previously illustrated; 
           [0049]      FIG. 19  is a schematic block diagram of a system that is an alternate to that of  FIG. 18 ; 
           [0050]      FIG. 20A  is an elevational view of ac motorcycle fitted with a plurality of transmitters; and 
           [0051]      FIG. 20B  is a plan view of the motorcycle of  FIG. 20A . 
           [0052]      FIG. 21  is schematic diagram of another embodiment showing a more general case of modulated light being transmitted from a building or sign; 
           [0053]      FIG. 22  is a plan diagram showing the transmitter of  FIG. 21  incorporated in a fuel sign and communicating with a vehicle; 
           [0054]      FIG. 23A  shows a standard 8-bit word format that may be used with the processor of  FIG. 2 ; 
           [0055]      FIG. 23B  shows an 8-bit format word with added redundancy for error detection or correction purposes that is an alternate to that of  FIG. 21A ; 
           [0056]      FIG. 24A  is a more detailed schematic block diagram of an modulator arrangement for use in systems such as those of  FIG. 10  or  18 ; 
           [0057]      FIG. 24B  shows an improved format word as transmitted by the circuit of  FIG. 22A ; 
           [0058]      FIG. 25A  shows a word format that is an alternate to that of  FIG. 22B ; 
           [0059]      FIG. 25B  shows a word format that is an alternate to those previously illustrated; and 
           [0060]      FIG. 26  shows a word format that is an alternate to those previously illustrated. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0061]    Referring to  FIG. 2 , previously mentioned LED array  12  is shown connected with electrical connectors  19  and employing LEDs  12 C connected in series (cathode to anode), but may also be arranged in parallel or series/parallel configurations. Terminal VCC of processor  10  is connected to potential +V of supply  18  and terminal GND of processor  10  is connected to ground. Processor  10  is a microcontroller having memory  14 . Processor  10  includes a modulator which is implemented in software to be described presently, although other embodiments may employ a separate discrete modulator. Terminal OUT of processor  10  is connected to the input of amplifier  16  whose output is connected to the anode end of LED array  12  whose opposite cathode end is connected to ground. 
         [0062]    Referring to  FIG. 3 , the previously mentioned LED array  12  is shown assembled into a disc-shaped fixture  13 . Previously mentioned LEDs  12 C are shown set into openings of fixture  13 , to be visible through a non-opaque plastic cover  15  attached to fixture  13 . Fixture  13  has on its rear side a number of pins (not shown) designed to fit into a socket (also not shown). 
         [0063]    As shown in  FIG. 4 , fixture  13  is designed to be used as a taillight/brake light in vehicle  20 . While vehicle  20  a shown as an automobile, other vehicle types are contemplated, including trucks, vans, minivans, SUVs, motorcycles, bicycles, trailers, aircraft, watercraft, etc. Fixture  13  is mounted to vehicle  20  by any well known fastening method. Pins (not shown) on fixture  13  will plug into a vehicle socket (not shown). 
         [0064]    Referring again to  FIG. 3 , conventional vehicle wiring  18 A and  18 B would ordinarily be connected directly to fixture  13  to illuminate LEDs  12 C when, for example, the brake pedal is depressed. (The brake pedal, turn signal lever, light switches etc. in the vehicle&#39;s passenger compartment for operating various externally observable lights are herein referred to as an operator controllable assembly (or vehicle sensitive apparatus) for providing an operator initiated signal for controlling operator controllable vehicle lights.) Specifically, wire  18 B is grounded and wire  18 A supplies potential +V when the operator of vehicle  20  depresses the brake pedal (to produce what is herein referred to as a dynamic signal signifying traveling information associated with dynamic operation of the vehicle). This normal wiring is shown modified and connected to printed circuit board  30  (PCB  30 ) by means of wires  17 A,  17 B, and  17 C whose proximal ends are soldered into holes on board  30 . 
         [0065]    Board  30  is installed by splicing into the wires  18 A and  18 B which ordinarily connect to LED array  12 . In this Figure, wire  18 A was cut leaving fragment  18 A′ running to fixture  13 . The insulation is stripped from the cut ends of wires  18 A and  18 A′ to facilitate a wire wrap connection to the distal ends of PCB leads  17 A and  17 B, respectively. Also, the insulation is removed from a portion of wire  18 B to expose its conductor  18 B′ to allow a wire wrap connection to the distal end of PCB lead  17 C. Alternatively, these connections may be made using other methods such as soldering or the use of crimp connectors. In addition, a combination of connection methods may be used as well. 
         [0066]    Previously mentioned processor  10  is shown on PCB  30  as an integrated circuit microcomputer, and previously mentioned signal amplifier  16  is shown as a power transistor  16 A. Other components exist on PCB  30  but are not shown for simplification purposes. PCB  30  may be mounted in an enclosure  30 A with an opening to allow routing of PCB leads  17 A,  17  B, and  17 C in order to facilitate installation. Such an enclosure would provide protection for PCB  30  in a vehicle. This enclosure  30 A may be mounted to vehicle  20  at the fenders, quarter panels, passenger compartment, trunk or any other suitable location that will contain and protect the enclosure from the elements and road debris. 
         [0067]    Wire  18 A coming from potential +V of power supply  18  is connected through PCB lead  17 A to a trace (not shown) on PCB  30  to processor  10 ; specifically to terminal VCC previously shown in  FIG. 2 . Wire  18 A′ coming from LED array  12  is connected to the distal end of PCB lead  17 B using solder, wire wrap, or any other method of making an electrical connection. The proximal end of wire  17 B is similarly connected to PCB  30 , and then electrically connected by a trace (not shown) to the output of amplifier  16 , as was shown in  FIG. 2 . Wire  18 B is connected through PCB lead  17 C to a ground bus (not shown) on PCB  30  and thus to terminal GND of processor  10  as was shown in  FIG. 2 . 
         [0068]    The above wiring modifications accomplish the connection shown in  FIG. 2 ; that is, +V and ground are connected to processor  10  and the output of amplifier  16  connected to array  12 . These connections divert the current in wire  18 A that ordinarily flowed directly to LED array  12  so this current now flows to PCB  30  in order to intensity modulate LED array  12  as described below. 
         [0069]    The operation of the device shown in  FIGS. 2-4  is described as follows: When the brake pedal (not shown) of vehicle  20  is undepressed, power supply  18  does not apply potential +V to PCB  30  so LED array  12  remains off. When the vehicle operator depresses the brake pedal, potential +V of power supply  18  is provided to PCB through lead  17 A to terminal VCC of processor  10  (which may therefore be considered a modulator input for receiving an occupant-initiated control signal). Processor  10  is thereby powered and a predetermined pulse train is output as an encoded main signal from terminal OUT of processor  10  to amplifier  16  in a manner to be described presently. Signal amplifier  16  brings the pulse train to an appropriate power level to drive LEDs  12 C of LED array  12 . 
         [0070]    Referring to  FIG. 5 , the illustrated flowchart depicts the program running in processor  10  of  FIG. 2  for generating a pulse train. Once powered by brake pedal depression, step S 1  is immediately executed by processor  10  where it is initialized and prepares to execute the program stored in memory (memory  14  of  FIG. 2 ). In step S 2 , processor  10  uses programmed timers to produce a pulse train having a pattern based on a data sequence stored in memory. In step S 3 , the pulse train is output with the appropriate timing sequence via terminal OUT ( FIG. 2 ) of processor  10  to signal amplifier  16 . 
         [0071]    Processor  10  now loops from step S 3  to step S 1  and the process is repeated indefinitely until power is removed from terminal VCC of processor  10 . 
         [0072]    With the foregoing, full illumination of LED array  12  can represent a digital 1, while a digital 0 can be represented by the off state (dark) or a dimmed state. The pulse train may be generated using any one of a variety of communications protocols such as ISO OSI, EIA RS-232, and TCP/IP. Various other types of modulation techniques may be used as well, including PPM, PCM, etc. 
         [0073]    The nominal repetition rate of the pulse train is sufficiently high so that LED array  12  appears continuously on even though LEDs  12 C are actually modulated by the pulse train. In addition, the duty cycle of the pulse train may be selected to prevent noticeable dimming. This can be accomplished either by adjusting the duty cycle of the pulse train itself or by providing pulse bursts separated by sufficiently long intervals so that the overall duty cycle remains high. To prevent objectionable flickering the modulation will be kept at or above a critical flashing frequency. In some embodiments the pulse repetition rate of the modulation will be higher than 15 Hz or for superior performance, 150 Hz or more. Alternatively, the modulation can be conducted with a pulse duration that is human imperceptible, e.g., less than 30 ms; or for superior performance 3 ms or less. 
         [0074]    In any event the pulse repetition rate will be kept high enough to distinguish it from the flashing normally associated with turn signals, caution signals, and the like. Specifically, the pulse repetition rate will be kept higher than 15 Hz, a rate that is referred to herein as a critical flashing frequency. In some cases the pulse repetition rate may be less than the critical flashing frequency but the pulse duration will be kept small enough so as to not be human perceptible. For the purposes of this disclosure a pulse duration of less than 30 ms will be considered human imperceptible. On the other hand, in most embodiments, superior performance is achieved if the pulse repetition rate is kept higher than 150 Hz or the pulse duration is kept less than 3 ms. 
         [0075]    In this embodiment the pulse train output from terminal OUT of processor  10  is encoded with the message STOP. This message is appropriate for this LED array, which functions as a brake light. Other messages appropriate for LED arrays with various other intended uses will be described presently. 
