Patent Description:
Projectile flight is often stabilized by a high spin rate. Spin stabilized artillery munitions were originally designed to provide precise ballistic fire on long-range stationary targets. However, in today's military operations, many targets can be relocatable, moving, or both. In order to accommodate such dynamic targets, munitions are sometimes provided with terminal-homing seekers having imaging-seekers and flight control mechanisms to autonomously track and home in on the target. The high spin rate of spin-stabilized munitions complicates the tracking and homing process. For example, the high spin rate can interfere with acquisition of clear images by imaging-seekers that have long exposure times suitable for use with low ambient conditions. Additionally, imaging-seekers can be physically affected or damaged by the high spin rate and shocks incurred during munition launch. For example, gimbaled seekers that pivot for stabilizing captured images against high spin rates can be prone to failure when subjected to munition launch. <CIT> and <CIT> disclose image seekers for spinning projectiles.

While conventional methods and systems have generally been considered satisfactory for their intended purpose, there is still a need in the art for reliable image seeking systems and methods for a spin-stabilized projectile that can support terminal homing guidance of the projectile.

The purpose and advantages of the below described illustrated embodiments will be set forth in and apparent from the description that follows. Additional advantages of the illustrated embodiments will be realized and attained by the devices, systems and methods particularly pointed out in the written description and claims hereof, as well as from the appended drawings. To achieve these and other advantages and in accordance with the purpose of the illustrated embodiments, in one aspect, there is provided an imaging-seeker for a spin-stabilized projectile that spins about a longitudinal axis of the projectile as claimed in claim <NUM>.

In another aspect, a method of generating a course-correction signal for a spin-stabilized projectile is provided as claimed in claim <NUM>.

In a further aspect, a spin-stabilized projectile is provided that spins about a longitudinal axis of the projectile as claimed in claim <NUM>.

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a block diagram of an exemplary embodiment of a projectile in accordance with the disclosure is shown in <FIG> and is designated generally by reference character <NUM>. Methods associated with terminal homing guidance operations of the projectile <NUM> in accordance with the disclosure, or aspects thereof, are provided in <FIG>, as will be described. The systems and methods described herein can be used to provide improved homing seeking by a spin-stabilized projectile.

Projectile <NUM> is configured to be launched, such as from a portable or stationary rifled cannon (not shown) toward a target <NUM>. The projectile <NUM> is launched in a manner that causes the projectile <NUM> to be rifled for spin-stabilizing the projectile <NUM> as it is guided towards target <NUM>. The spin-stabilization is achieved by rotating the projectile <NUM> about a longitudinal axis <NUM> at a rotational frequency of ωp. The projectile <NUM> includes a housing <NUM>, flight control members <NUM>, and an imaging-seeker <NUM>.

The imaging-seeker <NUM> is strapped-down, meaning it is secured in a fixed relationship with respect to the housing <NUM>. In the example shown, the imaging-seeker <NUM> forms a nose portion of the projectile <NUM>. The imaging-seeker <NUM> can be fixedly mounted to the housing <NUM> or housed within the housing <NUM>. The imaging-seeker <NUM> spins at the same rate ωp as the projectile <NUM>, capturing time-sequenced images as it spins. The imaging-seeker <NUM> can use short wave infrared (SWIR) imaging to capture the images, which enables image capture using short exposure times. The captured images are processed to determine a rotation angle between consecutive images or consecutive sampled images. The rotation angle is used in a feedback loop to control a shutter of the imager seeker <NUM> for controlling the exposure time and/or frame rate for capturing the images. The captured images, or sampled captured images, can be further processed and used in an open loop to output target homing information to a flight controller <NUM> The flight controller can use the output target homing information to control the flight control members <NUM>. The flight control members <NUM> can be mounted, for example, to the housing <NUM> and configured to control the flight path of the projectile <NUM> toward the target <NUM> for providing terminal guidance of the projectile <NUM> towards the target <NUM>. The target homing information can be provided, for example, in the form of horizontal and vertical bearing angles, which describe an angle with respect to the housing <NUM> of the projectile <NUM> at which the projectile is directed to bear.

<FIG> shows a schematic diagram of exemplary embodiments not being within the claimed subject matter of the imaging-seeker <NUM>. Imaging-seeker <NUM> includes an imager <NUM>, a roll gyro <NUM>, samplers <NUM>, an Affine Scale-Invariant Feature Transform (ASIFT) correlator <NUM> shutter control logic component <NUM>, a de-blur component <NUM>, an image rotator <NUM>, a target acquisition component <NUM>, a target tracker <NUM>, and an un-rotate angle component <NUM>.

