Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-04-14
2003-01-07
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06504633
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the simultaneous dual use of radiation, e.g., visible light, received from a transmitter, for both a conventional application, e.g., illumination, combined with the additional application of receiving information over a wireless media. The present invention further relates to electronic circuits capable of receiving information-bearing transmissions from a “dual use” transmitter and decoding or presenting the information to a user. The present invention further relates to the presentation of this data as an audio signal. The present invention further relates to the presentation of this data as a text or graphical signal. The present invention further relates to the presentation of this data as any digital or analog information signal for another electronic circuit or electronic or electromechanical system. The present invention further relates to schemes for efficient receiving and decoding of transmitted signals designed to maximize the bandwidth or information transfer capability of the optical data channel. The present invention further relates to the construction of receivers for the detection of modulated information in transmitted light.
BACKGROUND OF THE INVENTION
A communication network is a means for conveying information from one place to another. The information can be digital data, audio, video, text, graphics, data, sign language, or other forms. Establishing and maintaining communication networks is one of the oldest known activities of mankind, ranging from the shouting and drum signals of prehistory through written messages, signal flags, signal fires, smoke signals, signal mirrors, heliographs, signal lanterns, telegraphs, radios, telephones, televisions, microwave signals, linked computers and the internet. Improving communication networks, and finding new, inexpensive ways to meet the growing demand for transmission capability will continue to be a major technical focus in the future. We have developed a communication network that makes “dual use” of sources of radiated transmissions. One implementation of this communication network, such as a wide bandwidth intranet, uses conventional light fixtures, like fluorescent lights, as transmitters. Information is encoded in the lamp light by modulating the electric lamp current with an information signal. If the modulation is done with care, the lamp continues to emit light with no perceptible visual flicker to the human eye. However, an electronic circuit or receiver can be used to decode information in the transmitted light. The lights continue to serve their primary function as a source of illumination, while simultaneously creating a wireless optical data path for information transmission. The purpose of this invention is to disclose efficient means for creating a receiver that decodes information in the lamp light with the highest possible bandwidth or information carrying capacity over the transmitted channel. While the focus of this discussion is on visible lighting systems, it is understood that the dual use transceiver concept could be applied to any system that employs electromagnetic radiation, e.g., a RADAR set, for some purpose and which could also be simultaneously modulated to provide information transmission capability.
This invention is the first to propose establishing a transceiver system using any radiating transmitter with dual utility where the primary utility is any application, not just illumination but also possibly range finding, lane marking, or other applications, and the secondary utility is communication. This invention is the first to propose the transmission of bandlimited analog information such as audio signals by using frequency modulation, which enhances the noise immunity and available bandwidth over previous schemes while specifically avoiding sensory perceptible flicker in the transmission. It is the first to propose the efficient transmission of digital data using pulse code frequency modulation, and also the first to propose encoding digital bits in sidebands around the carrier frequency of the transmitter. It is the first to propose the use of a nonlinear detector in a dual-use network receiver to improve settling and detection time of pulse-coded data. These schemes for the transmission and reception of digital data substantially enhance the available data transmission rate in comparison to schemes in the prior art, again while elimination perceptible flicker. It is the first to disclose schemes for creating multiple data transmission channels using the same transmitter, and the first to propose a receiver in a “dual-use” network capable of selecting one channel from a spectrum of available choices. It is the first to propose a receiver with variable “lock-in” or transmitter capture characteristics, allowing the tailoring of the behavior of the receiver as it locks on to different transmitters. This feature could be especially important for optimizing the receiver's behavior in way-finding applications, and in environments with many different closely spaced transmitters, to ease the process of acquiring and holding a data channel between the transmitter and receiver.
There have been a few reports of the use of visible lighting as a carrier in electronic communication networks. The earliest reference to using lighting to send electronic information as well as to provide illumination appears to be Dachs (U.S. Pat. No. 3,900,404) disclosing an analog amplitude-modulation (AM) scheme to modulate the arc current in a fluorescent lamp, the “carrier” signal, with an audio information signal. King, Zawiski and Yokoun (U.S. Pat. No. 5,550,434) disclosed an updated electronic circuit that also provides for AM modulation of the arc current with an analog signal. Smith (U.S. Pat. No. 5,657,145) teaches a method for encoding low-bandwidth digital information into the lamp light using a pulsed AM technique. The encoding technique involves chopping 100 microsecond slices of current out of the arc waveform. Nakada (Japanese Patent application 60-32443, Feb 19, 1985.) reports the use of FM modulation and a frequency shift keying (FSK) scheme to transmit digital data using visible lighting. Gray (U.S. Pat. No. 5,635,915 Jun. 3, 1997 and PCT WO90/13067, Oct. 11, 1991.) has reported a phase modulated (PM) product pricing system for supermarket shelf labels where a signal is sent from visible lighting to individual product price labels on shelves to cause the listed prices to change when desired.
Other communication schemes have been proposed that do not use the lamp light as the carrier, but instead use the lamp fixture as an antenna for transmitting conventional radio wave or microwave signals. In Uehara and Kagoshima (U.S. Pat. No. 5,424,859), for example, the inventors disclose techniques for mounting a microwave antenna on the glass surface of fluorescent and incandescent lamps. Buffaloe, Jackson, Leeb, Schlecht, and Leeb, (“Fiat Lux: A Fluorescent Lamp Transceiver,” Applied Power Electronics Conference, Atlanta, Ga., 1997) first outlined the possibility of using pulse-code modulation to transmit data with a fluorescent lamp. In the latter reference, a three-level code shifts the arc frequency to one of three possibilities every 2 milliseconds. The result is a steady light output, on average, with no perceptible flicker. This transceiver set relies on an encoded clock embedded in the three-level, transmitted waveform to synchronize the decoding process in the receiver. We have developed a dual-use transceiver system that can transmit and receive frequency modulated transmissions carrying either analog or digital data. Our experiments confirm that frequency modulated (FM) transmissions provide the best signal recovery properties in a dual-use transceiver employing, for example, fluorescent lamps as a transmitter. We have found that, with care in the design of the transceiver set, analog signals in the audio frequency range can be used to frequency modulate fluorescent lamps without causing flicker visible to the human eye in th
Hovorka George B.
Jackson Deron
Leeb Steven B.
Lupton Elmer C.
Choate Hall & Stewart
Pascal Leslie
Talking Lights
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