         [0076]    In the embodiment just described, processor  10  is dedicated to producing a single encoded message appropriate for the intended function of modulated LED array  12 . For autonomous embodiments where the encoded message is determined locally without influence from some remote controller, such autonomous embodiments are referred to as “stand alone” embodiments. 
         [0077]    Referring to  FIGS. 6A and 6B , two stand alone arrangements are shown as one-piece bulbs used in place of a conventional bulb. This arrangement eliminates the need to modify the existing vehicle wiring. 
         [0078]      FIG. 6A  shows a replacement bulb having a housing base  29  supporting a platform  113  containing previously mentioned LED array  12 . Mounted inside housing base  29  is printed circuit board  130 , which contains the same circuitry previously shown in connection with PCB  30  of  FIG. 3 . In particular, PCB  130  is connected to receive power from the conventional contacts on housing base  29  and is arranged to modulate light emitters, namely, LED array  12 . The bulb in  FIG. 6A  is designed to replace a conventional bayonet-type bulb. 
         [0079]      FIG. 6B  shows a bulb similar to the bulb in  FIG. 6A  except housing base  27  is designed to thread into conventional screw sockets. An optional transparent lens  31  may be used to give the replacement bulb substantially the same physical outline as a conventional incandescent bulb. 
         [0080]    The bulbs shown in  FIGS. 6A and 6B  are driven in the manner just described in connection with PCB  30  and LED array  12  of  FIG. 3 . The bulbs repetitively output a predetermined message for purposes described herein. The bulbs may be mechanically keyed so as to fit only in their proper location; for example, a brake light bulb will be keyed to fit only in a brake light socket. Alternatively, keying may be provided electronically wherein information is received by a bulb from the socket base in which it is installed. The bulb would then operate in the appropriate manner depending on whether it is placed in a stop light, tail light, or other socket base. The stand alone embodiments described above send a single message repeatedly whenever energized. In some embodiments the bulb may encode the lighting assembly serial number (or a vehicle identification number), which will then be transmitted and used to identify the vehicle as part of larger network of vehicles. In other embodiments to be described presently it is desirable to send different messages at different times 
         [0081]    Referring to  FIG. 7 , previously described LED array  12  will again be used as a vehicle brake light. Processor  110  is similar to processor  10  shown in  FIG. 2  (and is deemed to include a modulator implemented by software) except processor  110  has terminal IN for receiving signals from an external source such as data source  42  via line  40 . Source  42  may be considered as providing modulator input for representing an occupant-initiated control signal. Memory  114  of processor  110  stores a program and numerous pulse train patterns for outputting a variety of messages. In this embodiment, potential +V of power supply  18  is connected to terminal VCC of processor  110  so that it is powered only when the brake pedal (not shown) is depressed. 
         [0082]    The flowchart of  FIG. 8  illustrates the program contained in memory  114  of processor  110  of  FIG. 7 . When the brake pedal is depressed, potential +V of power supply  18  is applied to terminal VCC of processor  110  causing it to initialize and enter step S 11 . Processor  110  then immediately proceeds to step S 12  and looks for a selection signal on its terminal IN from data source  42  of  FIG. 7 . This control signal will signify a response desired from processor  110 . If no signal is detected, processor  110  loops back to step S 11  and will continue to loop between steps S 12  to step S 11  until a signal is detected on terminal IN of processor  110 . In that event, step S 12  will then branch to step S 13 . 
         [0083]    In step S 13 , the selection signal from data source  42  of  FIG. 7  is analyzed to determine which pulse train pattern data the source  42  is requesting. After a specific pulse train pattern is identified, the program proceeds to the associated one of the steps S 14 ( 1 ) through S 14 ( n ) to assemble the pulse train pattern being requested. In step S 15 , the requested pulse train is output as an encoded main signal to drive LED array  12  of  FIG. 7 . 
         [0084]    The program then loops back to step S 12  and continues to look for a signal from data source  42 . If the same signal is present as before, the program will produce an output just as before. If a different signal is present, the program will produce the newly requested output. If no signal is present, the program will again loop between steps S 11  and S 12 , waiting for a new signal. 
         [0085]    The program will continue to loop through the flowchart of  FIG. 8  until the brake pedal is no longer depressed at which time potential +V is removed from terminal VCC of processor  110  and no output is possible regardless of any signal being sent by source  42  of  FIG. 7 . 
         [0086]    Data source  42  of  FIG. 7  may continuously send a signal correlating to a request for an encoded STOP message. In some embodiments data source  42  is capable of detecting depression of the brake pedal, in which case the STOP signal may be transmitted only when the brake pedal is depressed. Furthermore, when the brake pedal is not depressed data source  42  produces no signal so that the LED array  12  is extinguished. 
         [0087]    In the embodiment just described, data source  42  may send token signals such as a byte encoded under some communication protocol. Processor  110  interprets the token signals and correlates them with pulse trains stored in memory  114  in order to assemble the output messages such as STOP, LEFT TURN, RIGHT TURN, etc. These assembled pulse trains when applied to LED array  12  produce light pulses that carry information under a generally accepted code so that a wide class of observers can interpret the message. Accordingly, the token code used by source  42  may in general be different from the code transmitted by LED array  12 . 
         [0088]    Instead of using a single token code correlating to a multiple letter message, the signals from data source  42  may consist of a sequence of data signifying letters making up a message. In particular, data source  42  may send a signal to processor  110  signifying the start of the transmission followed by a sequence of data signifying letters making up a message. Data source  42  would eventually send a signal to processor  110  signifying the end of the transmission. Processor  110  would then correlate the message received with one of several pulse train patterns stored in memory  14  of processor  110 . Alternatively, each letter may be correlated with a pulse subsequence contained in memory  114 , which will then be used together with other subsequences to assemble the complete pulse train. 
         [0089]    In other embodiments, the signals from data source  42  to processor  110  may consist of the actual pulse train pattern to be transmitted. Data source  42  would send a signal to processor  110  signifying the start of the transmission followed by a sequence of data signifying the actual pulse train to be transmitted. Data source  42  would finally send a signal signifying the end of the transmission. 
         [0090]    In some cases because of the programming of processor  110 , a brief occurrence of a signal from data source  42  may cause LED array  12  to transmit a message repetitively for a longer, preprogrammed duration or a preprogrammed number of repetitions. In still other cases, the message transmitted by LED array  12  may be repeated a specific number of times based on data encoded in the signal sent from data source  42  to processor  110 . 
         [0091]    In some cases potential +V of power supply  18  is continuously provided to terminal VCC of processor  110  of  FIG. 7 . Data source  42  would then signal processor  110  what pulse train to output, when to output it, and for how long. In this case, any of the previously mentioned formats for allowing data source  42  to communicate with processor  110  may be used. It will be noticed that for this latter arrangement, source  42  can be used as a controller to simply turn LED on and off without impressing any modulation. 
         [0092]    Data source  42  may employ an operating panel  42 A (an operator controllable assembly for producing an occupant-initiated signal (or dynamic signal)) with one or more manual controls such as dedicated pushbuttons each correlated to a predetermined message; a keypad that allows the user to compose a message with one or more characters; or any other device that can transmit an electrical signal. Also, an electronic control unit  42 B carried by a vehicle may receive vehicle data from various sensors such as a brake pedal switch, a turn signal switch, and a headlight switch (and therefore may operate as an operator controllable assembly for producing an occupant-initiated signal). The electronic control unit  42 B would forward the signals (to produce what is herein referred to as a dynamic signal signifying traveling information associated with dynamic operation of the vehicle) through data source  42  to processor  110 , which would then output pulse trains to LED array  12  in response. 
         [0093]    It will be appreciated that data source  42  can communicate not just with processor  110  but with multiple processors (not shown). For example, data source  42  could be connected in parallel with four processors: two modulating two LED arrays used as brake lights; and two modulating two LED arrays used as turn signals. In this case, the data sent by source  42  will include an address identifying which processors or to respond to the request to produce a modulated message. 
         [0094]    In addition source  42  can operate processor  110  in a conventional unmodulated mode. For example, a driver may wish to simply illuminate a brake light with steady (unmodulated) voltage when, for example, parking lights are turned on. When a brake pedal is later depressed, the brake light is brightened to indicate braking and modulated to send an encoded stop message in a modulated mode. 
         [0095]    Referring to  FIG. 9 , previously mentioned processor  110  and LED array  12  operate as described previously in  FIG. 7 ; however, in this embodiment, the data source  42  transmits signals to processor  110  as a modulated carrier on the power line conducting potential +V of power supply  18 . Specifically, data source  42  transmits a signal to terminal DATA IN of driver  38 . Output terminals T 1  and T 2  of driver  38  connect to line coupler  34 . Line coupler  34  is inductively coupled to the line carrying potential +V of power supply  18 , which in turn connects directly to terminal IN of processor  110  and indirectly through low pass filter  47  to terminal VCC of processor  110 . 
         [0096]    Coupler  34  employs a coil acting as an electromagnetic coupler that is capable of electromagnetically coupling to a line, much like a transformer primary couples to a secondary. Terminals T 1  and T 2  of driver  38  supply coupler  34  with a modulating pulse train having a generally high frequency content. The spectrum is chosen so that the modulation is not easily masked by other frequencies normally appearing on potential +V of power supply  18 . In alternative embodiments, the electromagnetic coupler may be replaced with a current shunt (ohmic coupling) and associated hardware. In yet another embodiment, potential +V of power supply  18  may be perturbed by a capacitively connected coupler. In still another embodiment the power line voltage can be modulated by using a switching circuit, either electronic or relay circuit. 
