U.S. patent application number 12/555069 was filed with the patent office on 2010-05-06 for object detection system having an image detection system.
This patent application is currently assigned to DIEHL BGT DEFENCE GMBH & CO. KG. Invention is credited to Joachim Barenz, Rainer Baumann, Hans-Rainer Mayer, Eugen Romasew, Hans Dieter Tholl.
Application Number | 20100108800 12/555069 |
Document ID | / |
Family ID | 41478934 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100108800 |
Kind Code |
A1 |
Mayer; Hans-Rainer ; et
al. |
May 6, 2010 |
OBJECT DETECTION SYSTEM HAVING AN IMAGE DETECTION SYSTEM
Abstract
An object detection system has an image detection system with an
imaging detector, a position detection system with a position
detector, and optics which guide incident radiation onto both
detectors. The two detectors are arranged one behind the other, in
particular adjacent to one another, in the beam path. This makes it
possible to achieve a simple, compact and reliable object detection
system.
Inventors: |
Mayer; Hans-Rainer;
(Stockach/Hindelwangen, DE) ; Baumann; Rainer;
(Uberlingen, DE) ; Barenz; Joachim; (Uberlingen,
DE) ; Romasew; Eugen; (Uberlingen, DE) ;
Tholl; Hans Dieter; (Uberlingen, DE) |
Correspondence
Address: |
LERNER GREENBERG STEMER LLP
P O BOX 2480
HOLLYWOOD
FL
33022-2480
US
|
Assignee: |
DIEHL BGT DEFENCE GMBH & CO.
KG
Uberlingen
DE
|
Family ID: |
41478934 |
Appl. No.: |
12/555069 |
Filed: |
September 8, 2009 |
Current U.S.
Class: |
244/3.16 ;
250/203.1 |
Current CPC
Class: |
F41G 7/226 20130101;
F41G 7/2293 20130101; F41G 7/2253 20130101; F41G 7/008
20130101 |
Class at
Publication: |
244/3.16 ;
250/203.1 |
International
Class: |
F41G 7/26 20060101
F41G007/26 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2008 |
DE |
10 2008 046 362.0 |
Claims
1. An object detection system, comprising: an image detection
system with an imaging detector; a position detection system with a
position detector; and optics disposed to guide incident radiation
along a beam path onto said imaging detector and onto said position
detector; wherein said imaging detector and said position detector
are disposed one behind another in the beam path.
2. The object detection system according to claim 1, wherein said
imaging detector and said position detector are disposed directly
adjoining one another.
3. The object detection system according to claim 1, wherein said
imaging detector and said position detector are disposed adjacent
one another.
4. The object detection system according to claim 1, wherein said
position detector is configured to allow radiation, for which said
imaging detector is sensitive, to pass through said position
detector.
5. The object detection system according to claim 1, wherein said
imaging detector and said position detector are arranged on an
image plane of the beam path.
6. The object detection system according to claim 1, wherein said
position detector is a lateral effect detector.
7. The object detection system according to claim 1, wherein said
imaging detector and said position detector cover fields of view of
mutually different sizes.
8. The object detection system according to claim 1, wherein the
two detectors cover fields of view of a common size.
9. The object detection system according to claim 1, wherein a
field of view of said imaging detector is located in a field of
view of said position detector.
10. The object detection system according to claim 9, wherein the
field of view of said imaging detector is centered in the field of
view of said position detector.
11. The object detection system according to claim 1, wherein said
imaging detector is disposed centrally with respect to said
position detector.
12. The object detection system according to claim 1, wherein said
position detector is mounted rigidly on a housing of said imaging
detector.
13. The object detection system according to claim 1, wherein said
position detector forms an inlet window of said imaging
detector.
14. The object detection system according to claim 1, which further
comprises a spectral filter having a transmission window in a
wavelength range of said position detector, a transmission window
in a wavelength range of said imaging detector, and an opaque area
between said transmission windows.
15. The object detection system according to claim 1, which
comprises a cooling unit connected to said position detector and a
cooling unit connected to said imaging detector, and wherein said
cooling units for said detectors are disposed within one
another.
