BACKGROUND OF THE INVENTION Electro-optical sensor assemblies use optical components to route and focus received radiation onto an electro-optical detector. The detector may be responsive to longwave infrared radiation (approximately 8 to 10 micron wavelengths), midwave infrared radiation (approximately 3 to 5 micron wavelengths), near-infrared radiation (approximately 0.7 to 0.9 micron wavelengths), laser light (such as 1.06 to 1.54 micron wavelengths), or radiation having other wavelengths. Frequently, a sensor assembly will be a multi-spectral device having two or more detectors which are responsive to radiation at respective different wavelengths, and which require separate imaging optics.

The size and weight of electro-optical sensor assemblies has always been a significant design consideration, and the problem is compounded when a sensor assembly includes multiple detectors. In an airborne application, the size of the sensor assembly dictates the

size of the required gimbal, which in turn affects the overall system size and weight. Since the sensor assembly and gimbal may both be in the airstream, the size of each can affect the overall aircraft drag. In ground applications, where a head mirror is used for elevation pointing, the number of optical apertures and the size of these apertures dictate the head mirror size. In turn, the head mirror size affects the size and weight of the surrounding armor plate.

Multi-detector sensor assemblies may have other requirements that affect size, weight and/or performance.

Imaging optics with long optical paths can result in optical losses, or in other words poor optical transmission. Also, two-dimensional infrared staring arrays with excellent resolution are becoming available, and where one or more of the detectors in a sensor assembly is such a staring array, optical-mechanical image motion stabilization (IMS) may be required in order to permit the overall system to output an image having the high resolution which the staring array itself is capable of producing.

One known approach for reducing the size of a multi- detector sensor assembly is to use a common aperture for two or more of the detectors. One known system uses a completely reflective afocal up front, which transmits all wavelengths. Tilted beam splitters are used after the afocal in order to separate different wavelengths for the respective detectors. A respective different refractive lens system is typically provided after the beam splitters for each detector.

In this known approach, the tilted beam splitters are located in collimated light, where aberrations are not a problems. However, the afocal itself is rather large.

Moreover, multiple fields of view are difficult to achieve with a completely reflective afocal. The afocal can be

totally bypassed for a second field of view, but if three fields of view are required, the optical system must transmit at all sensor wavelengths. If additional fields of view are made refractive, the materials used may not transmit some wavelengths of interest. If reflective optics are employed, large fields of view are difficult to achieve.

An all-refractive optic approach has been used in a single aperture, multi-spectral sensor assembly, one example of which is U. S. Patent No. 4,621,888. This assembly can be used to achieve a common aperture for visible wavelengths and for infrared wavelengths up to 12 microns. However, only the front lens is common to both detectors, and the optical paths are relatively long, so that the size of the assembly is relatively large. U. S.

Patent Nos. 4,871,219 and 4,999,005 are other examples of multi-spectral systems having refractive optics which use a common aperture. In these systems, the detectors are limited to detection of just infrared radiation.

SUMMARY OF THE INVENTION From the foregoing, it may be appreciated that a need has arisen for a sensor apparatus which has a plurality of detectors responsive to radiation at respective wavelengths, which has a compact physical size, which has a relatively low weight, and which permits use of image motion stabilization to provide high resolution from one or more of the detectors. According to the present invention, a sensor assembly is provided to address this need.

More specifically, a sensor assembly according to the invention includes a focusing mirror arrangement which is operative to receive radiation traveling along a first optical path and to focus the radiation to travel along a second optical path. A beam splitter disposed along the second optical path is operative to cause a first portion of the radiation which has a first wavelength to be

directed along a third optical path, and to cause a second portion of the radiation which has a second wavelength different from the first wavelength to be directed along a fourth optical path different from the third optical path.

A first detector disposed along the third optical path is operative to detect radiation at the first wavelength, and a second detector disposed along the fourth optical path is operative to detect radiation at the second wavelength. A first lens arrangement is disposed along the third optical path between the beam splitter and the first detector, and a second lens arrangement is disposed along the fourth optical path between the beam splitter and the second detector.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the present invention will be realized from the detailed description which follows, taken in conjunction with the accompanying drawings, in which: FIGURE 1 is a diagrammatic perspective view of selected components of a compact sensor assembly which embodies the present invention, and which uses focusing mirrors and refractive optics ; FIGURE 2 is a diagrammatic sectional view of an infrared staring array detector and associated optical elements, which are all components of the sensor assembly of FIGURE 1; FIGURE 3 is a diagrammatic sectional view of a television detector and associated optical elements, which are all components of the sensor assembly of FIGURE 1; FIGURE 4 is a diagrammatic sectional view of a system of optical elements which provides a wide field of view for the staring array detector, all of which are components of the sensor assembly of FIGURE 1;