         [0097]    The modulation signal thus induced is blocked by filter  47  to eliminate interference on supply terminal VCC of processor  110 . On the other hand, this modulation signal is received at terminal IN of processor  110  for further processing in a manner to be described presently. 
         [0098]    Optional light emitter  72  illuminates when +V potential is supplied through filter  47  from power supply  18 , in this embodiment, when the brake pedal is depressed. Because filter  47  supplies filtered (unmodulated) power to LED array  72 , fewer than all LED arrays of a light assembly  12 / 72  are employed for modulation. 
         [0099]    Referring now to  FIG. 10 , a receiver has in this embodiment an omni directional or directional photosensor  80  operating as a luminance sensing device that is capable of receiving a signal from LED array  12  and other ambient light sources. In some embodiments the photosensor may employ a parabolic reflector to enhance directionality. 
         [0100]    LED array  12  may emit light over a large solid angle, but only in a narrow band of the visible or infrared spectrum. Accordingly, sensor  80  may be sensitive only to this specific spectrum either inherently or because of a built-in filter. 
         [0101]    Communication of inter-vehicle messages may be implemented as follows: A transmitting vehicle  20  may have “stand alone” bulbs, as shown in  FIG. 6A  (or  6 B), that are used as brake lights, turn signals, headlamps, tail lamps, fog lamps, running lights, or the like. (It will be appreciated that in some embodiments transmission may be accomplished using the alternate arrangements of  FIG. 3 ,  7 , or  9 .) 
         [0102]    As an example, the operator of vehicle  20  may notice an obstacle and immediately depress the brake pedal, causing the car to rapidly decelerate. Depression of the brake pedal also energizes the vehicle&#39;s “stand alone” bulb of  FIG. 6A  thereby applying potential +V of power supply  18  to terminal VCC of processor  10  ( FIG. 2 ). Processor  10  immediately begins outputting a pulse train, encoded with the message STOP, at terminal OUT, which is connected through signal amplifier  16  to drive the LEDs  12 C of LED array  12  (LED array  12  shown in both  FIGS. 6A and 10 ). 
         [0103]    The sensor  80  of vehicle  21  as shown in  FIG. 10  will produce a composite signal responding to all luminance sources in its field of view. Because sensor  80  is particularly sensitive to the spectrum from array  12 , its modulated light will be prominent. This signal is sent to terminal IN of processor  82  (referred to as an analyzer that is part of a utilization device). Also, because the modulated light has relatively high frequency components in a narrow band, these can be made more prominent by appropriate bandpass filtering in processor  82 . 
         [0104]    Processor  82  processes the modulated signal and produces at its terminal OUT a recovered signal indicating the presence and the coding associated with that signal. This signal is sent to terminal IN of processor  86 , which operates as an annunciator that translates the encoded signal into a digitized synthesized speech pattern output on terminal OUT. The output of processor  86  is converted in digital to analog converter  90  before being applied to speaker  92 . Specifically, speaker  92  broadcasts the synthesized speech, in this case, the word “stop”. The operator of the receiving vehicle  21  might not have immediately noticed the lighting of brake lights  12  in the transmitting vehicle  20 , but will more likely respond to the audible “STOP” announcement. 
         [0105]    In order for the communications system to work, both the transmitter and the receiver must work with signals using an agreed communications protocol, although in some cases the receiver can be designed to recognize any one of several protocols that may be used by a transmitter. 
         [0106]    Various messages of the foregoing type may be sent using the modulated light communication links described above. Simple codes carried in the modulated light signals may represent various messages. For example, one simplified code (e.g., a byte) can signify STOP, another LEFT TURN, still another RIGHT TURN, etc. These simplified codes can direct the receiving unit to synthesize one of several speech messages. In some embodiments these messages may be presented instead as distinctive tones the driver eventually learns to associate with different messages. Alternatively, processor  82  can produce a signal to illuminate a warning light, buzzer, bell, character display (e.g., liquid crystal display) or other annunciator. In still other embodiments a warning light or a character display (e.g. liquid crystal display) may be used to as an annunciator. 
         [0107]    In another embodiment processor  82  may connect over a parallel data bus directly to DAC  90 . In still other embodiments, the output of processor  82  may connect to an amplifier driving speaker  92  or be connected directly to speaker  92 , in which case processor  82  produces a pulse train with a duty cycle that varies in accordance with the desired audio waveform. 
         [0108]    The foregoing described an arrangement for broadcasting a dedicated message with the processor  10  of  FIG. 2 . In other embodiments the transmitting vehicle  20  may employ processor  110  of  FIG. 7 , in which case varying messages may be specified by data source  42  ( FIG. 7 ). As noted previously, data source  42  may include an operating panel  42 A that is mounted in the passenger compartment. Panel  42 A may have several manual controls pre-programmed to initiate certain messages: For example, STOP TAILGATING, CONGESTION AHEAD, DRIVE CAREFULLY, CALL FOR EMERGENCY ASSISTANCE, CHANGING LANES, etc. These buttons and messages may be programmed at the factory or programmed by the user after purchase. Also, information may be transmitted in one language or code but may on receipt be recoded or annunciated, or displayed in another language, which is user selectable or otherwise. 
         [0109]    In some cases, source  42  may have a keypad so that the driver may stop and type a message that is then broadcast repeatedly even after the driver resumes traveling. A laptop computer or PDA (personal digital assistant) may also be used as part of the data source  42  to generate messages that are converted into a format that is usable by processor  110  of  FIG. 7 . 
         [0110]    While the foregoing system transmitted modulated visible light using LEDs, other systems may employ IRLEDs, incandescent lamps, electrical discharge lamps, strobe lights or other types of signalers that will be modulated to transmit encoded messages. Also, intensity modulation of a vehicle&#39;s headlights may be used to transmit encoded messages for capture and interpretation by a receiving device in an opposing vehicle. In some cases the headlights may be incandescent and will not therefore sustain rapid modulation. Nevertheless, modulation is possible but will be done at a slower data rate with redundancy to increase the accuracy of transmission. Different modulation techniques may be used depending on the light source to be modulated thereby allowing any light source on a vehicle to be used as a transmitter. 
         [0111]    With the foregoing arrangements, modulated light is only transmitted when the vehicle&#39;s lights are lit in a traditional manner. For brake lights and turning signals this operation is of course intermittent. When modulated light transmission is desired at any time at the driver&#39;s independent discretion, the driver may use daytime running lamps (DRLs). In some cases these DRLs will simply be a matter of turning on and modulating the vehicle&#39;s headlights, parking lamps, tail lamps, fog lamps, etc., although dedicated lights of various types can be mounted on the vehicle&#39;s body for this sole purpose. 
         [0112]    The communications links described above may also send digitized audio messages originating from a microphone or other source. In such a case the processor may transmit modulated light on the taillights of one vehicle which is captured by a receiver in a trailing vehicle. The operator of the trailing vehicle may return the voice transmission by using a similar microphone and processor to produce a pulse train that modulates the intensity of the trailing vehicle&#39;s headlights or other light dedicated to or adapted for signal transmission. The leading vehicle can receive this return message using a rearward-facing image sensor, before conversion into an audible signal in the manner previously described. The operators of the leading and trailing vehicles are therefore able to communicate with each other in half duplex, or full-duplex fashion. 
         [0113]    In some embodiments the communications links will be used for general purposes such as transferring word processor files, spreadsheet files, JPEG images or any other any other type of file that is susceptible to encoding and transmission as modulated light. 
         [0114]    In some embodiments luminance sensing device  80  of  FIG. 10  employs a video camera, CCD, CMOS sensor, vidicon tube or similar image-sensing device mounted in a motor vehicle  21  on, for example, a dashboard. Image sensor  80  can be synchronized or semi-synchronized at a known camera frame rate such as 60 Hz for NTSC. Image sensor  80  has a predetermined two dimensional field of view and is operable to produce a detection signal with spatial content for distinguishing a plurality of visual elements in the predetermined two dimensional field of view. Accordingly, image sensor  80  is able to distinguish spatially regionalized visual elements that occupy less than all of the two dimensional field of view of the sensor  80 . 
         [0115]    In this embodiment image sensor  80  performs a raster scan of a scene and records horizontal lines of pixels to capture successive frames of a scene. Image sensor  80  outputs successive frames to terminal IN of processor  82  (referred to as an analyzer that is part of a utilization device). Processor  82  processes the frames and outputs at terminal OUT a decoded signal indicating the presence and the coding associated with that signal in the manner to be described presently. 
         [0116]    The flowchart of  FIG. 11  illustrates a program running on processor  82  for handling two dimensional information from image sensor  80  of  FIG. 10 . In step S 21  frames captured by image sensor  80  are stored in the memory of processor  82 . The rate at which the frames are scanned (frame rate) and saved to memory is chosen based upon several factors. One factor is the speed of modulation selected for LED array  12  in vehicle  20  ( FIG. 10 ). The frame rate must be sufficiently high to ensure capture of the modulated signal from LED array  12 . A frame rate of twice the highest transmitted modulation frequency will ensure that a pulse cycle does do not occur between captured frames. Another factor is the rate at which objects in the scene appear to move. The image of fast moving objects captured with a slow frame rate may cause processor  82  to use resources to analyze dramatic changes in the image. 