16. The object detection system according to claim 1, wherein said
position detector has detector outputs connected to amplifier
electronics via a coupling capacitor, in order to suppress
background radiation.
17. The object detection system according to claim 1, which
comprises an amplifier for signals received from said position
detector, said amplifier being designed for variable gain
matching.
18. The object detection system according to claim 1, which
comprises a control device having a memory with a position
calibration of said position detector stored therein.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority, under 35 U.S.C.
.sctn.119, of German patent application DE 10 2008 046 362.0, filed
Sep. 9, 2008; the prior application is herewith incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention relates to an object detection system having
an image detection system with an imaging detector, a position
detection system having a position detector and optics which guide
incident radiation onto both detectors.
[0003] Various optical systems for the detection of a target and
for keeping it in view are known for guiding unmanned missiles in
the direction of a target. In the case of a passive guidance
system, the target can be selected by an operator before the
missile is launched, and a reference image of the target scene,
with the marked target, can be passed to the missile. During target
approach, the target is detected by the missile on the basis of the
reference image, which is highly up-to-date because its age is only
a few seconds, and the missile can steer itself autonomously to the
target.
[0004] In the case of a semi-active laser guidance system, the
target selected by an operator is illuminated with a marking laser,
and a position detection system in the missile detects the angle
offset of the illuminated spot relative to its field of view by
imaging the radiation reflected from the illuminated spot onto the
position detector. The extent of the angle offset is in this case
determined by the position or the orientation of the imaged
illuminated spot on the radiation-sensitive surface of the position
detector. The missile is steered in the direction of the
illuminated spot as a function of the determined angle offset, and
is thus guided to the target. In this case, the target illumination
must be maintained until the missile reaches the target. The target
can be illuminated by an observer in an advanced position. Pulsed
radiation and pulse repetition rates of about 10-20 Hz are
typically used for illumination, with the pulse repetition rate
being used to code the laser designator, in order to make is
possible to approach the correct target even when there are a
plurality of illuminated targets in the seeker field of view. The
pulse code of the target illuminator is transmitted to the missile
before launch. By way of example, one position detection system is
disclosed in commonly assigned German published patent application
DE 10 2004 029 343 A1 and its counterpart U.S. Pat. No. 7,304,283
B2.
[0005] In order to reduce the danger to an illuminator, for example
an observer in an advanced position, it is known for the target to
be illuminated for only a short time, for example one second, and
for the target to be assigned to the missile in this way. The
missile has the characteristic, in the sense of a dual-mode system,
of using an imaging system to identify targets which have been
marked with a laser target illuminator. The missile can be guided
passively to the target with the aid of the image detection system
once the target has been transferred by the target illumination and
the position detection or, to be more precise, the angle offset of
the missile with respect to the target has been determined by means
of the position detection system in the missile.
SUMMARY OF THE INVENTION
[0006] It is accordingly an object of the invention to provide an
object detection system, which overcomes the above-mentioned
disadvantages of the heretofore-known devices and methods of this
general type and which specifies such a system by means of which an
object can be reliably detected as a target and can be tracked in a
target scene, so as to allow a missile to be reliably steered to
the target.
[0007] With the foregoing and other objects in view there is
provided, in accordance with the invention, an object detection
system, comprising:
[0008] an image detection system with an imaging detector;
[0009] a position detection system with a position detector;
and
[0010] optics disposed to guide incident radiation along a beam
path onto said imaging detector and onto said position
detector;
[0011] wherein said imaging detector and said position detector are
disposed one behind another in the beam path. In particular, the
two detectors are disposed adjoining one another.
[0012] In other words, the objects of the invention are achieved by
an object detection system of the type mentioned initially in which
the two detectors are arranged one behind the other, in particular
adjacent to one another, in the beam path. The beam path is
therefore first of all guided to one of the detectors, and the same
beam path is then guided to the other detector. Arranging the
detectors one behind the other makes it possible to save valuable
physical space, and the optics can be used not only for the imaging
detector but also for the position detector, thus making it
possible to achieve a system of little complexity, and of compact
design.