FIGURE 5 is a diagrammatic sectional view similar to FIGURE 4, but depicting an alternative configuration of the optical elements that provides a middle field of view for the staring array detector; FIGURE 6 is a diagrammatic sectional view of a further staring array detector and associated optical elements, which are components of an alternative embodiment of the sensor assembly of FIGURE 1; FIGURE 7 is a diagrammatic sectional view similar to FIGURE 2, but showing an alternative embodiment of the optical system which utilizes diffractive optics; and FIGUREs 8 and 9 are diagrammatic sectional views respectively similar to FIGUREs 4 and 5, but showing an alternative embodiment of the optical system which utilizes diffractive optics.

DETAILED DESCRIPTION OF THE INVENTION FIGURE 1 is a diagrammatic perspective view of a compact, multi-spectral, electro-optical sensor assembly 10, which embodies the present invention. The sensor assembly 10 is disposed in a not-illustrated housing, which has at least two windows through which radiation can enter.

One of the windows is shown at 14. The broken line designated at 13 diagrammatically represents the optical aperture associated with window 14, and the broken line designated at 12 diagrammatically represents the optical aperture associated with the other window. The housing may have more than two windows or apertures, but only the apertures pertinent to an understanding of the present invention are illustrated and described here.

In a manner described in more detail below, radiation passing through the aperture 12 is handled by the sensor assembly 10 so that midwave infrared radiation (approximately 3 to 5 micron wavelengths) is routed to a forward looking infrared (FLIR) detector 16, near-infrared

radiation (approximately 0.7 to 0.9 micron wavelengths) is routed to a television (TV) detector 17, and laser light (such as 1.06 to 1.54 micron wavelengths) is routed to a laser detector 18. The FLIR detector 16 is a two- dimensional staring array infrared detector. The TV detector 17 is a two-dimensional charge-coupled device of the type commonly used in television cameras.

FIGURE 2 is a diagrammatic sectional view of a portion of the structure of the sensor assembly 10, and in particular shows the optical path from the aperture 12 to the FLIR detector 16. With reference to FIGUREs 1 and 2, the sensor assembly 10 includes a concave primary mirror 21 and a convex secondary mirror 22, which are focusing mirrors having a common optical axis. The primary mirror 21 is a parabolic mirror, and has a circular opening 23 provided through the center thereof. The secondary mirror 22 is a conic mirror, and faces the primary mirror 21. In the disclosed embodiment, the primary mirror 21 has a diameter of approximately 6", such that the aperture 12 also has a diameter of approximately 6". The secondary mirror 22 has a diameter substantially smaller than the diameter of the primary mirror 21.

Radiation entering the aperture 12 is focused by the primary mirror 21 onto the secondary mirror 22, and then is focused by the secondary mirror 22 back through the opening 23 in the primary mirror 21. The focusing is such that an image 26 is formed at a location between the secondary mirror 22 and the primary mirror 21, the image 26 being closer to the primary mirror 21 than the secondary mirror 22. After passing through the opening 23 in the mirror 21, the radiation reflected by the secondary mirror 22 encounters a tilted beam splitter 31. The beam splitter 31 is slightly wedge-shaped, and is located in converging radiation.

The beam splitter 31 of FIGUREs 1 and 2 passes midwave infrared radiation (approximately 3 to 5 micron wavelengths), and reflects other radiation upwardly in FIGUREs 1 and 2, as indicated diagrammatically by arrow 32 in FIGURE 2. The reflected radiation includes longwave infrared radiation, as well as near-infrared radiation and laser light. The midwave infrared radiation which is transmitted through the beam splitter 31 then passes through a converging lens 33 and a diverging lens 34, after which it is reflected by a planar mirror 36. The mirror 36 is supported for a small amount of movement, under the control of an image motion stabilization (IMS) mechanism 37.

The IMS 37 is provided in order to permit the system to take full advantage of the high resolution capabilities of the staring array detector 16. More specifically, when the housing which contains the assembly 10 is supported on a vehicle by a gimbal, the outer gimbal cannot always hold the assembly 10 sufficiently steady to allow the staring array detector 16 to accurately produce an image having the full resolution of which the detector 16 is capable.