         [0117]    In some embodiments the received pulses may have lower repetition rate if the image sensor  80  is synchronized to modulated optical signal, in which case each field or frame will have reliable bit information. This synchronization can occur by including in the transmitted optical signal a code indicating the pulse repetition rate (bit time synchronization information). Then the image sensor  80  can run its frame rate, field rate or line rate just below (or just above) this encoded rate value and then observe any phasing errors that occur. After a few frames, the image sensor can be quickly synchronized to the incoming optically modulated signal. 
         [0118]    In any event, in step S 22  two successive frames are compared. Assuming, for the present explanation, that nothing in the scene is moving, the only possible change in the scene will be LED array  12  ( FIG. 10 ) switching on or off. The two successive frames are compared pixel by pixel and a third frame is generated which represents the amount of change in intensity of each individual pixel from the earlier frame to the later frame. This third frame, hereinafter referred to as the delta intensity frame, is partitioned into a matrix of m×m spatial elements that is coarser than actual spatial resolution of device  80  in order to perform m×m averaging as follows: 
         [0119]    In step S 23 , m×m averaging is performed on the m×m matrix of spatial elements derived from the delta intensity frame. The coarseness of the matrix is dependent upon the desired resolution of the visual elements captured by image sensor  80 , the amount of noise the system is subject to, the expected size of the modulated area in a scanned frame, the need to deal with moving objects in a scene, as well as other factors. The change in intensity of the pixels that make up each element of the m×m matrix (these matrix elements also being referred to as spatially coincidental subframe regions) are averaged to create an averaged intensity value in order to generate a fourth frame (or matrix) containing the average change in intensity of each spatial element of the m×m matrix. Use of m×m averaging helps to reduce noise and edge effects. Alternatively, other methods such as n×m averaging may be used as well. 
         [0120]    Edge effects occur when objects are moving in the scene. As an object moves, significant intensity changes occur along the edge of the object from frame to frame. For example, consider two successive frames where an object in the scene moves from right to left a distance equivalent to one pixel. Pixels to the left of the object will change in intensity from object intensity to the background intensity. Moreover, pixels to the right of the object will change in intensity from the background intensity to the object intensity. 
         [0121]    If m×m averaging is not used, the change in intensity of one pixel involved in the edge effect becomes as prominent as pixels involved in the relevant modulation. However, dividing the frame into a grid and averaging the change in intensity of groups of m×m pixels reduces the problems associated with edge effect. Edge effects produce dramatic changes along a line of pixels but that effect is reduced by averaging those pixels with the neighboring unchanging pixels. Similarly, the noise manifesting itself as spuriously changing pixel intensity values will be reduced as well. On the other hand, intensity changes across broad areas within a spatial element of the m×m matrix corresponding to an object sending a modulated signal are not averaged down and therefore remain prominent. 
         [0122]    Step S 24  determines the intensity difference threshold that will be used to determine whether an intensity difference is great enough to be considered a possibly modulated signal. Processor  82  ( FIG. 10 ) analyzes the delta intensity frame over all elements of the m×m matrix and relies on predetermined criteria to make selections based on the median value of these average differences (although other embodiments may rely on the mean or the mode). This median value is used as the threshold below which intensity differences are ignored (alternatively, a different threshold value may be used, such as a value in the range of 50% to 80% of the median value). 
         [0123]    For example, suppose that two successive frames of a scene processed using steps S 21  through S 23  generate an m×m matrix of intensity differences, one for each matrix element. The area of a matrix element that corresponds to a modulated LED array  12  would exhibit a large change in intensity, typically greater than the threshold. All other areas of the scene would have a more modest change in intensity because the intensity measurement in each matrix element in each frame is averaged over the area associated with a matrix element. Although areas subject to edge effects will show some intensity difference, because of the m×m filtering these differences would be averaged down, normally to a level below the threshold. 
         [0124]    In particular, in step S 25  each element of the m×m delta intensity frame is compared with the threshold value determined previously in step S 24 . Any element with intensity changes that equal or exceed the threshold are passed to step S 26 , otherwise the program loops back to step S 21 . 
         [0125]    In Step S 26 , the changes in intensity of the matrix elements from frame to frame are assembled to eventually form pulse trains representing the transmitted message. Because the sampling frame rate is at least twice the highest transmitted pulse repetition rate, the system is able to reliably capture the pulse train without dropping pulses. The assembled pulse train is then compared pulse by pulse with the sequences stored in memory. When a match is found in step S 27  programming branches to step S 28 , which is executed next. In one embodiment, when a match is found the scan rate of sensor element  80  is immediately synchronized to the perceived sequence. In one embodiment, the modulated signal can include a pulse burst for synchronizing the receiver in order to optimize data capture at a particular baud rate. 
         [0126]    In step S 28 , the program determines whether the m×m matrix elements exceeding the threshold are a spatially coincidental subframe region (typically contiguous elements or elements clustering in a relatively small region) and therefore form a broad area of interest. If one or more broad areas of interest are determined the system will give those areas and their neighborhoods a high priority, making certain that they are always under analysis. Areas that only show transient activity will not be further processed until a sustained activity is established. 
         [0127]    In the succeeding step S 29 , the message received from the object sending the modulated signal (in this case LED array  12 ) is tagged with a local identifier. Next, the associated one of the steps S 30 ( 1 ) through S 30 ( n ) produces a corresponding one of the outputs OUT( 1 ) through OUT(n). In step S 30 ( 1 ) through S 30 ( n ), the message is output from terminal OUT of processor  82  in a format appropriate for any one of a variety output devices described herein. The program then loops back to step S 21  and the process is repeated. 
         [0128]    Steps S 21  through S 25  can be launched as one or more threads that run continually on processor  82 . Steps S 26 -S 27 , step S 28 , and steps S 29 -S 30  may also be run as separate threads on processor  82 . Steps S 21  through S 25  will then continually look for an area that exceeds the threshold value. Whenever an area exceeds the threshold in step S 25 , the processor  82  will invoke steps S 26 -S 27 . If a portion of the captured pulse train matches a known sequence stored in the memory of processor  82 , the threads involving steps S 28  through S 30  are invoked using information obtained in step S 27 . These threads are active and continually analyze a specific area of the captured image in order to output an appropriate message for as long as the object of interest continues to send an appropriately modulated signal. 
         [0129]    In this embodiment each of the outputs OUT 1 -OUTn of steps S 30 ( 1 )-S 30 ( n ) assemble a serial data stream corresponding to synthesized speech. In particular, processor  86  ( FIG. 10 ) outputs a data stream in a speech synthesized format through UART  86  to input IN of analog to digital converter  90 , which converts the parallel data to an analog signal for driving speaker  92 . 
         [0130]    Various techniques may be used to reduce the amount of memory required to perform the frame analysis in steps S 22  through S 25  of  FIG. 11 . For example, the comparison of a first frame at time t 1  to a second frame at time t 2  in order to create a derived frame (delta intensity frame) may be performed by overwriting the t 1  frame data so that only two frames are stored in memory, not three. The t 2  frame would not be immediately overwritten, as it is needed when analyzing a third frame at time t 3 . 
         [0131]    Referring to  FIGS. 12A ,  12 B and  12 C, a hypothetical captured video frame  120  is shown with a number of vehicles  20  and a traffic light  132 . In  FIG. 12B  scan line  131  indicates one of the raster lines of the video. Assuming that only light  12 B is illuminated and that the rest of the image along line  131  is dark or low contrast, then the resultant video  145  will have a single, relatively square pulse  143  associated with relatively bright light  12 B. 
         [0132]    In  FIG. 12A  successive subframe regions  133 ,  135 ,  137 ,  139  . . . are shown overlaying frame  120  in order to enhance the image processing by performing continual template comparison in disjoint regions, or even in regions that overlap as a template is stepped across the image raster-like, one or more pixels at a time (horizontally and vertically). A template is a small representation of an image or shape; for example, a number of contours representing the outline of a target image. A library of templates is stored in the memory of the processor (processor  82  of  FIG. 10 ) and are compared against patterns in the visual elements in each of the of the subframe regions  133 ,  135 ,  137 ,  139  . . . . For an incremental progression of templates moving one or a few pixels at a time, see the sequence of templates  133 ′- 137 ′ in  FIG. 12C . 
         [0133]    Assuming traffic signaling device  132  is under consideration, this object will be analyzed over a succession of regions. The first region to intersect traffic signaling device  132  will be compared to each of the templates in memory. This region under consideration will be convolved with each of these templates to produce a sequence of scalar values representing the degree of matching to each of the various templates. In one embodiment, the convolution is performed by determining the percentage of the captured image that falls within the template. 
         [0134]    For example, suppose the region under consideration contains circular object  12 B ( FIG. 12B ). The edges of this circle will be detected and compared to the various templates. One of those templates will in fact be a circle, which if properly aligned over circular object  12 B produces a 100% match in the convolution. In some circumstances alignment is off, and only a portion of an arc of circle  12 B will be captured. Convolving the image of an arc of a circle with a circular template will produce a partial match but the correlation will still be significant. Likewise, if the captured image is a circle viewed at an angle (i.e., an ellipse) the convolution will detect a partial but significant correlation, which will be used as a predetermined criteria for determining template matches. 