[0013] The two detectors are expediently arranged adjacent to one
another, for example immediately adjoining one another, or
separated from one another only by a layer, for example an adhesive
layer or an optically active layer, such as a filter.
[0014] The detectors are advantageously mounted such that they
cannot move with respect to a missile housing.
[0015] The imaging detector is preferably mounted on the cooling
unit of a cooler, in order to increase its sensitivity. By way of
example, the cooler may be a cold finger. It is feasible, of
course, to also provide a cooling capability for the position
detector.
[0016] With a clever design, the optics have an optical element
which not only images the beam path on the imaging detector but
also guides it to the position detector. The optical element
therefore guides the same beam path both onto the imaging detector
and onto the position detector. Radiation which is guided onto the
position detector can therefore also be guided onto the imaging
detector. It is expedient to arrange the last beam-forming or
beam-deflecting optical element in the beam path in front of the
detectors, and this may be a lens, a mirror, a prism or planar
optics. The beam path which is imaged on the imaging detector is
expediently completely guided to the position detector. The beam
path can be imaged on the imaging detector by arranging the imaging
detector on an image plane in the beam path.
[0017] The object detection system may be a component of a seeker
head of a missile. The image detection system is used to detect an
image on which an object which may be marked as a target is imaged.
The imaging detector may be a point detector, a line detector or a
matrix detector. In the case of a point detector or line detector,
the image which reproduces the object can be recorded sequentially
by scanning and can be assembled to form the complete image. The
position detection system is used to detect a position or to
determine an angle offset of the object relative to a coordinate
system which, for example, is firmly linked to a missile axis. The
position detector can thus be designed such that it outputs angle
coordinates which correspond to the offset angle of the target
being aimed at, relative to the fixed coordinate system. The angle
offset may be detected once, a plurality of times, or continuously.
For example, the optics can be carried by the object, corresponding
to the position, and a line of sight spin rate can be detected,
which is used to steer the missile. Alternatively, in the case of
optics which are arranged in a fixed position in the missile, the
missile can be steered on the basis of the position itself, with
the position being maintained on the missile axis, for example by
appropriately steering the missile.
[0018] Radiation for which the imaging detector is sensitive can
advantageously pass through the position detector. The two
detectors may be arranged one behind the other in the beam path,
without the rear detector being shadowed. Transmissibility is
achieved with a transmission level of at least 50%, in particular
at least 80%.
[0019] In a further advantageous embodiment of the invention, the
two detectors are arranged on the image plane of the beam path.
Both the object and the illumination spot can be imaged in focus on
both detectors. In this context, the image plane is understood as
being a plane with a thickness at right angles to the optical axis
of the beam path which is no greater than 10% of the focal length
of the beam path on the image plane, in particular 3%.
[0020] In order to produce the position detection system, a lateral
effect detector is advantageous, which is expediently arranged
rigidly in front of the imaging detector. A lateral effect detector
may have a very compact design and may be designed to be
transmissive for medium infrared and far infrared, which means that
an imaging detector which operates in these wavelength ranges can
be arranged behind the lateral effect detector, without shadowing.
High-purity silicon is advantageous as a detector substrate for the
position detector. Furthermore, a lateral effect detector can be
made very large, for example up to (20 mm).sup.2, as a result of
which its field of view covers a wide angle range. A wide field of
view can be used for reliable target detection since a large angle
scatter can occur in the case of an indirect launch with a
ballistic flight path in the direction of the target.
[0021] A further advantage of lateral effect detectors, detectors
with a transmissively radiation-sensitive surface, is that they can
be operated without cooling, and dispensing with a cooling
capability makes it possible to save both the costs required for
this purpose and physical space.
[0022] The two detectors advantageously cover fields of view of
different size. While the field of view of the position detector is
advantageously large, for example with a diameter of at least
5.degree., and preferably of at least 15.degree., the field of view
of the imaging detector can be kept small, that is to say for
example less than 5.degree. or even less than 1.degree., since the
alignment of the narrow field of view with the target can be
carried out by the position detector. The narrow field of view
makes it possible to achieve high angle resolution of the imaging
detector.
