The most critical component in lidar is its laser scanner, which delivers pulsed or CW laser to target with desirable field of view (FOV). Most existing lidars use a rotating or oscillating mirror for scanning, resulting in several drawbacks.
A lidar scanning technology was developed that could achieve very high scanning speed, with an ultra-miniature size and much lighter weight. This technology promises at least a 10× performance improvement in these areas over existing lidar scanners. Features of the proposed ultra-miniature lidar scanner include the ability to make the entire scanner <2 mm in diameter; very high scanning speed (e.g. 5–20 kHz, in contrast to several hundred Hz in existing scanners); structure design to meet stringent requirements on size, weight, power, and compactness for various applications; and the scanning speed and FOV can be altered for obtaining high image resolutions of targeted areas and for diversified uses.
This technology employs a singlemode optical fiber attached to the end of a mini tube made of piezoelectric material. The two-degrees-of-freedom (DOF) piezo tube is driven at the first mode of mechanical resonance frequency of the fixed-free cantilevered fiber. The gain of mechanical resonance allows a small vibration at the tip of the piezo tube to be amplified several hundred times to vibrate the tip of the optical fiber. The laser beam is delivered through the single-mode fiber and the vibrating fiber at high resonance frequency (e.g., 5–20 kHz), and generates scanning patterns with desirable FOV.
A laser beam is delivered via the single fiber core to the target surface. The direction of the light beam delivered by the single fiber is controlled by two piezoelectric drivers mounted orthogonally on the mounting base of the single fiber to generate a controllable motion of the cantilevered fiber with two degrees of freedom. With proper optics, the directed light beam produces a bright spot on the object surface. The reflected light energy from this spot is collected by multiple optical fibers embedded into the outer housing. These light collectors form a “fiber ring.” The time duration between the beginning of the laser pulse and receiving pulse (in the case of pulse laser) or phase difference between emitted and received signals (in the case of CW laser) determines the target distance, based on time-of-flight principle.
The single-fiber core moves in an area-fill fashion to produce laser light spot sequentially over a target surface, and light collectors record the timing and brightness of these data points in a pixel-by-pixel fashion. The signal receiver, piezo controller, and the laser source are all connected to the distal end via flexible fiber/wire bundle with diameter less than one millimeter. A control computer is used to control the piezo driver motion, laser timing and intensity, returned signal processing, and 3D data construction and visualization.
This work was done by Jason Geng of Xigen LLC under the Small Business Innovation Research Program for Kennedy Space Center. KSC-13570