The field of view of optical imaging systems is limited, making it difficult to meet the needs of continuous tracking of multiple targets in different orientations in a wide spatial domain, even in the 4 π spatial domain. Therefore, based on the two-dimensional tracking rotating platform, an unscented Kalman motion estimation algorithm based on target motion characteristics and an optimization algorithm for multi-objective switching tracking based on motion target matching, tracking convergence, and platform rotation ability have been proposed. The ultimate goal is to achieve continuous tracking of multiple spatial targets over a wide area. The development of a light and small space two-dimensional rotating platform tracking system is completed. The target detection coverage achieved is better than ± 180° in both pitch and azimuth directions. Continuous observation and tracking of better than 8 targets has been achieved through target motion estimation and switching tracking methods.
When the Satellite-borne very high infrared spectrometer performs atmospheric composition analysis, it needs to use the sun as a light source for occultation detection. The stability of the light source is related to the detection accuracy. In general, it is believed that the light distribution within the maximum solar intensity range is the most stable and it is necessary to accurately identify and track this range. However, due to the inhomogeneous atmosphere and the change of atmospheric density, the solar image will have deformation or block, which affects the accuracy of target recognition and tracking. This paper proposes a multi-objective clustering-based recognition method to solve the problem of accurate multi-target identification under the large dynamic light intensity range, and uses the hardware structure of FPGA+DSP to realize the imaging and tracking system.
The line-of-sight (LOS) stable platform is the most important technology of UAV (unmanned aerial vehicle), which can reduce the effect to imaging quality from vibration and maneuvering of the aircraft. According to the requirement of LOS stability system (inertial and optical-mechanical combined method) and UAV’s structure, a rapid prototype is designed using based on industrial computer using Peripheral Component Interconnect (PCI) and Windows RTX to exchange information. The paper shows the control structure, and circuit system including the inertial stability control circuit with gyro and voice coil motor driven circuit, the optical-mechanical stability control circuit with fast-steering-mirror (FSM) driven circuit and image-deviation-obtained system, outer frame rotary follower, and information-exchange system on PC. Test results show the stability accuracy reaches 5μrad, and prove the effectiveness of the combined line-of-sight stabilization control system, and the real-time rapid prototype runs stable.
When sun is used as the light source for atmospheric composition detection, it is necessary to image sun for accurate identification and stable tracking. In the course of 180 second of the occultation, the magnitude of sun light intensity through the atmosphere changes greatly. It is nearly 1100 times illumination change between the maximum atmospheric and the minimum atmospheric. And the process of light change is so severe that 2.9 times per second of light change can be reached. Therefore, it is difficult to control the integration time of sun image camera. In this paper, a novel adaptive integration time control method for occultation is presented. In this method, with the distribution of gray value in the image as the reference variable, and the concepts of speed integral PID control, the integration time adaptive control problem of high frequency imaging. The large dynamic range integration time automatic control in the occultation can be achieved.
The novel support structure design of high stability for space borne primary mirror is presented. The structure is supported by a ball head support rod, for statically determinate support of reflector. The ball head assembly includes the supporting rod, nesting, bushing and other important parts. The liner bushing of the resistant material is used to fit for ball head approximated with the reflector material, and then the bad impact of thermal mismatch could be minimized to minimum. In order to ensure that the structure of the support will not be damaged, the glue spots for limitation is added around the reflector, for position stability of reflector. Through analysis and calculation, it can be seen that the novel support structure would not transfer the external stresses to the reflector, and the external stresses usually result from thermal mismatch and assembly misalignment. The novel method is useful for solving the problem of the bad influence form thermal stress and assembly force. In this paper, the supporting structure is introduced and analyzed in detail. The simulation results show that the ball head support reflector works more stably.