[0023] It is, of course, also feasible to design the fields of view
of the two detectors to be the same size. This offers the advantage
that increased functionality can be achieved. For example, if only
an image of inadequate quality can be obtained using the imaging
detector, the position of the target with respect to the missile
can be determined once again using the position detector. This
therefore provides a mutual monitoring capability between the two
detectors. The result which one of the detectors produces can
therefore be checked by the result which the other detector
produces. This allows the missile to be guided particularly
reliably to the target.
[0024] The field of view of the imaging detector is expediently
located in the field of view, in particular centered in the field
of view, of the position detector. A simple optics geometry can be
achieved by arranging the imaging detector centered with respect to
the position detector.
[0025] It is also proposed that the position detector be mounted
rigidly on a housing of the imaging detector. There is no need for
additional holding elements, and the system can be designed to be
compact.
[0026] A high degree of compactness is likewise achieved if the
position detector forms an inlet window of the imaging detector.
This can be coated with a spectral filter, expediently on the side
facing away from the imaging detector, in order to filter the
radiation to the imaging detector.
[0027] Irrespective of its position, the spectral filter is
expediently designed such that it has a transmission window in the
wavelength range of the position detector, a transmission window in
the wavelength range of the imaging detector, and an opaque area
between the two transmission windows. A single spectral filter can
be used for both detectors, thus allowing the object detection
system to be kept compact.
[0028] If the two detectors are each connected to their own cooling
unit, with the cooling units being arranged in one another, then
the object detection system can likewise be designed to be compact
and simple.
[0029] For exact detection of the position of the target being
aimed at, it is advantageous for detector outputs of the position
detector to be connected to amplifier electronics via a coupling
capacitor in order to suppress background radiation, thus resulting
in a bias T circuit.
[0030] The detector outputs of the position detector preferably
have a DC bias voltage applied to them, in order to increase the
speed of the detector and thus to widen the bandwidth. If the
already mentioned coupling capacitor is in this case arranged
downstream from the DC bias voltage supply, then it can not only
ensure suppression of background radiation but also outputting of
the DC bias voltage and/or AC coupling.
[0031] When approaching the target--with the target being
illuminated uniformly at the same time--the irradiation intensity
(which is detected by the position detector) of the positioning
emitter becomes stronger. In order to avoid reaching the saturation
range of the position detector, it is advantageous for the object
detection system to have an amplifier for signals from the position
detector, which amplifier is designed for variable gain
matching.
[0032] In addition, the object detection system advantageously
comprises a control means for controlling the position detection
and, expediently, the image processing of the image detection
system.
[0033] If the control means has a memory in which a position
calibration of the position detector is stored, then this makes it
possible to ensure that little mechanical adjustment effort is
required for the positioning system by means of an electronic
calibration.
[0034] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0035] Although the invention is illustrated and described herein
as embodied in an object detection system having an image detection
system, it is nevertheless not intended to be limited to the
details shown, since various modifications and structural changes
may be made therein without departing from the spirit of the
invention and within the scope and range of equivalents of the
claims.
[0036] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying drawings.
The drawing and the description relate to numerous features in
combination, which a person skilled in the art will expediently
also consider individually and will combine them to make further
worthwhile combinations.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0037] FIG. 1 shows a schematic illustration of an object detection
system with Cassegrain optics and with two detectors, attached to
one another, on the image plane of the optics; and
[0038] FIG. 2 shows a schematic circuit illustration of a position
detector.
DETAILED DESCRIPTION OF THE INVENTION
[0039] Referring now to the figures of the drawing in detail and
first, particularly, to FIG. 1 thereof, there is shown a seeker
head 2 in the front part of a missile 4 with a viewing window 6 in
the form of a dome, behind which an object detection system 8 is
arranged. The system 8 contains optics 10 in the form of Cassegrain
optics with two mirrors 12, 14, by means of which radiation from an
object scene 16 with a target 18 is imaged in one beam path 20 onto
a detector system 22. The detector system 22 comprises a position
detector 24, also referred to as a positioning detector 24, and an
imaging detector 26, which is arranged in the beam path 20
immediately behind the position detector 24. The mirror 14 is an
optical element which not only guides the beam path 20 onto the
imaging detector 26 but also guides the same beam path and/or the
same radiation onto the detector 24, for example radiation in the
far infrared, which passes through the detector 24 and is guided
onto the detector 26.