A bore-site of the imager <NUM> is aligned with longitudinal axis <NUM> of the projectile <NUM>, wherein the longitudinal axis <NUM> is the spin axis of the projectile <NUM>. Co-aligned with longitudinal axis <NUM> is the roll gyro <NUM>. The roll gyro <NUM> is a gyroscope that senses instantaneous roll spin rate ωx of the projectile <NUM>. The roll gyro <NUM> outputs the spin rate ωx to the de-blur component <NUM>.

The imager <NUM> is an imager that is able to capture two-dimensional images using a relatively short exposure time and outputs images that have stable features. The imager <NUM> can operate in the SWIR, MWIR, LWIR and visible ranges provided that the above criteria are met. Imagers that operate in the visible and SWIR ranges primarily sense reflected energy and imagers that operate in the MWIR and LWIR primarily sense emitted energy. Images produced using emitted energy may have fewer and less detailed features, albeit sufficient features, that can be used to for correlation of images. While exposure times may be increased under low ambient lighting conditions, the imager <NUM> is able to capture images that can be usable by applying techniques for de-blurring by the de-blur component <NUM>. The imager <NUM> can capture images based on the frame rate, such as <NUM> images/sec and provide the captured images in time-sequence as In to the de-blur component <NUM>.

The de-blur component <NUM> receives the time-series images In from the imager <NUM> and the spin rate ωx from the roll gyro <NUM>, and outputs de-blurred images Ide-blur. The de-blur component <NUM> is configured to provide image de-convolution to the time-series images In by removing image blur caused by motion of the imager <NUM> during exposure time windows during capture. The spin rate ωx of projectile <NUM> is the primary motion which causes image blurring, hence blurring can be decreased by the de-blur component <NUM> based on this spin rate ωx. Using spin rate ωx to perform deconvolution saves a significant computation load relative to de-convolution that is performed blindly when the source of the blurring is unknown.

One or more samplers <NUM> can sample the de-blurred images Ide-blur and provide a first sample every Ts seconds and a second sample every KTs seconds to the ASIFT correlator <NUM>. For example, when K = <NUM> and Ts = <NUM> second, the images sampled at the higher rate (in this example, one second intervals) are compared to a respective corresponding images sampled at the lower rate (in this example, <NUM> second intervals). Each image sampled at the lower rate corresponds to the immediately preceding (or subsequent) image sampled at the higher rate. The ASIFT correlator <NUM> can use an image sampled at the lower rate as a reference image to determine a relative rotation angle of the corresponding images sampled at the higher rate.

The ASIFT correlator <NUM> receives the first and/or second samples of the de-blurred images and compares two consecutive images from one of the first and second samples. The ASIFT correlator <NUM> determines the relative camera motion (translation, rotation, and/or roll) that occurred to capture overlapping portions of the same scene in the two consecutive images. In the current example, the ASIFT correlator <NUM> determines a relative roll angle Δφ that the imager <NUM> rolled to capture the two consecutive images.

The shutter control logic component <NUM> receives the roll angle Δφ and controls the shutter of the imager <NUM> (by command signals Cmd) for controlling exposure duration and frame rate of the imager <NUM> based on the roll angle Δφ. Furthermore, the shutter control logic component <NUM> is configured to provide a discrete time stamp that coincides with a time each image is captured. By adjusting the frame rate based on the roll angle Δφ, the shutter control logic component <NUM> can advance or retard timing of the next frame.

In the embodiment shown in <FIG>, a feedback loop <NUM> is formed that includes the imager <NUM>, de-blur component <NUM>, ASIFT correlator <NUM>, and shutter control logic component <NUM>. The feedback loop <NUM> allows the image seeker <NUM> to adjust (advance or retard) the exposure times use by imager <NUM> so that Δφ ≈ <NUM>, meaning the background of the scene being imaged is stabilized to have the same orientation with respect to rows and columns used by the imager <NUM>. This also allows the imager frame rate to be an integer division of the projectile spin rate ωx.

