In order to solve the problem of push-broom optical camera’s imagery quality difficult to content request which windows size is too large, the author proposed a kind of project for camera’s following windows. The author analysed the characteristic of the push-broom optical camera’s windows, and proposed the ideal model of the push-broom optical camera’s windows. Simultaneously, analyzed the transformational rule of the windows’ location and size in the ideal condition. The author proposed the design project of the push-broom optical camera’s following windows according to the result of the ideal windows’ analysis, and performed an analysis of kinematics simultaneously. Finally, the author designed and analyzed kinematics for the following windows in allusion to a certain push-broom optical camera. According the analysis result, this project could decrease a half size of the light opening area compare with the current technique. It could decrease the stray light’s influence of the camera’s imagery quality, the following windows move smoothly, and this project could be satisfied to the requirements of engineering use.
A imaging system of area-array CCD cameras based on FPGA was designed. The overall structure and design of the system was introduced in detail. According to the working mode and driving timing requirements of this CCD image sensor, the driving schedule under the control of FPGA was designed. The working mode and parameters of such an imaging system were aligned with the control signals in accordance with the general requirements of space CCD cameras. With FPGA device as the platform of hardware design, the hardware of integrated timing and control system was described in VHDL language. The A/D converter AD9945 based on the correlated double sampling was used to realize the analog-digital (A/D) conversion of ICX285AL output signals. The XQR2V3000-4CG717V developed by Xilinx was chosen to accomplish the design of this hardware circuit. Through simulation, the correctness of driving schedule was verified, thus preparing necessary hardware for the final development of space area-array CCD cameras with high performance.
The optical system of lunar rover navigation camera has a direct influence on imaging quality, and an indirect influence on the programming of march forward of lunar rover. One type of lunar rover navigation camera optical system with the symmetrical structure was introduced. It also set up the suitable position of stop to achieve the relative distortion lower than 0.053 percent under the 60 degrees wide field-of-view. It applied the hyperfocal distance principle to achieve the clear imaging from 0.5 meter to infinity. The modulation transfer function is close to diffraction limit at the Nyquist frequency (at standard object distance). Considering the complicate environment of lunar surface and the demand of exploration, it selected the appropriate work spectral coverage and was cooperated by the irradiation reinforce. As a result, it can bear 1×10<sup>4</sup> Rad (Si) space irradiation and is capable of keeping working normally in the severe environment with its temperature varying from -60°C to + 90°C.
An automatic seamless image mosaic method based on SIFT features is proposed. First a scale-invariant feature extracting algorithm SIFT is used for feature extraction and matching, which gains sub-pixel precision for features extraction. Then, the transforming matrix H is computed with improved PROSAC algorithm , compared with RANSAC algorithm, the calculate efficiency is advanced, and the number of the inliers are more. Then the transforming matrix H is purify with LM algorithm. And finally image mosaic is completed with smoothing algorithm. The method implements automatically and avoids the disadvantages of traditional image mosaic method under different scale and illumination conditions. Experimental results show the image mosaic effect is wonderful and the algorithm is stable very much. It is high valuable in practice.
Development of the next generation star sensor is tending to miniaturization, low cost and low power consumption, so the imaging system based on FPGA in the past could not meet its developing requirements. A novel design of digital imaging system is discussed in this paper. Combined with the MT9P031 CMOS image sensor’s timing sequence and working mode, the sensor driving circuit and image data memory circuit were implemented with the main control unit TMS320DM3730. In order to make the hardware system has the advantage of small size and light weight, the hardware adopted miniaturization design. The software simulation and experimental results demonstrated that the designed imaging system was reasonable, the function of tunable integration time and selectable window readout modes were realized. The communication with computer was exact. The system has the advantage of the powerful image processing, small-size, compact, stable, reliable and low power consumption. The whole system volume is 40 mm *40 mm *40mm,the system weight is 105g, the system power consumption is lower than 1w. This design provided a feasible solution for the realization of the subminiature star sensor’s imaging system.
In recent years, a novel optical zooming technique has been paid much attention. With the help of optical leveraging effect, it is possible to alter the system focal length dramatically without moving elements involved in by only changing the curvature radius of VCM (variable curvature mirror) slightly. With no doubt, VCM is the key to realize non-moving element optical zooming and it has to provide large enough saggitus variation while still maintaining the high surface figure accuracy to ensure high quality imaging. In our previously published paper, an annular force based VCM has been designed, fabricated and tested. Experiments demonstrate that with the aperture of 100mm and thickness of 2mm, the VCM could generate a large saggitus variation exceeding 30λ (λ=632.8nm). However, the optical quality degrades very fast and this makes such a VCM unsuitable for optical imaging in visible band. Therefore in this manuscript, a multipoint actuation array, which is composed of totally 49 piezoelectric actuators, is embedded into the annular structure to aim to correct the surface figure distortion caused by large saggitus variation. The new structure model has been designed and numerical simulation indicates that the surface figure distortion could be well corrected as long as the degraded surface figure accuracy is better than 1.8λ (λ=632.8nm) (RMS). Based on this, a new prototype VCM is being fabricated and intermediate results are reported here.
