Solid state pulsed coherent laser radar for short range velocimetry applications

A single frequency laser system, wherein a high energy pulse signal is generated as an analysis beam and a lower energy flat top pulse is generated as a reference beam, both being generated from a laser source single frequency pulse signal, said laser system capable of providing interferometric type analysis of the two beams when heterodyned, which comprises:

• a laser source which generates a single frequency, plane polarized, high energy pulse signal beam;
• means for splitting said pulse signal beam simultaneously into an analysis beam and a reference beam, said analysis and reference beams holding the plane polarization of said laser source beam;
• means for converting said analysis beam to circular polarization and directing it to a partially reflective external target medium whereby part of said analysis beam becomes a reflected beam returning back upon itself,
• means for reforming said local oscillator beam pulse into a lower energy, flat top signal of a preset time period, said time period set to extend for a minimum time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• means for receiving said reflected beam and adjusting its polarization to match the polarization of said reference beam;
• means for combining said reference beam and said reflected beam to allow them to be heterodyned together interferometrically;
• means for detecting;
• and
• means for measuring preselected properties of said heterodyned beam.

A laser radar system which comprises:

• a laser source which emits a single frequency, plane polarized, high energy pulse;
• means for splitting said high energy pulse emitted by said laser source into a target beam pulse and a local oscillator beam pulse;
• means for controlling the polarization of said target beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• means for reforming said local oscillator beam pulse into a lower energy, flat top signal of a frequency shifted a preselected amount from said local oscillator's original frequency and of a preset time period, said time period set to extend for a minimum time which ensures that said return beam pulse will be overtapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• means for receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• means for combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically;
• and
• detecting means.

A laser radar system for measuring the air speed of an aircraft which comprises:

• a laser source which emits a single frequency, plane polarized, high energy pulse;
• means for splitting said high energy pulse emitted by said laser source into a target beam pulse and a local oscillator beam pulse;
• means for controlling the polarization of said target beam pulse and directing it to an external, atmospheric aerosol medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• means for reforming said local oscillator beam pulse into a lower energy, flat top signal of a preset time period, said time period set to extend for a minimum time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• means for receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• means for combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically;
• detecting means;
• and
• means connected to said detecting means for determining and displaying the relative airspeed of the aircraft.

A laser radar system for measuring the air speed of an aircraft which comprises:

• a laser source which emits a single frequency, plane polarized, high energy pulse;
• means for splitting said high energy pulse emitted by said laser source into a target beam pulse and a local oscillator beam pulse;
• means for controlling the polarization of said target beam pulse and directing it to an external, atmospheric aerosol medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• means for reforming said local oscillator beam pulse into a lower energy, flat top signal of a frequency shifted a preselected amount from said local oscillato's original frequency and of a preset time period, said time period set to extend for a minimum time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• means for receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• means for combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically;
• detecting means;
• and
• means for determining and displaying the relative airspeed of the aircraft.

A laser radar system which comprises:

• a laser source which emits a single frequency, plane polarized, high energy pulse with pulse width .tau..sub.P ;
• means for splitting said high energy pulse emitted by said laser source into a target beam pulse and a local oscillator beam pulse;
• means for controlling the polarization of said target beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• means for reforming said reference beam into a lower energy, flat top signal of a preset time period equal to C .tau..sub.P and set to extend for a time period which covers the transit time of said analysis beam to a target medium and back to said laser system;
• means for receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• means for combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically;
• and detecting means.

A laser radar system which comprises:

• a laser source which emits a single frequency, plane polarized, high energy pulse with pulse width .tau..sub.P ;
• means for splitting said high energy pulse emitted by said laser source into a target beam pulse and a local oscillator beam pulse;
• means for controlling the polarization of said target beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• means for reforming said local oscillator beam pulse into a lower energy, flat top signal of a frequency shifted a preselected amount from said local oscillator's original frequency and of a preset time period equal to C.tau..sub.P, said time period set to extend for a time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• means for receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• means for combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically;
• and
• detecting means.

A laser radar system which comprises:

• a laser source which emits a single frequency, plane polarized, high energy pulse with pulse width .tau..sub.P and an envelope approximating P(t)=P.sub.0 e.sup.-(t/.tau..spsb.P.sup.).spsp.2 where P.sub.0 is the laser peak power and t is time;
• means for splitting said high energy pulse emitted by said laser source into a target beam pulse and a local oscillator beam pulse;
• means for controlling the polarization of said target beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• means for reforming said local oscillator beam pulse into a lower energy, flat top signal approximating the function P.sub.AOM (t).apprxeq..eta.[V.sub.RF (t-t.sub.d)].sup.2 rP(t) where .eta. is the AOM deflection efficiency, V.sub.RF is the applied voltage, t.sub.d is the time delay associated with said reforming means, and r is the fraction of the laser energy directed toward said reforming means, and with a frequency shifted a preselected amount from said local oscillator's original frequency, and of a preset time period equal to C.tau..sub.P, said time period set to extend for a time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together,
• means for receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• means for combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically;
• and
• detecting means.

