The image phase coherences (PCs) remain invariant when brightness and contrast changes. A new method of remote sensing image registration is proposed. PCs are firstly extracted from the reference image and the input image. In order to improve the registration efficiency, in the first step the PCs are firstly down-sampled using Gaussian pyramid method, and the coarse translation parameters are calculated using phase correlation. In the second step, Harris corners are detected from the two images, and normalized cross-correlation (NCC) function based on PCs is used to find the corresponding matching corners of the two images, and then obtain parameters of an alignment transform model. Experiments have demonstrated that the coarse-to-fine method can be successfully applied to multi-source images registration.
In this paper an accurate measurement method for optics system based on the lunar imaging is presented, and this method has the following steps. Firstly, the optical imaging system observes the lunar and acquires the image on the ground or in orbit, and records the position and the time simultaneously, with which the distance to the lunar can be computed. Secondly, the initial region of the lunar in the acquired image is decided by the gray value threshold, and the Canny edge detection method with parabola fitting is used to acquire the sub-pixel image edge points. Thirdly, the extracted edge points are used to preliminary fit the lunar disc, and the lunar ring is formed based on the fitted lunar disc expanded two pixels, then the initial coarse fitting disc is acquired according to the maximum number of edge points located in the lunar ring. Fourthly, the sub-pixel lunar disk can be obtained via the least squares fitting on the base of the initial coarse fitting disc. At last, the focal length of the optical imaging system can be computed with the position relationship between the optical imaging system and the lunar. Experiments show that this method has the ability to focal length measurement with high accuracy and frequency. By the means of imaging to the lunar, taking advantage of the long distance, sub-pixel edge detection and fitting for the lunar disc diameter, etc, whether in the full lunar and the waning lunar,the focal length could be measured accurately. It has a wide application prospects both in the developing and in orbit operating stage for optical imaging system.
This paper provides a relative radiometric calibration method based on the linear CCD imaging the same region of non-uniform scene, which makes full use of the ability of yaw angle control to ensure all the linear CCD detectors imaging the same scene. Firstly, when it is needed to perform the satellite relative radiometric calibration task, the initial drift angle will be calculated, according to which the yaw angle can be adjusted to ensure on-orbit satellite performing the calibration imaging mode, and in this mode the linear CCD and the satellite motion are in the approximate direction. Secondly, in calibration imaging process the yaw angle will be continuously adjusted to control the push-broom direction, and the linear CCD camera can be sequentially on the same region of non-uniform scene, which can obtain the remote-sensing image observing the same region with all the CCD detectors. Finally, after obtaining the same region image with the linear CCD camera, histogram matching method is used to establish the high-precision nonlinear relative radiometric calibration model, and this method overcomes the nonlinear response problem caused by the camera photon noise, the dark current noise. This method needs neither the on orbit calibration device, nor the ground uniform scaling field, and the general earth observation scene can meet the requirements. This method does not need a lot of on-orbit imaging data for statistical analysis compared with the statistical method, and each track is scaled to meet the conditions for calibration imaging, which avoids the unreliable problem of the calibration source itself caused by the unstable differences between the different tracks.
Multispectral camera is the principal payload in China's first hazards mitigation satellite, which is designed for hazards
monitoring, assessment, and management. However, the camera's dynamic range of scenery is not as wide as expected
and partly influences imaging quality on-orbit. This paper analyzed the reason of this phenomenon, discussed potential
solutions and proposed a strategy of on-orbit gain control. The key point of this strategy is to update the radiation
property of imaging area dynamically, to effectively narrow down the flux range and sufficiently employ system
capability of quantification. A case study on urban scene achieved gains for different latitudes and different seasons to
generate a lookup table. And the effect of the strategy was validated by simulation and comparison between before and
after use of the strategy. The result demonstrated that the strategy could effectively improve dynamic range and
imaging performance. This study can provide guidance for future camera design.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.