. Points within the TV imagery can be automatically highlighted to provide a human operator the visual imagery needed to manually verify his defensive guns are on target to prevent collateral damage incidents. The TWS would cue the IR camera of the tracking sensor to initiate track of any launched threat munitions to shorten the active track response timeline. The resulting 3-D track would determine if the flash was small arms, a rocket, RPG, flash-bang countermeasure, etc. The following table describes the TWS specifications.
Wavelengths 3.2-4.7 microns.
Additional variants of dual mirror 40 degree field of regard basic concept include modification of the scan area to optimize search for target launches from the ground by preferentially scanning 80 degrees in azimuth and 12 degrees in elevation. Such configurations are commercially available from GSI Lumonics and from Cambridge Technology.
Utilizing a Cambridge Technology model 6400 and model 6900 scanner and x-y or az-el scanning system can be fabricated with custom designed mirrors and a 75 mm clear aperture. This aperture will increase the range of the RTATS acquisition by 63% over the 46 mm design employed in the original description. Mirrors of this size are not commercially available with moments of inertia low enough to result in useful step and settle times for such a scanner.
Applicants have designed a pyrex mirror which is light weighted and meets the moment of inertia requirements.
The FOR for the two mirror system described above is limited by the galvanometer-like optical positions of the two mirrors. For many applications, which require autonomous operation over a large angular field, this is not sufficient. Therefore Applicants have designed and demonstrated a new concept to extend the FOR to nearly hemispherical coverage, by placing the galvanometer on an azimuthally rotating mount. This version of the dual scanner concept provides a system with 360 degree azimuth coverage. Such a system is constructed by mounting the dual mirror scanner on a high torque azimuth motor and coupling this configuration to the optical instrument package.
Applicants have constructed a prototype system. A control system which is designed to move the azimuth motor to a target location simultaneously while moving the fast scanning mirrors has been shown to results in step and settle times twice as fast as using the azimuth motor alone. On prototype systems Applicants have measured angular step and settle times of greater than 390 degrees/s.
The multi-stage concept is a simple open loop approach that measures positional errors in the slower, motor position loop which provides the large field of regard, and spills this error into the scanner position control loop which can rapidly ‘make up’ for the error. The result is a compound mechanism that provides a wide field of regard together with rapid rise and settling times. This control loop is described in FIG. 16.
The RTATS system is designed to produce a real-time 3D track of targets by generating azimuth and elevation measurements with the mid-wave or other cameras, and range data from the laser range module. In order to maintain the laser spot fixed a predetermined pixel on the focal plane array it is required to stabilize the laser pointing. Such a system has been designed and tested. The laser range system beam is sampled by a partially reflecting mirror. The sample mirror is equipped with two axis beam steering. The sampled beam is sent to a monitor camera, and motion of the spot is used to provide position feedback for the laser pointing mirror. This system has been shown to stabilize the laser output beam to a 20 micro-radian accuracy.
In order to differentiate targets from background we have devised a scheme to eliminate or map out stationary or slowly changing background features which interfere with identification of correct targets. The clutter map is a series of bounding boxes in fixed space (independent of where out mirrors are pointing) indicating area where false targets are prevalent and need to be ignored. The supervisor processor can be loaded with bounding boxes (in Az/El space) that specify keep out regions. Any centroid it gets that is within a keep out region will not be added to an existing target nor will it start a new target. Ignored centroids are still sent to the user interface computer and are logged, but they are flagged as being ignored. The local horizon is treated as another clutter map keep out zone. The clutter map is generated on the user interface computer, or any other computer and transferred to the user interface computer.
A scan pattern of the area is performed and all centroids from it are logged.
Additional scans are done approximately ten minutes apart for at least an hour. They could continue longer or even be done on additional days.
A histogram of all the centroids is made and the user can select which area to include as a keep out area in the clutter map.
Existing programs like excel will be helpful in displaying and picking which areas/regions are to be included in the clutter map.
