GB2188166A

GB2188166A - Curved reflector having zones with different focal points

Info

Publication number: GB2188166A
Application number: GB08705876A
Authority: GB
Inventors: George T Pinson
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 1986-03-13
Filing date: 1987-03-12
Publication date: 1987-09-23
Anticipated expiration: 2007-03-12
Also published as: FR2595874B1; GB8705876D0; FR2595874A1; GB2188166B

Abstract

A dual-mode signal separator 10 has a single reflector 12 fabricated with two or more zones 14,18 of different radii of curvature, the different zones 14,18 of the reflector providing focal points 16,20 at different distances along an optical axis 11 of the reflector through the centre thereof. The different zones may be fabricated into concentric rings, concentric spirals, flat segments or other types of surfaces for providing the different focal points along the optical axis. The separator may receive infrared, millimetre, radio frequency, ultraviolet or other wavelengths.

Description

SPECIFICATION Dual-mode signal separator Background ofthe invention This invention relates to a wavelength signal separatorand more particularly, but not byway oflimi- tation,toa dual-mode signal separator for receiving various types of wave signals thereon and separating the signals using different reflector zones having different radii of curvature.

Heretofore, there have been various types of radar and infrared scanning antennas with different types of convex and concave reflectors used in the ant ennas. These types of antennas and signal separators are described in the following United States patents: U.S. Patent No. 1,906,546 to Darbord; U.S.

Patent No. 2,559,092 to Reulos; U.S. Patent No.

2,636,125 to Southworth; U.S. Patent No.2,702,859 to Robinson; U.S. Patent No. 2,895,127 to Padgett; U.S. Patent No.3,114,149 tojessen,Jr.; U.S. Patent No. 3,392,397 to Schwartz; U.S. Patent No.3,394,378 to Williams et al; U.S. Patent No. 3,500,419to Leitner et al; U.S. Patent No.4,282,527 to Winderman et al; U.S. Patent No.4,348,677 to Salmond, U.S. Patent No. 4,477,814to Brumbaugh etal. None ofthe above-mentioned patents provide the uniquefeatures and advantages ofthe subject invention as described herein.

Summary ofthe invention The subject dual-mode separator may have any number of zones up to 1,2,3 N. The concept is not limited to concentric rings since the design ofthe primary reflector can also have zones using concent ric spirals, flat segments orsurfaces dimpled such as in a golf ball where each dimple represents a small reflector embedded in a substrate. This type of design is particularly suited for "N" different focal lengths and for radio frequency applications where continuous current paths are desired.

The dual-mode separator may be used for ultraviolet, optical, infrared, radio frequency, millimeter and various other types ofsignal wavelengths. Further, the zoning concept ofthe separator can be used for off axis reflectors as well as on axis reflectors. Also different anti-reflective or reflective coatings can be used on the surface to reducecrosstalkorenhance the surface properties for specific applications.

The dual-mode signal separator for receiving infrared, millimeter radio frequency, ultraviolet and other wave signals thereon includes a primary reflectorfor receiving signals thereon. The reflector has an optical axis through the center thereof. A first reflector zone is fabricated in the primary reflector. A second reflector zone is also fabricated in the primary reflector. The first zone has a different radii of curvature from the second zone. The two zones having different focal points along the optical axis of the primary reflector.

The advantages and objects of the invention will become evident from the following detailed description ofthe drawings when read in connection with the accompanying drawings which illustrate prefer red embodiments ofthe invention.

Briefdescription ofthe drawings Figure lillustratesthe subject dual-mode signal separator with a zoned primary reflector.

Figure2 illustrates the primary reflector with a radio frequency horn, a secondary reflector and an infrared detector.

Figure 3A illustrates the primary reflector with an optical detector and radio frequency horn.

Figure 38 illustrates the use of the primary reflector with secondary reflectors fortwo different zones.

Figure 3C illustrates the use of coalignment of secondary reflectors and a receptor.

Figure 3D illustrates the use of a radio frequency feed and detector with the primary reflector.

Figure 3E illustrates the use of a fresnel zoned reflector with multiple focal parts.

Figure 4 illustrates the use of an off axis zoned reflector.