[0040] The object detection system 8 comprises a gyro system on air
bearings with a gyro 28 which is monitored by a control means 30,
which is also used as evaluation electronics for the two detectors
24, 26. The gyro 28 is connected to the optics 10, which image the
incident target radiation onto the large-area position detector 24
and the considerably smaller imaging detector 26. Optics 10 pass
the radiation to the two detectors 24, 26 and therefore, because of
the different detector sizes, cover two different fields of view.
The imaging detector 26 is seated on a cold finger 32 and has only
a smaller field of view. The larger position detector 24 is
connected to a housing 34 of the imaging detector 26, which is
passed around the cold finger 32. The two detectors 24, 26 are
mounted rigidly relative to the housing of the missile 4, via the
housing 34.
[0041] The imaging detector 26 is in the form of a line detector,
whose individual images are assembled in a scanning mode to form
the overall image of the object scene 16. The metallic housing 34
is used for mounting the position detector 24. The position
detector 24 is sensitive in the near infrared spectral range, and
detects laser radiation from a target marker which emits in the
near infrared, and derives from this the angle offset of the target
being aimed at.
[0042] The position detector 24 is a lateral effect detector. The
infrared light which falls on its active area generates a
photocurrent which flows away in the direction of the p-doped and
n-doped regions. In contrast to a simple photodiode, the detector
24 has a plurality of electrical contacts, however. This leads to
splitting of the photocurrent at the electrodes, which are arranged
at the side, as a function of the position of the light spot. The
position in the x and y directions can be determined by forming the
current difference between two opposite electrodes. Normalization
of the total current makes the position signal independent of the
incident light intensity.
[0043] The viewing window 6, which is in the form of a dome and
acts as a protection apparatus against external influences, may be
used as the first optical element, for example as a lens, for
imaging the object scene 16 onto the two detectors 24, 26. It is
composed of a material which has good transmission both for the
near infrared and for the medium and far infrared, and which at the
same time is very strong. For example, zinc-sulphide
Cleartran.RTM., a water-free form of zinc sulphide with a
relatively broad transmission range from 0.5 to 14 .mu.m, is very
highly suitable for the spectral range from the near infrared to
the far infrared.
[0044] A spectral bandpass filter 38 is fitted to the position
detector 24, to be precise on its side facing the mirror 14, in
order to suppress background radiation and for interference
suppression. The filter 38 is opaque in the near infrared
wavelength range, except for the specific wavelength range of the
marking laser, which can pass through the filter. Medium infrared
and long-wave infrared can pass through the filter.
[0045] FIG. 2 shows a schematic circuit diagram of the lateral
effect detector 24 and amplifier electronics connected to it. The
detector 24 comprises four signal outputs 42, which are each
connected to reading electronics 40, only one of which is
illustrated in FIG. 2, for the sake of clarity. The reading
electronics 40 are likewise connected to the control means 30,
which are also provided for target guidance and thus for steering
the missile 4. The irradiation of light onto a spot 44 on the
detector 24 initiates a signal at each of the signal outputs 42.
The strength of the respective signal depends on the intensity of
the light irradiated onto the spot 44 and the position of the spot
44 within the area 46 of the detector 24. The closer the spot 44 is
to one of the signal outputs 42, the stronger is the signal at this
signal output 42, and the weaker the signal is at the opposite
signal output 42. If the spot 44 is positioned precisely at the
center point of the area 46, the four signals are all equally
strong.
[0046] Because of the use of the continuous light-sensitive area
46, the detector 24 can easily be calibrated electronically. The
control means 30 have a memory in which a position calibration of
the position detector 24 is stored. This position calibration
includes the discrepancy between the optical axis and the position
on the area 46 at which all four signals are the same.
