EP0882941B1 - Infrared seeker head for homing missile - Google Patents

Description

Technical field

The invention relates to an infrared search head for target-seeking missiles, in which a field of view through an imaging optical system on a main detector is reproducible, which detects a target located in your visual field, and a second Detector is provided, which responds to the high-intensity radiation, the Seeker contains a facility to prevent interference by going from the target the missile emitted, high-intensity radiation is caused and by the second detector can be activated.

Underlying state of the art

Infrared search heads for missiles are widely known.

An infrared search head for target-seeking missiles is, for example, by EP-B-0 538 671 known. The seeker head contains an optical system that gimbals over an inner and an outer frame with respect to a structure movable on all sides is stored. The optical system creates an image of a Field of view. Signals are obtained which are sent via two frame actuators direct the viewfinder towards a detected target.

A gyro-stabilized viewfinder is known from DE-PS-3 925 942. The seeker contains an imaging optical system through which a field of view Detector means is mapped. The detector means generate target signals, from which Alignment signals are generated. The orbital axis becomes a through the alignment signals Rotors aimed at a target. The detector means are in a dewar arranged and are cooled.

To ward off attacks from target-seeking missiles are used by one Aircraft under attack applied measures to disrupt the infrared seeker head.

FR 2 740 638 A1 relates to an arrangement which is intended to prevent a Infrared detector can be detected or disturbed by enemy laser radiation. To for this purpose, a second, special detector is provided which is suitable for the To detect the occurrence of such laser radiation. If such a disturbance occurs Laser radiation is e.g. the field of view scanning of the infrared detector is interrupted. The special detector in one version of FR 2 740 638 A1 contains one Monochromator, being the distinguishing criterion between laser radiation and thermal radiation of a target the monochromatic character of laser radiation serves. In another embodiment, the laser radiation is higher as a light pulse Performance recognized.

Disclosure of the invention

The invention has for its object in a seeker head of the aforementioned Kind after detection of disruptive laser radiation and appropriate shutdown or shielding the main detector to avoid losing a target.

According to the invention, this object is achieved in that the second detector is on the location of the light source emitting the high-intensity radiation is more appealing The function of the position-sensitive detector is its high-intensity radiation is not affected.

The devices for preventing interference from high-intensity radiation, usually a laser beam directed at the search head of the missile be of different types. Different solutions, individually or in suitable Combination can be used are the subject of the subclaims.

Embodiments of the invention are below with reference to the associated drawings explained in more detail.

Brief description of the drawings

Fig.1

Fig. 3 is a schematic perspective view showing a Embodiment of the infrared seeker head according to the invention.

Fig.2

Figure 4 is a block diagram illustrating signal processing at an infrared seeker head according to the invention.

Figure 3

is a flowchart illustrating the control of the infrared search head according to the invention and in addition an optional Operating mode of the infrared search head.

Figure 4

shows an embodiment in which the field of view during normal operation is scanned by means of a detector line via an oscillating mirror and when a high-intensity interference radiation occurs, the oscillating mirror into a Position is moved in which the detector line is not from the Interference radiation is applied.

Figure 5

shows an embodiment in which as a protective measure to protect the Main detector before high-intensity interference radiation in front of the main detector arranged mechanical or electro-optical aperture is closed.

Figure 6

shows an embodiment in which as a protective measure to protect the Main detector in front of high-intensity interference radiation Beam path is pivoted, the interference radiation from the main detector distracting.

Figure 7

shows an embodiment, two against each other by a piezo actuator movable prisms in the position in which that of the optical System detected light is directed to a main detector.

Figure 8

shows the embodiment of Figure 7 in a position in which the optical system detected light is directed to an auxiliary detector which is designed to receive the high-intensity interference radiation.

Preferred embodiments of the invention

In Fig. 1, an infrared seeker head is shown schematically. The search head can be in the nose an air-to-air missile and an infrared-transmissive dome be protected. The infrared seeker head is rotatable on an axis 10 mounted inner frame 12 of a gimbal system. The inner frame 12 carries that entire opto-electronic receiving system whose optical axis through appropriate deflection of the frame axes is aimed at a target. A first one Detector system 14 contains infrared optics 16 as the imaging optical system. This detector system 14 forms a conventional passive infrared detector, which is based on Thermal radiation appeals. The infrared optics 16 form a field of view (and the target) via a scanning device arranged behind with a movable optical Deflector from an infrared detector line as the main detector. The one from it derived infrared data are arranged in a structure-fixed manner in the missile Signal processing forwarded.

