Optics: measuring and testing – Photometers – Comparison
Patent
1997-08-01
1999-09-28
Kim, Robert H.
Optics: measuring and testing
Photometers
Comparison
356213, 356222, 356445, G01J 110
Patent
active
059597275
ABSTRACT:
An energy beam threat discrimination system (110) adapted for use with laser beam energy (134). The system (110) includes an first detector (114) for detecting a first laser signal. A second detector (112) detects a coherent laser signal. A timer circuit (124, 126) establishes a time interval between the detection of the first laser signal and the detection of the coherent laser signal and provides an output (130) in response thereto. A control circuit (128, 130) determines, based on the output (130), if the first laser signal and/or the second laser signal is threatening. In a specific embodiment, the first detector (114) provides an event detection flag (118) as an output in response to the detection of a first laser signal. The first detector (114) includes a high sensitivity laser light detector (142), a pre-amplifier (144), and an analog threshold circuit (146). The coherent detector (112) provides a coherent detection flag (116) as an output in response to the detection of the coherent laser signal. The timing circuit (124, 126) receives the event detection flag (118) as input and includes a digital clock circuit (124) that starts a timer (126) upon receipt of the event detection flag (118). The control circuit (128) includes a digital comparator circuit (128) in communication with the timing circuit (124, 126), and receives the coherent detection flag (116) as input. The digital comparator circuit (128) is activated by the receipt of the coherent detection flag (116) which triggers a comparison between the output (130) of the timer circuit (124, 126) and a time threshold (131) and provides a reflection signal output indicating if the laser signal is a potential threat or not. The time threshold (131) is the maximum time value allowable for the output (130) for determining that the laser signal is a potential threat and is approximately 10 nanoseconds. Alternatively, the time threshold is the maximum time value allowable for the output (130) for determining that the laser signal is not a potential threat and is approximately 40 microseconds.
REFERENCES:
patent: 4494873 (1985-01-01), Perlmutter et al.
patent: 4804832 (1989-02-01), Gardner
Kim Robert H.
Lenzen, Jr. G. H.
Ratliff Reginald A.
Raytheon Company
Schubert W. C.
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