[0047] The reading electronics 40 comprise in each case a
bias-voltage source 48, with the bias-voltage sources 48 having a
positive bias voltage applied from two opposite signal outputs 42,
for example of +15 V, and with the bias voltage sources 48 of the
two other signal outputs 42 having a corresponding negative voltage
applied, corresponding to the p-doping and n-doping. In order to
decouple the bias voltage from the amplifier electronics 50, each
of the reading electronics devices 40 has a coupling capacitor 52.
The pulses from the marking laser result in an alternating current
at the signal outputs 42, as a result of which the coupling
capacitor 52 does not lead to any signal interruption. This
alternating-current coupling of the detector 24 to the amplifier
electronics 50 is used to reduce the background component, and to
output the DC bias voltage. A controllable resistor 56 is connected
across an amplifier element 54, thus making it possible to vary the
signal gain, controlled by the control means 30. The signal can
thus be reduced as the missile approaches the target, thus making
it possible to avoid overdriving of the detector 24 and of the
amplifier electronics 50.
[0048] The currents from the signal outputs 42 are supplied via the
reading electronics 40 to signal processing electronics which, for
example, may be arranged in the control means 30 or between the
control means 30 and the reading electronics 40. These signal
processing electronics digitize the signals and process them as a
function of the functional phase, that is to say as a function of
whether the signal is intended to be found as such with the aid of
the transfer code, or whether the aim is to find offset angles, by
means of a specific algorithm. For a digital interface, these
status or offset signals are passed to the autopilot. A further
electrical interface is used for the operating voltage supply.
[0049] The object detection system 8 may be operated as follows. In
an initialization phase, all the hardware and software functions of
the detectors 24, 26 and of the electronics are activated by the
control means 30 and are switched to the basic state. In addition,
the frequency code with which the target is being illuminated by
the marking laser is passed to the control means 30. The
initialization phase may be initiated, for example, by a
launch.
[0050] In a subsequent first acquisition phase, the control means
30 in conjunction with the position detector 24 and with the aid of
the code search for the marking laser light. For this purpose, all
pulses which exceed a threshold value are detected. A pulse
sequence of three to six pulses is required for reliable
synchronization, depending on the algorithm.
[0051] In the subsequent first tracking phase, the current offset
angles produced by the detector 24--for example in the form of two
mutually perpendicular vectors--are determined precisely with
respect to a coordinate system that is fixed to the seeker head,
and are used for slaving the gyro system. For example, the optics
10 can be guided in the direction of the identified target on the
basis of the offset angle, with the gyro 28 identifying the
movement of the optics 10 and the control means 30 aligning the
missile 4 in the direction of the target 18, on the basis of
corresponding control-surface signals.
[0052] If the optics 10--or in the case of rigid optics 10, the
missile 4--are or is at least essentially aligned with the target
18, the second acquisition phase starts, in which the imaging
detector 26 identifies the target 18. For this purpose, the
instantaneous offset angles are transferred to the infrared image
of the detector 26, with target marking thus being carried out,
thus uniquely defining the target 18. In the second, subsequent
tracking phase, the offset angles of the target 18 are determined
by means of image processing algorithms by the control means 30,
for slaving of the optics 10, from which angles the gyro 28 is used
to determine a line of sight spin rate, which is used to guide the
missile 4. This phase may continue until the target 18 is
reached.
[0053] After the second acquisition phase, that is to say after
identification of the target 18 by the image processing, the
missile 4 can be guided to the target 18 both with the aid of the
imaging detector 26 and the imaging processing and--when the target
is being marked--solely by the position detector 24 and the
corresponding reading electronics 40. The approach phase can
therefore be carried out both using the semi-active laser system
and using the imaging system. In consequence, the target guidance
is particularly insensitive to disturbances. Alternatively, after
the image processing acquisition phase, the marking of the target
18 by the marking laser can be ended, and the missile 8 can be
guided to the target 18 solely with the aid of the imaging detector
26 and the image processing.
* * * * *