         [0135]    Referring to  FIGS. 12D and 12E , previously mentioned template  139  is shown with a prototypical circle  149  so that the template can detect circular objects. Composition lines  136  indicate that the template is being compared against image data that was averaged using the m×m matrix (step S 23  of  FIG. 11 ). As shown in  FIG. 12E  the template moves incrementally along scanline  141  or more pixels at a time before each template correlation (convolution). It will be understood that after each scanline is completed the template will be shifted one or more pixels downwardly to begin another parallel scanline. In each scanline the template performs successive correlations in regions that partially overlap other regions that were previously correlated in the current and previous scanlines. 
         [0136]    The results of the successive correlations are shown in the family of outputs  150  (specifically outputs  150 ( a ) through  150 ( g )). Each of these outputs is essentially zero (no correlation) except when the template  139  intercepts circular light  12 B. (To simplify this Figure, it is assumed for now that only light  12 B is illuminated and that the other lights  12 A and  12 C do not contrast with their background and therefore are not detected by the template matching process.) 
         [0137]    In  FIG. 12E  scanline  140  is shown intersecting the top of circular light  12 B to produce partial correlation with template  136  ( FIG. 12D ). This partial correlation results in a trapezoidal pulse  151  in output  151 ( b ) as template  139  moves from right to left across light  12 B. The next scanline will be displaced downwardly to produce the larger trapezoidal pulse shown in output  150 ( c ). The scanline after that intersects the center of light  12 B and therefore produces the maximum pulse as shown in output  150 ( d ). Subsequent scanlines will produce progressively decreasing pulses as shown in outputs  150 ( e ) through  150 ( g ). 
         [0138]    As template  139  progresses across traffic signaling device  132  the scalar result of the convolution peaks as the analysis region arrives close to the center of the target image, here a circle. By sensing where this peak occurs the system can determine the approximate center of the target image. The system will consider any correlations significant only when they satisfy predetermined criteria. 
         [0139]      FIG. 13 , shows the results of the template matching step of  FIG. 12  (In this illustration template matching is assumed to occur for all three lights  12 A,  12 B, and  12 C). Here, the three circular lights  12 A,  12 B, and  12 C from the previously mentioned traffic signaling device  132  are passed but the surrounding regions are blanked. Other than the lights of traffic signaling device  132 , all other regions of the scene are blanked (shown in crosshatch). 
         [0140]    Template matching reduces the resource demand on processor  82  by identifying spatially regionalized visual elements in a captured frame where signal modulation is occurring or is most likely to occur. Template matching may be used in conjunction with the process described in the flowchart of  FIG. 11 . 
         [0141]    In addition to detecting areas of modulation and receiving signals transmitted via light sources, the above described frame capture and analysis techniques may be used for other purposes. For example, a receiver located in a trailing vehicle may detect a leading vehicle that may or may not be currently transmitting a message. The receiver repeatedly examines the captured images to determine if there is a change in the size of the image of the vehicle or the vehicle&#39;s lights. As the trailing vehicle gets closer to the leading vehicle, the size of the vehicle or the vehicle&#39;s lights in subsequent captured frames would become larger. A processor interprets this change in size as a change in the distance between the vehicles and alerts the driver of the trailing vehicle by outputting an audio or visual signal such as a warning tone or an image on a display. The processor may alternatively be designed to deactivate a vehicle&#39;s cruise control as a precursor of braking. In an another embodiment, the processor may begin to actuate the vehicle&#39;s brakes as well. 
         [0142]    Various types of sensors may be used to capture and identify the modulated light from an LED array and the like. While the foregoing employed relatively high resolution image acquisition, adequate information may also be obtained from low-resolution, wide-angle image sensors as well. 
         [0143]    Referring to  FIG. 14 , the previously mentioned vehicle lights (e.g., LED arrays  12 / 13  of  FIGS. 3 ,  6 A and  6 B) are fitted with an additional diagnostic transmission element  75 . Element  75  constitutes additional circuitry added to PCB  30  of  FIG. 3  or to PCB  130  of one of the bulbs displayed in  FIGS. 6A and 6B . Element  75  includes a data source  142  whose terminal IN connects to the previously mentioned processor (e.g. processors  10  and  110  of  FIGS. 2 ,  7  and  9 ). 
         [0144]    Terminal DATA OUT of data source  142  connects to terminal DATA IN of driver  138 . Terminals T 1  and T 2  of driver  138  are connected to line coupler  134 , which is arranged the same as the previously mentioned coupler (coupler  34  of  FIG. 9 ). Accordingly, coupler  134  is electromagnetically coupled to the power line  141  line carrying potential +V of power supply  18 . 
         [0145]    Diagnostic device  77  may be mounted in the vehicle&#39;s passenger compartment for the diver&#39;s benefit. In particular, the previously mentioned line  141  carrying potential +V of power supply  18  connects directly to terminal IN and indirectly through low pass filter  147  to terminal VCC of processor  210 . Terminal GND of processor  210  is grounded. Terminals OUT 1  through OUTn of processor  210  are connected through respective amplifiers  116  to the anodes of corresponding LED  32 , whose cathodes are grounded. 
         [0146]    Data source  142  outputs a signal that modulates potential +V of power supply  18  as previously described in connection with  FIG. 9 . This self test signal may be a periodically recurring encoded signal, a unique pilot frequency, or a distinctive heartbeat signal indicating that the self testing unit is operating properly. The lack of a particular modulation signal may indicate that a particular vehicle light or light modulation unit is no longer functioning. 
         [0147]    Data source  142  receives on input IN status information transmitted from the processor (processor  10  or  110  of  FIGS. 2 ,  7 , and  9 ). This status information may be serial or parallel data or in some cases one or more simple flags. These flags can indicate individually (or as a combination) various faults detected by the processor. In still other embodiments data source number  142  may have its own sensors (not shown) to detect failures in the associated light. The sensed failures can be lack of continuity through a lamp, inappropriate short or open circuits, lack of proper power to the processor, etc. 
         [0148]    In operation, the modulation applied to potential +V of power supply  18  by line modulator  134  is transmitted to terminal IN of processor  210 . After processor  210  initially recognizes the modulated signal, it regularly checks for its continued existence. If one of the expected signals from the self-testing lights terminates, processor  210  will consider that a failure of the associated light. Alternatively, the modulated signal may itself carry information indicating the identity of the failed light and in some cases additional information about the type of failure. If one or more of the lighting elements are determined to be malfunctioning, processor  210  outputs a signal on one or more of terminals OUT( 1 ) through OUT(n) thereby illuminating some or all of the LED  32  to indicate to the faulty lighting elements of the vehicle. 
         [0149]      FIG. 15  shows a portable diagnostic device  25  containing the diagnostic circuitry  77  previously described in  FIG. 14 . Status display  23  is located at the base of a frustro-conical head  200  that merges into main body  202 , which has a tapered end  204 . Main body  202  is sized to fit into a cigarette lighter or standard utility power socket (not shown) of a vehicle. 
         [0150]    For this embodiment of diagnostic tool  25 , display  23  has a permanent icon of a vehicle with underlying LEDs  32  mounted at several locations on the icon to represent the self-testing lights of the vehicle. LEDs  32  illuminate (or extinguish) to identify the malfunctioning lights or modulation units as described before in connection with  FIG. 14 . In another embodiment, processor  210  of  FIG. 14  can produce messages indicating the malfunctioning lights or modulation units using messages such as “LEFT INSIDE TAIL” displayed on an LCD (not shown). 
         [0151]    Referring to  FIG. 16 , a building such as house  100  is fitted with a panel  100  that operates as a house number sign containing the following electronic circuitry: Pull-up resistor R 1  is connected between potential +V of power supply  318  and terminal IN 1  of processor  310 . Terminal IN 1  is also connected to one terminal of switch SW 1  whose other terminal is connected to ground. A number of other serially connected resistor/switch pairs (e.g., resistor Rn and switch SWn) are similarly connected between potential +V and ground with their junction connected to one of the terminals IN 1  through INn of processor  310 . 
         [0152]    Processor  310  is a microcontroller having memory  314 . Terminal OUT of processor  310  is connected to the input of amplifier  316  whose output is connected to the anode end of previously described LED array  12  whose cathode end is connected to ground. 
         [0153]    The foregoing circuitry is packaged in panel  100  with LED array  12  exposed for transmitting light modulated to indicate the house number of house  104 . Panel  100  may bear on its face glyphs indicating the house number. The panel  100  may be mounted at the front of house  104  and powered from a switch (not shown) located inside the house when the occupant desires the house number to be optically transmitted on the LED array  12  (although in some cases the device may be powered continuously). 
         [0154]    The operation of the signaling device shown in  FIG. 16  is as follows: A program stored on memory  314  of processor  310  begins running whenever processor  316  is powered. The program first looks at terminals IN 1  through INn and interprets that switch pattern as a house number. In some embodiments the switches SW 1 -SWn may simply be read as digits of a binary number, but for embodiments where consumers operate the switches, other input methods such as an ordinary numeric keypad may be employed instead. In still other embodiments switches SW 1 -SWn are jumpers on a PCB which are cut in a custom pattern. 
         [0155]    After the program determines the house number to be displayed, the appropriate pulse train is assembled by processor  310  and then repetitively produced at terminal OUT. Signal amplifier  316  brings the pulse train to an appropriate power level to drive LED array  12 . Passing vehicles carrying the previously described receiver ( FIG. 10 ) can capture the modulated light signal from LED array  12 , which then may be converted to a numeric display or synthesized speech. 