Accordingly, the IMS 37 is provided in order to dynamically fine tune the position of the mirror 36 in a manner which compensates for the motion imparted to the sensor assembly 10 by the vehicle, so that the image focused on the sensor 16 is steady and can be sensed to the full resolution capability of the detector 16.

After radiation is reflected by the mirror 36, it passes through a converging lens 41, and then passes through a window 42 which is made of infrared-transparent material, such as silicon or germanium. An image from the radiation is focused on the surface of the detector 16, which outputs an electrical signal representative of the image.

As mentioned above, radiation other than midwave infrared radiation is reflected upwardly at 32 by the beam splitter 31. The optical path of this radiation will now be described with reference to FIGUREs 1 and 3, where FIGURE 3 is a diagrammatic sectional view of the optical path for radiation traveling from the beam splitter 31 to the TV detector 17 (FIGURE 1). More specifically, the radiation reflected in the direction 32 by the beam splitter 31 travels upwardly through a converging lens 46, and is then reflected by a folding mirror 47. This reflected radiation is then reflected again by a moveable mirror 51, which is controlled by a further IMS mechanism 52. The function of the IMS 52 is similar to that described above for the IMS 37. The radiation reflected from the mirror 51 travels downwardly through a diverging lens 56, a converging lens 57, a converging lens 58, a diverging lens 61, and a converging lens 62. The lenses 57 and 58 have mating surfaces which are bonded to each other, for example using a known cement. Similarly, the lenses 61 and 62 have mating surfaces which are bonded to each other.

After passing through the lens 62, the radiation passes through a converging lens 67, a converging lens 68, and a converging lens 69, and then enters a beam splitter 73. With reference to FIGURE 1, the beam splitter 73 reflects downwardly-traveling radiation in the near- infrared waveband, so that it travels horizontally outwardly to and forms an image on the TV detector 17.

Downwardly-traveling laser light passes through the beam splitter 73 without being reflected, and then passes through a lens 77, which focuses the laser light on the laser detector 18.

The aperture 12 is used to provide the FLIR detector 16 and the TV detector 17 with a narrow field of view (NFOV). The aperture 13 is used to provide the FLIR detector 16 with a middle field of view (MFOV) and a wide

field of view (WFOV). An explanation will now be provided of how radiation entering through aperture 13 and window 14 can optionally be routed to the FLIR detector 16 in order to provide a WFOV or MFOV. For this purpose, and with reference to FIGURE 1, a folding mirror 81 can be removably inserted between the beam splitter 31 and the lens 33, so as to be parallel to and adjacent the beam splitter 31.

When the mirror 81 is physically removed from the position shown in FIGURE 1, midwave infrared radiation entering the aperture 12 is routed to the FLIR detector 16 in the manner discussed above in association with FIGURE 2. On the other hand, when the mirror 81 is disposed in the position shown in FIGURE 1, it interrupts the optical path between the aperture 12 and the detector 16, and instead creates an optical path from the aperture 13 to the detector 16, as discussed below in more detail with reference to FIGURE 4.

With reference to FIGUREs 1 and 4, infrared radiation entering the system through the aperture 13 and window 14 passes through a converging lens 83, and a diverging lens 84. It then passes through a lens system 85, which includes a diverging lens 86, a converging lens 87, a converging lens 88, and a diverging lens 89. The radiation is then reflected by a folding mirror 93, and passes through a converging lens 96 and a converging lens 97. The radiation then passes through a diverging lens 98 and a converging lens 99. The radiation is then reflected by the mirror 81, which is in the position shown at FIGURE 1, where it is adjacent to the beam splitter 31.

Following reflection by the mirror 81, the radiation follows an optical path which is the same as that described above in association with FIGURE 2, in that the radiation successively encounters lens 33, lens 34, mirror 36, lens 41, window 42 and detector 16. FIGURE 4 shows the lens configuration for the wide field of view. This lens configuration has been specifically designed so that

conversion to a middle field of view requires only the removal of the lens system 85 (lenses 86-89) from the optical path between the lens 84 and the mirror 93. More specifically, the middle field of view configuration is shown in FIGURE 5, and it will be noted that FIGURE 5 is identical to FIGURE 4 except that the lens system 85 of FIGURE 4 has been removed from the optical path.

Referring to FIGURE 1, and ignoring aperture 13 and the associated optical elements, it will be noted that the structure associated with aperture 12 is extremely physically compact. The three detectors 16-18, and all of the optical structure routing radiation to them, is disposed within a not-illustrated imagery cylinder which is coaxial with and has the same diameter as the primary mirror 21, and which has an axial length bounded by the secondary mirror 22 and the folding mirror 36. The physical length of this imaginary cylinder, from the secondary mirror 22 to the folding mirror 36, is less than 1.5 times the diameter of primary mirror 21. This compactness is due in part to the fact that the focusing mirrors 21 and 22 take up significantly less space than would be needed for an afocal which is totally reflective.

