The high-resolution remote sensing camera has higher requirements on the optical axis stability. However, during the in-orbit operation, the main structure of the remote sensing camera and the attitude drift of the satellite will cause the optical axis to be unstable and cause the image quality declines. In this paper, an optical image stabilization system based on fast steering mirror is designed on the basis of a large-aperture high-resolution gaze-type remote sensing camera. The system divides the sub-field of view at the edge of the field of the remote sensing camera, installs the high frame rate and high sensitivity to the camera in the field of view, and then uses the related characteristic of the acquired image to measure the image and obtain the jitter information of the optical axis. Finally, the system will feedback the information to the control system to drive the fast steering mirror, in order to achieve the optical axis of the jitter compensation to ensure the optical axis stability.For the typical ground scene image, the system can improve the control precision and bandwidth by optimizing the image shift measurement algorithm and improving the calculation speed. In summary, the image stabilization system with high precision, high bandwidth and high success rate.
A dictionary-learning-based image denoising algorithm is proposed in this paper. Since traditional methods seldom take into account the rotational invariance of dictionaries learned from image patches, an improved K-means singular value decomposition algorithm is developed. In our method, the rotational version of atoms is introduced to greedily match the noisy image in a sparse coding procedure. On the other hand, in a dictionary learning procedure, to maximize the diversity of atoms, a rotational operation on the residual error is adopted such that the rotational correlation among atoms is reduced. As the strategy exploits the rotational invariance of atoms, more intrinsic features existing in image patches can be effectively extracted. Experiments illustrate that the proposed method can achieve a better performance than some other well-developed denoising methods.
For space remote sensors with high resolution, large caliber, and long focal length, in-orbit automatic focusing technique
is a significant application technology. Minimum image entropy (MIE) technology applied to real-time autofocusing
system of space optical remote sensor possesses creativity and engineering significance. MIE's theoretical analysis,
algorithm's computer simulation, and "Experimental Optical System" experiment have successfully validated MIE's
validity as the criterion for optical remote sensor's auto-focusing. Related data indicate that for a diffraction-limited
optical system with the f-ratio of F<sup>#</sup><i>=</i>39, the detecting sensitivity for checking-focus can be better than 0.1 mm, by means
To compensate the image motion caused by random atmospheric turbulence and mechanical vibration, a high
performance correlation tracker designed for the Space Solar Telescope (SST) has been realized in National
Astronomical Observatories. Correlation tracker is to stabilize the image and provide the stabilized objective to CCD.
The main optical telescope can obtain the highest spatial resolution and ensure the image processing. Tip-tilt mirror is the
crucial element of the correlation tracker. The lightweight mirror is to adapt to work normally with space using and
satisfy the space environmental requirement. Tip-tilt mirror's material is SiC. Confirming the appropriate joint with the
platform and supporting mode through Finite Element Method. Then calculating the surface shape quality value (RMS)
of the mirror effected by inertial load and temperature. The calculation results show that the tip-tilt mirror has enough
stiffness and intensity. The mirror's surface shape quality value can satisfy the optical requirement of the correlation
The novel remote sensor of the Space Solar Telescope (SST) is scheduled for launch in 2008. It will be uniquely designed to be the world’s first facility capable of observing with γ = 0.1" spatial resolution in vector magnetograms in the photosphere and the chromosphere, and 0.5" in soft X-rays. The high spatial resolution makes the on-orbit automatic focus (AF) the key technique to catch images. The paper brings forward a new method of the minimum entropy (ME) criterion for the astro-observation. Further more, we have applied such technology to the on-orbit AF of SST. The emulational program calculated the image entropies of different off-focus states. Data indicate that the minimum image entropy is corresponding to the optimal image plane; the ME criterion is more suitable for the heavenly bodies of low contrast and the focusing precision is 0.01 mm (δ' = 0.01mm).
A prototype of correlation tracker (CT) designed for the Space Solar Telescope (SST) has been realized in National Astronomical Observatories of CAS. We designed a special optical system for the development and test of the CT system. We estimate the image motion by cross-correlation method via FFT and take full advantage of the real-valued FFT to reduce the amount of calculation. For a possible realization of the processing unit used in space, we use a "1 bit correlation" method, which will greatly simplify the hardware implementation of FFT. A resolution of 0.01" has been obtained corresponding to the object space of the telescope, with the -3dB closed-loop error cutoff frequency of 38Hz along x axis and 40Hz along y-axis achieved.
The image motion in the focal plane of the Space Solar Telescope (SST) can be compensated essentially by means of a correlation tracker. The method is based on determining, in real time, the relative displacements between successive images ofgranulation, by means ofcorrelation techniques. This paper reports on a simulation system, which used to simulate the satellite attitude of the SST. An overview of the complete system including optical design, system analysis, etc. is shown together with preliminary results. Using this simulation system, we demonstrate the correlation tracker really work under the estimated satellite condition.