Seeker, particularly for target seeking missiles

A seeker, particularly for target seeking missiles, includes an imaging optical system which is universally movably supported with respect to a structure using a gimbal mount via an inner gimbal and an outer gimbal, and further includes a detector at which an image of the field of view can be produced by the optical system. In such seeker, the imaging optical system comprises optical members which are disposed at the inner gimbal on the side of the object and which define an optical axis of the imaging optical system. The optical system contains a deflecting mirror for folding a path of rays such that the deflected optical axis coincides with a gimbal axis of the inner gimbal. Image rotating reflecting means is arranged on the gimbal axis of the inner gimbal and reverses the deflected path of rays in order to direct the reversed, deflected path of rays to a detector which is retained at the outer gimbal, placed on the gimbal axis of the inner gimbal and designed as a detector array. The reflecting means is attached to the outer gimbal and driven for rotation about the gimbal axis of the inner gimbal.

BACKGROUND OF THE INVENTION 
The present invention relates to a new and improved construction of a 
seeker, particularly for target seeking missiles. 
In its more specific aspects, the invention relates to a new and improved 
construction of a seeker, particularly for target seeking missiles, 
including an imaging optical system which is universally movably supported 
with respect to a structure by means of a gimbal mount via an inner gimbal 
and an outer gimbal, and a detector at which an image of the field of view 
can be produced by means of the optical system. In such seeker, 
(a) the imaging optical system comprises an optical member which is 
arranged at the inner gimbal on the side of the object and which defines 
an optical axis of the imaging optical system, 
(b) the imaging optical system includes a deflecting mirror which is 
disposed at the inner gimbal and which folds a path of rays defined by the 
imaging optical system, and 
(c) reflecting means are provided and reverse the path of rays. 
In a known seeker, an infrared receiving system conjointly with a 
rotational speed sensor and the associated controlling and amplifying 
electronics are rigidly interconnected in a housing. The infrared 
receiving system therein comprises a gas-cooled multi-element detector, an 
imaging optical system in the form of a folded lens system and a scanning 
device for scanning a field of view covered by the seeker. The imaging 
optical system images the field of view in a plane defined by the 
detector. The scanning device causes the image of the field of view to be 
moved relative to the detector such that the multi-element detector scans 
the field of view. 
The aforementioned housing defines a rotatable gimbal of a gimbal system 
and such rotatable gimbal is rotatable about the pitch axis and the yaw 
axis. The seeker, therefore, can be rotated relative to a structure like, 
for example, the airframe of the missile, through a limited angular range 
and thereby is aimed at a target. During such rotation through the limited 
angular range, the electrical conductors of the multi-element detector as 
well as the high-pressure gas infeed conduits must be flexibly guided 
across the two gimbal axes, namely the pitch axis and the yaw axis. Such 
arrangement is constructionally and spatially expensive. The seeker head 
becomes undesirably large in size and heavy in weight. Furthermore, there 
result unduly high gimbal moments of inertia. 
There are further known seekers in which the imaging optical system is 
arranged at a gimbal which is supported for movement about two axes 
whereas the infrared detector is structurally fixedly mounted. The focused 
beams of infrared rays are passed through the gimbal axes using additional 
optical elements, namely lens systems and mirrors, and intermediate 
images. An infrared image is thus produced in the structurally fixed plane 
of the infrared detector. This requires a very complicated and expensive 
imaging optical system. Moreover, transmission losses and scattering 
losses will additionally occur at the optical elements in such 
construction particularly in the infrared region. Furthermore, losses are 
incurred in image resolution. 
In a seeker such as described, for example, in German Published Patent No. 
2,454,480, published on Dec. 11, 1975, an outer gimbal is arranged for 
rotation about the lengthwise axis of the missile. An inner gimbal can be 
rotated relative to the outer gimbal about an axis which extends 
perpendicular to the gimbal axis of the outer gimbal. The inner gimbal 
supports a lens system which defines an optical axis, and further supports 
a deflecting mirror and an image rotating ridge mirror. In this 
construction, the path of rays extends from the lens system to the ridge 
mirror and therefrom to the deflecting mirror. The deflecting mirror can 
be swivelled about the gimbal axis of the inner gimbal by means of a 
gearing. The swivelling movement is effected through half of the 
rotational angle of the inner gimbal. In this manner, the path of rays is 
constantly directed into an optical system which is fixed with respect to 
the outer gimbal and which guides the light beam to a detector. 