Figure 5illustrates the dual-mode signal separator withwaveguidemillimeterduplexerand infrared de vector.

Figure Gillustrates the use of a spider to support secondary reflectors.

Figure 7illustrates the dual-mode signal separator integrated into a seeker head.

Detailed description ofthe drawings In Figure 1 the dual-mode signal separator is designated by general reference numeral 10 and having a zoned primary reflector 12 with an optical axis 11 through the center of the reflector 12. The reflector 12 includes a first reflectorzone 14 and a second reflec tor zone 18. The first zone 14 has a focal point 16 along the optical axis 11 forfocusing signals indicated by arrows 17 thereon. The second zone 18 has a different radii ofcurvature then the first zone 1 4for reflecting signals 19 onto focal point 20.

The multiple focal point zoned primary reflector 12 as shown in Figure 1 and any alternatives described herein may be fabricated using standard diamond cutting equipment and the like. Also, it may be replicated or molded using compression or injection moulding techniques. Further,to meet particular needs, multiple separator reflection can be used for ultraviolet, optical millimeter, infrared and radio from quencywavelength type systems. The important concepts as described herein is the use of "N" differentfocal lengths, different length reflectors can be designed, fabricated and integrated such that "N" different secondary reflectors or receptors can be mounted atorrelativeto individual focal points either on or off the optical axis.Also, it should be noted that the zoning concept as described herein can be used for off axis reflectors as well as on axis reflectors.

In Figure 2, the separator 10 is shown furtherin- cluding an infrared detector22forthefirstzone 14 and having a focal point 24. Also shown in this Figure is a secondary reflector 26 for receiving radio frequency radiation indicated by arrows 19 thereon and reflecting them through the primary reflector 12 between a radio frequency horn 30 where it is focussed onto a focal point 28.

The dimensioning ofthe zones on the primary reflector 12 has an effect on radio frequency pattern that has important applications. The first of the sec- ondary effects concerns the depth ofthe different zones. Ifan infrared zone is cut an average oft/4 where A is the wavelength of the radio frequency below the surface ofthe radio frequency reflector, then the optical reflective surface has no effect on the radio frequency antenna pattern. Also, the desirable distance between zones is All 0. This can be accomplished by diamond machining.This also shows that the ideal zoned reflectorwill be a fresnel design with dimensions of each zone a function of the wave lengths,the diameter of the reflector, and the effect- ive surface roughness of the combined surface.

From reviewing Figures 3A through 3D, it is ob vious that a wide variety of configurations are possible using the zone primary reflector 12. The zoned primary reflector 12 is equally valid where the primary reflectors are symmetrical orwhere on axis designs are used. An off axis design variation is shown in Figure 4 wherein an off axis zoned reflector 32 has a centerline 34 with an off axis secondary reflector or detector 36 forfocusing on a receptor 38.

Referring back to Figure 3A, the primary reflector 12 is shown with the first zone 14 and second zone 18 focusing the first zone signals 17 on an infrared, ul- travioletor optical detector 40 and with the second zone signals 19focused between a radio frequency horn 42.

In Fig u re 3 B, a secon da ry refl ecto r 44 is sh own fo r focusing signals 17 on a receptor 46 with the second zone reflecting signals 19 on a secondary reflector 48 and through the primary reflector 12 and between a radio frequency horn 50.

Figure 3C shows the use of coalignment between secondary reflectors 52 and 54 for reflecting signals 17 from the first zone 14 ofthe primary reflector 12 onto a receptor 56. The signals 19 are received between a horn 58.

Figure 3D illustrates the variation of using a radio frequency feed 60for receiving reflected signals 17 from the first zone 14ofthe primary reflector 12.Also the signals 19 are reflected from zone 18 onto a det ector62.

Figure 3E illustrates the use of a primaryfresnel zoned reflector 64 having Zone 1, Zone 2 Zone N for multiple focal parts and frequencies for reflecting signals onto a first detector 66, a second detector 68 and onto detector "N" 70 for additional zones.