         [0156]    In some embodiments the foregoing light can be focused or directed to propagate toward receivers presumed to be at a height of about 1 to 2 meters.  FIG. 17  shows transmitter  175  that can be used on panel  100  on the front of house  104  of  FIG. 16 . In particular, four shafts  184  (only two visible in this view) are screwed into base plate  188  at four corners of base plate  188 . Adjustable plate  190  is slidably mounted on shafts  184  and captured thereon by nuts  180 . Helical springs  176  are located around shafts  184  to bias plate  190  away from plate  188  and against nuts  180 . 
         [0157]    Shafts  184  have at opposite ends two threads  182  and  186  with different pitches. Fine pitch threads  186  are screwed into matching threads on base plate  188 . Coarse pitch threads  182  are threaded into nuts  180 , which have matching threads. Pins  178  projecting from adjustable plate  190  extend through holes or notches in nuts  180  to keep them from turning. 
         [0158]    Board  198  is mounted to adjustable plate  190  and has the circuitry shown  FIG. 16  for energizing LED  192 . Parabolic reflector  195  with reflective surface  194  is mounted on board  198  with LED  192  projecting through an axial bore in the center of reflector  195 . Lens  196  is mounted to the rim of reflector  195 . 
         [0159]    Transmitter  175  is mounted and adjusted in the following manner: Base plate  188  is mounted to the desired location with threaded shafts  184  screwed in place and springs  176  biasing plate  190  outwardly. The threads  182  and  186  of shaft  184  will all have the same orientation (for example, right handed threads) although threads  186  will be finer. Because of this thread difference rotation of shaft  184  will change the separation of plates  188  and  190  but at a rate proportional to the difference in pitch between threads  182  and  186 . Because there are four separate threaded shafts  184  the angular orientation of the axis of reflector  195  can be adjusted. Assuming base plate  188  is mounted vertically the axis of reflector  195  can be the adjusted to change its angle of elevation and azimuth. Accordingly, light from LED  192  can be directed to shine in the expected direction of approach of a receiver-equipped vehicle (and/or in such a direction that light intercepts a passing vehicle mostly on the side and somewhat toward the front, with the vehicle&#39;s receiver being oriented accordingly). Light from LED  192  can be modulated by using the pulsed signal produced by amplifier  316  of  FIG. 16 . 
         [0160]    Referring again to  FIGS. 3 and 12 , traffic signaling device  132  has lights  12 A,  12 B, and  12 C. Many such traffic lights currently use LED arrays in place of conventional incandescent bulbs, although as noted before modulation with incandescent lights is possible at a slower data rate. Assuming an existing traffic light using LED arrays, PCB  30  ( FIG. 3 ) may be installed in series with each LED array of traffic lights  12 A,  12 B, and  12 C in a manner similar to that shown in  FIG. 3 . Alternatively, instead of employing the retrofit arrangement of  FIG. 3 , some embodiments may use the stand-alone bulbs shown in  FIG. 6A  or  6 B in traffic signaling device  132 . 
         [0161]    In this embodiment, PCB  30  would begin sending a message repeatedly when power is applied to the corresponding red, amber or green lights  12 A,  12 B, and  12 C. An encoded token symbol or a message encoded to represent the word OKAY, or GO would be transmitted on green LED array  12 C when power is applied thereto. A token code or the encoded message CAUTION could be transmitted on amber LED array  12 B when powered, and a token code or the encoded message STOP on red LED array  12 A. These encoded messages are dynamic traffic information signals that may be interpreted by a vehicle&#39;s receiver, which will then produce an audible or visible message or other indication. Also, in some embodiments the received message could be used by the vehicle&#39;s control system. For example, a message that the preceding vehicle is braking can be used to reduce the speed dictated by a cruise control or, under appropriate circumstances, automatically apply the brakes. This decision to decelerate or break can be informed by analyzing an image of the preceding vehicle (or its brake lights) and determining whether the image is quickly growing, indicating rapid closure and potential collision. Also, in some embodiments the received message may be an objection to high beams in which case the receiving vehicle&#39;s control system can automatically switch to low beams. 
         [0162]    For simple dedicated messages the circuit of  FIG. 2  may be employed, but other embodiments may use the circuit of  FIG. 7  to transmit more complicated variable messages that originate from data source  42 . In some cases, the modulation circuits associated with each of the traffic lights  12 A,  12 B, and  12 C may receive data from a single common data source  42 . Under those circumstances, traffic signaling device  132  may transmit public-service messages regarding traffic, weather, or emergencies in addition to (or in place of) the ordinary stoplight information (stop/go/caution). 
         [0163]    The foregoing concept can be applied to traffic signaling devices and signs in general by installing a modulated LED array that can transmit information in a similar manner. For example, a sign indicating the speed limit may broadcast the speed limit by appropriately modulating an LED array mounted to the sign. The transmitter mounted on or near the traffic sign may additionally or alternatively transmit information regarding traffic, weather, or emergencies. In addition, lone roadside transmitters may be strategically located to broadcast information to drivers, such as emergency, traffic, or other information relevant to vehicles traveling along a highway. 
         [0164]    As another example, detour signs operating as a traffic signaling device may broadcast dynamic traffic information in the form of a detour message including alternate route information, presented as synthesized or pre-recorded speech. Alternatively, the transmitter may send a signal containing the message DETOUR as well as alternate route information in a format to be utilized by a vehicle&#39;s on board navigation system. The transmitter may also send a signal containing an image of a map indicating alternate route information that can be used by vehicles which are not equipped with a navigation system but have displays capable of presenting the image. In addition transmitters mounted on each detour sign along the alternate route may additionally transmit short directives such as TURN RIGHT, TURN LEFT, or DETOUR END in several formats so that the driver may receive an audible or visual indication of the detour instructions. Vehicles receiving this information may be suitably equipped to filter this information. For example, the information may be filtered to accept only traffic, navigation, or other designated information. 
         [0165]    Referring now to  FIG. 18  vehicle  20  is transmitting modulated light from array  12  is sending a message to previously mentioned luminance sensing device  80  of vehicle  21 . Previously illustrated processor  110  ( FIG. 7 ) is shown as before with its output terminal OUT connected through power amplifier  16  to LED array  12 . Unlike before, input terminal IN of processor  110  is connected to an output from PDA  103 , which then acts as a portable personal data source. 
         [0166]    Previously illustrated devices  82 ,  86  and  90  ( FIG. 10 ) are connected as before to image sensor  80 , and speaker  92 . Unlike before, display  102  connects to terminal OUT of processor  82 . 
         [0167]    The devices of  FIG. 18  operate as follows: The operator of vehicle  20  can store a variety of messages on PDA  103 . For example, PDA  103  can be programmed to display a number of standard message, such as TAKE NEXT EXIT. Using PDA  103 , a message is selected from the list displayed on the PDA in order to apply a corresponding output signal to terminal IN of processor  110 . In a manner similar to that previously described, processor  110  then outputs a corresponding signal pulse train at its terminal OUT, which is connected to the input of signal amplifier  16 . Signal amplifier  16  brings the pulse train to an appropriate level to drive LED array  12  which is then modulated with the pulse train. 
         [0168]    In a manner similar to that previously described, imaging sensor  80  captures sequential frames of the scene containing vehicle  20  and its LED array  12 . Processor  82  analyzes these successive images as previously described to extract the modulated signal. The extracted signal is then output at terminal OUT of processor  82  with two destinations. The signal is sent as image data to display  102 , which is designed with appropriate graphics processors so that incoming data is converted into a display image. Secondly, the signal is sent to processor  86  to be converted into a digital representation of synthesized speech for subsequent conversion into an analog signal in converter  90 , which drives speaker  92 . 
         [0169]    In addition to sending standard stored messages, custom messages may be composed and sent on-the-fly; or data such as word processing documents, spreadsheets, or JPEGs may be sent from PDA  103 . Besides PDAs, other devices such as laptop computers may be used to generate messages. 
         [0170]    In some embodiments, the vehicle  20  may be an emergency vehicle that is broadcasting messages using an omnidirectional light source or an emergency flasher as typically used on emergency vehicles. Messages may be entered by emergency personnel using a PDA, laptop computer or other device in order to broadcast official messages to vehicles in the vicinity. 
         [0171]    Referring to  FIG. 19 , publishable, positional information is communicated between two oncoming vehicles  20  and  21 . For simplicity, vehicle  20  is shown with a transmitting system and vehicle  21  with a receiving system, but it will be appreciated that both vehicles could additionally have a complementary transmitting and receiving system in order to establish two-way communications. 
         [0172]    Previously mentioned image sensor  80  connects to input IN 1  of processor  182  whose output terminal OUT connects to display  102  and a local transmitter similar to that in vehicle  20 . Input terminal IN 2  of processor  182  connects to output terminal OUT of GPS (global positioning system) receiver  94 , whose input terminal IN connects to antenna  98 . 
         [0173]    GPS receiver  94  continuously determines the vehicle&#39;s position by interacting in a known manner with satellites using antenna  98 . The publishable positional information is provided in a conventional manner at output terminal OUT of receiver  94  and then relayed through processor  182  (input terminal IN 2  to output terminal OUT) to the display  102 . This image may show the location of vehicle  21  on a map. 