On the inner frame 12 there is a second one close to the first detector system 14 Detector system arranged. Contains in the embodiment shown in Fig.1 the second detector system as "second detectors" two laser detector modules 18 and 20, which respond to laser radiation. The optical axes of the two laser detector modules 18 and 20 are defined to the optical axis of the first Detector system 14 aligned. The fields of view of the laser detector modules 18 and 20 are matched to the field of view of the first detector system 14 in such a way that Laser interference in the entire scanning range of the first detector system 14 can be detected.

The use of two laser detector modules 18 and 20 has the advantage that second detector system can also detect laser radiation if, depending on Deflection direction of the frame axis, one or the other laser detector module 18 or 20 at high squint angles covered by the dome bracket or other parts becomes.

The laser detector modules 18 and 20 each contain a four-quadrant detector and one entry lens 22 and 24 respectively. The received laser radiation is after conventional measurement method out of focus on the four-quadrant detectors.

The electronics of the are in a housing 26 on the inner frame 12 Seeker.

In Figure 2, the signal processing of the infrared seeker head of Figure 1 in one Block diagram shown. The signals (infrared data) of the first detector system 14 are fed to a signal processing unit 28. In the signal processing unit 28 these signals are evaluated and alignment signals are generated. The Alignment signals of the signal processing unit 28 are a switching logic 30 fed which tracking and steering signals for the seeker head tracking and Missile guidance delivers. This is indicated by an arrow 34.

Of the two laser detector modules 18 and 20, only the first laser detector module is shown in FIG 18 shown. The signals of the four-quadrant detector of the laser detector module 18 are fed to signal processing 32. In the Signal processing 32, these signals are evaluated and alignment signals are generated. These alignment signals are also supplied to the switching logic 30.

In the trouble-free case, i.e. if there is no laser radiation from the second detector system is detected, the seeker tracking and the missile guidance are based on the Alignment signal from the signal processing unit 28 of the first detector system 14. If the threat is detected, a laser steel is launched onto the target from the target Missile aligned, then this alignment signal, the signal processing 28 disturbed and unusable for the guidance of the missile. When inserting the Laser interference becomes both the signal from the second detector system and the signal of the first detector system 14 suddenly changed. This change is due to the Switchover logic 30 detected. The switching logic 30 then switches over so that the Search head tracking and missile guidance are based on the alignment signal of the Signal processing unit 32 of the second detector system supports. This can be done take place that the analog output data of the quadrant detectors in the electronics be processed and digitized if they have a predetermined threshold exceed.

With the onset of the laser radiation, the switching logic 30 continues to turn on Protection signal 36 generated by which measures to protect the first Detector system 14 can be initiated. As shown in Fig.2, the protection signal 36 of a protective signal processing unit 38, which are connected to a Output 40 gives a protection command to the first detector system 14. In the illustrated The field of view of the first detector system 14 with an Scanned scanner. As a protective measure we use the movable optical one Deflector of the scanning device when the protection signal occurs in one position stopped, in which the detector line of the first detector system 14 from the Laser radiation is not applied.

This is shown schematically in Figure 4. At 16 there is the imaging optical again System called, which is simply shown here as a lens. The imaging optical System 16 forms an infinite field of vision over a moving one optical deflection device 60 in the plane of a detector line 62. The optical Deflection device 60 is moved by a drive 64. The deflector 60 is shown as an oscillating mirror in FIG. The swinging motion is through one Double arrow indicated. The detector line 62 is a linear arrangement of detector elements, which extends perpendicular to the paper plane in Fig.4. When a Protection command at the output 40 (Fig.2) is the deflection device 60 by the drive 64 brought into the position shown in dashed lines in Figure 4. In this position the Deflection device 60 all radiation from the field of view captured by the system 16 past the detector line 62.