In Figure 5the separator 10 includes an infrared primary reflector 72 which may be made of either a solid metal reflective element or a plastic or other radio frequency transparent material. If transparent, the plastic surface is coated with an infrared reflective coating. A back surface 74 of the reflector 72 is coated with a radio frequency absorbent material to reduce energy scatter. A secondary reflector 76 is provided art a location consistentwith telescope design. The reflector 76 reflects infrared energy into an infrared detector 78 located at a focal plane along the optical axis of the telescope. Baffling and absorbent material 76 is used to minimize the loss in resolution caused by stray light. In a cassegrain telescope, a central portion 79 ofthe reflector 76 is normally unused.Therefore, in this portion 79 a feed horn 80 is mounted. The reflector76 is attached to and aligned buy a bracket 82. The feed horn 80 is incorporated into a spider shown in Figure 6. The primary reflector 72 is moved along a horizontal "X" axis by two rotating drive cams 84. The horn 80 is connected to a waveguide 86 which is connected to a millimeterduplexer 88.

In Figure 6 a spider assembly 90 is shown and made up of an infrared secondary reflector92, a mil- limeterfeedhorn 94 and an alignment bracket 96 attached to a telescope spider legs 98. A radio frequ encywaveguide 100 can be used and attached to one ofthe spider legs 98. The spider assembly 90 is rigidly attached to a field of regard seeker head 102 through the use of an adjustable spider attachment 104.

An integrated seeker head assembly 106 is illustrated in Figure 7. In Figure 7 control electronicsforthe assembly drive and primary reflector 10 is not shown.

The spider assembly 90 is shown with spider legs 98, infrared secondary reflector 92 and millimeter feedhorn 94 all rigidly attached to the seeker head 102 and moving as the head 102 moves.

The zoned primary reflector 12 is attached through a ball joint 108 to the seeker head 102. The seeker head 102 is driven independently from a reflector drive 110with cams 84. The cams84 movethe reflector 12within a desired ( +) or (-) X degrees in relation to seeker heads centerline. This permits the target area to be scanned in any two dimensional patterns while atthe sametimethe seeker head drive moves the seeker head 102 through a designated motion.

Itshould be noted from reviewing Figure7thatthe infrared detector 78 is not restricted to any given frequency and may be used for infrared detection, ultraviolet, visible and other frequencies. In addition,the detector78 can be replaced by a detector array for imaging purposes orto speed up the search rate of the seeker head 102.

Claims

1. A dual-mode signal separatorfor receiving infrared, millimeter, radio frequency, ultraviolet and other wavelength signals thereon, the separator comprising: a primary reflector for receiving the signals thereon, the reflector having an optical axis through the center thereof; a first reflector zone fabricated in the primary reflector; and a second reflector zone fabricated in the primary reflector, the first zone having a different radii of cu rvatu re tha n the second zone, the two zones having different focal points along the optical axis.

2. The separator as described in Claim 1 wherein the first reflector zone and second reflector zone may be concentric rings on the primary reflector orthe zones may be concentric spirals, flat segments or dimpled surfaces.

3. The separator as described in Claim 1 further including an infrared detector disposed along the op tical axis for receiving reflected signalsthereon from the first reflector zone.

4. The separator as described in Claim 1 further including a second reflector disposed along the optical axis for receiving reflected signals thereon from the second zone and reflecting the signals onto a focal pointalongthe length oftheoptical axis.

5. The separator as described in Claim 1 further including a radio frequency horn disposed along the optical axis for receiving reflected signals from the second reflector zone.

6. A dual-mode signal separator for receiving infrared, millimeter, radio frequency, ultraviolet and other wavelength signals thereon, the separator comprising: a primary reflectorfor receiving the signals thereon, the reflector having an optical axis through the center thereof; a first reflector zone fabricated in the primary reflector; a second reflector zone fabricated in the primary reflector, the first zone having a different radii of curvature from the second zone, and two zones having different focal points along the optical axis; an infrared, ultraviolet or optical detector disposed along the optical axis for receiving reflected signals from the first reflector zone; and a second reflector disposed along the length of the optical axis for receiving reflected signals from the second zone and focussing the signals through a radio frequency horn onto a focal point along the optical axis.

7. A dual-mode signal separator substantially as herein described with reference to and as shown in Figures 1,2, 3A, 3B, 3C, 3D, 3E, 4,5,6 or7 ofthe accompanying drawings.