2009 Vol. 2, No. 6
The NextView program initiated by the National Geospatial-intelligence Agency(NGA) was put forward in the background of the failure of Future Imagery Archtecture(FIA) plan. The NextView program contained two commercial optical remote satellites, namely, WorldView-1 and GeoEye-1. With the GSD resolutions of 0.5 m and 0.41 m, respectively, both of them are the first two commercial optical remote satellites with the highest resolution in the world. This paper introduces the working objects of the NextView program and describes the technical specifications and characteristics of the WorldView-1 and GeoEye-1. It also gives the working modes of two satellites. Finally, it predicts the developing tends of remote sensing satellites, and points out that the future optical remote satellites will be higher, faster, smaller, higher precision and more colorful.
The corner feature is the important feature of an image. The corner feature needs small calculated amount and can be matched easily. Moreover, the corner feature can keep the invariance after being rotated, translated or scaled. Therefore, it plays an important role in the application fields such as image registration and matching, object recognition, motion analysis and target tracking. A new method of vector matching based on the corner feature is presented in this paper. Firstly, a Harris operator is used to extract the corners of a target, and then the feature vector of the target comes out from the moment feature of corners. Finally, the match feature vector in the sequence images can be used to track the target. Using this method, more than 80% of corners in the normal condition and 70% of corners in the shelter conditions can be matched. Processing speed can achieve 20 frames/s to meet the real-time requirements. Experiment result shows that this method can effectively resist the deformation of the target, shelter and so on.
Using single-ring microresonators with loss to realize the light speed control encounters difficulties of heavy light loss and serious pulse distortion. Based on the symmetry between the transfer characteristics of resonators with loss and with gain, the transmission, group index, and group velocity dispersion of a single-ring microresonator are calculated and analyzed. The action mechanism of the loss and gain on the transfer characteristics of the micro-ring resonator is demonstrated. The light speed control behavior of the resonator with gain is calculated and compared with that of the resonator with loss. Calculation results indicate that the resonator with gain can produce the nonsplitted pulses with higher intensities and their pulse delay and pulse advancement are greater than those of the resonator with loss. These results show that the resonator with gain can be used to control the speed of light and to overcome the pulse loss and distortion in dissipative resonators.
In order to solve the problem of heat conduction of a solar simulation xenon lamp array used in a vacuum tank, a special heat conduction mechanism for xenon lamps is designed by using a heat pipe technology. The heat conduction ability of the cooling system is calculated, and the results indicate that the temperature change ΔT of liquid nitrogen cooling system is 2.074 1 K, lower than a super cooling temperature of 4 K, which points out that the liquid nitrogen cooling system can export the heat of solar simulation xenon lamp array out from the vacuum tank. A heat conduction mechanism is designed, and the finite element analysis is used to carry out thermal simulation analysis. The thermal simulation analysis results show that the temperatures for the anode and cathode of xenon lamp and the bulb of xenon lamp are about 100 ℃ and 655 ℃, respectively. Moreover, the temperatures of an optical integrator and mirror are both about 200 ℃ and the temperature of an ellipsoidal mirror is about 135 ℃, which meets the normal working conditions for a long period. The results obtained prove that the thermal design is feasible and reasonable.
It is not perfect to estimate the reliability of primary mirror supporting structures in space cameras based on the peak value of stress response at a random vibration environment. In accordance with the fracture of supporting structure in a random vibrating test, this paper presents an analysis method of vibration fatigue life to explore the reliability of primary mirror supporting structures, and uses a simulation technology to predict the fatigue lifespan of a supporting structure. Based on the theories of Finite Element Method and random vibration fatigue, the random vibrating fatigue life of the primary mirror supporting structure for a space camera is analyzed by an analysis software. The fatigue lifespan distribution of the whole body and the lifespan values of the most dangerous points are obtained. Experimental results indicate that the simulation results are consistent with the experimental data, which means the proposed method is feasible.
In order to obtain a high testing precision in the measurement of optical surfaces and focal length of a long focal length lens at the same time, the Computer-generated Holograms(CGH) method was presented by adding a diffractive optical element in the spherical optical path. Firstly, the optical surface test formula and the focal length test formula of the long focal length lens were derived, and the error of the focal length test formula was analyzed. In Zemax, the optical surface and focal length of a lens were tested with the CGH, which should be etched on a flat glass substrate, the PV value of the optical surfaces interference pattern is 0.003 4λ, and the test precision of the focal length is -0.11%. Finally, the influences of two errors on the test result were analyzed particularly, and the influence is no more than 0.1λ for the position error of the two optical elements and about 0.01λ for the fabrication error of CGH, where the radial position error is about 2 μm and the step error is about 5 nm. Considering the effects of all test errors, the test precision of the method can be controlled within 2λ/25.
With the aim to improve the measuring precision of a roll angle based on Moiré fringe method, the influence of inconsistent periods of two gratings on the measurement precision is analyzed. From the basic calculation formula of roll angle measurement based on the Moiré fringe method, the relation of inconsistent grating periods and measuring precision is discussed. It is pointed out that the grating score error and the unparallel planes of two gratings are the main factors to produce inconsistent grating periods, while the former is a more important reason. The experimental results show that when the ratio of equivalent periods of two gratings β and measuring range are less than 1.001 and ±15′; respectively, the measuring error caused by inconsistent periods can be controlled less than 1.6″ by choosing a grating period of 50 μm and the width ranges of Moiré fringe of 1 400-1 800 μm.
