The space-borne remote sensor is the modern high performance astronautic detecting tool without limit of
domain. It has high ability on object finding and widely used in military and civil field. The image quality of space
remote sensor is often determined by its optical design, manufacture, system adjustment and etc... But on the other
hand, the space environment such as the vibration and shaking of satellite, the wind of solar and so on have heavy
influence on the quality of image. All these facts often result the jitter of the optical axis. And the jitter would
greatly decrease the image quality. In order to realize the diffraction resolution limit of optical design, an image
tracking system must be used in the space remote sensor. On the basis of previous study, a complete and systematic
analysis is conducted on the effect of jitter on the image quality of a push-broom camera. Compared the merit and
demerit of space based image tracking technology; the star image tracking system is suggested since the fast
detecting speed. The simulation test bed is designed and the experiments show that the centroid location
algorithm's precision achieves 0.1 CCD pixels in theory and 0.3 CCD pixels in this test bed.
Thermal distortion of the optical elements can greatly reduce the high resolution of the space-borne camera. The
general thermal effect on mirror is analyzed and the optical aberration of the optical surface resulting from 3 kinds of
thermal gradient is discussed. The thermal distortion simulating experiment of a large aperture flat mirror is designed and
the optical aberration is tested on 18" ZYGO with the different axial thermal disturb. The testing results conclude that the
small thermal gradient can greatly affect the wave-front, the aberration of this large aperture flat mirror can be used to
simulate the thermal distortion on space, and MTF is also reduced greatly when this large aperture flat mirror is used in
the real space-borne camera under the same thermal environment. In order to correct the thermal distortion and keep the
high resolution, the 37-units adaptive optics correction close loop experiment is designed and installed in the above
camera. The correction results show that MTF of the testing camera will not reduced greatly under the large thermal
distortion. So employing adaptive optics on a high resolution space camera is the necessary and the valid method to
The color appearance of an image is different from that of a uniform color patch because of spatial pattern effects. We have studied how the color appearance of square wave bars varies with stimulus strength and spatial frequency. The asymmetric matching method is used in the experiments, which means the color of uniform patch is adjusted by an observer to match the color appearance of the bars in square wave patterns. The square wave patterns have relatively low spatial frequencies of 1, 2, 4 and 8 cycles per degree (c p d). The area of a square wave pattern box only spreads a 2° field to the observers which means the matching is established mainly in the fovea. We find the matches are not colorimetric matches. The experiment data are analyzed and a conclusion that the cone contrast of the uniform patch is nearly proportional to the square wave stimulus strength is obtained, which reveal the property of color- homogeneity. Therefore the matches would have the basic properties of a linear system. In the article, all analyses are based on the opponent-color system. Precision of the experiments and some reasons about the data diversity are also discussed. The final conclusion suggests that the pattern separable mode could be used to predict the matches.
In general, the high precise color meter uses spectrophotometer to measure sample's reflection or transmission rate and then calculate all kinds of color parameters. About spectrophotometer, to design the monochrome parts is very important. At present, the spectrophotometer designed for color meter never use grating scanning but linear array sensors. Its advantage is greatly reducing the measuring time and making the miniature and portable instruments possible. This article will select the linear photodiode array as an example to discuss how the relationship among the wavelength ?, the grating parameter d, the incidence angle ?, the focus length f', and the number of sensitive cells n in the array. We will deduce the formula of them and calculate the theory results. At last we analyze the difference between the real results and the theory results, discuss some reasons and recommend some methods to improve the wavelength accuracy. These formula and methods will be very useful for spectrophotometer design based on linear array sensors.
Proc. SPIE. 4922, Color Science and Imaging Technologies
KEYWORDS: Image fusion, Visual process modeling, Spatial frequencies, Composites, Colorimetry, Visual system, Human vision and color perception, Modulation transfer functions, Contrast sensitivity, Color vision
There are lots of experimental results concerned with chromatic contrast detection (based on changes in chromatic distribution over space or time), but compared with luminance contrast detection, there has been no theory to describe chromatic contrast detection and thus no mathematic model for isoluminant contrast sensitivity function. After reviewing of many papers, two reasons may contribute to this: I . Isoluminant contrast sensitivity function has the same description method as the isochromatic contrast sensitivity function which is unfit to express the chromatic changes. 2. The color vision is so complicated that further study is needed. Based on detailed analysis of previous works, this paper utilizes colorimetry fundamental principle to present a new theory for color contrast detection, and indicates that isoluminant contrast sensitivity function can be described by two aspects of chromatic changes——dominant wavelength and colorimetric purity. This theory can well explain that red-green and yellow-blue contrast sensitivity functions have similar characteristics.
A mini adaptive optics system is developed in which a micro-machined membrane deformable mirror and the technique of cross-folded optical path are employed. The system has a volume of 30x20x10cm3, a weight of 4kg, while its bandwidth is 17Hz, and the accuracy of its wave-front sensor is ?/15 mis. The system is aimed at improving the image quality of space-based optical systems, but it is versatile. The control host is a PC computer, and various functions are realized, such as, real time display of image or wave-front, testing of the response matrix of the deformable mirror, and closed-loop control. An experimental system is also setup to test the performance ofthe AO system. The results of the experiments show that the AO system is very effective in compensation for thermal deformations and dynamic disturbances.