Image rotator <NUM> receives the roll angle Δφ and sampled two-dimensional de-blurred images Ide-blur. Image rotator <NUM> rotates pixel values in the sampled de-blurred images Ide-blur by the roll angle Δφ. The rotation can be performed using a geometric transform that maps a pixel position (x1, y1) of respective pixels in an input image of the de-blurred images Ide-blur onto a position (x2, y2) in an output image by rotating the pixel position through the roll angle Δφ about a pixel location that is aligned with the bore-site and situated at the center of the input image. The image rotator <NUM> outputs rotated images Ide-spun that ideally appear as if they were captured while the projectile <NUM> was not spinning.

Over time, the feedback loop <NUM> may achieve the exposure times and frame rate of the imager <NUM>'s shutter being controlled such that the roll angle Δφ ≈ <NUM>. However, over time, the spin rate ωx can decay. The feedback loop <NUM> can take time to adjust to the decay. Thus, the image rotator <NUM> can rotate the images it receives to compensate for roll angle Δφ detected by the ASIFT correlator <NUM> whenever the roll angle Δφ ^ ≈ <NUM>.

With additional reference to <FIG> shows diagrams 300a-300d of a scene <NUM> having a target <NUM>. In diagram 300a, a series of images <NUM> captured by imager <NUM> are shown. The orientations of the different images <NUM> are effectively random due to the shutter of the imager <NUM> not being synchronized with the spin rate ωx of the image seeker <NUM>. Eventually, the feedback loop <NUM> can synchronize the shutter of the imager <NUM> to an integer multiple of the spin rate ωx, which will cause all the images to be oriented in the same direction.

Diagram 300b shows a sampled image 308a of a portion of the scene <NUM>. Image 308a was captured at a first exposure of the shutter of the imager <NUM> and sampled by one of samplers <NUM>. Image 308a is provided as a first input image to the ASIFT correlator <NUM>.

Diagram 300c shows a second sampled image 308b of the scene <NUM>. Image 308b was captured a second exposure of the shutter of the imager <NUM> that occurred after the first exposure, and was sampled by one of samplers <NUM>. Image 308b is provided as a second input to the ASIFT correlator <NUM>. The ASIFT correlator <NUM> outputs a rotation angle Δφ between the first image 308a and the second image 308b.

Diagram 300d shows the second image 308b after being rotated (e.g., using a pixel-wise transform) by the image rotator <NUM> through the angle Δφ. The rotation provides alignment of the first image 308a and rotated second image 308b. Alignment means that the direction North, for instance, is the same in each of the first and second images 308b and 308d, making it feasible to track the target <NUM> in the first image 308b and the rotated second image 308d. Inset <NUM> shows the imaged target <NUM> as it appears in a captured image before the de-blurring component <NUM> de-blurs that image. Inset <NUM> shows the imaged target <NUM> after it was de-blurred by the de-blurring component <NUM>, improving the image of the target <NUM> and the likelihood of the target acquisition component <NUM> and the target tracker <NUM> to acquire and track the target <NUM>.

The target acquisition component <NUM> uses target acquisition algorithms to acquire a target from the rotated images Ide-spun, as would be understood by a person skilled in the art. The target acquisition component <NUM> can consult target templates to acquire the target. Target templates can be stored in a library that can be accessed by the target acquisition component <NUM>, such as target template library <NUM> shown in <FIG> and <FIG>. The target acquisition component <NUM> instructs the target tracker <NUM> when to begin tracking the target by sending a Track-Start signal.

The target tracker <NUM> tracks the target in the rotated images Ide-spun, as would be understood by a person skilled in the art. The target tracker <NUM> can determine bearing angles that would be used by the flight controller (such as flight controller <NUM> shown in <FIG>) to flight control members <NUM> to steer the projectile <NUM> toward the tracked target, as would be understood by a person skilled in the art. In addition, the target tracker <NUM> can determine and output target velocity.

The un-rotate angle component <NUM> then un-rotates the bearing angles to reverse the effects of the rotation performed by the image rotator <NUM>. For example, the rotation angle can be reversed by mapping pixel positions of the target into an un-rotated position. The un-rotated bearing angles are used for directing the projectile <NUM> towards the target <NUM>, thus providing terminal homing guidance of the projectile <NUM>.

<FIG> shows a schematic diagram of further exemplary embodiments of the imaging-seeker, shown as imaging-seeker <NUM>'. Differences between operations of the components of the imaging-seeker <NUM>' relative components of the imaging-seeker <NUM> are described. Components and operations of imaging-seekers <NUM> and <NUM>' for which differences are not described can be configured substantially the same.

