Pulsed-laser detection with pulse stretcher and noise averaging
First Claim
1. In a laser detection system of the type having a photodetector and a decision network, wherein the photodetector receives an optical signal and converts it to an electrical signal and the decision network receives the electrical signal and evaluates it to determine whether it represents a valid laser signal, said decision network comprising:
- pulse stretching means for receiving the electrical signal and converting it into a first signal having an increased pulse width relative to the received electrical signal;
noise averaging means for receiving the electrical signal and converting it into a second signal corresponding to an average noise component of the received electrical signal;
envelope generating means for generating a threshold reference signal which is a linear function of the difference in magnitude between the first signal and the second signal;
first comparator means for receiving the first signal and the threshold reference signal and for comparing the magnitude of the first signal to the magnitude of the threshold reference signal, wherein the first comparator means generates a first logic output which is true when the magnitude of the first signal is greater than the magnitude of the threshold reference signal;
second comparator means for receiving the electrical signal and the threshold reference signal and for comparing the magnitude of the electrical signal to the magnitude of the threshold reference signal, said second comparator means having a characteristic response time, wherein the second comparator means generates a second logic output which is true when the magnitude of the electrical signal is greater than the magnitude of the threshold reference signal and the pulse width of the electrical signal as a function of time is greater than the response time of the second comparator;
logic means responsive to the first logic output and to the second logic output for generating a first alert signal when the first logic output is true and the second logic output is false; and
first indicator means responsive to the logic means for indicating the alert signal.
26 Assignments
0 Petitions
Accused Products
Abstract
A photodetector receives an optical signal and converts it an electrical signal. A pulse stretcher converts the electrical signal into a first signal which is characterized by having an increased pulse width relative to the electrical signal. A noise averager converts the electrical signal into a second signal which is representative of the average noise component of the electrical signal. A threshold reference is generated as a linear function of the potential difference between the first signal and the second signal. A first comparator compares the magnitude of the first signal and the threshold reference signal and generates a first logic output which is true if the magnitude of the first signal is greater than the magnitude of the threshold reference signal. A second comparator compares the magnitude of electrical signal and the threshold reference signal and generates a second logic output which is true if the pulse width of the electrical signal measured as a funtion of time is greater than the response time of the second comparator. A logic circuit generates an alert indication if the first logic output is true and the second logic output is false.
150 Citations
6 Claims
-
1. In a laser detection system of the type having a photodetector and a decision network, wherein the photodetector receives an optical signal and converts it to an electrical signal and the decision network receives the electrical signal and evaluates it to determine whether it represents a valid laser signal, said decision network comprising:
-
pulse stretching means for receiving the electrical signal and converting it into a first signal having an increased pulse width relative to the received electrical signal; noise averaging means for receiving the electrical signal and converting it into a second signal corresponding to an average noise component of the received electrical signal; envelope generating means for generating a threshold reference signal which is a linear function of the difference in magnitude between the first signal and the second signal; first comparator means for receiving the first signal and the threshold reference signal and for comparing the magnitude of the first signal to the magnitude of the threshold reference signal, wherein the first comparator means generates a first logic output which is true when the magnitude of the first signal is greater than the magnitude of the threshold reference signal; second comparator means for receiving the electrical signal and the threshold reference signal and for comparing the magnitude of the electrical signal to the magnitude of the threshold reference signal, said second comparator means having a characteristic response time, wherein the second comparator means generates a second logic output which is true when the magnitude of the electrical signal is greater than the magnitude of the threshold reference signal and the pulse width of the electrical signal as a function of time is greater than the response time of the second comparator; logic means responsive to the first logic output and to the second logic output for generating a first alert signal when the first logic output is true and the second logic output is false; and first indicator means responsive to the logic means for indicating the alert signal. - View Dependent Claims (2, 3, 4, 5, 6)
-
Specification