United States of America As Represented by the Administrator of Nasa

The United States of America As Represented by the Administrator of the

Farzin Amzajerdian

Diego Fernando Pierrottet

Glenn D Hines

Bruce W Barnes

George E Lockard

Larry B Petway

Michael J Kavaya

Alexander Bulyshev

Michael D Vanek

George E Busch

An FMCW Doppler lidar system and method for use in a host vehicle includes a laser system, lenses, a homodyne receiver, and a signal processing unit (SPU). The laser beam is modulated to generate a frequency waveform with three segments, i.e., Doppler, up-ramp, and down-ramp. The lenses transmit laser beams toward a target-of-interest, and receive return beams reflected from the target-of-interest. The homodyne receiver has photoreceptors configured to mix the return beams with a respective local oscillator beam to generate a three-section return waveform. The SPU is coupled to the photoreceptors and calculates a respective magnitude and frequency of an up-ramp, down-ramp, and/or Doppler IF section of the return waveform, estimates a sign of the IF sections, and calculates a range and/or velocity relative to the target-of-interest using the estimated sign, and controls the host vehicle using the range and/or velocity.

Ambiguity mitigation for FMCW lidar system

Aspects of the present disclosure are directed to imaging an environment and providing velocity characteristics of one or more objects in the imaged environment. As may be implemented in accordance with one or more embodiments, objects in a local environment are scanned with laser light, and reflections of the scanned laser light from the objects are received and processed to generate a 3D image of the local environment. Distance and velocity of each object is provided or detected based on a frequency delay and frequency shift of one or more reflections of the scanned laser light from the object. For instance, the 3D image may provide relative position of an object and indicate velocity of the object, which may be ascertained based on a frequency shift.

Lidar imaging with velocity acquisition

A hybrid fiber rod includes a fiber core and inner and outer cladding layers. The core is doped with an active element. The inner cladding layer surrounds the core, and has a refractive index substantially equal to that of the core. The outer cladding layer surrounds the inner cladding layer, and has a refractive index less than that of the core and inner cladding layer. The core length is about 30 to 2000 times the core diameter. A hybrid fiber rod laser system includes an oscillator laser, modulating device, the rod, and pump laser diode(s) energizing the rod from opposite ends. The rod acts as a waveguide for pump radiation but allows for free-space propagation of laser radiation. The rod may be used in a laser resonator. The core length is less than about twice the Rayleigh range. Degradation from single-mode to multi-mode beam propagation is thus avoided.

Compact hybrid laser rod and laser system

A system for generating a frequency modulated linear laser waveform includes a single frequency laser generator to produce a laser output signal. An electro-optical modulator modulates the frequency of the laser output signal to define a linear triangular waveform. An optical circulator passes the linear triangular waveform to a band-pass optical filter to filter out harmonic frequencies created in the waveform during modulation of the laser output signal, to define a pure filtered modulated waveform having a very narrow bandwidth. The optical circulator receives the pure filtered modulated laser waveform and transmits the modulated laser waveform to a target.

System and method for generating a frequency modulated linear laser waveform

A Doppler lidar sensor system includes a laser generator that produces a highly pure single frequency laser beam, and a frequency modulator that modulates the laser beam with a highly linear frequency waveform. A first portion of the frequency modulated laser beam is amplified, and parts thereof are transmitted through at least three separate transmit/receive lenses. A second portion of the laser beam is used as a local oscillator beam for optical heterodyne detection. Radiation from the parts of the laser beam transmitted via the transmit/receive lenses is received by the respective transmit/receive lenses that transmitted the respective part of the laser beam. The received reflected radiation is compared with the local oscillator beam to calculate the frequency difference therebetween to determine various navigational data.

Coherent doppler lidar for measuring altitude, ground velocity, and air velocity of aircraft and spaceborne vehicles

A method for enhancing a three dimensional image from frames of flash LIDAR data includes generating a first distance Rfrom a first detector i to a first point on a surface S. After defining a map with a mesh &#x398; having cells k, a first array S(k), a second array M(k), and a third array D(k) are initialized. The first array corresponds to the surface, the second array corresponds to the elevation map, and the third array D(k) receives an output for the DEM. The surface is projected onto the mesh &#x398;, so that a second distance Rfrom a second point on the mesh &#x398; to the detector can be found. From this, a height may be calculated, which permits the generation of a digital elevation map. Also, using sequential frames of flash LIDAR data, vehicle control is possible using an offset between successive frames.

Method for enhancing a three dimensional image from a plurality of frames of flash LIDAR data

A lidar remote sensing system wherein a laser signal is transmitted along an optical path through a telescope having a primary and secondary mirrors and a rotating prism at the telescope output. When the reflected signal from the target is received it is passed back through the system to a detector, where it is heterodyned with a signal from a local oscillator to detect Doppler frequency shifts in the returned signal. Since the prism is rotating, the prism will be at one position when the signal is transmitted and at another when the returned signal is received. This causes the reflected signal to be off the optical path, reducing the power of the returned signal. To correct this problem a de-rotator or prism is mounted for rotation, in synchronism with the rotating prism, about the optical path in a position to intersect the returned beam and refract it back onto the optical path to reduce the power loss in the returned signal.

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Yorktown, VA, United States of America

Farzin Amzajerdian