Imaging-seeker <NUM>' is shown to include feedback loop <NUM>', wherein the feedback loop <NUM>' includes imager <NUM>, sampler <NUM> and image buffer <NUM>, ASIFT correlator <NUM>, and shutter control logic <NUM>. The shutter control logic <NUM> generates uses the roll angles Δφ provided by the ASIFT correlator <NUM> to estimate the spin rate ωp of the projectile <NUM>. The de-blur component <NUM> is positioned outside of the feedback loop <NUM> and de-blurs images In output by the imager <NUM> using the estimated spin rate ωp. The de-blur component <NUM> outputs the de-blurred images Ide-blur to the image rotator <NUM>.

Since the de-blur component <NUM> is outside of the feedback loop <NUM>', the images In and Im received by the ASIFT correlator <NUM> are not de-blurred. Accordingly, the exposure time of the imager <NUM> needs to be sufficiently short to minimize blur of images Im and In that are received by the ASIFT correlator <NUM>.

Since the shutter control logic <NUM> estimates the spin rate ωp of the projectile <NUM>, the roll gyro (not shown in <FIG>) output is not needed for performing the functions of the imaging-seeker <NUM>' that are shown are described. Accordingly, the imaging-seeker <NUM>' does not require a highly accurate roll gyro. Additionally, the de-blur component can operate on sampled images In such that the de-blur process is not performed on every image generated by the imager <NUM>. Since the de-blurring algorithm uses relatively high amounts of computing and power resources, moving the de-blur component <NUM> outside of the feedback loop <NUM> can significantly lower the computational load of the imaging-seeker <NUM>'.

Imaging-seeker <NUM>' is shown to include an image buffer <NUM> and one sampler <NUM>. The ASIFT correlator <NUM> of imaging-seeker <NUM>' receives first images In and second images Im from the imager <NUM> and image buffer <NUM>, respectively. First images In are received from the imager <NUM> at the rate that the imager captures the images (e.g., <NUM> images per second) and second images Im are received from the image buffer <NUM> after being sampled at a selected rate, such as one image per <NUM> seconds. A person skilled in the art will recognize that all sampling rates can be adjusted per design. Implementation in software of samplers <NUM> and image buffer <NUM> can be performed in the same or similar ways.

Imaging-seeker <NUM>' is shown to include a target template library <NUM>. One skilled in the art will recognize that imaging-seekers <NUM> and <NUM>' can use a library and/or logic for performance of target acquisition.

<FIG> shows a schematic diagram of further exemplary embodiments of the imaging-seeker, shown as imaging-seeker <NUM>". Differences between operations of the components of the imaging-seeker <NUM>" relative to components of the imaging-seeker <NUM> are described. Components and operations of imaging-seekers <NUM>' and <NUM>" for which differences are not described can be configured substantially the same.

The de-blur component <NUM> is moved to receive rotated images from the image rotator <NUM> and to provide the de-blurred images Ide-blur to the target acquisition component <NUM>. As in the embodiments shown in <FIG>, the de-blur component <NUM> receives the estimated projectile spin rate ωp from the shutter control logic <NUM>. Ideally, the target acquisition component <NUM> performs target acquisition only once per target. Target acquisition may need to be repeated if the target tracker <NUM> loses track of the target. Accordingly, the de-blurring may only need to be performed before each target acquisition operation performed by the target acquisition component <NUM>, significantly decreasing the computational load caused by the de-blurring process.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the illustrated embodiments, exemplary methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.

It must be noted that as used herein and in the appended claims, the singular forms "a", "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a stimulus" includes a plurality of such stimuli and reference to "the signal" includes reference to one or more signals and equivalents thereof known to those skilled in the art, and so forth.

It is to be appreciated the embodiments of the disclosure include software algorithms, programs, or code that can reside on a computer useable medium having control logic for enabling execution on a machine having a computer processor. The machine typically includes memory storage configured to provide output from execution of the computer algorithm or program.

As used herein, the term "software" is meant to be synonymous with any code or program that can be in a processor of a host computer, regardless of whether the implementation is in hardware, firmware or as a software computer product available on a disc, a memory storage device, or for download from a remote machine. The embodiments described herein include such software to implement the logic, equations, relationships and algorithms described above. One skilled in the art will appreciate further features and advantages of the illustrated embodiments based on the above-described embodiments. Accordingly, the illustrated embodiments are not to be limited by what has been particularly shown and described, except as indicated by the appended claims.

