Optical communication system

• US 3,900,404 A
• Filed: 08/02/1973
• Issued: 08/19/1975
• Est. Priority Date: 08/02/1973
• Status: Expired due to Term

• Current Assignee: Martin R. Dachs
• Original Assignee: Martin R. Dachs
• Inventors: Dachs, Martin R.
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Psitos, Aristotelis M.
• Application Number:
  US05/384,798
• Time in Patent Office: 747 Days
• Field of Search: 250/199 315/DIG.25,29CD
• US Class Current: 398/172
• CPC Class Codes: H04B 10/114 Indoor or close-range type systems

Abstract

A fluorescent lamp light output is used as a carrier which is varied in intensity with an audio information signal. The current through the fluorescent lamp is varied not only by the audio information signal to be transmitted but also by a signal having an above audible frequency. This super-audio frequency signal stabilizers the fluorescent tube oscillations and thus prevents noise oscillations at audio frequencies. A line of sight receiver having a photo-electric transducer provides the audio signal output.

Claims

1. THE TRANSMITTER OF AN OPTICAL COMMUNICATION SYSTEM COMPRISING:

A FLUORESCENT LAMP, AUDIO SIGNAL MEANS TO PROVIDE AN AUDIO FREQUENCY SIGNAL FOR CONVEYING WHATEVER AUDIO COMMUNICATION IS TO BE TRANSMITTED, OSCILLATOR MEANS TO PROVIDE SUPER AUDIBLE FREQUENCY SIGNAL, A SUMMING AMPLIFIER COUPLED TO SAID AUDIO SIGNAL AND TO SAID SUPER AUDIBLE SIGNAL TO PROVIDE A SUM SIGNAL, AND A CONTROL VALVE RESPONSIVE TO SAID SUM SIGNAL AND COUPLED TO SAID FLUORESCENT LAMP, TO VARY THE CURRENT THROUGH SAID FLUORESCENT LAMP AS A FUNCTION OF SAID SUM SIGNAL, SAID FLUORESCENT LAMP PROVIDING A LIGHT OUTPUT VARYING IN INTENSITY AS A FUNCTION OF SAID AUDIO SIGNAL.

2. The transmitter of claim 1 further comprising:

a momentary starting switch having first and second normally open contacts, a starting circuit including a resistor and capacitor in series across said lamp, said capacitor being connected to a first terminal of said lamp, means to charge said capacitor, said first contact connected to discharge said capacitor upon actuation of said switch to provide a momentary pulse at said first terminal of said lamp, a transformer having a secondary connected across the filament at said first terminal of said lamp and a primary connected through said second contact of said switch to provide a pulse of heating current upon actuation of said switch.

3. An optical communication system comprising:

a fluorescent lamp, audio signal means to provide an audIo frequency signal for conveying whatever audio communication is to be transmitted, oscillator means to provide a super audible frequency signal, a summing amplifier coupled to said audio signal and to said super audible signal to provide a sum signal, a control valve responsive to said sum signal and coupled to said fluorescent lamp, to vary the current through said fluorescent lamp as a function of said sum signal, said fluorescent lamp providing a light output varying in intensity as a function of said audio signal, a photo-electric transducer optically coupled to said light output from said fluorescent lamp, an optical filter at the optical input to said transducer, an audio amplifier coupled to the output of said transducer, and an earphone coupled to the output of the audio amplifier, the response characteristics of said transducer causing the output of said transducer to track with the audio frequency variation of the light input to said transducer, said response characteristic being the sole demodulation characteristic provide within said receiver, said audio amplifier causing the earphone to track the audio frequency variation of light input to said transducer enabling the message to be heard, said optical filter having an attenuation characteristic that substantially cuts out light having wavelengths longer than the ultraviolet.

4. The optical communication system of claim 3 further comprising:

a momentary starting switch having first and second normally open contacts, a starting circuit including a resistor and capacitor in series across said lamp, said capacitor being connected to a first terminal of said lamp, means to charge said capacitor, said first contact connected to discharge said capacitor upon actuation of said switch to provide a momentary pulse at said first terminal of said lamp, a transformer having a secondary connected across the filament at said first terminal of said lamp and a primary connected through said second contact of said switch to provide a pulse of heating current upon actuation of said switch.