A method for a laser radar system which comprises:

• generating a single frequency, plane polarized, high energy laser pulse with pulse width .tau..sub.P ;
• splitting said high energy laser pulse into a target beam pulse and a local oscillator beam pulse;
• controlling the polarization of said target beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• reforming said reference beam into a lower energy, flat top signal of a preset time period equal to C.tau..sub.P and set to extend for a time period which covers the transit time of said analysis beam to a target medium and back to said laser system;
• receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• and
• combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically.

A method for a laser radar system which comprises:

• generating a single frequency, plane polarized, high energy laser pulse with pulse width .tau..sub.P ;
• splitting said high energy laser pulse into a target beam pulse and a local oscillator beam pulse;
• controlling the polarization of said tar-get beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• reforming said local oscillator beam pulse into a lower energy, flat top signal of a frequency shifted a preselected amount from said local oscillato's original frequency and of a preset time period equal to C.tau..sub.P, said time period set to extend for a time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• and
• combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically.

A method for a laser radar system for measuring the air speed of an aircraft which comprises:

• generating a single frequency, plane polarized, high energy laser pulse;
• splitting said high energy laser pulse into a target beam pulse and a local oscillator beam pulse;
• controlling the polarization of said target beam pulse and directing it to an external, atmospheric aerosol medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• reforming said local oscillator beam pulse into a lower energy, flat top signal of a preset time period, said time period set to extend for a minimum time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically;
• and
• detecting, determining and displaying the relative airspeed of the aircraft from the heterodyned beam.

A method for a laser radar system for measuring the air speed of an aircraft which comprises:

• generating a single frequency, plane polarized, high energy laser pulse;
• splitting said high energy laser pulse into a target beam pulse and a local oscillator beam pulse;
• controlling the polarization of said target beam pulse and directing it to an external, atmospheric aerosol medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• reforming said local oscillator beam pulse into a lower energy, flat top signal of a frequency shifted a preselected amount from said local oscillator's original frequency and of a preset time period, said time period set to extend for a minimum time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically;
• detecting, determining and displaying the relative airspeed of the aircraft from the heterodyned beam.

A method for laser radar system which comprises:

• generating a single frequency, plane polarized, high energy laser pulse with pulse width .tau..sub.P and an envelope approximating P(t)=P.sub.0 e.sup.-(t/.tau..spsb.P.sup.).spsp.2 where P.sub.0 is the laser peak power and t is time;
• splitting said high energy laser pulse into a target beam pulse and a local oscillator beam pulse;
• controlling the polarization of said target beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• reforming said local oscillator beam pulse into a lower energy, flat top signal approximating the function P.sub.AOM (t).apprxeq..eta.[V.sub.RF (t-t.sub.d)].sup.2 rP(t) where .eta. is the AOM deflection efficiency, V.sub.RF is the applied voltage, t.sub.d is the time delay associated with said reforming means, and r is the fraction of the laser energy directed toward said reforming means, and with a frequency shifted a preselected amount from said local oscillator's original frequency, and of a preset time period equal to C.tau..sub.P, said time period set to extend for a time which ensures that said return beam pulse will be overtapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• and
• combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically.

A method for a self seeding laser radar system which comprises:

• generating a single frequency, plane polarized, high energy laser pulse width pulse width .tau..sub.P ;
• splitting said high energy laser pulse into a target beam pulse and a local oscillator beam pulse;
• controlling the polarization of said target beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• reforming said reference beam into a lower energy, flat top signal of a preset time period equal to C.tau..sub.P and set to extend for a time period which covers the transit time of said analysis beam to a target medium and back to said laser system;
• receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• and
• combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically.

A method for a self seeding laser radar system which comprises:

• generating a single frequency, plane polarized, high energy laser pulse with pulse width .tau..sub.P ;
• splitting said high energy laser pulse into a target beam pulse and a local oscillator beam pulse;
• controlling the polarization of said target beam pulse and directing it to an external, partially reflective medium whereby part of the energy of said target beam pulse becomes a reflected beam to return to said laser radar system;
• reforming said local oscillator beam pulse into a lower energy, flat top signal of a frequency shifted a preselected amount from said local oscillato's original frequency and of a preset time period equal to C.tau..sub.P, said time period set to extend for a time which ensures that said return beam pulse will be overlapped by the reformed local oscillator beam pulse in order that said beams can be heterodyned together;
• receiving said reflected beam pulse and adjusting its polarization to match said reformed local oscillator beam pulse;
• and
• combining said local oscillator beam and said reflected beam to allow them to be heterodyned together interferometrically.