Multimode seeker system with RF transparent stray light baffles

• US 7,786,418 B2
• Filed: 11/21/2008
• Issued: 08/31/2010
• Est. Priority Date: 11/21/2008
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Jenkins, David G., Taylor, Byron B.
• Primary Examiner(s): Gregory; Bernarr E
• Application Number:
  US12/276,201
• Publication Number:
  US 20100127113A1
• Time in Patent Office: 648 Days
• Field of Search: 250/200, 250/201.1, 2502031-2037, 250/336.1, 250/338.1, 250/353, 244 31- 33, 89/11.1, 342 52- 55, 342 61- 66, 342/175, 342/195, 343/700.R, 343/720, 343/721, 343725-728, 343/781.R, 343/781.CA, 343/872
• US Class Current: 244/3.16
• CPC Class Codes: F41G 7/008 Combinations of different guidance systems
• 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 7/2286 using radio waves
• CPC Class Codes: F41G 7/2293 using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 13/865 Combination of radar systems with lidar systems
• CPC Class Codes: G01S 13/867 Combination of radar systems with cameras
• 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: G02B 17/0808 on-axis systems with at least one of the mirrors having a central aperture
• CPC Class Codes: G02B 23/14 Viewfinders for photographic apparatus G03B13/02
• CPC Class Codes: G02B 27/0018 with means for preventing ghost images anti-reflection coatings G02B1/11
• CPC Class Codes: G02B 5/003 Light absorbing elements

Abstract

There is disclosed a multimode seeker including an imaging infrared seeker and a radio frequency seeker. The imaging infrared seeker and the radio frequency seeker may share an optical system adapted to form an infrared image of an outside scene on a focal plane array image detector and to collimate radio frequency radiation transmitted from a radio frequency transceiver and focus millimeter ware radiation received from the outside scene onto the radio frequency transceiver. The shared optical system may include a plurality of baffles to block sunlight from reaching the focal plane array image detector, each baffle comprising a material that is opaque to infrared radiation and transparent to radio frequency radiation.

Claims

1. A multimode seeker, comprising:

an imaging infrared seeker including a focal plane array

a radio frequency seeker including a radio frequency transceiver

wherein the imaging infrared seeker and the radio frequency seeker share an optical system to

form an infrared image of an outside scene on the focal plane array

collimate radio frequency radiation transmitted from the radio frequency transceiver and focus radio frequency radiation received from the outside scene onto the radio frequency transceiver

wherein the shared optical system includes a plurality of baffles to shield the focal plane array from sunlight incident at an angle greater than a predetermined sun exclusion angle, each baffle comprising a material that is opaque to infrared radiation and transparent to radio frequency radiation.

2. The multimode seeker of claim 1, wherein the shared optical system comprises:

a primary mirror and a secondary mirror disposed along a common optical axis

the primary mirror disposed to receive infrared and radio frequency radiation from a scene

the secondary minor disposed to receive reflected infrared and radio frequency radiation from the primary mirror, and to reflect infrared radiation through a central aperture of the primary minor towards the focal plane array image detector.

3. The multimode seeker of claim 2, wherein

the imaging infrared seeker operates in a selected portion of the infrared spectrum and the radio frequency seeker operates in a selected portion of the radio frequency spectrum

the primary mirror is reflective to at least the selected portion of the infrared spectrum and reflective to at least the selected portion of the radio frequency spectrum

the secondary mirror is reflective to the selected portion of the infrared spectrum and transmissive to the selected portion of the radio frequency spectrum.

4. The multimode seeker of claim 2, wherein the plurality of baffles comprises:

a first baffle having a generally conical inner surface proximate to a marginal ray propagating from the primary minor to the secondary minor.

5. The multimode seeker of claim 4, wherein the first baffle extends outward from a perimeter of the secondary minor.

6. The multimode seeker of claim 4, wherein the plurality of baffles further comprises:

a second baffle having a central aperture, a generally conical inner surface and a generally conical outer surface

the outer surface of the second baffle proximate to an inner ray propagating from the primary minor to the secondary minor

the inner surface of the second baffle proximate to the marginal ray propagating from the secondary minor towards the focal plane array.

7. The multimode seeker of claim 6, further comprising

a field lens disposed along the optical axis between the secondary mirror and the focal plane image detector

wherein the second baffle extends forward from a perimeter of the field lens.

8. The multimode seeker of claim 1, wherein the material is an optically-opaque dielectric foam.

9. An apparatus, comprising:

a focal plane array

an optical system to form an infrared image of an outside scene on the focal plane array, the optical system including a primary minor and a secondary minor disposed along a common optical axis

a first baffle having a generally conical inner surface proximate to a marginal ray propagating from the primary minor to the secondary minor

a second baffle having a central aperture, a generally conical inner surface, and a generally conical outer surface

the outer surface of the second baffle proximate to an inner ray propagating from the primary minor to the secondary minor

the inner surface of the second baffle proximate to the marginal ray propagating from the secondary minor towards the focal plane array.

10. The apparatus of claim 9, wherein

the primary minor receives and reflects infrared radiation from a scene

the secondary minor receives reflected infrared radiation from the primary mirror, and reflects infrared radiation through the central aperture of the primary minor towards the focal plane array image detector.

11. The apparatus of claim 9, wherein the first baffle extends outward from a perimeter of the secondary mirror.

12. The apparatus of claim 9, further comprising

a field lens disposed along the optical axis between the secondary mirror and the focal plane image detector

wherein the second baffle extends forward from a perimeter of the field lens.