• Das erste Detektorsystem kann durch Abblendmittel geschützt werden. Hierbei kann es sich sowohl um eine mechanische als auch um eine trägheitslose Blende (z.B. eine elektro-optische Kerr-Zelle) handeln. Das ist in Fig.5 schematisch dargestellt. Bei der Ausführung von Fig.5, die im übrigen ähnlich ausgebildet sein kann wie die Ausführung von Fig.1 bis 3, erzeugt das abbildende optische System 16 ein Bild des Gesichtsfeldes in der Ebene eines infrarotempfindlichen CCD-Matrixdetektors 66. Vor dem CCD-Matrixdetektor 66 sitzen Abblendmittel 68, die von dem Schutzbefehl am Ausgang 40 ansteuerbar sind und in Fig.5 von einer Kerrzelle gebildet werden.
• Es können auch Strahlablenkmittel vorgesehen sein, welche die Strahlung von dem Haupt-Detektor beim Auftreten des Schutzsignals ablenken. Dies kann in einfacher Weise durch einen verschwenkbaren Umlenkspiegel realisiert sein, welcher beim Auftreten des Schutzsignals so verschwenkt wird, daß die Strahlung nicht mehr auf den Haupt-Detektor fällt.

However, the protective measures can also be of a different nature:

• The first detector system can be protected by shielding agents. This can be both a mechanical and an inertia-free diaphragm (eg an electro-optical Kerr cell). This is shown schematically in Fig.5. In the embodiment of FIG. 5, which can be configured similarly to the embodiment of FIGS. 1 to 3, the imaging optical system 16 generates an image of the field of view in the plane of an infrared-sensitive CCD matrix detector 66. In front of the CCD matrix detector 66 are dimming means 68, which can be controlled by the protection command at the output 40 and are formed by a Kerr cell in FIG.
• Beam deflecting means can also be provided which deflect the radiation from the main detector when the protective signal occurs. This can be implemented in a simple manner by means of a pivotable deflecting mirror, which is pivoted when the protective signal occurs so that the radiation no longer falls on the main detector.

This is shown in Fig. 6. At 16 there is the imaging optical system again and a 66 CCD matrix detector (or other two-dimensional Arrangement of detector elements). If a protection command occurs, the Imaging beam path a deflection mirror 70 swung in, which is dashed in Figure 6 is drawn.

When laser radiation has been detected and the seeker head is in the laser-controlled one Operation, it is continuously checked whether the laser radiation is interrupted becomes. If this is the case, then it will go back to regular infrared operation switched back.

3 shows the sequence of switching between the two operating modes in one Flow chart shown: Furthermore, there is an optional process at short distance shown between search head and target. First, it is assumed that the Search head is switched to regular infrared mode. This is through block 42 shown. A query takes place (block 44) whether laser radiation is received or not. If no laser radiation is received ("NO"), then it remains Seeker head in this infrared mode. If laser radiation is received ("YES"), the protective measures for the first detector system 14 are initiated (cf. Switching logic 30 in Fig.2). This is represented by block 46. At the same time, the Search head switched to laser-controlled operation (block 48). It finds one repeated query instead (block 50) as to whether laser radiation is still being received. If Laser radiation is no longer received ("NO"), the seeker head is in infrared mode (Block 42) switched back. If laser radiation is received ("YES") then the seeker head remains in laser controlled mode (block 46). This process corresponds the representation in Figure 2 and is shown in Figure 3 with solid lines.

Optionally, the infrared search head can also be used to check whether the target is within a short time Distance. In this case, the target image is larger than the laser interference in the picture, so that at least parts of the target in the signal processing unit 28 of the first detector means 14 can be recognized and "valid" alignment signals can be generated. This process is shown in Figure 3 by dashed lines. If in that laser-controlled operation (block 48) when queried (block 50) continues laser radiation is detected ("YES"), in this case a query takes place as to whether the destination is within a short time Distance. This is represented by block 52. If not ("NO"), then the seeker head remains in laser controlled mode (block 48). If If the target is a short distance away ("YES"), the search head is placed in the Infrared mode switched (block 54).

7 and 8, an imaging optical system 72 generates the represented by a lens, an image of the field of view on a CCD matrix detector 74. In the beam path is a pair of complementary prisms 76 and 78 arranged.