As discussed above, the beam splitter 31 of FIGURE 1 passes midwave infrared radiation, and the FLIR detector 16 detects midwave infrared radiation. It will be recognized that the detector 16 could be replaced with a similar staring array detector responsive to longwave infrared radiation rather than midwave infrared radiation, and that the beam splitter 31 could be replaced with a similar beam splitter that passes longwave infrared radiation rather than midwave infrared radiation. In association with this change, the lens system provided for the midwave detector 16 would need to be replaced with a lens system suitable for imaging longwave infrared radiation, which in

particular may be similar to a lens system which is shown in FIGURE 6 and described in more detail later.

The sensor assembly 10 of FIGURE 1 can alternatively be modified so as to have two separate FLIR detectors that each have a narrow field of view through the aperture 12, one of these two detectors sensing midwave infrared radiation and the other sensing longwave infrared radiation. More specifically, the detectors 17 and 18, and the optical elements disposed between these detectors and the beam splitter 31, would be replaced with the structure shown in FIGURE 6. In this alternative embodiment, midwave infrared radiation is still routed to the detector 16 in the manner described above in association with FIGURE 2.

With reference to FIGUREs 1 and 6, longwave infrared radiation is reflected upwardly by the beam splitter 31 in the direction 32, and then passes through a converging lens 111 and a diverging lens 112 to a mirror 116. The mirror 116 is supported for a small amount of movement, such movement being controlled by an IMS 117, which is comparable in function to the IMS 37 discussed above in association with FIGUREs 1 and 2.

The radiation reflected by mirror 116 passes through a converging lens 121 and an infrared-transparent window 122, and is focused on a FLIR detector 123. The FLIR detector 123 is a staring array detector, which is similar to the detector 16 of FIGURE 1, except that the detector 123 detects longwave infrared radiation, whereas the detector 16 detects midwave infrared radiation.

As discussed above, the sensor assembly 10 of FIGURE 1 has two mirrors 36 and 51 which are controlled by respective IMS mechanisms 37 and 52. According to yet another alternative embodiment, the IMS mechanisms 37 and 52 may be both be omitted, and the mirrors 36 and 51 may be fixedly secured in position. In place of the two IMS mechanisms 37 and 52, and with reference to FIGURE 2, the

secondary mirror 22 would be moveably supported, and a single IMS mechanism 127 would be provided to control movement of the secondary mirror 122, so as to effect image motion stabilization for all three of the detectors 16,17 and 18.

All of the lenses in the embodiment of FIGURE 1 are refractive. Through the use of diffractive optics, it is possible to reduce the number of lens required. FIGUREs 7- 9 show an alternative embodiment, which uses diffractive optics in order to reduce the number of lens. The embodiment of FIGUREs 7-9 is equivalent to the embodiment of FIGURE 1, except for the differences specifically described hereinafter.

More specifically, with reference to FIGURE 7, infrared radiation passing through the beam splitter 31 passes through a converging lens 131, which has a diffractive surface 132 on a side thereof opposite from the beam splitter 31. The radiation is then reflected by the mirror 36, passes through a converging lens 133 and the window 42, and forms an image on the detector 16. It will be noted that there are only two lenses 131 and 133 between the beam splitter 31 and the detector 16, whereas the embodiment of FIGURE 2 has the three lens 33,34 and 41 between the beam splitter 31 and the detector 16.

Referring to FIGURE 8, radiation which enters through the aperture 13 and associated window 14 passes through a converging lens 141 having a diffractive surface 142 on a side thereof opposite from the window 14. The radiation then passes through a lens system 144, which includes a diverging lens 146 having a diffractive surface 147 on a side thereof opposite from the window 14, and which includes a converging lens 148 having a diffractive surface 149 on a side thereof opposite from the window 14. The radiation is then reflected by the folding mirror 93, and

passes through a converging lens 152 having a : diffractive surface 153 on the side thereof facing the mirror 93.

Thereafter, the radiation passes through a converging lens 156, and then through a further converging lens 158 which has a diffractive surface 159 on a side thereof which faces the mirror 93. After leaving the lens 158, the radiation is reflected by the mirror 81. The remainder of the optical path is the same as that just described in association with FIGURE 7, including the lens 131, mirror 36, lens 133, window 42 and detector 16.

