Active seeker head system

Patent metadata

Field	Value
Publication number	US-11236970-B2
Application number	US-201816646607-A
Country	US
Kind code	B2
Filing date	Sep 5, 2018
Priority date	Sep 12, 2017
Publication date	Feb 1, 2022
Grant date	Feb 1, 2022

Abstract

Disclosed herein is an active seeker system for detection and/or tracking of moving targets. The system includes: an illumination module generating an illumination beam to be output from the system; an optical assembly for shaping the solid angle of the field of view (FOV) of the output beam; an optical path scanning module adapted for angularly deflecting the output optical path of the output beam about a scan axis to perform one or more scanning cycles; and an imaging module adapted to image light in the spectral regime of the beam, arriving from a certain field of view about the output optical path of the beam. In some cases, the solid angle of the output light beam is shaped such that it has an elongated FOV cross-section extending along a certain lateral of the beam; and the output optical path is angularly deflected in a direction travers to the longer axis of the elongated FOV of beam so as to swipe the elongated FOV of the beam to cover a desired field of regard (FOR) with one dimensional scanning. In some implementations, the system is adapted for monitoring the FOR for detecting and tracking the target. The monitoring may include a target detection stage during which the FOV of the light beam is set to an extent smaller than the FOR and the FOR is imaged in a scanning imaging mode. The monitoring may include a target tracking stage during which one or more imaging parameters are adjusted according to certain estimated properties associated with the target being tracked.

First claim

The invention claimed is:

1. A system for mounting on a movable platform for detecting and tracking an object with respect to the movable platform; the system comprising:
an illuminator configured and operable for generating a light beam for propagation along an output optical path of the system;
a detector operable for imaging light in a spectral regime of the light beam, which arrives from said output optical path;
an optical assembly comprising a beam shaper adapted for shaping said light beam to form an output light beam for illuminating a field of view (FOV);
a scanner configured and operable for angularly deflecting a direction of said output optical path about a scan axis, whereby said scanner is adapted to perform a scanning cycle by swiping the field of view of the output light beam to cover a field of regard (FOR);
a controller connectable to said detector and configured and operable for monitoring said field of regard in search for said object by receiving a sequence of images captured by said detector during the scanning cycle, and processing said images for detecting the object illuminated by said light beam; said detecting comprises determining whether returning light of said light beam being reflected/scattered from said object is captured by one or more pixels of at least one image in said sequence of images;
wherein at least one of the following:
a. intensity of the returned light being reflected/scattered from the object and captured by said one or more pixels in the at least one image is a function of τ and 1/R, whereby R is a distance between the detector and the object, and τ is exposure time of the at least one image; and wherein said controller is adapted dynamically adjust exposure times τ'S of said images according to said intensity to thereby enable to reduce a total time T of said scanning cycle while maintaining a Signal to Noise Ratio (SNR) of said detection above a predetermined threshold; and
b. intensity of the returned light being reflected/scattered from the object and captured by said one or more pixels in the sequence of images is proportional to T/(R4*Ω) whereby R is a distance between the detector and the object, Ω is the solid angle of a total field of regard (FOR) covered by the scanning cycle, and T is time duration of the scanning cycle; and wherein said controller is adapted to carry out a plurality of scanning cycles for tracking the object, while dynamically adjusting at least one of the time durations T of the scanning cycles and the solid angles Ω of the FOR being scanned in said scanning cycles.

2. The system of claim 1 , wherein said output light beam has an elongated cross-section extending to cover a first lateral dimension of said FOR and the scanner is configured and operable for carrying out said one dimensional scanning cycle by deflecting the direction of said output optical path to scan a certain angular extent about said scan axis so as to swipe said light beam to cover a second dimension of the FOR being imaged in the one dimensional scanning cycle.

3. The system of claim 2 wherein said beam shaper is configured and operable for shaping said light beam such that the field of view of the elongated output light beam has a line shape with a lateral aspect ratio of the order of 40 between wide and narrow lateral dimensions of said elongated light beam.

4. The system of claim 1 , wherein during tracking of said object, said controller is adapted to dynamically reduce the time duration T of the scanning cycles as said distance R of the object becomes shorter thereby dynamically optimizing frame rate 1/T of the FOR frames scanned during the scanning cycles respectively.

5. The system of claim 1 , wherein said controller is adapted to determine an angular velocity of the object during tracking of said object and dynamically adjust the solid angle Ω of the FOR covered by one or more scanning cycles to thereby optimize agility of said tracking.

6. The system of claim 1 , wherein the detector is configured with a field of view larger than a field of view of said illuminator to thereby image the field of view illuminated by the output light beam onto a subset of pixels of a two dimensional photodetector array of the detector.

7. The system of claim 6 , comprising a false alarm processor adapted to process images captured by the two dimensional photodetector array to determine false detection of an object by comparing parameters of light intensity captured by said subset of pixels to corresponding noise related parameters associated with light intensity measured by other pixels of the two dimensional photodetector array.

8. The system of claim 7 , wherein the noise related parameters are estimated utilizing one or more of the following: average background clutter level and slope associated with standard deviation of said clutter, estimated size of structures in said images, and comparison between said images.

9. The system of claim 1 , wherein at least one of the following:
said scan axis is a lateral axis traverse to said output optical path;
said scan axis is not orthogonal, and is preferably parallel, to said certain lateral axis along which the light beam is elongated.

10. The system of claim 1 , wherein said scanner comprises a gimbal rotatable about said scan axis configured and operable for carrying out said angularly deflecting of the direction of the output optical path; and wherein said gimbal comprises an actuator for rotating about said scan axis.

11. The system of claim 10 , wherein at least one of the following:
said detector is mounted on said gimbal;
said detector is external to said gimbal and has a fixed imaging optical path relative thereto, and wherein the optical assembly comprises one or more imaging optical elements arranged on said gimbal and configured and operable for directing light arriving from said output optical path to propagate along said fixed imaging optical path for imaging by said detector.

12. The system of claim 10 , wherein at least one of the following:
said illuminator is mounted on said gimbal;
said illuminator is external to said gimbal and has a fixed light projection optical path along which said light beam emanates from the illuminator, and wherein the optical assembly comprises one or more light directing optical elements arranged on said gimbal and configured and operable for directing said light beam arriving from said fixed light projection optical path to propagate along said output optical path.

13. The system of claim 1 , wherein said scanner comprises one or more scanning optical deflectors configured and operable for carrying out said angularly deflecting of the direction of the output optical path.

14. The system of claim 1 , wherein said beam shaper is configured and operable for adjusting a lateral aspect ratio of the output light beam; and
wherein the controller is configured to operate, upon detection of said object, for initiating a tracking stage for tracking the location of the object; and wherein during said tracking stage the controller halts operation of said scanning and initiates a snapshot operational mode in which the output light beam is directed for continuously illuminating the object, and operates said beam shaper to adjust the cross-section of said output light beam such that a solid angle of the field of view of said output light beam covers an angular extent of said object.

15. The system of claim 14 , wherein said beam shaper is configured and operable for expanding the field of view of said light beam; and wherein during said tracking stage the controller processes images captured by sai

Assignees

• Israel Aerospace Ind Ltd

Inventors

• Levy Shahar

Classifications

• H04N23/667

  Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes · CPC title

• H04N23/56

  provided with illuminating means · CPC title

• H04N23/73

  by influencing the exposure time · CPC title

• H04N23/54

  Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils · CPC title

• H04N23/74

  by influencing the scene brightness using illuminating means · CPC title