KEYWORDS: Motion estimation, Image processing, Video, Image enhancement, Algorithms, Digital signal processing, Video processing, Image analysis, Digital imaging, Video coding
When the image matching method is used for motion estimation, the performance parameters like searching scope, searching speed, accuracy and robustness of the method normally are significant and need enhancement. In this paper, a novel method of block matching containing the wide range image block matching strategy and the strategy of multi-start points and parallel searching are presented. In the wide range matching strategy, the size of template block and searching block are same. And the average value of cumulative results by pixels in calculation is taken to ensure matching parameters can accurately represent the matching degree. In the strategy of multi-start points and parallel searching, the way of choosing starting points evenly is presented based on the characteristic of the block matching search, and the adaptive conditions and adaptive schedule is established based on the searching region. In the processing of iteration, the new strategy can not only adapt to the solution that lead the objective to the correct direction, but also adapt to the solution that have a little offset comparing with the objective. Therefore the multi-start points and parallel searching algorithm can be easy to keep from the trap of local minima effectively. The image processing system based on the DSP chip of TMS320C6415 is used to make the experiment for the video image stabilization. The results of experiment show that, the application of two methods can improve the range of motion estimation and reduce the searching computation.
In the uncooled infrared imaging system by the optical readout method with the micro-cantilever, the images obtained have obvious noise. The noise is generated due to the imaging device technology and stray light effects. The noise has a bad affect for the image quality, and even the continuous noise pixels form holes, which make the target difficult to be identified. Therefore, the novel infrared image enhancement method based on the mask convolution is presented. In the method, the information of convolution mask like size can be obtained by Hough transform, and the convolution mask can be built based on the characteristics of optical readout method in uncooled infrared imaging system. The position of mask on the image is changed pixel by pixel, and convolution is made between mask and pixels in the image. Then, an evaluation parameter threshold is established for eliminating the noise of the image. In the image after denoising, a mean filter is made to fill noise pixels and unit intervals of micro-cantilever. Finally, the Enhanced infrared image can be gained.
Sun is used as light source for spectrum analysis of atmosphere material with sunlight through atmosphere. The stronger
sunlight enters the detector, the more accuracy can be achieved. However, due to the inhomogeneity of the atmosphere,
the gray image of sun is not only irregular, even the interference of clouds will divide sun into different parts. Thus,
when the light intensity, shape and location of sun in the image keep changing, it is critical for obtaining and following
the position of the strongest sunlight accurately. In the paper, a novel method of sun scene simulation for observation of
the sun through the atmosphere is presented. The method based on the active optical control system, is used in sun scene
simulation with the variation of light intensity, shape and position. The method has a simple theory and is easy to be
realized. This simulation system composing with computer, projection devices, micro deformable mirror and the optical
lens group can be used for simulating optical properties of atmosphere with different density, humidity, and air flow rate,
for ensuring the accuracy and real-time sun scene simulation.
For high resolution satellite remote sensing cameras, the line of sight (LOS) moving during the image exposure period
will cause the modulation transfer function (MTF) degradation and image blurring. Image stabilization component is
used to improve image quality by actively removing the apparent motion induced by vibration, tracking error and attitude
instability. In this paper, the image stabilization component is considered as a kind of closed loop servo control system,
and the image stabilization effect is converted into servo control performance for research. Firstly, the image
stabilization servo loop scheme and transfer function model are constructed and the LOS jitter is considered as the output
of a stochastic system derived by white-Gaussian noise. Based on the proposed model, the demand boundary of jitter
rejection function is described, and the design criterion to be satisfied is obtained according to the requirement of image
stabilization performance. And then, a discrete Kalman estimation algorithm is introduced into image stabilization servo
loop to filter out the noise caused by pixel-shift sensor (PSS) and compensate for the delay due to the PSS measurement.
Based on the given design criterion, the control law is designed by using the output of Kalman filter. The computer
simulation is achieved to show that the proposed control strategy can significantly improve the image stabilization
performance.
A method for capturing the solar shape and location on occurrence of solar occultation is presented. On occurrence of
occultation when the Sun is covered by atmosphere, the solar shape viewed by satellite-borne detector on certain orbit
through atmosphere at different heights varies greatly due to such factor as the in homogeneity of atmosphere and cloud
covering, etc. During the varying of heights of atmosphere, the gray image of Sun also changes, which even appears
several parts in different size due to the disturbance of cloud layer. Based on which, the Paper proposes a method for
capturing solar shape and intensity on occurrence of solar occultation. First, taking the solar grey image without
atmospheric refraction effects as a reference; then the refraction angle of Sun ray after being refracted by atmosphere can
be reversely calculated by using Abel integral function and the vertically distributed data of index of refraction; Last, the
solar shape after passing atmosphere can be obtained by calculating the refraction angle of the ray on solar limb. We
have obtained the image of solar shape and intensity at the occultation central point of contact from 5km to 60km when
the detector is located at the defined satellite orbit (600km) by simulation. This method is of great significance for
realizing the solar simulator which can reflect solar shape and intensity in a comparatively truly degree under the
circumstance of existing various affecting factors for application in the fields like measuring and calibration of posture
parts of satellite, remote sensing technology and material measure, etc.