The lens system which is shown in FIGURE 8 provides a wide field of view. This can be converted to a middle field of view by physically removing the lens system 144 from the optical path, in order to achieve the optical arrangement shown in FIGURE 9.

TABLEs 1 to 8, below, set forth prescriptions for optical surfaces disposed along the optical paths which are respectively depicted in FIGUREs 2 to 9. It will be recognized that there are variations and modifications of the disclosed optical arrangements, including variations in the optical prescriptions, which lie within the spirit and scope of the present invention.

TABLE1-OPTICALPRESCRIPTIONfFIGURE2t RDYTHI GLA -8.88721-3.950000 REFL K-1.000000 2-1.16584 3.243684 REFL K-1.819652 3 INFINITY 1.925635 4 INFINITY 0.080000 SILICN ADE-45.000000 BDE 0.000000 CDE 0.000000 5 INFINITY 0.000000 XDE 0. 000000 YDE 0.016884 ZDE 0.000000 ADE 0. 031826 BDE 0 CDE 0 6 INFINITY 0.979992 XDE 0. 000000 YDE 0.000000 ZDE 0.000000 ADE 44. 849390 BDE 0.000000 CDE 0.000000 7 3. 00428 0.229902 SILICN 8-20.17644 0.066548 GERM 10 15.04614 0.943093 11 INFINITY-1.050000 REFL 12-0.43653-0.303679 SILICN A 0. 680091E01 B 0.133182E+01 C 106800E+02 D 0.817163E+02 13-0.22936-0.142110 14 INFINITY-0.032000 SAPHIR <BR> <BR> 15 INFINITY-0.030000<BR> <BR> <BR> <BR> <BR> STO INFINITY-0.895732<BR> <BR> <BR> <BR> <BR> IMG INFINITY 0.000000 TABLE 2-OPTICAL PRESCRIPTION (FIGURE 3)<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> RDY THI GLA REFL K-1.000000 4-1. t6584 3. 221544 REFL <BR> <BR> K-1.819652<BR> <BR> <BR> <BR> <BR> <BR> 5 INFINITY 1.947774 6 INFINITY-0.700000 REFL 7-10.52917-0.272591 LASFN31 _SCHOTT 8 3.55635-0.131975 9 INFINITY-0.650000 10 INFINITY 0.700000 REFL 11 INFINITY 0. 850000 12 INFINITY-0.750000 REFL 13 8.56940-0.120059 ZNS 14-2.20159-0.020000 A-. 775984E-01 B-. 124042E-02 C-. 124669E+00 D-236223E-01 15-1.766)4-0.3372)0LASFN3ISCHOTT 16 1.06951-0.080405 SLAL56_0HARA 17 1. 18814-0.200000 18 1.18927-0.099974 SFISCHOTT 19-0.78292-0.540847 LASFN3)SCHOTT 20 15. 80815 -0. 466823 LASFN3 SCHOTT 22-0.93583-0.020000 23-0.32484-0.120000 ZNS 24-0.23015-0.126342 LASFN31SCHOTT 26-0.18568-0.050000 <BR> <BR> 27 INFINITY-0.350000 LASFN31 SCHOTT<BR> <BR> <BR> 28 INFINITY-0.278709<BR> <BR> <BR> IMG INFINITY 0.000740 TABLE3-OPTICALPRESCRIPTION (FIGURE4i RDY THI GLA 1 41. 22953 0. 250000 SILICN 2-4. 73676 0. 123771 3-3.47895 0. 150000 GERM 4-6.00630 0.150000 5-4.49933 0.100000 GERM A-. 976266E01 B 0.693325E+01 C-. 200766E+03 D 0.198054E+04 1 <BR> <BR> <BR> <BR> <BR> <BR> <BR> 6 2. 45456 0.864134<BR> <BR> <BR> <BR> <BR> 7 INFINITY 0. 312387 SILICN A 0. 140095E+00 B-. 362783E+00 C 0.487027E+01 D-. 382764E+02 9-2.12001 0.519730 10 1.54617 0.180000 SILICN I1-5. 16359 0. 038133 12-2.99417 0. 100000 GERM 13 11.04500 0. 591050 A 0. 799886E01 B-. 885354E01 C 0.501114E01 D 0.221278E+00 14 INFINITY-0.766401 REFL 15-0.47504-0.150000 SILICN A-. 