A further seeker such as known, for example, from German Published Patent 
No. 2,637,735, published on Apr. 5, 1979, includes scanning means for 
scanning a field of view by means of a detector using a rotating facetted 
mirror. The seeker head comprises an outer gimbal and an inner gimbal. A 
stabilizing gyro rotor is supported at the inner gimbal and carries an 
annular facetted mirror. A lens system is seated at the inner gimbal and 
defines an optical axis. A deflecting mirror disposed at the inner gimbal 
deflects the path of rays laterally obliquely to the facetted mirror from 
which the imaging light beam is directed to the detector, which is fixed 
with respect to the inner gimbal, via further optical members. 
SUMMARY OF THE INVENTION 
Therefore, with the foregoing in mind it is a primary object of the present 
invention to provide a new and improved construction of a seeker of the 
initially mentioned type and which seeker is not afflicted with the 
drawbacks and limitations of the prior art constructions. 
Another and more specific object of the present invention is directed to 
the provision of a new and improved construction of a seeker which is of a 
comparatively small and lightweight design. 
An important object of the present invention is directed to providing a 
seeker of the initially mentioned type and which seeker is devoid of the 
light losses and image resolution losses which occur in the prior art 
seeker constructions. 
Now in order to implement these and still further objects of the invention, 
which will become more readily apparent as the description proceeds, the 
seeker of the present development is manifested by the features that, 
among other things, 
the deflecting mirror is fixedly arranged at the inner gimbal and on the 
object side of the reflecting means such that the deflected optical axis 
coincides with the gimbal axis of the inner gimbal, 
the detector is retained in the outer gimbal on the gimbal axis of the 
inner gimbal, and 
the reflecting means is also arranged on the gimbal axis of the inner 
gimbal and reverses the deflected path of rays which is deflected by the 
deflecting mirror in the direction of the gimbal axis of the inner gimbal 
and towards the detector. 
In such arrangement, the optics become very simple. The inner gimbal only 
supports the imaging optical system and the deflecting mirror. The 
detector is placed on the outer gimbal. No conductors are required to be 
passed from the inner gimbal onto the outer gimbal. 
The detector may constitute a multi-element detector. In such case, the 
reflecting means may form a single planar mirror. Advantageously the 
detector, however, constitutes a detector array. The reflecting means, 
then, form image rotating means which can be driven about the gimbal axis 
of the inner gimbal. 
The reflecting means is arranged advantageously at the outer gimbal. This 
facilitates driving the reflecting means as, for example, the image 
rotating means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Describing now the drawing, it is to be understood that only enough of the 
construction of the seeker has been shown as needed for those skilled in 
the art to readily understand the underlying principles and concepts of 
the present development, while simplifying the showing of the drawing. 
Turning attention now to the single Figure of the drawing, there is shown 
therein a structure, especially the airgimbal of a missile, generally 
designated 10. The front end thereof is closed by means of a dome 12. A 
seeker 14 is retained within the airgimbal 10. Screws 18 connect a seeker 
housing 16 to the airgimbal 10. Within the seeker housing 16, an outer 
gimbal 20 is supported for pivoting about a pitch axis defined by the 
missile. The support is not visible in the drawing. The pivot axis extends 
through the center 22 and perpendicular to the plane of the drawing. An 
inner gimbal 24 is supported in the outer gimbal 20 about a gimbal axis 
which is defined by the yaw axis of the missile. The gimbal axis 26 of the 
inner gimbal 24 extends through the aforementioned center 22 and 
perpendicular to the yaw axis which defines the gimbal axis of the outer 
gimbal 20. 
A lens 28 is placed at the inner gimbal 24 and images a field of view of 
the seeker in the plane of a detector 30. The lens 28 is made of a 
material which is transparent for infrared radiation. The lens 28 defines 
an optical axis 32. This optical axis 32 extends perpendicular to the 
gimbal axis 26 of the inner gimbal 24 and through the center 22. 
Furthermore, a deflecting mirror 34 constituting a planar mirror, is 
arranged at the inner gimbal 24. The deflecting mirror 34 has an 
inclination of substantially 45 degrees relative to the optical axis 32 as 
defined by the lens 28. The reflecting plane of the deflecting mirror 34 
also extends through the center 22. A light beam received at the lens 28 
is deflected by 90 degrees by the deflecting mirror 34 in a manner such 
that the thus deflected optical axis 38 coincides with the gimbal axis 26 
of the inner gimbal 24. 
