Tri-mode seeker

• US 6,606,066 B1
• Filed: 10/29/2001
• Issued: 08/12/2003
• Est. Priority Date: 10/29/2001
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Fawcett, James M., Schwerdt, Christopher B., Baldwin, Gary D.
• Primary Examiner(s): NGUYEN, HOANG V
• Application Number:
  US10/003,188
• Time in Patent Office: 652 Days
• Field of Search: 343/720, 343/725, 343/781.CA, 343/786, 343/781.P, 343/779
• US Class Current: 343/725
• CPC Class Codes: F41G 7/008 Combinations of different guidance systems
• CPC Class Codes: F41G 7/2213 maintaining the axis of an orientable seeking head pointed at the target, e.g. target seeking gyro
• CPC Class Codes: F41G 7/2246 Active homing systems, i.e. comprising both a transmitter and a receiver
• CPC Class Codes: F41G 7/2253 Passive homing systems, i.e. comprising a receiver and do not requiring an active illumination of the target
• CPC Class Codes: F41G 7/226 Semi-active homing systems, i.e. comprising a receiver and involving auxiliary illuminating means, e.g. using auxiliary guiding missiles
• CPC Class Codes: F41G 7/2286 using radio waves
• CPC Class Codes: F41G 7/2293 using electromagnetic waves other than radio waves
• CPC Class Codes: G01J 1/4257 applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam monitoring arrangements for lasers in general H01S3/0014
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 5/026 Control of working procedures of a pyrometer, other than calibration; Bandwidth calculation; Gain control
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/0808 Convex mirrors
• CPC Class Codes: G01J 5/0815 Light concentrators, collectors or condensers
• CPC Class Codes: G01J 5/0846 having multiple detectors for performing different types of detection, e.g. using radiometry and reflectometry channels
• CPC Class Codes: G01J 5/0893 Arrangements to attach devices to a pyrometer, i.e. attaching an optical interface; Spatial relative arrangement of optical elements, e.g. folded beam path G01J5/049 takes precedence
• CPC Class Codes: G01J 5/602 using selective, monochromatic or bandpass filtering
• CPC Class Codes: G01S 13/86 Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G01S 7/4812 : transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/4813 : Housing arrangements
• CPC Class Codes: H01Q 1/281 : Nose antennas
• CPC Class Codes: H01Q 15/0033 : used for beam splitting or combining, e.g. acting as a quasi-optical multiplexer H01Q19/191 and H01Q19/195 take precedence
• CPC Class Codes: H01Q 19/13 : the primary radiating source being a single radiating element, e.g. a dipole, a slot, a waveguide termination H01Q19/15 takes precedence

Abstract

A single receiving aperture used, for example, in an airborne seeker system collects energy for three discrete energy sensors/receivers including a laser spot tracker, an RF (millimeter wave) transmitter/receiver, and an infrared detector. The RF transmitter/receiver is located at the focus of a primary reflector located on a gimbal assembly. A selectively coated dichroic element is located in the path of the millimeter wave energy which reflects infrared energy from the primary reflector to an optical system which re-images the infrared energy on the infrared detector. The outer edge or rim of the primary reflector is deformed so that the incoming laser energy focuses to a location beyond the RF transmitter/receiver. The laser sensor is positioned adjacent the RF transmitter/receiver at this location in a back-to-back orientation. The laser energy is then detected using a secondary reflector and an optical system which directs the laser energy from the secondary reflector to a laser detector.

Claims

1. A multi-mode receiving aperture, comprising:

a laser energy sensor for detecting incident laser energy; and

at least one other energy sensor coaxially aligned with the laser energy sensor along a central axis and sharing a common primary reflector,

wherein said laser energy sensor is located forward of the primary reflector and includes a secondary reflector for receiving incoming laser energy reflected from a peripheral region of the primary reflector and an immersion lens for focusing the laser energy reflected from the secondary reflector to a laser energy detector.

2. A multi-mode receiving aperture according to claim 1 wherein said at least one other energy sensor comprises an RF energy sensor.

3. A multi-mode receiving aperture according to claim 2 wherein the RF energy sensor comprises a millimeter wave (MMW) transmitter/receiver.

4. A multi-mode receiving aperture according to claim 1 wherein said at least one other energy sensor comprises an infrared energy sensor.

5. A multi-mode seeker system mounted on a gimbal assembly of an airborne platform, comprising:

a laser spot tracker assembly including a laser energy sensor; and

at least one other energy sensor coaxially aligned with the laser energy sensor along a common axis and sharing a common primary reflector,

wherein said at least one other energy sensor comprises both an infrared energy sensor and an RF energy sensor.

6. A multi-mode seeker system according to claim 5 wherein the RF energy sensor comprises a millimeter wave (MMW) transmitter/receiver.

7. A multi-mode seeker system according to claim 6 wherein said MMW transmitter/receiver is located at a focus of the primary reflector, said primary reflector having an outer edge or rim portion which is deformed so as to focus laser energy to a location beyond the MMW transmitter/receiver, and wherein the laser energy sensor is located at said location.

8. A multi-mode seeker system according to claim 6 and additionally including a dichroic element located in the path of energy reflected from the primary reflector for feeding received RF energy to the MMW transmitter/receiver and reflecting received infrared energy to the infrared energy sensor.

9. A multi-mode seeker system according to claim 8 and additionally including one or more optical elements located between the dichroic element and the infrared energy sensor for directing incoming infrared energy to an infrared detector.

10. A multi-mode seeker system according to claim 9 wherein the MMW transmitter/receiver and the laser energy sensor are coaxially mounted in back-to-back orientation along the central axis.

11. A multi-mode seeker system according to claim 10 wherein the secondary reflector comprises a discrete mirror element located adjacent the optical system of the laser energy sensor for focusing laser energy reflected from the primary reflector to the laser energy detector.

12. A multi-mode seeker system according to claim 10 wherein the secondary reflector is formed as part of the optical system of the laser energy sensor.

13. A multi-mode seeker system according to claim 10 wherein said optical system of the laser energy sensor includes an immersion lens and wherein the secondary reflector comprises a curved reflective surface of the immersion lens.

14. A multi-mode seeker system according to claim 10 wherein the primary and secondary reflectors include a parabolic reflective surface.

15. A multi-mode seeker system according to claim 10 and additionally including a light filter member placed in the path of laser energy reflected from the primary reflector to the secondary reflector.

16. A multi-mode seeker system according to claim 15 wherein the light filter member is affixed to the optical system of the laser energy sensor.

17. A multi-mode seeker according to claim 10 wherein the infrared sensor is located in a central aperture of the primary reflector.

18. A multi-mode seeker according to claim 5 wherein the laser energy detector comprises a quadrant detector.