447986E+00 B 0.624460E+01 C-. 121326E+03 D 0.787966E+03 16-0.45938-0.095879 17 INFINITY-0.506957 18-1.14087-0.170000 SILICN 19 1.69435-1.049478 A -149896E+O1 B 0.207350E+02 C-. 913289E+03 D 0. 152986E+05 20 1.17647-0.150000 GERM 21 2.20899-0.070799 22 1.79488-0.190622 SILICN 23 1.02253-0.799923 24INFINITY0.719988 REFL 25 3. 00428 0.229902 SILICN 26-20.17644 0.066548 GERM 28 15. 04614 0.943093 29 INFINITY-1.050000 REFL 30-0.43653-0.303679 SILICN A 0. 680091E01 B 0.133182E+01 C-. 106800E+02 D 0.817163E+02 31-0.22936-0.142110 32 INFINITY-0.032000 SAPHIR 33 INFINITY 0.030000 STO INFINITY -0. 895732 IMG INFINITY 0.000000 TABLE4-OPTICALPRESCRIPTION (FIGURE5i<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> RDY THI GLA 41. 22953 0.250000 SILICN 2-4.73676 0. 123771 3-3.47895 0. 150000 GERM 4-6.00630 2.976229 5 INFINITY-0.766401 REFL SILICN A-. 447986E+00 B 0.624460E+Oi C-. 121326E+03 D 0.787966E+03 7-0.45938-0.095879 8 INFINITY-0.506957 9-1.14087-0.170000 SILICN 10 1. 69435-1.049478 A-. 149896E+01 B 0.207350E+02 C-. 913289E+03 D 0.152986E+05 11 1. 17647-0. 150000 GERM 12 2.20899-0.070799 13 1.79488-0.190622 SILICN 14 1.02253-0.799923 15 INFINITY 0. 719988 REFL 16 3. 00428 0.229902 SILICN 17-20.17644 0.065548 GERM 19 15. 04614 0.943093 20 INFINITY-1.050000 REFL 21-0.43653-0.303679 SILICN A 6. 80091E01 B 0.133182E+01 C-. 106800E+02 D 0.817163E+02 22-0.22936-0.142110 23 INFINITY-0.032000 SAPHIR <BR> <BR> <BR> 24 INFINITY-0.030000<BR> <BR> <BR> <BR> <BR> STO INFINITY-0.895732<BR> <BR> <BR> <BR> <BR> <BR> IMG INFINITY-0.000000 TABLE OPTICAL PRESCRIPTION (FIGURE 6)<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> RDY Tlll GLA 1-9.70474-4.09740 REFL A 0. 148305E-03 B 0.567092E-06 C 0.395959E-07 D-. 128865E-08 REFL A 0. 477868E-01 B-. 981358E-02 C 0.154320E-01 D-. 137317E-01 3 INFINITY 2.885000 4 20. 08498 0. 351716 GERM 5-8.42436 0.365692 A 0. 302448E-02 B-. 22601 OE-03 C-. 355913E-04 D 0.141616E-04 6 4. 68457 0.300000 ZNSE 7 3. 57396 0.89908 8 INFINITY -0.699455 REFL 9 -. 053876 -0.300000 GERM A -. 500203E-02 B 0. 235943E-01 C-. 226562E+00 10 -0.33206-0184758 11 INFINITY-0032000 GERM <BR> <BR> <BR> 12 INFINITY-0.030000<BR> <BR> <BR> <BR> <BR> STO INFINITY-0.855955<BR> <BR> <BR> <BR> <BR> IMG INFINITY 0.000234 TABLE6-OPTICALPRESCRIPTIONfFIGURE7) RDY THI GLA -8.73419-3.950000 REFL K-1. 000000 2-0.96869 3. 003971 REFL <BR> <BR> <BR> K-1.748867<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> 3 INFINITY 2. 166618 4 INFINITY 0.080000 SILICN ADE-45.000000 BDE 0.000000 CDE 0.000000 5 INFINITY 0.000000 XDE 0. 000000 YDE 0.020970 ZDE 0.000000 ADE 0. 027830 BDE 0.000000 CDE 0.000000 6 INFINITY 0.980005 XDE 0. 000000 YDE 0.000000 ZDE 0.000000 ADE 44. 943985 BDE 0.000000 CDE 0.000000 7 6. 52861 0.229926 SILICN 8-21.32900 1.350000 HOE: <BR> <BR> <BR> HV1: REA HV2 REA HOR :-1<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> HX 1: O. OOOOOOE+00 HYI O. OOOOOOE+00 HZ 1: 0. 