Optical warning system

• US 5,057,820 A
• Filed: 05/01/1989
• Issued: 10/15/1991
• Est. Priority Date: 05/01/1989
• Status: Expired due to Term

• Current Assignee: Airborne Research Associates Inc.
• Original Assignee: Airborne Research Associates Inc.
• Inventors: Markson, Ralph J., Govaert, Johan A.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Sutcliffe, Geoff
• Application Number:
  US07/345,720
• Time in Patent Office: 897 Days
• Field of Search: 340/600, 340/601, 340/522, 340/961, 340/981, 340/982, 324/133, 324/72, 73/170 R, 250/214 B, 250/214 RC
• US Class Current: 340/600
• CPC Class Codes: G01S 3/16 using amplitude comparison of signals derived sequentially from receiving antennas or antenna systems having differently-oriented directivity characteristics or from an antenna system having periodically-varied orientation of directivity characteristic

Abstract

A lightning and strobe light detector and warning system capable of distinguishing strobe light and lightning flashes and indicating to an operator of the existence of a flash even under high illumination background conditions. The device may comprise a plurality of detectors and therefore not only distinguish between the strobe and lighting flashes but also indicate the direction of a flash.

Claims

1. A lightning and strobe light detection system comprising:

an optical detector for producing a first electrical output signal in response to a lightning flash and light from a strobe lamp, and

a signal discrimination circuit operative to determine whether said electrical output signal has been produced in response to lightning and whether said electrical output signal has been produced in response to light from a strobe lamp and operative to provide a first indication of lightning if said electrical output signal has been produced in response to lightning and operative to provide a second indication of light from a strobe lamp if said electrical output signal has been produced in response to light from a strobe lamp.

2. The system of claim 1 further comprising:

a second optical detector for producing a second electrical output signal in response to a lightning flash and a strobe lamp flash, and

a coincidence circuit responsive to said first electrical output signal and said second electrical output signal and which generates a coincidence output signal only when said first and second electrical output signals are received at essentially the same time, said discrimination circuit being responsive to said coincidence output signal.

3. The system of claim 1 further comprising:

an RF detector for producing a third electrical output signal in response to lightning flash, and

a coincidence circuit for receiving said first electrical output signal and said third electrical output signal and generating a first coincidence output signal only when said first electrical output signal and said third electrical output signal are received at essentially the same time, said discriminator ion circuit being responsive to said first coincidence output signal.

4. The system of claim 3 further comprising:

a second optical detector for producing a second electrical output signal in response to a lightning flash and a strobe lamp flash, and

a second coincidence circuit responsive to said first electrical output signal and said second electrical output signal and which generates a second coincidence output signal only when said first and second electrical output signals are received at essentially the same time,

said first coincidence circuit being responsive to said third electrical output signal and said second coincidence output signal, said first coincidence circuit producing a first coincidence output signal only when said second coincidence signal and said third electrical output signal are received at essentially the same time,

said discrimination circuit being responsive to said first coincidence output signal.

5. The system of claim 1 further including a rate indicator responsive to said indication by said discrimination circuit to indicate whether a predetermined flash rate is exceeded.

6. The system of claim 1 further comprising:

a second optical detector,

a second band pass filter connected so as to receive the output signal from said second detector,

a second threshold adjustment device which receives the output signal from said second filter,

a second level detector which receives the output signal from said second filter and the output from said second threshold adjustment device; and

wherein said signal discrimination circuit further comprises;

a coincidence circuit responsive to the output of said first threshold adjustment device and the output of said second threshold adjustment device, which produces an output signal only when an input signal is received by the coincidence circuit from each of said threshold adjustment devices at essentially the same time, said signal discrimination circuit being responsive to the output of said coincidence circuit.

7. The system of claim 1 wherein said threshold adjustment device automatically sets its detection threshold to a level just above that of the noise level generated by background light in the field of view of said detector.

8. The system of claim 2 wherein said discriminator comprises circuitry for determining if a flash of light includes more than one pulse of light.

9. A lightning and strobe light detecting system comprising:

an optical detector capable of responding to the optical emissions of strobe lamp and lightning flashes, said detector producing an output signal proportional to the level of light detected;

a band pass filter connected so as to receive the output signal from said detector and allowing only those signals which fall within the band pass of the filter to pass through;

a threshold adjustment device which receives the signal from the band pass filter and determines the response of the detector to a background level of illumination, said adjustment device generating an output signal which is indicative of the background illumination level;

a level detector which receives the signal from the filter and the signal from the threshold adjustment device and produces an output signal only if the signal from the filter exceeds the background level from the threshold device;

a discriminator for determining whether said detected light is from lightning or a strobe lamp, said discriminator receiving said signal from said level detector and producing one output signal if lightning is detected and a second output signal if a strobe light from lamp is detected; and

a display which indicates the occurrence of a flash of light and whether the flash was caused by lightning or a strobe lamp, as indicated by the output signal of the level detector,

wherein said discriminator comprises circuitry for determining if a flash of light includes more than one pulse of light,

wherein said discriminator comprises a timing circuit which determines elapsed time between the pulses of light,

wherein said discriminator circuitry includes a first monostable multivibrator and a second monostable multivibrator, said first monostable multivibrator enabling said second monostable multivibrator if two of said pulses of light occur within a predetermined period of time,

wherein said pulses must occur between approximately 15 msec. and 75 msec. of each other.

10. A lightning and strobe light detection system comprising:

A. a plurality of optical units, each optical unit comprising

i. a detector, capable of responding to the light emissions of strobe lamps and lightning flashes, said detector producing an output signal proportional to the level of light detected,

ii. a band pass filter, connected so as to receive the output signal from said detector, said filter having a band pass allowing only an output signals having a predetermined range of frequencies to pass through;

iii. a threshold adjustment device which receives the output signal passing through said filter and determines the response of said detector to a background level of illumination, said adjustment devices generating an output signal which is indicative of the background illumination level within the field of view of said detectors;

iv. a level detector which receives the signal from said filter and the signal from said threshold adjustment device and produces an output signal only if the signal from said filter exceeds the background level from said threshold device;

B. a signal discriminating circuit operative to determine, for each detector, whether said output signal has been produced in response to lightning and whether said output signal has been produced in response to light from a strobe lamp and operative to provide, for each detector, a first indication of lightning if said output signal has been produced in response to lightning and operative to provide a second indication of light from a strobe lamp if said output signal has been produced in response to light from a strobe lamp; and

C. a display which indicates the occurrence and bearing of said light emissions and whether the light emission was caused by lightning or a strobe lamp, said optical units being positioned so that each detector detects light emissions from a different direction.

11. The system of claim 10 wherein said optical units comprise a second detector such that said discriminating circuit does not produce said indicator signal unless both detectors detect said light emission at essentially the same time.

12. The system of claim 10 wherein said discriminating circuit further includes a weighing circuit which provides directional information from said output signals of said level detectors of said optical units to said display.

13. A method for detecting lightning and light from strobe lamps comprising the steps of:

detecting flashes of light with an optical detector;

determining whether said flashes of light are due to lightning and whether said flashes of light are due to strobe lamps; and

producing a first lightning indication when lightning is detected and a second strobe indication when light from strobe lamps are detected.