Sun is used as light source for spectrum analysis of atmosphere material with light through atmosphere. The stronger
sunlight enters the detector, the more accuracy can be achieved. However, due to the inhomogeneity of the atmosphere,
the gray image of sun is not only irregular, even the interference of clouds will divide sun into different parts. A novel
method for gray centroid of sunlight based on image recognition is presented. This method aiming at accurately
obtaining the strongest sunlight through the atmosphere for detector uses the gray image of sun to calculate the actual
gray centroid of sunlight.
For the limitation of detecting materials, the images from the novel un-cooled infrared system based on visible light
readout are blurry and have low contrast. The images also have more noise and larger holes. Especially after
pseudo-color processing, the noise and holes will become much clearer. For the characteristics of images in the
un-cooled IR system, the traditional image processing methods for IR images are not suitable for the image in our
research. Therefore, an advanced one-dimensional triple wavelet analysis in row for infrared images is presented based
on the characteristics of un-cooled infrared system. In this method, the triple wavelet decomposition is made in each row
of image, and detail coefficients and approximation coefficients of each row can be obtained. The detail coefficients in
the first time of wavelet decomposition express the whole details of image containing noise and the edge of object. So
after low-pass filter, the noise in the image can be suppressed. By the wave reconstruction made between the
approximation coefficients in triple wavelet decomposition and the detail coefficients after low-pass filter, each row in
images without noise and holes can be gained. In wavelet reconstruction, a weight being proportional with the filtering
window is multiplied with detail coefficients. The weight can make sure the gray value of whole picture and the contrast
cannot be lower after low-pass filter. The images from un-cooled infrared system are processed in the computer with the
software of MATLAB. The results support that compared with traditional methods the novel method can be more
effective to eliminate the noise and fill holes, and better response to the temperature details of objects.
This paper presents a novel fast block matching algorithm based on high-accuracy Gyro for steadying shaking image. It
acquires motion vector from Gyro firstly. Then determines searching initial position and divides image motion into three
modes of small, medium and large using the motion vector from Gyro. Finally, fast block matching algorithm is
designed by improving four types of templates (square, diamond, hexagon, octagon). Experimental result shows that the
algorithm can speed up 50% over common method (such as NTSS, FSS, DS) and maintain the same accuracy.
The method about how to distinguish the object from the standing wave, eliminate the wave patterns in CW THz images
based on phase analysis is reported. The standing wave of CW THz images result from the interference of the wave-front
reflected from the object and other optics in the system. Therefore, the information of the surface of the object and the
background is included in the interference pattern of the images. Because the objects have different Phase Gradients
from the background, they could be extracted from the image by utilizing the phase information of the interferential
waves. The waves of the image can be removed with Election-pass filter, and the result of the filtering would not
deteriorate the result because there is no object in the image. At last, the image of object and the image without standing
wave can be fused together to make the image better for eyes. The scope of CW THz imaging's application can be
extended and the quality of images can be improved by applying this approach.
KEYWORDS: Digital imaging, Video, Digital image processing, Motion estimation, Image processing, Digital image correlation, Image enhancement, Digital signal processing, Video processing, Image analysis
The image block matching algorithm based on motion vectors of correlative pixels in oblique direction is presented for
digital image stabilization. The digital image stabilization is a new generation of image stabilization technique which can
obtains the information of relative motion among frames of dynamic image sequences by the method of digital image
processing. In this method the matching parameters are calculated from the vectors projected in the oblique direction.
The matching parameters based on the vectors contain the information of vectors in transverse and vertical direction in
the image blocks at the same time. So the better matching information can be obtained after making correlative operation
in the oblique direction. And an iterative weighted least square method is used to eliminate the error of block matching.