In order to realize real-time signal identification and processing of spatial transient light, the features and the energy of the captured target light signal are first described and quantitatively calculated. Considering that the transient light signal has random occurrence, a short duration and an evident beginning and ending, a photodiode detector based spatial transient light detection and processing system is proposed and designed in this paper. This system has a large field of view and is used to realize non-imaging energy detection of random, transient and weak point target under complex background of spatial environment. Weak signal extraction under strong background is difficult. In this paper, considering that the background signal changes slowly and the target signal changes quickly, filter is adopted for signal’s background subtraction. A variable speed sampling is realized by the way of sampling data points with a gradually increased interval. The two dilemmas that real-time processing of large amount of data and power consumption required by the large amount of data needed to be stored are solved. The test results with self-made simulative signal demonstrate the effectiveness of the design scheme. The practical system could be operated reliably. The detection and processing of the target signal under the strong sunlight background was realized. The results indicate that the system can realize real-time detection of target signal’s characteristic waveform and monitor the system working parameters. The prototype design could be used in a variety of engineering applications.
Zoom mirror is a kind of active optical component that can change its curvature radius dynamically. Normally, zoom mirror is used to correct the defocus and spherical aberration caused by thermal lens effect to improve the beam quality of high power solid-state laser since that component was invented. Recently, the probable application of zoom mirror in realizing non-moving element optical zoom imaging in visible band has been paid much attention. With the help of optical leveraging effect, the slightly changed local optical power caused by curvature variation of zoom mirror could be amplified to generate a great alteration of system focal length without moving elements involved in, but in this application the shorter working wavelength and higher surface figure accuracy requirement make the design and fabrication of such a zoom mirror more difficult. Therefore, the key to realize non-moving element optical zoom imaging in visible band lies in zoom mirror which could provide a large enough saggitus variation while still maintaining a high enough surface figure. Although the annular force based actuation could deform a super-thin mirror having a constant thickness to generate curvature variation, it is quite difficult to maintain a high enough surface figure accuracy and this phenomenon becomes even worse when the diameter and the radius-thickness ratio become bigger. In this manuscript, by combing the pressurization based actuation with a variable thickness mirror design, the purpose of obtaining large saggitus variation and maintaining quite good surface figure accuracy at the same time could be achieved. A prototype zoom mirror with diameter of 120mm and central thickness of 8mm is designed, fabricated and tested. Experimental results demonstrate that the zoom mirror having an initial surface figure accuracy superior to 1/50λ could provide at least 21um saggitus variation and after finishing the curvature variation its surface figure accuracy could still be superior to 1/20λ, which proves that the effectiveness of the theoretical design.
To binocular camera, the consistency of optical parameters of the left and the right optical system is an important factor that will influence the overall imaging consistency. In conventional testing procedure of optical system, there lacks specifications suitable for evaluating imaging consistency. In this paper, considering the special requirements of binocular optical imaging system, a method used to measure the imaging consistency of binocular camera is presented. Based on this method, a measurement system which is composed of an integrating sphere, a rotary table and a CMOS camera has been established. First, let the left and the right optical system capture images in normal exposure time under the same condition. Second, a contour image is obtained based on the multiple threshold segmentation result and the boundary is determined using the slope of contour lines near the pseudo-contour line. Third, the constraint of gray level based on the corresponding coordinates of left-right images is established and the imaging consistency could be evaluated through standard deviation σ of the imaging grayscale difference D (x, y) between the left and right optical system. The experiments demonstrate that the method is suitable for carrying out the imaging consistency testing for binocular camera. When the standard deviation 3σ distribution of imaging gray difference D (x, y) between the left and right optical system of the binocular camera does not exceed 5%, it is believed that the design requirements have been achieved. This method could be used effectively and paves the way for the imaging consistency testing of the binocular camera.
High accuracy star map identification results are the basis of astronomical positioning. The traditional triangle star identification algorithm has a higher redundancy and a poor robustness to noise. Considering the specific requirements of the star map identification of the astronomical camera, in allusion to this default, proceeding with selection of guide stars, construction of guide star catalogue and realization of matching algorithm, a modified triangle algorithm based on traditional one is presented. With the proposed algorithm, the guide star is selected from astronomical durchmusterung. In order to speed up guide star indexing, the guide star catalogue is founded after dividing the sky using the overlapping rectangle method. The guide star sub-catalogue is constructed by the radius of guide triangle circumcircle and the two sides of guide triangle. The characteristic radius is used for indexing and sorted in an ascending order to improve the searching efficiency in the processing of star map identification. The matching scope of the angular distance is narrowed and the matching rate of angular distance is improved by the matching of the characteristics radius. If there exists redundancy, a normalized magnitude is used to eliminate it. Within the observing area of the real sky, the 1050 star maps continuously are calculated. The simulation results show that, the identification rate of this algorithm is greater than 97. 83% when the noise of position error is two pixels, and the average identification time is about 25. 07ms. Compared with the traditional triangle algorithm, this modified algorithm has a couple of advantages, including the smaller storage capacity of guide star catalogue, better robustness to position and magnitude error, higher rate of correcting star map identification and lower redundancy.
Space sensors are used in navigation sensor fields. The sun, the earth, the moon and other planets are used as frame of reference to obtain stellar position coordinates, and then to control the attitude of an aircraft. Being the “eyes” of the space sensors, Optical sensor system makes images of the infinite far stars and other celestial bodies. It directly affects measurement accuracy of the space sensor, indirectly affecting the data updating rate. Star sensor technology is the pilot for Space sensors. At present more and more attention is paid on all-day star sensor technology. By day and night measurements of the stars, the aircraft’s attitude in the inertial coordinate system can be provided. Facing the requirements of ultra-high-precision, large field of view, wide spectral range, long life and high reliability, multi-functional optical system, we integration, integration optical sensors will be future space technology trends. In the meantime, optical technologies for space-sensitive research leads to the development of ultra-precision optical processing, optical and precision test machine alignment technology. It also promotes the development of long-life optical materials and applications. We have achieved such absolute distortion better than ±1um, Space life of at least 15years of space-sensitive optical system.