The prisms 76 and 78 form isosceles right-angled triangles in cross section, the hypotenuses of the triangles facing each other. The prism 76 has an entry surface 80 and an inclined surface 82 facing the prism 78. The Prism 78 has a prism 76 facing, parallel to the inclined surface 82 Inclined surface 84 and an exit surface 86 parallel to the entry surface 80. The Sloping surface 84 is coated with a semiconductor layer 88. The semiconductor layer 88 is transparent to the infrared radiation received by the CCD matrix detector 74, but shows a non-linear absorption behavior. This non-linear Absorption behavior can be caused, for example, by two-photon processes his. The consequence of the nonlinear absorption behavior is that the semiconductor layer for the low intensities of the infrared radiation with which the CCD matrix detector 74 is usually acted on as the main detector, has a high transmission, high intensities, such as those from a laser aimed at the missile generated, strongly absorbed.

The two prisms 76 and 78 are mutually perpendicular by a piezo actuator 90 to the planes of the two inclined surfaces 82 and 84 between one shown in FIG first position and a second position shown in Figure 8 movable. Perpendicular to the entry surface 80, the prism 76 has an exit surface 92. The level of Exit surface 92 is perpendicular to the plane of exit surface 86 of prism 78.

A second detector 94 is arranged opposite the exit surface 92. The second Detector 94 responds to the high-intensity radiation, namely that of the target Missile-directed laser beam. The second detector 94 is a detector that is less sensitive to radiation than the main detector 74. The second detector 94 should detect the incidence of high-intensity radiation. He doesn't need the weak To address the natural radiation of a distant target like the main detector. The second Detector 94 is a four quadrant detector.

The imaging optical system 72 forms the prisms 76 and 78 in the first position (FIG. 7) the field of view through the two prisms 76 and 78 and the layer 88 sharp on the CCD matrix detector 74. In the second position of prisms 76 and 78 (FIG. 8) is through the piezo actuator 90 between the inclined surfaces 82 of the prism 76 and the semiconductor layer 88 applied to the inclined surface 84 has a narrow air gap 96 educated. The width of the air gap 96 can be on the order of light wavelengths lie. The air gap 96 leads to that on the inclined surface 82 of the Prism 76 a total reflection takes place. The optical system 72 does not produce an image the CCD matrix detector 74 but on the second detector 94 essentially the source of the high-intensity radiation. This illustration is done somewhat out of focus on the detector 94 designed as a four-quadrant detector.

The individual detector elements of the CCD matrix detector build during an "integration time" due to the light falling on analog signals, each corresponds to the time integral of the light falling on the detector element. During one After the "readout time", the detector elements are read out line by line. This change of integration and readout time takes place cyclically. Useful information of CCD matrix detectors therefore only deliver that during the integration period incident light. During the readout time, the imaging light beam from the CCD matrix detector 74, without affecting the sensitivity of the CCD matrix detector is impaired.

In the arrangement shown in FIGS. 7 and 8, the prisms 76 and 78 become during the integration time into the first position shown in FIG. 7 and during the readout time in brought the read position shown in Fig.8. The light thereby acts on the CCD matrix detector only during the integration period. The light turns on during the readout time directed to the second detector 94 by the total reflection on the inclined surface 82. This means - without loss of sensitivity during normal operation - that of the CCD matrix detector 74 falling radiation in relation to integration time Total cycle time (integration plus readout time) reduced. That plays with normal Operation does not matter, but reduces the exposure to the CCD matrix detector 74 when high-intensity radiation such as a laser beam emitted by the target is incident. at A continuous wave laser can thereby act on the CCD matrix detector 74 high intensity radiation can be reduced to a value at which the less There is a risk of damage or destruction of the CCD matrix detector 74.

Switching between the first position of Fig.7 and the second position of Fig.8 can be done by the piezo actuator 90 at high frequency.

The arrangement described has another advantage: the light is periodic, namely during the readout times, also directed to the second detector 94. The second detector 94 detects the occurrence of high-intensity radiation. If such Radiation is detected, the prisms 76 and 78 can be in their second position being held. Then the CCD matrix detector 74 is completely against that shielded from incident radiation.

