Optical assembly for laser radar

Abstract

A compact optical assembly for a laser radar system is provided, that is configured to move as a unit with a laser radar system as the laser radar system is pointed at a target and eliminates the need for a large scanning (pointing) mirror that is moveable relative to other parts of the laser radar. The optical assembly comprises a light source, a lens, a scanning reflector and a fixed reflector that are oriented relative to each other such that: (i) a beam from the light source is reflected by the scanning reflector to the fixed reflector; (ii) reflected light from the fixed reflector is reflected again by the scanning reflector and directed along A line of sight through the lens; and (iii) the scanning reflector is moveable relative to the source, the lens and the fixed reflector, to adjust the focus of the beam along the line of sight.

We claim: 
     
         1 . An apparatus, comprising:
 an optical fiber;   a translatable reflector situated to receive a beam from the optical fiber that is incident to the translatable reflector along a first axis and to direct the beam along a second axis;   a fixed reflector situated to receive the beam from the translatable reflector along the second axis and reflect the beam back to the translatable reflector such that the beam exits the translatable reflector along the first axis; and   a focusing lens situated to receive the beam that exits the translatable reflector and focus the exit beam at a target.   
     
     
         2 . The apparatus of  claim 1 , wherein the translatable reflector is translatable along the first axis or the second axis. 
     
     
         3 . The apparatus of  claim 1 , wherein the first axis and the second axis are parallel. 
     
     
         4 . The apparatus of  claim 1 , wherein the translatable reflector is a corner cube or a roof prism. 
     
     
         5 . The apparatus of  claim 1 , wherein the translatable reflector is an air corner cube. 
     
     
         6 . The apparatus of  claim 1 , wherein the optical fiber is situated to emit the beam along the first axis. 
     
     
         7 . The apparatus of  claim 6 , further comprising a spider mount situated to retain the optical fiber on the first axis. 
     
     
         8 . The apparatus of  claim 7 , wherein the spider mount is situated between the translatable reflector and the focusing lens along the first axis. 
     
     
         9 . The apparatus of  claim 8 , wherein the spider mount includes a plurality of struts that define air spaces situated to transmit the beam exiting the translatable reflector to the focusing lens. 
     
     
         10 . The apparatus of  claim 9 , further comprising a laser diode coupled to the optical fiber so as to provide the beam that is received by the translatable reflector from the optical fiber. 
     
     
         11 . The apparatus of  claim 10 , further comprising a pointing laser that is configured to emit a visible laser beam, wherein the visible laser beam is coupled to the optical fiber. 
     
     
         12 . A measurement apparatus, comprising:
 an optical assembly configured to direct a beam to a target and receive a portion of the beam from the target, the optical assembly comprising an optical fiber, a fixed reflector, and a focusing lens that are fixed with respect to each other, and a scannable reflector configured to adjust a propagation distance of the beam from the fiber to the focusing lens so as to focus the beam at a selected target distance;   a rotatable housing configured to retain and rotate the optical assembly so as to direct the beam to the target at a selected target location;   a base configured to support the rotatable housing; and   a signal processing system situated in the base.   
     
     
         13 . The measurement apparatus of  claim 12 , wherein the signal processing system is located in the base and is coupled to receive the portion of the returned optical beam, and estimate a target distance. 
     
     
         14 . The measurement apparatus of  claim 12 , wherein the optical assembly includes a spider mount configured to retain the optical fiber. 
     
     
         15 . The measurement apparatus of  claim 14 , wherein the spider mount includes a plurality of struts that define apertures situated to transmit a returned portion of a probe beam from the target to the scannable reflector. 
     
     
         16 . The measurement apparatus of  claim 15 , wherein the spider mount is situated so that the beam directed to the target is incident to apertures of the spider mount and then to the focusing lens. 
     
     
         17 . The measurement apparatus of  claim 12 , wherein the scannable reflector is translatable in a direction parallel to an axis of the focusing lens. 
     
     
         18 . The measurement apparatus of  claim 17 , wherein a translation distance of the scannable reflector is associated with a propagation distance change between the fiber and the focusing lens of four times the translation distance. 
     
     
         19 . The measurement apparatus of  claim 12 , wherein the scannable reflector is situated to receive the beam from the fiber and direct the beam to a fixed reflector such that the fixed reflector returns the beam to the scannable reflector so as to be incident to the focusing lens. 
     
     
         20 . The measurement apparatus of  claim 12 , wherein the scannable reflector is situated to receive a portion of the beam from the target and direct the beam to a fixed reflector such that the fixed reflector returns the beam to the scanable reflector and then to the optical fiber. 
     
     
         21 . A laser radar method, comprising:
 pointing a laser beam at a target;   receiving a portion of the laser beam from the target; and   focusing the laser beam at the target by scanning a reflector with respect to a fixed focusing lens.   
     
     
         22 . The laser radar method of  claim 21 , further wherein the reflector is a corner cube or a roof prism, and scanning comprises translating the reflector substantially along an axis of the fixed focusing lens.