1 OOOOOE+ 19 HX2: O. OOOOOOE+00 HY2 O. OOOOOOE+00 HZ2: 0.100000E+19 HWL: 3500.00 HTO ASP HCT: R HCO Cl 1. 5368E-03 C67: 2.2154E-03 C68:-3.0826E-04 C69: 0585E-04 9 INFINITY-0749455 REFL 10-0.41708-0.295184 SILICN A 0. 421957E-01 B 0.819910E+00 C-. 686491E+01 D 0.605438E+02 11-0. 20278-0. 122472 13 INFINITY-0.032000 SAPHIR 14 INFINITY-0.030000 STO INFINITY-I. 000000 IMG INFINITY 0.000000 RDY THI GLA 1 14. 87561 0. 180000 SILICN 2-37.87158 0.349941 HOE: HV 1: REA HV2: REA HOR:-I HX: O. OOOOOOE+00 HYI: O. OOOOOOE+00 Hz1 : 0.100000E+19 HX2: O. OOOOOOE+00 HY2: O. OOOOOOE+02 HZ2: 0.100000E+19 HWL: 3500.00 HTO: ASP HCT: R HCO Cl : 1. 0912E-03 C67 7.4476E-04 C68 1. 2570E-04 C69:-3.0273E-04 C70 2.1942E-04 3 3.44265 0.150000 SILICN 4 1.39773 2.340032 HOE: HV 1 : REA HV2: REA HOR:-I HX1: O. OOOOOOE+00 HYI: O. OOOOOOE+00 HZ1: 0.100000E+19 HX2: O. OOOOOOE+00 HY2: O. OOOOOOE+00 HZ2 0.100000E+19 HWL: 3500.00 HTO: ASP HCT: R HCO Cl: 2.0297E-03 C67 : -3. 7770E-03 C68: 1.0127E-02 C69: 4.4296E-01 C70:-1.9658E+00 5 4.64861 0.150000 SILICN 6-5.09494 0.371998 HOE: HV1 : REA HV2: REA HOR:-I 0. 100000E+ l 9 HX2: O. OOOOOOE+00 HTO: O. OOOOOOE+00 HZ2: 0. 1OOOOOE+19 HWL: 3500.00 HTO: ASP HCT: R HCO Cl: 7.0778E-03 C67: 3.8250E-02 C68: 7.1455E-03 C69:-2.4665E-01 C70: 1.0457E+00 7 INFINITY-0.850000 REFL 8-1.44947-0.080000 SILICN HOE: HV 1: REA HV2 : REA HOR: HX 1 : O. OOOOOOE+00 HY 1: O. OOOOOOE+00 HZ1 : . 1OOOOOOE+19 HX2: O. OOOOOOE+00 HY2: O. OOOOOOE+00 HZ2:-. OOOOOOE+I9 HWL: 3500.00 HTO: ASP HCT: R HCO Cl: 1.1918E-02 C67:-4.7186E+00 C68: 1. 0213E+02 C69:-9.5443E+02 C70: 1. 9665E+03 9-1.51046-0.082989 10 INFINITY-0.645891 ll -0. 76374 -0. 1 SILICN 12 6.87896-1.006413 A:-. 138886E+01 B: 0. 598669E+01 C:-. 246475E+02 D: 36.4635 13 1.33202-0.170000 SILICN HOE: IIV 1: REA HV2 : REA HOR : HX 1: O. OOOOOOE+00 HY): O. OOOOOOE+00 HZ 1 :. 1000000E+ l 9 HX2: O. OOOOOOE+00 HY2 : O. OOOOOOE+00 HZ2:-. IOOOOOOE+19 HWL: 3500.00 HTO: ASP HCT: R HCO Cl:-1.6467E-02 C67: 5.6615E-02 C68:-7.0949E-02 C69: 1. 7753E-01 C70:-2.0174E-01 14 15 INFINITY 0.750000 REFL ADE: 44.948000 BDE: 0.000000 CDE: 0.000000 16 6.52861 0.229926 SILICN 17-21. 32900 1.350000 HOE: HV 1: REA HV2: REA HOR: HXI: O. OOOOOOE+00 HY1: O. OOOOOOE+00 HZ1 : 0.100000E+19 HX2: O. OOOOOOE+00 HTO: O. OOOOOOE+00 HZ2: 1.00000000000 e+18 HWL: 3500.00 HTO: ASP HCT: R HCO Cl: 1. 5368E-03 C67: 2.2154E-03 C68:-3.08263-04 C69: 4.7999E-04 C70:-2.0585E-04 18 INFINITY-0.749455 REFL 19-0. 41708-0. 295184 SILICN A-0.41957E-01 B: 0.819910E+00 C :-6. 86491 D: 0.605438E+02 21 INFINITY-0.032000 SAPHIR 22 INFINITY-0.030000 STO: INFINITY-1.000000 IMG: INFINITY 0.000000 TABLE 8-OPTICAL PRESCRIPTION (FIGURE 9) RDY THI GLA 1 14. 87561 0. 180000 SILICN 2 -37.87158 3.361971 HOE: HV): REA HV2: REA HOR:-I HX 1: O. OOOOOOE+00 HY I: O. OOOOOOE+00 HZ 1: 0. IOOOOOE+19 HX2: O. OOOOOOE+00 HY2: O. OOOOOOE+00 HZ2: O. IOOOOOOE+19 HWL: 3500.00 HTO: ASP HCT: R HCO Cl: 1. 