Now a second detector 94 designed as a four-quadrant detector is used Image of the light source of high intensity radiation generated. The four quadrant detector now delivers target placement signals from the laser beam, by means of which the missile enters the Goal is led. The laser beam thus sets the highly sensitive CCD matrix detector 74 out of function. For this, he now provides a means by which To guide missiles into the target.

If the laser beam is no longer present, the system is immediately switched back to normal operation: the prisms are brought into the position of Fig. 7, and the CCD matrix detector 74 takes over the observation of the target again. It also happens when the laser beam is pulsed.

A prism arrangement with piezo actuators, as described in FIGS. 7 and 8, can can also be used in place of the mirror 7 in FIG.

The periodic switching between the positions of Fig. 7 and Fig. 8 during the integration time and the readout time of the CCD matrix detector 74 and / or the upstream of the semiconductor layer 88 with non-linear absorption behavior can u.U. the high-intensity radiation can be attenuated so far that the CCD matrix detector 74 continues to lead even without switching to a detector 94 of the missile into the source of this high-intensity radiation without being blinded or damaged.

Claims (10)

1. Infrared seeker head for target seeking missiles, wherein a field of view is adapted to be imaged by imaging optical means (16; 72) on a main detector (62; 66; 74), the main detector being adapted to detect. targets in the field of view, wherein a second detector (18; 94) is provided responsive to high intensity radiation and wherein the seeker head further comprises means (18, 60, 68, 70, 30, 38) for counteracting the high intensity interference radiation emitted by said target towards said missile and which is activatable by the second detector, characterized in that the second detector (18; 94) is a position sensitive detector which is responsive to the position of a source of said high-intensity radiation, and the function of the second detector is not adversely affected by high intensity radiation.
2. Infrared seeker head according to claim 1, characterized in that

   (a) guidance signals for guiding the missile can be derived from the first and the second detector (14; 18) and

   (b) a switching means (30) is provided whereby the generation of the guidance signals can be switched from the signals of the first detector (14) to the signals of the second detector (18) if the infrared seeker head is exposed to high-intensity radiation,

   (c) whereby the missile is then guided towards the source of the high intensity radiation.
3. Infrared seeker head according to claim 1 or 2, characterized in that a blocking means (68) in front of the main detector (66) is arranged to be activated by the second detector as a protective measure when it is exposed to high intensity radiation.
4. Infrared seeker head as claimed in claim 1, characterized in that

   (a) the field of view is adapted to be periodically scanned by means of a linear detector array (62) through a movable, optical, deflecting element (60) arranged in the optical path,

   (b) the moving of the optical deflecting element (60) is stopped in a position, in which the linear detector array (62) is not exposed to the radiation from the imaging optical system as a protective measure by the second detector (18) when it is exposed to high intensive radiation.
5. Infrared seeker head according to claim 1, characterized in that a beam deflecting means (70) in front of the main detector (66) is arranged to be activated by the second detector as a protective measure when it is exposed to high intensity radiation.
6. Infrared seeker head according to claim 1, characterized in that

   (a) the main detector (74) is a CCD matrix detector wherein pixel-signals are periodically built up during an integration period and read out during a read-out period,

   (b) a controlled, optical, beam-deflecting element (76, 78) for deflecting the optical path is arranged in front of the main detector (74), and

   (c) the optical, beam-deflecting element (76, 78) is adapted to be periodically activated during the read-out period in synchronization with the read-out of the CCD matrix detector.
7. Infrared seeker head according to claim 6, characterized in that the beam deflecting element comprises a pair of complementary prisms (76, 78), which are arranged such that an air gap can be generated therebetween by means of a piezoelectric actuator element (90) and where the incident light is reflected in total reflection.
8. Infrared seeker head according to any of claims 1 to 7, characterized in that a filter layer (88) is arranged in the imaging optical path in front of the main detector (74), the layer having a transparency decreasing with increasing intensity of the incident radiation.
9. Infrared seeker head according to claim 8, characterized in that the filter layer (88) is mounted on inclined surface (84) of the prism (78) on the side of the detector limiting the air gap (96) and being on the side of the incident beam.
10. Infrared seeker head according to claim 1, characterized in that the device for counteracting interferences is adapted to be deactivated if the target image on the main detector is substantially larger than the image of the source of the high intensive radiation at small distances between the missile and the target.

Images