<FIG> is a block diagram of an exemplary system generating a course-correction signal for a spin-stabilized projectile. In <FIG>, guidance system <NUM> for spin-stabilized projectile <NUM> (depicted in <FIG>) includes imaging-seeker <NUM>, guidance, navigation, and control unit (GNC) <NUM> and flight control transducer(s) (FCT) <NUM>. Imaging-seeker <NUM> interfaces with both GNC <NUM> and FCT(s) <NUM>. In some embodiments, imaging-seeker does not directly interface with FCT(s) <NUM>, but instead indirectly interfaces with FCT(s) <NUM> via GNC <NUM>. In some embodiments, GNC <NUM> provides flight telemetry and navigation information to imaging-seeker <NUM>. In various embodiments, imaging-seeker <NUM> can include more or fewer components.

Imaging-seeker <NUM> includes processor(s) <NUM>, forward-looking imager <NUM>, storage device(s) <NUM>, GNC interface <NUM>, FCT(s) interface <NUM>, and input/output interface <NUM>. Processor(s) <NUM> can receive program instructions from storage device(s) <NUM>. Processor(s) <NUM> can be configured to generate course-correction signals for spin-stabilized projectile <NUM> based on received program instructions. For example, processor(s) <NUM> can be configured to receive, from forward-looking imager <NUM>, a time sequence of images. Processor(s) <NUM> can perform image processing algorithms upon each of the time sequence of images, so as to select a target amongst objects captured within the time sequence of images, and to generate course-correction signals so as to direct spin-stabilized projectile to the selected target.

Processor(s) <NUM>, in some embodiments, can be configured to implement functionality and/or process instructions for execution within imaging-seeker <NUM>. For instance, processor(s) <NUM> can be capable of processing instructions stored in storage device(s) <NUM>. Examples of processor(s) <NUM> can include any one or more of a microprocessor, a controller, a digital signal processor(s) (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other discrete or integrated logic circuitry having similar processing capabilities.

Storage device(s) <NUM> can be configured to store information within imaging-seeker <NUM> during operation. Storage device(s) <NUM>, in some examples, is described as computer-readable storage media. In some examples, a computer-readable storage media can include a non-transitory medium. The term "non-transitory" can indicate that the storage medium is not solely embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium can store data that can, over time, change (e.g., in RAM or cache). In some examples, storage device(s) <NUM> is a temporary memory, meaning that a primary purpose of such storage device(s) <NUM> is not long-term storage. Storage device(s) <NUM>, in some examples, is described as volatile memory, meaning that storage device(s) <NUM> do not maintain stored contents when power to imaging-seeker <NUM> is turned off. Examples of volatile memories can include random access memories (RAM), dynamic random access memories (DRAM), static random access memories (SRAM), and other forms of volatile memories. In some examples, storage device(s) <NUM> is used to store program instructions for execution by processor(s) <NUM>. Storage device(s) <NUM>, in one example, is used by software or applications running on imaging-seeker <NUM> (e.g., a software program implementing image processing algorithms) to temporarily store information during program execution.

Storage device(s) <NUM>, in some examples, can also include one or more computer-readable storage media. Some storage device(s) <NUM> can be configured to store larger amounts of information than is sometimes stored in volatile memory. Storage device(s) <NUM> can further be configured for long-term storage of information. In some examples, storage device(s) <NUM> include non-volatile storage elements. Examples of such non-volatile storage elements can include magnetic hard discs, optical discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories.

GNC interface <NUM> can be used to communicate information between imaging-seeker <NUM> and GNC <NUM>. In some embodiments, such information can include aircraft conditions, flying conditions, and/or atmospheric conditions. In some embodiments, such information can include data processed by imaging-seeker <NUM>, such as, for example, range data. GNC interface <NUM> can also include a communications module. GNC interface <NUM>, in one example, utilizes the communications module to communicate with external devices via one or more networks, such as one or more wireless or wired networks or both. The communications module can be a network interface card, such as an Ethernet card, an optical transceiver, a radio frequency transceiver, or any other type of device that can send and receive information. Other examples of such network interfaces can include Bluetooth, <NUM>, <NUM>, and Wi-Fi <NUM> radio computing devices as well as Universal Serial Bus (USB). In some embodiments, communication with the GNC <NUM> can be performed via a communications bus, such as, for example, an Aeronautical Radio, Incorporated (ARINC) standard communications protocol. In an exemplary embodiment, communication with the GNC <NUM> can be performed via a communications bus, such as, for example, a Controller Area Network (CAN) bus.

