Laser beam boresight system

• US 4,385,834 A
• Filed: 07/28/1980
• Issued: 05/31/1983
• Est. Priority Date: 07/28/1980
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Maxwell, Richard F. Jr.
• Primary Examiner(s): Punter, William H.
• Application Number:
  US06/172,785
• Time in Patent Office: 1,037 Days
• Field of Search: 356/138, 356/141, 356/152-153, 358/125-126, 219/121 LU, 219/121 LV, 219/121 LW, 219/121 LX
• US Class Current: 356/153
• CPC Class Codes: F41G 3/326 for checking the angle between the axis of the gun sighting device and an auxiliary measuring device F41G3/323 takes precedence

Abstract

Boresighting of an outgoing first laser beam axis to an imaging sensor reference axis is described by aligning a second laser beam axis, which is in fixed relation to the first laser beam axis, to an electromagnetic source reference beam axis and detecting the angular displacement between the second laser beam and the reference beam axes. The sensor reference axis is in fixed relationship to the reference beam axis. Error signals are generated by the detector which are proportional to the angular displacement and are utilized to correct the angular displacement to align the second laser beam and the reference beam axes. When the first laser beam is boresighted to the sensor reference axis, the image of the reference beam source in the sensor display will represent the target object to which the outgoing first laser beam is directed.

Claims

1. Apparatus for directing a laser beam to an object in a field of view, for aligning said laser beam and for indicating the position of said laser beam in said field of view comprising:

first means for displacing said laser beam in response to an error signal;

second means for both reflecting a first portion of said laser beam and for transmitting the remainder of said laser beam;

third means for both directing said first portion of said laser beam to an object in a field of view and for directing radiant energy from said field of view through said second means into a fourth means for focusing said radiant energy upon a means for indicating;

said second means being transmissive to said radiant energy from said field of view;

fifth means positioned for intercepting said remainder of said laser beam and having a reflective surface at the wavelength of said laser beam for reflecting said remainder of said laser beam onto a detector;

a beam of radiant energy;

said fifth means being transmissive to said beam of radiant energy;

sixth means for focusing said beam of radiant energy through a focal point prior to passing said beam of radiant energy through said reflective surface of said fifth means at the same location said remainder of said laser beam is reflected;

said beam of radiant energy and said sixth means are positioned to direct said beam of radiant energy to said second means;

said second means including means for reflecting said beam of radiant energy into said fourth means;

said fourth means including means for focusing said beam of radiant energy upon said means for indicating; and

said detector including means for generating an error signal as a function of the position on said detector where said remainder of said laser beam impinges;

said error signal coupled to said first means.

2. The apparatus of claim 1 wherein said first means for displacing includes means for laterally positioning said laser beam.

3. The apparatus of claim 1 wherein said beam of radiant energy emits energy in the visible electromagnetic spectrum and said means for indicating is a vidicon.

4. The apparatus of claim 1 wherein said beam of radiant energy emits energy in the infrared electromagnetic spectrum and said means for indicating is a thermal imager.

5. The apparatus of claim 1 wherein said error signal comprises at least two error signal components corresponding to the displacement of said remainder of said laser beam along two orthogonal axes transverse to said laser beam.

6. The apparatus of claim 1 wherein the center of said beam of radiant energy at the position passing through said reflective surface of said fifth means is equidistant from a focal point of said reflected remainder of said laser beam at said detector and from said focal point of said beam of radiant energy when said error signal is below a predetermined value.

7. The apparatus of claim 1 wherein the wavelength of said laser beam is independent of the wavelength of said beam of radiant energy.

8. The apparatus of claim 1 wherein said second means includes a dichroic mirror.

9. The apparatus of claim 1 wherein said fifth means includes a dichroic mirror.

10. In a laser beam boresight system including a laser beam source, a reference beam source, and a sensor responsive to a target scene and said reference beam source, a method for boresighting a laser beam axis to a reference axis comprising the steps of:

coupling a first laser beam having a first laser beam axis to a second laser beam having a second laser beam axis;

separating said second laser beam into a third laser beam having a third laser beam axis and a fourth laser beam having a fourth laser beam axis, said third laser beam axis and said fourth laser beam axis having a predetermined relationship with said second laser beam axis;

separating an electromagnetic radiation beam from said reference beam source into a first reference beam having a first reference beam axis and a second reference beam having a second reference beam axis;

detecting the angular displacement between the first reference beam axis and the third laser beam axis and generating an error signal in response to the detected displacement between said axes;

focusing on said sensor an image of said second reference beam and an image of a beam of radiant energy of a target scene, said beam of target scene radiant energy having an axis colinear with said second reference beam axis;

positioning said second laser beam axis in response to said error signal and thereby concomitantly angularly displacing said fourth beam axis into boresight with said target scene radiant energy beam axis whereby the sensor image of said second reference beam corresponds to a target in the target scene with which said fourth laser beam axis intersects.

11. In a laser beam boresight system including a laser beam source, a reference beam source, and a sensor, apparatus for boresighting the laser beam comprising:

means for separating a laser beam from said laser beam source into a first laser beam having a first laser beam axis and a second laser beam having a second laser beam axis, wherein said second laser beam is pointed to a target in a target scene;

said means for separating including means for dividing a reference beam from said reference beam source into a first reference beam and a second reference beam each having a respective reference beam axis;

means for detecting an angular displacement between said first laser beam axis and said first reference beam axis and for generating an error signal indicative of said angular displacement;

means for focusing an image of a target scene and an image of said second reference beam on said sensor wherein the second reference beam axis line of sight intersects said target scene and said sensor images;

means for positoning said laser beam in response to said error signal to cause said angular displacement to reduce until said first laser beam axis is aligned with said first reference beam axis and concomitantly said second laser beam axis is boresighted with said second reference beam axis whereby said second reference beam image corresponds to a target with which said second laser beam axis intersects.

12. The laser beam boresight system in claim 11 wherein said laser operates at a first predetermined wavelength and said reference source operates at a second predetermined wavelength whereby said first and second wavelengths are independent of each other.

13. The laser beam boresight system as defined in claim 11 wherein said first laser beam and said second laser beam have a predetermined angular relationship with each other.

14. The laser beam boresight system as defined in claim 11 wherein said first reference beam and said second reference beam have a predetermined angular relationship with each other.

15. In a laser beam boresight system including a laser beam source, a reference beam source, and a sensor responsive to a target scene and said reference beam source, a method for boresighting a laser beam to a reference axis comprising the steps of:

separating the laser beam from the laser beam source into a first laser beam and a second laser beam, wherein said second laser beam is directed to a target scene, and a reference beam from the reference beam source is divided into a first reference beam and a second reference beam, each of said beams having its respective beam axis;

detecting and generating an error signal indicative of the angular displacement between said first laser beam axis and said first reference beam axis;

focusing an image of a target scene and an image of said second reference beam on said sensor wherein said second reference beam axis extended intersects a target in said scene and said image of said target on said sensor;

positioning said laser beam in response to said error signal to cause said angular displacement to reduce until said first laser beam axis is aligned with said first reference beam axis and thereby concomitantly displacing said second laser beam axis into boresight with said second reference beam axis whereby said second reference beam image on said sensor corresponds to said target with which said second laser beam axis intersects.