SHORT RANGE LASER OBSTACLE DETECTOR

• US 3,781,111 A
• Filed: 03/16/1972
• Issued: 12/25/1973
• Est. Priority Date: 03/16/1972
• Status: Expired due to Term

• Current Assignee: Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, N/a,, William L. Kuriger
• Original Assignee: Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, N/a,, William L. Kuriger
• Inventors: Kuriger, William L., Fletcher, James C. Administrator of the National Aeronautics & Space, N/a,
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US05/235,268
• Time in Patent Office: 649 Days
• Field of Search: 250/217SS 350/6 356/157,158,141,152,4,5 331/94.5K,94.5S
• US Class Current: 356/5.08
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/931 of land vehicles

Abstract

A short range obstacle detector for surface vehicles is provided by an array of laser diodes operated one at a time, one for each of a plurality of adjacent azimuth sectors. A vibrating mirror a short distance above the surface provides continuous scanning in elevation for all azimuth sectors. A diode laser selector is synchronized with the vibrating mirror to enable one diode laser to be fired by pulses from a clock pulse source a number of times during each elevation scan cycle. The time for a given pulse of light to be reflected from an obstacle and received is detected as a measure of range to the obstacle.

Claims

1. A laser scanning system comprised of a linear array of lasers, means for selecting for operation one laser at a time in a predetermined sequence, meanS for pulsing each laser selected a number of times to produce a pulsed beam before another laser is selected, optical means for collimating said pulsed beam of each laser and aiming it in the desired direction to form a fan-shaped azimuth scan pattern of pulsed beams, means for cyclicly deflecting said azimuth scan pattern in elevation, said deflecting means being synchronized with said selected means to complete one cycle of deflection while one laser is being selected, a photodetecting means mounted near said array of lasers, and optical means for receiving reflected pulsed laser beams and directing said reflected pulsed laser beams into said photodetecting means.

2. A laser scanning system as defined in claim 1 wherein said optical means for receiving reflected pulsed laser beams and directing said reflected pulsed laser beams into said photodetecting means includes a spherical lens and an aperture which in combination limit the area from which radiation could be directed into said photo-detecting means to the area being illuminated by the combination of said deflecting means and any one of said pulsed laser beams, and means for scanning said area in elevation, said elevation scanning means being synchronized with said deflecting means for deflecting in elevation said azimuth scan pattern of pulsed beams.

3. A laser scanning system as defined in claim 2 wherein said deflecting means is comprised of one end of a vibrating mirror and said elevation scanning means comprises another end of said vibrating mirror.

4. A laser scanning system as defined in claim 3 wherein said photodetecting means is comprised of a single photodetector and said optical means for receiving reflected pulsed laser beams includes a cylindrical lens between said deflecting means and said spherical lens for providing a horizontal fan-shaped field of view, thereby obviating any need for scanning received pulsed laser beams in azimuth.

5. A laser scanning system as defined in claim 2 wherein said photodetecting means is comprised of a single photodetector and said optical means for receiving pulsed laser beams includes a cylindrical lens in front of said spherical lens for providing a horizontal fan-shaped field of view, thereby obviating any need for scanning received pulsed laser beams in azimuth.

6. A laser obstacle detector mounted on the front of a moving vehicle at a small distance above the surface of the terrain comprised of a convergent lens a plurality of lasers arranged in a horizontal array along the focal plane of said convergent lens to transmit a fan-shaped pattern of laser beams for a predetermined angle of scan in azimuth as said lasers are activated one at a time in a predetermined sequence, a vibrating mirror positioned to oscillate about an axis parallel to said array of lasers thereby to receive a beam from a given laser and to deflect it in elevation, means for maintaining vibration of said mirror at a substantially constant frequency, means for selectively activating said lasers for operation in said sequence in synchronism with said vibrating mirror, only one laser being activated during each cycle of vibration, means for pulsing a selected laser at a predetermined repetition rate during a cycle of said vibrating mirror, thereby effectively scanning a sector of said azimuth pattern in elevation with time spaced pulses of light, a cylindrical lens having its cylindrical axis parallel to the axis of oscillation of said mirror, said cylindrical lens being positioned to receive reflected returns of said laser beams from said mirror and to provide a field of view in a fan shape corresponding to the azimuth fan-shaped scan pattern of transmitted laser beams, a photodetector, a spherical lens following said cylindrical lens to focus the fan-shaped field of view into said photodetector, and means responsive to said photodetector and said pulsing means for producing a signal proportional to the time lapse between the time a laser is pulsed and the time a reflected pulse of light is received and detected by said photodetector after each pulsing of a lesser.

7. A laser obstacle detector as defined in claim 6 including data processing means connected to receive signals from said range measuring means and said laser selecting means for determining the presence and azimuth of obstacles.