The weights are related with the pixels' rotational angle. The center of rotation and the global emotion estimation of the
shaking image can be obtained by the weighted least square from the estimation of each block chosen evenly from the
image. Then, the shaking image can be stabilized with the center of rotation and the global emotion estimation. Also, the
algorithm can run at real time by the method of simulated annealing in searching method of block matching. An image
processing system based on DSP was used to exam this algorithm. The core processor in the DSP system is
TMS320C6416 of TI, and the CCD camera with definition of 720×576 pixels was chosen as the input video signal.
Experimental results show that the algorithm can be performed at the real time processing system and have an accurate
matching precision.
To achieve a good quality of image, piston of segment mirrors is required to be detected and removed down to a small
part of
λ. The details of the diffraction-interference pattern formed by the subaperture are sensitive to piston when
observed on the image plane. An improved image matching method is introduced to detect piston according to the
characters of the interference-diffraction patterns. Templates are made according to the parameters of the system.
One-dimension projecting production-moment correlation method and projecting central moment eigenvector method
are used in different conditions. The great advantage of this method is that there is no need of calibration so the
measurement error is reduced. The operation is simplified to reduce the computation complexity by three matching steps.
The measurement range is about um 25 ±um and the measurement error is less than 10nm. The experiment is carried out
on a platform. Piston is introduced to the parallel-light by a piston generator which is controlled by a PZT. CCD with the
pixel size 4.65um*4.65um is used to receive the image. The experiment result is basically consistent with the theory.
A novel image block matching algorithm based on motion vectors of correlative pixels in oblique direction is presented
for digital image stabilization. Digital image stabilization is the new generation of image stabilization technology which
can obtains the information of relative motion between frames of dynamic image sequences through the method of
digital image processing. The image matching algorithm is one of the digital image stabilization methods. But when the
grey values of pixels in the matching image block don't have obvious change or the shaking frame has rotational motion
with the referenced frame, the matching effect of the traditional algorithm is not ideal. The novel matching algorithm
calculated in 45 degrees oblique direction is presented. The matching parameters in this method contain transverse
vectors and vertical vectors in the image blocks at the same time. More veracious matching information can be obtained
after making correlative operation in the oblique direction. The novel method can make sure that matching precision can
be less than 0.5 pixels when the excursion value in shaking frame are 40 pixels. When the image sequences have
rotational motion less than 15 degree, the right matching blocks also can be obtained in this algorithm.
Not only could the segmented mirrors synthetic aperture optical system improve the sensitivity and
resolution of telescope system, but also meet the demands of NGST (next generation space
telescope).In order to ensure segmented mirrors keep the same optical performance of mono-mirror,
that is, the phase error less thanλ/20, each segmented mirror should have its own nano-grade high
precision correcting device. In this paper, the synthetic aperture is composed of three segmented
mirrors, one fixed and the other two adjustable, each of which achieved 6-DOF adjustment by three
micro-displacement actuators and the characters of the actuators are researched. For the purpose of
nano-grade positioning, PZT is used as the micro-displacement actuator. In our research, the jointing
process is rough-tuned by mechanical structure before fine-tuned by PZT, so there's no need for the
PZT to work in the full range. In order to provide basic support for nano-grade phase error correction, it
is very necessary to calibrate the relationship between the elongation distribution of each PZT and the
regulating voltage for each actuator, in its own scope of work with small step, because of the hysteresis
of PZT.
In segmented-mirror telescopes, wave-front discontinuities caused by segment misalignment are a major problem
because they severely degrade optical performance. So for segmented-mirror system, it's necessary to exactly acquire
position and gesture of each mirror. In this paper, Hough transform is used to obtain the edge of each segmented mirror,
and then each separated segmented can be solely processed. And a new method to calculate tilt, tip and piston of
spherical segmented mirror is given. This algorithm is based on the character of acclivitous spherical mirror which turns
around any axis in different position and different angle, so it is useful to obtain each spherical segmented mirror's
position and gesture. A mount which is allowed to do the segmented mirrors' tilt, tip and piston movement is designed.
With the FISBA phase shifting interferometer the phase of whole system can be obtained, and in the method proposed in
this paper tilt, tip and piston can be calculated to calibrate the spherical segmented-mirror system.
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