Laser vehicle speed detection system

A method for detecting speed of an aircraft, the method comprising:

• transmitting a laser beam into an atmosphere from the aircraft during flight of the aircraft;
• receiving a backscatter light generated in response to transmitting the laser beam;
• measuring a first beat frequency from interfering a first portion of the backscatter light with a reference light derived from the laser beam;
• introducing a time delay to a second portion of the backscatter light to form a time delayed backscatter light;
• measuring a second beat frequency from interfering the time delayed backscatter light with the reference light;
• determining a difference between the first beat frequency and the second beat frequency;
• and
• determining a speed of the aircraft using the difference and a beat frequency selected from one of the first beat frequency and the second beat frequency.

A speed detection system that comprises:

• a laser beam generator configured to emit a laser beam into an atmosphere from a vehicle;
• an interference system configured to:
• interfere a first portion of a backscatter light received with a reference light to form a first beat frequency;
• introduce a time delay to a second portion of the backscatter light to form a time delayed backscatter light;
• and interfere the time delayed backscatter light with the reference light to form a second beat frequency, wherein the backscatter light is received in response to the laser beam being emitted into the atmosphere and the reference light is derived from the laser beam;
• a detection system configured to measure a first beat frequency from interfering the first portion of the backscatter light with the reference light and measure the second beat frequency from interfering the time delayed backscatter light with the reference light;
• and
• a speed analyzer configured to determine a speed for the vehicle using the first beat frequency and a difference between the first beat frequency and the second beat frequency.

A speed detection system comprising:

• a laser beam generator configured to emit a laser beam into an atmosphere from a vehicle;
• a first path that interferes a first portion of a backscatter light received with a reference light and measures a first beat frequency from the first portion of the backscatter light interfered with the reference light;
• a second path that introduces a time delay to a second portion of the backscatter light to form a time delayed backscatter light, interferes the time delayed backscatter light with the reference light, and measures a second beat frequency from interfering the time delayed backscatter light with the reference light;
• and
• a speed analyzer that is in communication with the first path and the second path, wherein the speed analyzer receives the first beat frequency from the first path, receives the second beat frequency from the second path, and determines a speed of the vehicle using the first beat frequency and determines the speed using the second beat frequency in response to the first path being out of tolerance.

A speed detection system comprising:

• a laser beam generator configured to emit a laser beam into an atmosphere from a vehicle;
• an interference system configured to interfere a first portion of a backscatter light received with a reference light to form a first beat frequency, introduce a time delay to a second portion of the backscatter light to form a time delayed backscatter light, and interfere the time delayed backscatter light with the reference light to form a second beat frequency, wherein the backscatter light is received in response to the laser beam being emitted into the atmosphere and the reference light is derived from the laser beam;
• a detection system configured to measure a first beat frequency from interfering the first portion of the backscatter light with the reference light and measure the second beat frequency from interfering the time delayed backscatter light with the reference light;
• and
• a speed analyzer configured to determine a first speed using the first beat frequency;
• determine a second speed using the second beat frequency;
• determine a third speed using a difference between the first beat frequency and the second beat frequency;
• and determine a speed for the vehicle as an average of the first speed, the second speed, and the third speed.