         [0174]    In vehicle  20 , antenna  99  connects to input terminal IN of GPS receiver  95  whose output terminal OUT connects to the input terminal IN of processor  96  and input terminal IN 2  of processor  410 . The output terminal OUT of processor  96  connects to terminal IN 1  of processor  410 , whose output terminal OUT connects through power amplifier  16  to previously illustrated LED array  12 . Processor  96  also connects to a local receiver similar to that shown in vehicle  21 . 
         [0175]    As vehicle  20  travels, GPS receiver  95  continuously determines the vehicle&#39;s position (i.e., travel history) by interacting with satellites using antenna  99 . Vehicle position information continually provided at terminal OUT of GPS receiver  95  is analyzed by processor  96 . Processor  96  is programmed to process this publishable, positional information and generate a table listing discrete positions of vehicle  20  distributed over a preceding period of time; in this case, approximately 20 minutes. 
         [0176]    The publishable information stored in this table is provided at terminal OUT of processor  96  to processor  410 , which converts this publishable information into a pulse train on terminal OUT, in a manner similar to that described in connection with processor  110  of  FIG. 7 . This pulse train is applied through amplifier  16  to LED array  12 , which may be a front parking light, a mirror light, or a dedicated light transmitter on the front of vehicle  20 . In some embodiments the vehicle&#39;s headlights will be modulated. 
         [0177]    As vehicle  21  approaches vehicle  20 , previously mentioned imaging sensor  80  captures sequential frames of a scene containing images of vehicle  20  and its array  12 , which is transmitting a modulated light signal as previously described. The sequential images from imaging sensor  80  are applied to processor  182 , which is designed to analyze the received signals in a manner similar to that described in connection with processor  82  of  FIG. 10 . This received information can be arranged to reveal either the position of vehicle  20  at various times, or, after processing (in either vehicle), the speed of vehicle  20  at various positions along a highway. Moreover, this captured information may be supplemented with travel data received from similar oncoming vehicles having transmission equipment similar to that in vehicle  20 . 
         [0178]    This received information about the travel history of vehicle  20  and other vehicles may not be directly relevant to the driver of vehicle  21 , but may be useful to other vehicles. In fact it will be understood that vehicle  20 , using its own receiver, has collected just this type of information from vehicles recently passed. Accordingly, the publishable information collected by vehicle  20  about other vehicles represents traffic conditions vehicle  21  will soon confront. With this in mind, vehicle  20  transmits through LED array  12  publishable information about the travel history of vehicles recently passed by vehicle  20 . Thus, vehicle  20  will transmit and vehicle  21  will receive not only the travel data concerning vehicle  20  but the travel data collected by vehicle  20  concerning other oncoming vehicles. 
         [0179]    The publishable information collected by vehicle  20  concerning other oncoming vehicles is received by image sensor  80  and sent to processor  182  for analysis. Processor  182  will sort speed data from the vehicles&#39; history based on location. This location can be included explicitly in the transmitted data or can be derived by integrating the speed data over time. Processor  182  uses this publishable information to determine traffic conditions and prepare a graphical display for display  102 . In this embodiment the roads on the map shown by the display  102  can be highlighted with a specific color correlated with the traffic conditions on the road. 
         [0180]    For example, if vehicle  20  while traveling southbound passes an accident that has been blocking northbound traffic for the last hour, the travel information vehicle  20  receives from those stopped vehicles will indicate that the vehicles have been stopped for at least the last 20 minutes. Vehicle  20  continues to travel southbound past the traffic jam broadcasting its own travel data for the last 20 minutes as well as travel data received from vehicles passed; in particular those vehicles stopped due to an accident on the northbound lane. 
         [0181]    Vehicle  21 , when approaching vehicle  20  captures this broadcast information and processes it as previously described. The driver of vehicle  21  noticing the stopped vehicles ahead (where a section of the road is marked in red on the display  102 ) may then decide to take another route with less traffic. Furthermore, vehicle  21  will use its own transmitter to relay its travel history and that travel history of vehicles it passes to oncoming traffic. 
         [0182]    In another scenario, information related to roads or highways other than the one currently being traveled may be relayed. For example, if vehicle  20  while traveling westbound passes an accident that has been blocking eastbound traffic for the last hour, the travel information vehicle  20  receives from those stopped vehicles will indicate that the vehicles have been stopped for at least the last 20 minutes. Vehicle  20  exits the highway and enters another highway traveling southbound. Vehicle  20  travels southbound broadcasting its own travel data for the last 20 minutes as well as travel data received from vehicles passed; in particular those vehicles stopped due to an accident on the westbound lane of the highway previously traveled. 
         [0183]    Vehicle  21  traveling northbound, when approaching vehicle  20  captures this broadcast information and processes it as previously described. The driver of vehicle  21  originally intending to travel eastbound on the highway vehicle  20  was previously traveling on, noticing that traffic is stopped on the eastbound side of the desired highway (where a section of the road is marked in red on the display  102 ) may then decide to take another route with less traffic. Furthermore, vehicle  21  will use its own transmitter to relay its travel history and that travel history of vehicles it passes to oncoming traffic. 
         [0184]    A vehicle so equipped with a forward facing image sensor may receive modulated signals from various sources and interpret the signals to produce a map of traffic conditions in the vicinity. Information gathered from modulated light from traffic lights, LED arrays on roadway signs, the lights of other vehicles, and other signal sources could then be utilized in a variety of ways. For example, a navigation program running on an onboard computer may compare traffic information received from various sources to the vehicle operator&#39;s intended route to determine if another route would be faster or determine the fastest of all possible routes. 
         [0185]    Referring to  FIGS. 20A and 20B , a motorcycle  206  is equipped with a plurality of signalers  208  and  212  employing LEDs or other light emitting devices driven in a manner similar to that previously described in connection with  FIG. 2 ,  7 , or  9 . In this embodiment signaler  212  is a brake light/turning signal assembly that can either be driven conventionally or modulated to produce an encoded signal in rearwardly projecting beam  216 . Assembly  208  includes a headlight that produces a forward beam  214 F and turning signals producing right beam  214 R and left beam  214 L. 
         [0186]    Signalers  208  and  212  can produce modulated and encoded signals of the Thai previously described. In particular, beams  214 R and  214 L may produce encoded signals indicating that the rider of motorcycle  206  intends to change lanes. 
         [0187]      FIG. 21  shows a schematic block diagram of the transmitter of  FIG. 2  suitably modified and installed on a building such as indicated in  FIG. 16 . 
         [0188]    Utility tracking entity  222  has output OUT which outputs to both processor  10  at input IN 2 , and location modulation means  224 , the output of which is presented to processor  10  at input IN 1 . Processor  10  generates a signal suitably modulated and presented to amplifier  16 , which in amplifies the signal and passes it to LED assembly  12 , which is similar to assembly  12  of  FIG. 16  used for illumination of street numbering. 
         [0189]    Utility tracking entity  222  provides an output stream suitably encoded to provide a signal at terminal OUT indicative of at least one of: resource usage, cost, fuel cost, potential or a combination of both. Suitably encoded data stream from output OUT of utility tracking entity  222  is presented to input pin IN 2  of processor  10 . 
         [0190]    Entity  224 , provided at input pin IN, with data stream from pin OUT of utility tracking entity  222 , is a circuit, printed, integrated, or a combination thereof. Entity  224 , not shown physically, is equipped with a jumper arrangement to encode at least one of street number, fuel price, energy price per unit, or a combination thereof. This is passed in turn to processor  10 , equipped with memory means (not shown) wherein it is suitably amplified by amplifier  16  and encoded to modulate LEDs on assembly  12 , with appropriate encoded optical information. Beam  220  is oriented by means of the orientation entity of  FIG. 17 . 
         [0191]    Light from so generated is coincidentally used to illuminate at least one of: the street number, to indicate the price of fuel, the price of energy, or a combination thereof. 
         [0192]    Use of this arrangement may coincidentally make use of a portable navigation device such as GPS, PND, or cellphone infrastructure to encode the location at which this data is taken with at least street number or location information. 
         [0193]      FIG. 22  shows a transmitter operating in the visible part of the spectrum that is installed on a sign  242 . Sign  242  can be driven to display different prices and is therefore considered adjustable signage. Fuel price sign  242  contains the circuitry of  FIG. 21  (not shown in  FIG. 22 ). The circuitry is suitably programmed to have emitted beam  240  encoded to transmit fuel price. The beam  240  is oriented at angle  238  to intersect the likely direction of travel  234  of vehicle  20 . Vehicle reception angle  236 , coincidentally the same as sign transmission angle  238  is the angle in plan view between the vehicle axis and the perceived reception angle. It will be understood that beam  240  is oriented such that the optical transmission beam transmits to a point at a standard height above the ground at the location of vehicle reception. The anticipated reception angle is suitably oriented, within practical alignment limits, at the opposite angle so as to maximally receive the transmitted beam. 
         [0194]    In another embodiment, not shown, the vehicle transmits an modulated optical signal with sufficient strength so as to be capable of reception at the sign. This vehicle transmitted signal is encoded with a network address permitting addressing of where the information concerning the price of fuel can be sent, such that an occupant of the vehicle can further use this or information based on this price. 