A scan pattern of the area is performed and all image frames from it are archived.
All the images from a scan pattern are stitched together to make a super image of the entire field of regard.
Those super images then analyzed to determine where clutter areas are.
Programs for analyzing these super images will be developed internally.
An additional method that can be used to suppress clutter in the scene is to use a polarizing element in the mwir optical path. Such a system has been tested and shown to reduce the background signal by 50%.
The RTATS Supervisor shall enable/disable the application of a Laplacian filter, described below, by means of a bit-write via the VME-bus to the VidIf board. If the designated bit is set, the filter shall be applied to each incoming camera image following application of the NUC (Non-uniformity correction) and prior to any subsequent image-processing steps and blob processing. Non-filtered images shall be forwarded to the VidIf FPDP ChannelLink Interface prior to application of the Laplacian filter. The Laplacian Filter may be enabled independently of frame-subtract mode and image registration mode (described later herein).
The Laplacian filter consists of a 7×7 Finite-Impulse-Filter, whose coefficients are provided in the following table.
All pixels in the 3-pixel border of the image shall be given the pixel value of zero. And negative pixel values shall be clipped to a value of zero.
Upon completing calculation of the matrix G, the VidIf board shall assert an interrupt request to the Supervisor. Upon receiving an interrupt from the VidIf board, the Supervisor shall read the 45 matrix elements of G from the VidIf board via the VME-bus, and store for future use in step 3.2.
Upon completion of the calculation of H, the VidIf board will again assert an interrupt request, signaling the Supervisor that H is ready for processing.
H=G·w, where vector w contains 9 (3×3) FIR filter coefficients.
The supervisor shall then write the coefficients of w back to the same memory/register space on the VidIf board, and signal the VidIf board via a bit-write, that vector w is ready.
The VidIf board shall then proceed with frame-subtraction and blob processing as usual, subtracting previous registered image g′ from current image h prior to performing blob detection.
FIG. 17 illustrates the anticipated signal flow, timing, and interactions between the VidIf board and the Supervisor.
b. Target position and velocity are sent to the gimbal and the gimbal then follows the target in a continuous velocity track.
c. The position and a velocity of zero is sent to an Innovative Integrations DSP with specs shown below (FIG. 1), controlling the mirrors.
d. At 10 kHz, the DSP reads the gimbal position encoder and determines where to point the mirrors such that they remain pointed at the same spot with a zero velocity.
e. The mirror position is set by supplying a control voltage to the galvanometers using an analog output module.
f. The effect of this is that the gimbal continues to follow the target while the mirrors do an effective step & stare pattern to following the target. Frame to frame subtraction can the be done between the frames.
e. Bin all the possible velocities and locations across all the frames.
f. Eliminate Velocity and locations that don't match user specified boundaries.
g. When the occurrence of a velocity and location is observed (N times) enough times (threshold set by user), a target track is started with those observations preloaded into it.
a. The range (minimum and maximum number) of pixels that can be in any given blob processed by the PC.
b. The range of x and y blob size.
c. The range of intensities defined as the sum of pixel values less a background. Such selection is termed a Pre-filter on the MOTS system. The use of suitable pre-filter settings allows the user to eliminate various types of spatial noise that can cause artifacts in the image resulting in false target acquisitions. By suitable choice of pre-filter settings we have demonstrated the ability to suppress false targets generated by intrinsic camera pixel noise, and false targets such as clouds, or ground clutter such as mountains or other geographical features. Furthermore the pre-filters may be used to distinguish between targets of different sizes such as mortars and aircraft at comparable ranges.
Another technique for suppressing false targets in the RTATS and MOTS MWIR trackers is through the use of a polarizing optical element inserted in the optical path shown in FIG. 3. In the optical design the a variable polarizer was inserted near the intermediate focus point of the pupil plane relay optics. The polarizer was used to suppress solar glint from wave-tops in the use of the RTATS system to track small boats. The insertion of the polarizer reduced the occurrence of false targets.
While