Method and apparatus for determining the range, direction and velocity of an object

An apparatus for determining the range, direction and velocity of an object with respect to said apparatus, said apparatus comprising:

• a laser comprising an optical cavity having a first end and a second end, said first and second ends each comprising a surface which is partially transmissive and partially reflective, said optical cavity having a laser medium therein which is excitable to produce radiation emissions;
• means for detecting light and for producing electrical signals in response to the light detected, said means for detecting light disposed in proximity to said second end for receiving light transmitted through said second end of said laser;
• means for collimating light disposed in proximity to said first end of said laser for collimating light transmitted through said first end of said laser and for projecting a collimated beam of light onto the object;
• means for processing the electrical signals produced by said means for detecting light, said means for processing being electrically coupled to said means for detecting light for receiving the electrical signals produced by said means for detecting light, wherein a frequency modulated electrical signal is supplied to said laser for causing said laser to generate a frequency modulated standing light wave having a frequency which is equal to or greater than .pi. times the highest frequency at which the optical path between the object and said laser is modulating, wherein causing said standing wave generator to generate a frequency modulated standing wave having a frequency equal to or greater than .pi. times the highest frequency at which the optical path between the object and said laser is modulating prevents aliasing, and wherein said means for processing the electrical signals determines the mode hop rate of said laser;
• and
• means for determining the range, direction and velocity of the object with respect to said apparatus on the basis of the mode hop rate.

A method for determining the range, direction and velocity of an object, said method comprising the steps of:

• (1) frequency modulating a standing wave generator with a frequency modulated electrical signal to produce standing waves wherein the frequency of the frequency modulated electrical signal is equal to or greater than .pi. times the highest frequency at which the optical path between the object and the standing wave generator is modulating such that aliasing is prevented;
• (2) projecting the standing waves onto the object;
• (3) detecting interference coupling between the standing waves generated by the standing wave generator and standing waves reflected from the object;
• (4) determining a mode hop rate of the standing wave generator resulting from the interference coupling of the standing waves;
• and
• (5) determining the distance, direction of motion and velocity of the object based on the determined mode hop rate.

A method for determining the range, direction and velocity of an object which is modulating with respect to a laser of a laser range finding system, said method comprising the steps of:

• (1) frequency modulating the laser of the laser range finding system with a frequency modulated electrical signal to produce a standing wave of laser light having a frequency which is equal to or greater than .pi. times the highest frequency at which the optical path between the object and the laser is modulating, wherein frequency modulating the laser to produce a standing wave of laser light having a frequency equal to or greater than .pi. times the highest frequency at which the optical path between the object and the laser is modulating prevents aliasing;
• (2) projecting the laser light onto the object, wherein light reflected from the object is reflected back into the laser as external optical feedback, and wherein at least some of the external optical feedback constructively interferes with the standing wave of laser light produced by the laser to create a plurality of standing light waves of different modes;
• (3) detecting the plurality of standing light waves of different modes;
• (4) determining the mode hop rate of the laser over a predetermined period of time;
• and
• (5) determining the distance, direction and velocity of the object independently of each other based on the mode hop rate determined over the predetermined period of time.