         [0195]    In some embodiments the luminance sensing apparatus located on vehicle  20  accumulates data pertaining to the price of fuel and location, which was optically encoded and radiated in essence in the visible spectrum. The accumulated data is relayed to a network that accumulates this information, tracks vehicle position and makes a calculation as to where the most efficient location to refuel is based on available information. This calculation is made available to at least one member of a fleet of vehicles. The data is optically encoded with an LED in sign  242 , which employs a reflector mounted at a 45 degrees to the expected path from which vehicle  20  arrives in plan view and oriented in a descending path inclined 15 degrees to level, in such a way as to intersect the middle of a vehicle in the position most likely to be occupied at least at one point in time by an oncoming vehicle, at a height of 1.5 m above ground. Vehicle  20  may have a sensing apparatus employing a PIN diode, with a reflector, mounted about 1.5 m above ground, and in such orientation as to optimize capture of rays arriving from 45 degrees ahead of the vehicle, passenger side, and arriving from 15 degrees above the horizontal. 
         [0196]    Referring to  FIG. 23A , a standard 8-bit word format has initial signal level  244 , considered here to be the illuminated state, start bit  256 , parity bit  260 , stop bit  252  and subsequent level  254 . In the simplest configuration the data following start bit  256 , occurs at expected bit times  246 ,  248 ,  250  and so on for bits 1,2,3 and so on shown by  258 . This is shown with an 8 bit word. Other lengths of word are equally acceptable. Bit position  260  is an optional parity bit. Level  252  is a non-optional stop bit and must be of sufficient length so as to permit the perception of the light being illuminated constantly 
         [0197]    To ensure that the beam is always illuminated, the state of the data stream between modulations is to remain in the illuminated state,  244 , and after the modulation word, state  254 . 
         [0198]    The application benefits from redundancy of signal. This redundancy can be in different forms. The first and simplest form is the parity bit  260  of  FIG. 23A , which is appended to the data word to indicate whether the number of bits in the word is odd or even. This permits a form of error detection. 
         [0199]    The foregoing signal can be further enhanced by including error detection. This error detection can be any one of several known schemes and can include error correction, encoding redundancy, and voting filtered signal recovery. 
         [0200]      FIG. 23B  shows the same standard 8-bit format word with even more redundancy permitting error correction and greater error detection at the receiving end. In  FIG. 23B  several bits  262  are appended to the basic word (taken here as 8 bit, but can be any number). The extra bits  262  permit error correction, an important aspect in this application where many different visible optical noise sources exist. Processing of this additional data at the receiving end of the link permits a more robust link. 
         [0201]    Supplementing the data with redundant or semi-redundant information, shown in either case as bits  262 , permits the recovery of the correct information due to noise, such as other light sources. In an alternate embodiment this can be a cyclic redundancy checksum or CRC, as it is commonly known in the industry. 
         [0202]    Data words that are sent can be doubled up, tripled up or sent in any number of multiples such that failure of corrupted words shall not necessitate loss of data. A simple arrangement for recovery includes data voting on a word by word basis where words are tripled up and the odd word is discarded. An additional aspect of this is to use a data link in the opposite direction to indicate reception of the data, such as transmission control protocol (TCP). 
         [0203]    As shown in  FIGS. 23A and 23B , any of the bits can be in any state. This might necessitate either further data formatting before transmission, or disallowing certain members of the data set (unless the entire data word is always transmitted with the entire time from start to finish being less than the flicker duration threshold perceptible to humans). The exemplary modulator shown in  FIG. 24A  alleviates this difficulty. 
         [0204]    Human perceptibility limits are on the order of 30 times per second or roughly on the order of 30 ms. Optical sensors work by receiving the light, which is in turn turned into a charge, which increases with exposure time. The optical path will become more robust, and the likelihood of reception will be increased if the sensor can integrate for a larger fraction of the time window permitted by the potentially changing vehicle/infrastructure geometry. 
         [0205]    Using this improved modulator permits much longer integration times, consequently more robust optical segments, while remaining human imperceptible. The example of  FIG. 24A  shows a mechanism which permits a modulation which leaves a bit illuminated (here data bit 4 is a constant one) in the middle of the otherwise modulated word. This constricts the maximum fraction of the overall time for which the link will be continuously extinguished, hence permitting more data to be transferred without flicker, or the same data transferred more reliably without human perceived flicker. 
         [0206]    In  FIG. 24A  the modulation arrangement of  FIG. 2  is expanded to show in further detail processing means  264  with eight data outputs D 1  through D 8 . All the outputs D 1 -D 8 , except output D 4 , are coupled in parallel data stream  266  to corresponding inputs D 1 -D 8  of Universal Asynchronous Receiver Transmitter (UART)  268  which in turn presents a serially encoded and modulated signal  270  to optical transmitter  272  (corresponding to LED assembly in  FIG. 2 ). 
         [0207]    Optical transmitter  272  transmits optically encoded data  274  to optical receiver  276  which in turn outputs signal  278  to UART  280 , which in turn presents the parallel data (D 1  to D 8 ) to processing means  282  (corresponding e.g., to processing means  82  of  FIG. 10 ). 
         [0208]    This arrangement is enhanced with the presence of two exclusive OR gates  284  and  286 . The eight inputs of exclusive OR gate  284  are separately connected to the eight outputs D 1 -D 8  of processor  264  to produce a high output when those outputs have even parity (an even number of bits are high). The output of Exclusive OR gate  284  is presented to Even Parity Enable input EPE of UART  268  to control whether UART  268  will supply an extra parity bit to produce even (odd) parity. In effect, the bit stream will be as shown in  FIG. 24B  where the fourth data position is always high and the value normally appearing there will be represented by the value of the bit  260  in the trailing parity position. 
         [0209]    The use of the exclusive OR gate  284  permits data from bit 4, D 4 , to be interlaced with the rest of the data via the parity bit, (borrowed here) allowing the bit 4 input position to UART  268  to be tied to logic high allowing its position in the data stream, shown as  258 ′ in  FIG. 24B , to remain illuminated each time that it comes up. 
         [0210]    The eight inputs of exclusive OR gate  286  separately connect to parity error output PE, outputs D 1 -D 3 , and outputs D 5 -D 8  of UART  280 . The outputs D 1 -D 8  of UART  280  connect to the corresponding inputs D 1 -D 8  of processor  282 , except that the output of exclusive or gate  286  connect to input D 4  of processor  282 . Exclusive OR gate  286  by sampling the Parity Error Signal PE permits recovery of the parity bit and with sampling of the parity of the remaining data bits this can be presented to the signal processing means  282  prior to the Data Valid Signal DAV being asserted. UART  280  is configured to receive Even Parity. A complete set of data is thusly presented to data processing means  282  at inputs D 1 -D 8 . 
         [0211]    The arrangement shown in  FIG. 25A  involves enforcing an illuminated portion  264  of the data stream between the data bits so the extinguished portion is just less than the humanly discernable threshold. This signaling application, with potentially short contact intervals benefits from ensuring that the available time is used to a greater extent by the modulated signal wherein even with a maximum extinguished time flicker is not discernable to a human viewer. Start bit  256 , parity bit  260 , stop bit  252 , initial signal level  244 , bits  246 ,  248 ,  250  and so on as well as inter-word signal level  254  are other parts of the format. Bit numbers  258  are shown as Bits 1,2,3, and so on up to 8. 
         [0212]      FIG. 25A  shows the same standard word format wherein each bit time is interlaced with an on signal permitting a human to consider the transmitted word to be imperceptible from a solidly on transmission with repetitive on signals sufficiently wide and close permitting use with a receiver capable of increased signal resolution time. 
         [0213]    An alternate format is shown in  FIG. 25B  with relatively brief data bits and relatively long interbit intervals. Here the overall word should exceed the slowest flicker speed perceptible to humans. Start bit  256 , parity bit  260 , stop bit  252 , initial signal level  244 , bits  246 ,  248 ,  250  and so on as well as inter-word signal level  254  are the basic parts of the format. Bit numbers  258  are shown as Bits 1,2,3, and so on up to 8. Inter-bit signal levels are shown here as extinguished  266 . 
         [0214]      FIG. 25B  is an alternative format indicating that for sufficiently robust optical links the data acquisition phase, shown here by  246 ,  248 ,  250  and so on, can be significantly less than the duration of the phase used to keep the human viewer perceiving these bit intervals as solidly on. 
         [0215]      FIG. 25B  shows the same standard word format wherein each bit time is interlaced with an on signal wherein the off time is reduced to that which is barely human imperceptible from a solid on signal. 
         [0216]    Examples of this data format shown in  FIGS. 25A and 25B  are achievable by suitable processing in processor means  10  of  FIG. 2 .  FIG. 25A  is indicative of a format benefiting a link with illuminated elements shown in time interval  264 , which is on sufficiently often that the data shown in data elements  246 ,  248 ,  250  and so on can be either high (illuminated) or low (extinguished) without concern. 
         [0217]      FIG. 26  shows the word format for an arrangement with ongoing sampling, offering interstice illumination based on the previous data passed. In this example the data processing means keeps a running track of how long the optical link has been extinguished for and ensures that a bit in this case shown in the interstices between the data being sent marked as 1,2,3, and so on, is illuminated frequently enough as to have the human viewer perceive the illumination source as continuously on. In one case a high data bit will be followed by a low interstitial bit and vice versa. 
         [0218]    In general, the time that a vehicle is sufficiently optically aligned, between transmitter and receptor, should be used for data transfer, be it illuminated or extinguished, while retaining blanking intervals sufficiently short as to be imperceptible to humans. Thus, the data format should not modulate both data pulses and the inter-pulse blanking intervals concurrently, but rather one or the other. 
         [0219]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.