FCT interface <NUM> can be used to communicate information between imaging-seeker <NUM> and GNC <NUM>. In some embodiments, such information can include command signals for flight control members and/or feedback signals indicative of actual position of flight control members. FCT interface <NUM> can also include a communications module. FCT interface <NUM>, in one example, utilizes the communications module to communicate with external devices via one or more networks, such as one or more wireless or wired networks or both. The communications module can be a network interface card, such as an Ethernet card, an optical transceiver, a radio frequency transceiver, or any other type of device that can send and receive information. Other examples of such network interfaces can include Bluetooth, <NUM>, <NUM>, and Wi-Fi <NUM> radio computing devices as well as Universal Serial Bus (USB). In some embodiments, communication with FNC(s) <NUM> can be performed via a communications bus, such as, for example, an Aeronautical Radio, Incorporated (ARINC) standard communications protocol. In an exemplary embodiment, aircraft communication with FNC(s) <NUM> can be performed via a communications bus, such as, for example, a Controller Area Network (CAN) bus.

Input/output interface <NUM>, in some examples, is configured to receive input from a user. Input/output interface <NUM> can be used to acquire targeting information before spin-stabilized projectile <NUM> is launched, for example. In some embodiments, input communication from the user can be performed via a communications bus, such as, for example, an Aeronautical Radio, Incorporated (ARINC) standard communications protocol. In an exemplary embodiment, user input communication from the user can be performed via a communications bus, such as, for example, a Controller Area Network (CAN) bus. Input/output interface can include a display device, a sound card, a video graphics card, a speaker, a cathode ray tube (CRT) monitor, a liquid crystal display (LCD), a light emitting diode (LED) display, an organic light emitting diode (OLED) display, or other type of device for outputting information in a form understandable to users or machines. In some embodiments, output communication to the user can be performed via a communications bus, such as, for example, an Aeronautical Radio, Incorporated (ARINC) standard communications protocol. In an exemplary embodiment, output communication to the user can be performed via a communications bus, such as, for example, a Controller Area Network (CAN) bus.

A potential advantage of the various embodiments of the imaging-seeker disclosed is the ability to provide terminal guidance of spin-stabilized projectile provided with a strapped-down imaging-seeker. The terminal guidance uses images that can provide high precision, even when the target is mobile.

While shown and described in the exemplary context of airborne munitions related applications, those skilled in the art will readily appreciate that the munition <NUM> in accordance with this disclosure can be used in any other suitable application, including waterborne munitions or for spin-stabilized projectiles aimed at targets for delivery of non-artillery payloads or purposes other than delivery of a payload.

The present disclosure provides a method as claimed in claim <NUM>.

The blur may be minimized before comparing the respective current images to the corresponding previous images.

The present disclosure also provides a spin-stabilized projectile as claimed in claim <NUM>.

Claim 1:
An imaging-seeker for a spin-stabilized projectile (<NUM>) that spins about a longitudinal axis (<NUM>) of the projectile (<NUM>), the imaging-seeker comprising:
a forward-looking imager (<NUM>) configured to capture a time-sequence of images of a scene, the imager (<NUM>) capturing the images at a frame rate;
an image correlation component configured to:
compare respective current images of the time-sequence of images to a corresponding previous image of the time-sequence of images; and
determine rotation angles between the current and corresponding previous images based on the comparison;
shutter control logic (<NUM>) configured to:
control the frame rate of the imager (<NUM>) based on the rotation angles; and
estimate a spin rate of the projectile (<NUM>) based on rotation angles determined for iterations of a control loop, wherein the control loop is a feedback loop that includes the imager (<NUM>), the image correlation component and the shutter control logic (<NUM>);
an image rotator (<NUM>) configured to rotate the current images of the time-sequence of images using the rotation angles;
an image processor configured to acquire a target (<NUM>) in images of the time-sequence of images after rotation of the current images by the image rotator (<NUM>); and
a signal generator configured to generate target bearing angles for use by the projectile (<NUM>) to correct its course toward the target (<NUM>) using the target bearing angles;
a de-blur component (<NUM>) configured to minimize blur in at least a portion of the time-sequence of images, wherein minimizing the blur comprises de-convolving the time-sequence of images using the estimated spin rate, and minimizing the blur is performed before providing the time-sequence of images to the image processor for acquiring the target (<NUM>).