The deflecting mirror comprises a central gap 40. A detector assembly 42 
containing the detector 30 protrudes through the gap 40. The detector 
assembly 42 includes a Dewar vessel and cooling means for cooling the 
detector 30, as is well known in the art. In the illustrated example, the 
detector 30 preferably constitutes a detector array, i.e. a detector 
comprising a number of separate detector elements. The detector assembly 
42 is placed at the outer gimbal 20 which also supports reflecting means 
or mirror means 44. These reflecting or mirror means 44 are arranged at 
the gimbal axis 26 of the inner gimbal 24 and face the detector 30. The 
imaging light beam which is deflected by the deflecting mirror 34, 
impinges upon the reflecting or mirror means 44 and is returned thereby to 
the detector 30. In this manner the lens 28 produces, via the deflecting 
mirror 34 and the reflecting or mirror means 44, an image of the observed 
field of view in the plane of the detector 30. 
In the preferred embodiment, as indicated hereinabove, the detector 30 
constitutes a detector array. Therefore, the reflecting or mirror means 44 
is inherently constructed to form image rotating means which are driven 
for rotation and cause the image of the field of view to be continually 
rotated about the gimbal axis 26 of the inner gimbal 24. The image of the 
field of view is thus rotated relative to the detector 30 or detector 
array and, as a result, the image of the field of view is scanned by the 
detector 30 or detector array in the manner of a clock hand. In order to 
produce the desired image rotation, the reflecting or mirror means 44 is 
formed by a ridge mirror containing two mutually perpendicular planar 
mirrors 46 and 48. The edge 50 defined by the ridge mirror intersects with 
the gimbal axis 26 of the inner gimbal 24 at a right angle. The planar 
mirrors 46 and 48 are seated in a mount 52 including a shaft 56 which 
extends along the gimbal axis 26 of the inner gimbal 24. The shaft 54 is 
supported in bearings 56 and 58 within the outer gimbal 20. The rotor 60 
of a drive motor is placed on the shaft 54 and the stator of the drive 
motor is arranged at the outer gimbal 20. 
A rotational speed sensor 64 constituting a gyro is placed at the inner 
gimbal 24. 
The detector assembly 42 is placed in a sleeve-shaped mount 66 which is 
provided at the outer gimbal 20. The inner gimbal 24 is supported at this 
mount 66 by means of a ball bea-ring 68. Furthermore, the outer gimbal 20 
defines a collar 70 which is arranged coaxially with the gimbal axis 26 of 
the inner gimbal 24. The inner gimbal 24 is likewise supported at this 
collar 70 by means of ball bearings 72. The ball bearings 72 are 
surrounded by the annularly shaped rotor 74 of a motor for adjusting the 
inner gimbal 24 wherefore the rotor 70 is seated at the inner gimbal 24. 
The rotor 74 is surrounded, in turn, by a stator 76 of the adjusting motor 
and this stator 76 is arranged at the outer gimbal 20. The collar 70 
surrounds the reflecting or mirror means 44 and its mount 52. 
An angle sensor 78 detects the angular position of the inner gimbal 2 
relative to the outer gimbal 20. A corresponding angle sensor, which is 
not illustrated in the drawing, detects the angular position of the outer 
gimbal 20 about the pitch axis of the missile relative to the seeker 
housing 16. 
A scanning means or device 80 is placed at the inner gimbal 24 and 
constructed and arranged for scanning markings which are provided at the 
rim or rim portion of the mount 52. As a result, the scanning means or 
device 80 supplies scanning data indicative of the angular position of the 
image rotating reflecting or mirror means 44 relative to the inner gimbal 
24, and this is achieved although the mount 52 is supported at the outer 
gimbal 20. The image rotating reflecting or mirror means 44 containing the 
two planar mirrors 46 and 48 cause the image to be rotated at twice the 
frequency of the revolving frequency of the mount 52. A defined image 
point can thus be associated with each detector signal on the basis of the 
number of the detector element of the detector array and the angle data 
supplied by the scanning means or device 80. There are thus obtained, as a 
result of the image scan, signals which effect aiming the seeker at a 
detected target via the gimbal adjusting motor 74,76 and a corresponding 
second gimbal adjusting motor acting about the pitch axis. This is well 
known in the art and, therefore, not required to be described in detail. 
While there is shown and described a present preferred embodiment of the 
invention, it is to be distinctly understood that the invention is not 
limited thereto, but may be otherwise variously embodied and practiced 
within the scope of the following claims.