0912E-03 C67: 7.4476E-04 C68: 1.2570E-04 C69:-3.0273E-04 C70: 2.1942E-04 3 INFINITY-0.850000 REFL 4-1.44947-0.080000 SILICN HOE: HV 1: REA HV2: REA HOR: HX 1 ; O. OOOOOE+00 HY 1: O. OOOOOOE+00 HZ 1 :-. I OOOOOOE+ 19 HX2: O. OOOOOOE+00 HY2: O. OOOOOOE+00 HZ2:-. 1OOOOOOE+19 HWL: 3500.00 HTO: ASP HCT: R HCO C1: 1. 1918E-02 C67 -4. 7186E+00 C68: 1. 0213E+02 C69: -9.5443E+02 C70: 1.9665E+03 5 -1. 51046 -0.082989 6 INFINITY-0.645891 SILICN 8 A:. - 138386E+O1 B : 5. 98669 C:-. 246475E+02 D: 0.364635E+02 9 1. 33202-0. 170000 SILICN HOE: HV1: REA HV2: REA HOR: I HX 1: O. OOOOOOE+00 HY 1: O. OOOOOOE+00 HZ 1 :-. 1 OOOOOE+ 19 HX2: O. OOOOOOE+00 HY2: O. OOOOOOE+00 HZ2:-. I OOOOOOE+ 19 HWL: 3500.00 HTO: ASP HCT: R HCO Cl:-1. 6467E-02 C67 : 5.6615E-02 C68:-7.0949E-02 C69: 1. 7753E-01 C70:-2.0174E-O I 10 0.98157-0. 980151 11 INFINITY 0.750000 REFL ADE: 44.948000 BDE: 0.000000 CDE: 0.000000 12 6.52861 0.229926 SILICN<BR> 13-21. 32900 1.350000 HOE: HVI: REA HV2: REA HOR: t HX1: O. OOOOOOE+00 HYI: O. OOOOOOE+00 HZ1: O. OOOOOOE+i9 HX2: O. OOOOOOE+00 HY2: O. OOOOOOE+00 HZ2: O. OOOOOOE+19 HWL: ASP HCT: R HCO Cl : 1. 5368E-03 C67: 2.2154E-03 C68:-3.0826E-04 C69: 0585E-04 14 INFINITY-0.749455 REFL 15-0.41708-0.295184 SILICN A: 0. 421957E-0 B : 0.819910E+00 C :-. 686491E+O1 D: 0.605438E+02 16-0.20278-0.122472 17 INFINITY-0.032000 SAPHIR 18 INFINITY-0.030000 STO: INFINITY-1.000000 IMG: INFINITY 0.000000

The present invention provides a number ; of technical advantages. One such technical advantage is the realization of a sensor assembly which has a plurality of detectors and also image motion stabilization, but which is physically compact and has a relatively low weight. A further advantage is that several detectors all use a common, relatively large aperture for a narrow field of view. Yet another advantage is that there are relatively short optical paths with a minimum number of optical elements, which has the effect of minimizing optical losses. By reducing the overall size of the sensor assembly, there is a reduction in the drag which is created when the sensor assembly is disposed in the air stream of an airborne vehicle.

By reducing the size and weight of the sensor assembly, the size and weight of the gimbal required to support the sensor assembly is also reduced, which further reduces the drag factor they create in an air stream. A further technical advantage is that diffractive optics can optionally be used to further reduce the number of optical elements in the assembly.

Although selected embodiments have been illustrated and described in detail, it will be recognized that various changes, substitutions and alternations, including the rearrangement and reversal of parts, can be made without departing from the spirit and scope of the invention, as defined by the following claims.