System for processing reflected energy signals

• US 5,357,331 A
• Filed: 03/24/1993
• Issued: 10/18/1994
• Est. Priority Date: 07/02/1991
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Loral Vought Systems Corporation
• Inventors: Flockencier, Stuart W.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US08/036,348
• Time in Patent Office: 573 Days
• Field of Search: 356/5, 342/135, 342/136
• US Class Current: 356/5.08
• CPC Class Codes: G01S 17/14 wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection

Abstract

An energy pulse capture system senses, receives, and processes signals reflected from a target. In an illustrative embodiment, light pulses are reflected off of a target, received by optical equipment, converted into analog electrical signals, and then processed to obtain information therefrom. The invention basically identifies targets by measuring the time delay between a transmitted signal and a received or "return" signal. The invention includes a windowing system to more efficiently process digitized electrical signals representing the return signals. The windowing system effectively defines a "window" in memory within which the return signal is stored, and "locks" on to this window to reduce time spent searching for the return pulses among other data. In another aspect of the invention, a real time return system is used to more efficiently process the electrical signals representing the return pulses. The real time return system detects the maximum amplitude of the received signal in real time, and stores the current value of a counter used to clock data into memory, thereby facilitating later use of the stored counter value to locate signals representative of the return signal in the memory. The invention also concerns a timing delay system, which conserves memory of the invention by delaying storage of data until a return pulse is actually received.

Claims

1. A system for processing an analog light signal transmitted by a light source and reflected by a target, comprising:

(a) an analog-to-digital converter to receive analog light signals and convert the received light signals into digital electrical signals;

(b) a memory having a plurality of addresses to store digital signals received from the analog-to-digital converter;

(c) a counter providing counter values to regulate the storage of the digital signals in the memory;

(d) a real time return system including a peak detector operatively coupled to the converter to identify the receipt of a target-reflected signal and store the value of the counter occurring at the time of such receipt; and

(e) convolution and peak detecting circuits to utilize the stored counter value to located digital signals representative of the reflected pulse in the memory, and to process the representative digital signals.

2. The system of claim 1, wherein the real time return system further comprises an encoder to encode digital signals received from the converter for use by the peak detector.

3. The system of claim 1, wherein the light source comprises a laser.

4. A method of processing analog light signals transmitted by a light source and reflected by a target, comprising the steps of:

(a) receiving an analog light signal and converting the received light signal into a digital signal;

(b) storing the digital signal in a plurality of memory addresses in accordance with timing signals provided by a counter;

(c) independently detecting the receipt of the reflected signal and storing the counter value occurring when the reflected signal is stored in the memory;

(d) reading digital signals stored in a block of adjacent addresses in the memory, wherein the first address in the block corresponds to the stored counter value; and

(e) processing the digital signals so read.

5. The method of claim 4, wherein the step of independently detecting the receipt of the reflected signal is performed by a peak detecting circuit.

6. The method of claim 5, further including the step of resetting the peak detecting circuit subsequent to storage of the digital signal in the memory.

7. The method of claim 4, wherein the light source comprises a laser.

8. A system for processing an analog light signal transmitted by a light source and reflected by a target, comprising:

(a) an analog-to-digital comparator to receive analog light signals and convert the received light signals into digital electrical signals;

(b) a delay circuit electrically connected to the analog-to-digital comparator to delay digital signals of the comparator for a selected time;

(c) a memory electrically connected to the delay circuit, the memory having a plurality of addresses to store delayed digital signals received from the comparator;

(d) a counter providing clock values to regulate the storage of the delayed digital signals in the memory; and

(e) a timing circuit electrically connected to the analog-to-digital comparator to detect the receipt of a reflected signal and to selectively activate the memory to store the delayed digital signals in response to said detection.

9. The system of claim 8, wherein the delay circuit comprises a coil of wire.

10. The system of claim 8, wherein the delay circuit comprises a fiber optic link.

11. The system of claim 8, wherein the delay circuit comprises one or more transistors.

12. The system of claim 8, wherein the light source comprises a laser.

13. The system of claim 8, wherein the timing circuit includes a peak detector to detect the receipt of a reflected signal.

14. The system of claim 13 wherein the timing circuit includes a monostable multivibrator operatively coupled to the memory to initiate storage of delayed digital signals in the memory for a predetermined time in response to said detection.

15. A method of processing analog light signals transmitted by a light source and reflected by a target, comprising the steps of:

(a) receiving an un-delayed analog light signal;

(b) delaying the analog light signal to convert the delayed light signal into a delayed digital signal;

(c) detecting the receipt of a reflected signal in the un-delayed light signal; and

(d) initiating storage of the delayed digital signal in the memory in response to said detection.

16. The method of claim 15, wherein the light source comprises a laser light source.

17. The method of claim 15, wherein the step of detecting the receipt of the reflected signal is performed by a peak detecting circuit.

18. The method of claim 17, further including the step of resetting the peak detector subsequent to the step of detecting the receipt of the reflected signal.

19. A method of processing analog energy signals transmitted by an energy source and reflected by a target, comprising the steps of:

(a) receiving an analog light signal including a target-reflected signal and converting the received light signal into a digital signal;

(b) storing the digital signal in a block of memory addresses, the storage being synchronized with clock values supplied by a counter;

(c) defining in the block of memory addresses a window of adjacent memory addresses predicted to include data corresponding to the target-reflected signal based upon relationships between memory address blocks in which prior digital signals were stored in the memory and addresses in those blocks in which corresponding target-reflected signals were stored; and

(d) processing the digital signals stored in the memory addresses defined by the window.

20. The method of claim 19, wherein the light source comprises a laser.