In order to meet the demands of a microcosmic particle observing camera for its optical system, a unique focusing mechanism driven by a ball screw in the linear movement was presented and the stress and strain of the focusing mechanism were analyzed by the Finite Element method(FEM) in accordance with its temperature and the static loads. Results show that the biggest strain is 0.001 mm under the static load，and 0.002 4 mm under the temperature load. The accessory error and the assembly error were analyzed, it is shown that the total comparative error is 2.2%. In the specimen experiment, the resolving power of 0.005 mm at each step and the average backlash error of 0.001 mm are obtained, respectively, which meets the need of the system.
A micro distance controller based on a Nios processor was designed to locate precisely for a visual indicator in virtual imaging equipment. By using a Field Programming Gate Array(FPGA) to realize the subdividing drive of Pulse Width Modulation(PWM) controller for a stepper motor and to implement the phase identification and frequency doubling of output signals of a grating sensor, the digital system of the micro-distance controller was constructed. With the design tool of Quartus II from Altera′s and an Embedded Design Suite Nios, the Nios processor and programming hardware circuits were integrated into one chip, so the system shows excellent flexibility and speediness from the parts of software and hardware. Experimental results indicate that the proposed micro distance controller achieves a good visual indicator position in virtual imaging equipment, and the controlling accuracy of micro distance can reach 2.5 μm.
With the aim to realise the transmission of the digital image information with a high-speed and real-time processsing and to reduce the amount of data of the storage, a new theory for image compression, Compressed Sensing(CS), is investigated to solve the problem. The concept of CS theory is introduced and a system for the optical image based on the CS theory is designed, and then it presents a new algorithm for rebuilding the image—Harmonic Orthogonal Matching Pursuit(HXOMP) algorithm. The corresponding numerical simulation and expremental results show that the imaging mechanism can capture the image and compress the data at the same time, and this method can also obtain good results of rebuilding images. Due to small amount of the data used, this method is very useful to transform images with a long distance.
In order to solve the problem of “Egg-Chichen Absurdity” in the rate control model H.264, this paper presents an algorithm which can express the coding complexity of current macro-block using the average prediction residual. Firstly, a more precise bit allocation scheme is implemented according to the coding complexity of each macro-block, and then the quantization parameters of macro-block are calculated using the improved quadratic Rate-Distortion(R-D) prediction model and R-D optimization is achieved. Finally, the coefficients of the rate control model have been updated. This algorithm is implemented in JM8.6, and the experimental results show that the proposed method can improve 0.165 kb/s than JVT-H017 in the control accuracy, and improve 0.13 dB in PSNR on the average at the same rate. It can be concluded that the proposed method can control the rate more accurately and can obtain a higher quality subjective vision.
An improved fast Bayer interpolation algorithm based on the Field Programming Gate Array(FPGA) was presented to solve the problems of a traditional bilinear Bayer color image restoration on edge blurring and lumps in images. With the algorithm， a gradient algorithm was used to restore the green channel and the color groups corresponding to pixels to restore the blue channel for a image. Experimental results indicate that the algorithm can offer a better visual effect of the images, and the Signal to Noise Ratios(SNRs) of RGB channels obtained from the proposed algorithm are all higher 5 dB than those of obtained from the bilinear algorithm. Moreover, the time-consuming of the algorithm is less than that of the bilinear algorithm, and a 512× 512 full color image can be processed in 9.3 ms. These results can meet the requirements of real time image processing and have higher application values.
A long wave infrared optical system was designed and developed by setting the system parameters based on the performance of a non-refrigeration focal-plane array(FPA) detector and by calculating the sizes and detection distances of an infrared weak target, and then the target detection for weak signals was realized successfully. This infrared optical system based a field of view in 6°×6° is implemented with the image space centrifugal path. Analysis and calculation results show that the optical system with two pieces of Ge-based diffraction optics has advantages of lower weight, higher energy transmission ability and good image quality. As compared with that of the three-piece spherical surface Ge-AMTIR1-Ge system, the weight of the system has lighted by 25% and the efficiency has improved by 7%. Moreover, the image quality has improved 50% than that of the traditional aspheric surface Ge-Ge method. These results show that the optical system has a wider application future in infrared weak target detection fields.
Infrared effects of created models in this paper are studied via sensor vision and sensor works modules in real-time 3-D emulational software named Vega. The principle of infrared simulation flow is introduced and the simulation results are presented, and then the infrared simulation flow is given. To improve the precision of simulation, some methods are given. In combination with the mapping mechanism of the Vega, a more precise radiation-grey mapping under a far infrared wavelength is presented, meanwhile, a more factual formula of reflectance calculation for materials is obtained by improving the mapping in TMM. Using the established sensor model, the radiation warp is reduced to 1.145%~3.358%. Furthermore, the Verification, Validation and Accreditation(VVA) of the simulation system are discussed, and the creditability of whole simulation process is evaluated, which provides some references for further researches of the simulation systems.
In consideration of the shortcomings of traditional laser micro-manipulators, a laser micro-manipulator with the reflection structure was designed to improve the quality and reliability of spots. By taking a He-Ne laser as its indication light beam and a CO2 laser as its working light beam, the repeatability and sizes of the two spots were optimized. Furthermore, using the multi-configuration of a ZEMAX, the adjustable performance of working distance was realized from 200 mm to 400 mm. By carring out the corresponding experiment, then the optical system chart, diffraction encircled energy diagram and the spot diagram were given. The experimental results show that the repeatability of spots and the uniformity, stability and reliability of beams are improved a lot. With the characteristics of its clear operational visual field and treated safety, the laser micromanipulator can be combined with the operation microscopy to meet the long-term use need of the treatment.