Indicating system using pulsed optical techniques

• US 3,924,253 A
• Filed: 01/16/1974
• Issued: 12/02/1975
• Est. Priority Date: 01/16/1974
• Status: Expired due to Term

• Current Assignee: Burroughs Incorporated (Terreno Realty Corp.)
• Original Assignee: Francis C. Marino
• Inventors: Marino, Francis C.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/433,846
• Time in Patent Office: 685 Days
• Field of Search: 340/258B 331/75,111 315/2A 307/283
• US Class Current: 340/600
• CPC Class Codes: G08B 13/183 by interruption of a radiation beam or barrier

Abstract

A system for indicating the state of transparency of an optical path has: at one end of the path, a light pulse generator which includes a solid state means, such as a light-emitting diode, which emits light whenever current of sufficient amplitude passes therethrough and a periodically operating switching means which periodically causes current to flow from a current source through the solid state means; and at the other end of the path, a transducer for converting light pulses to electrical pulses which pass through an A.C. coupled amplifier to an indicator.

Claims

1. A light pulse generator comprising a reference potential means, a power supply, first and second serially connected current limiting resistors, the free end on said first current limiting resistor being connected to said power supply, a storage capacitor connected between the junction of said resistors and said reference potential means, a light emitting diode having one terminal thereof connected to the free end of said second current limiting resistor and a second terminal, a signal controlled swiTch for controllably connecting the other terminal of said light emitting diode to the reference potential means and having a control input, a uni-junction transistor having an emitter, and first and second bases, a load resistor having one end connected to the first of said bases, means for applying an operating potential between the second of said bases and the other end of siad load resistor, a timing resistor and a timing capacitor connected in that order between the other terminal of said light emitting diode and said reference potential means, means for connecting the junction of said timing resistor and timing capacitor to the emitter of said uni-junction transistor, and means for connecting the first base of said uni-junction transistor to the control input of said signal controlled switch.

2. An indicating system for indicating the state of transparency of an optical path comprising:

a light pulse generator at one end of the optical path, said light pulse generator comprising a source of an electrical current, solid state means for emitting light whenever an electrical current flows therethrough, a switching means for switching between current non-conductive and current conductive states in response to the receipt of signals, means for connecting said solid state means between said source and said switching means so that current flows from said source via said solid state means to said switching means whenever the latter is in the conductive state, and a free-running pulse signal generator means connected to said switching means for transmitting periodically recurring signals thereto said free-running pulse generator means comprising a unijunction transistor having an emitter, and first and second bases, a resistor having one end connected to the first of said bases, means for applying an operating potential between the second of said bases and the other end of said resistor, a timing resistor and a timing capacitor connected in that order between the junction of said solid state means and said switching means and a reference potential means, and means for connecting the junction of said timing resistor and timing capacitor to the emitter of said unijunction transistor; and

a light pulse sensor at the other end of the optical path, said light pulse sensor comprising a transducer means for converting light energy to electrical signals, amplifier means connected to said transducer means for amplifying only A.C. signals received from said transducer means, and indicator means connected to said amplifier means for giving an indication whenever said amplifier means transmits an A.C. signal.

3. The indicating system of claim 2 wherein said solid state means is a light-emitting diode.

4. The indicating system of claim 3 wherein said source of electrical current comprises a power supply, a storage capacitor and a further resistor connecting said storage capacitor to said power supply.

5. The indicating system of claim 2 wherein said indicator means includes integrator means which yields a continuous signal as long as it receives pulse signals which recur within a given time interval.