Bandgap tunability achievable using metamorphic epitaxy enables maximization of photodetector performance
at target wavelengths. However, an increase in threading dislocation density (TDD), which is inherent for the growth of
relaxed, lattice-mismatched layers, could offset this advantage and severely limit detector performance. In this regard,
we are investigating the performance of InxGa1-xAs and InzGa1-zP p-i-n photodetectors as a function of TDD, by utilizing
a number of different InxGa1-xAs buffer designs. In particular, internally lattice-matched metamorphic In0.20Ga0.80As and
In0.68Ga0.32P individual p-i-n detectors are studied to optimize the buffer design and performance of optically-aligned
In0.68Ga0.32P/In0.20Ga0.80As visible/near-infrared dual-photodetectors. Reverse-bias dark current density of In0.68Ga0.32P
detectors were found to be extremely sensitive to TDD compared to that observed for In0.20Ga0.80As detectors. Nearidentical
spectral response curves were obtained for both detectors as a function of TDD due to the relative insensitivity
of the p-i-n detector structure to the minority carrier lifetime. A comprehensive comparison between the different graded
buffer designs, TDD achieved and photodetector characteristics are presented.
A III-V/Si metamorphic epitaxy approach to achieve multi-junction solar cells having nearly ideal optical partitioning of
the solar spectrum is described. Following our previously-established methodology for the growth of defect-free GaP on
Si(100) substrates and demonstrations of heteroepitaxially integrated III-V-on-Si photovoltaics via GaAsyP1-y
metamorphic buffers, we discuss work undertaken on the further development and refinement of these processes and
materials, with the goal of minimization of threading dislocation densities in order to enable high-performance solar
cells. A substantial, non-trivial increase in growth temperature and general improvement of growth conditions and
designs has been achieved for both the heterovalent GaP/Si epitaxial integration process and the GaAsyP1-y compositional
grading. Improved dislocation glide and significantly more efficient epitaxial relaxation is found for the GaP/Si system,
while enhanced dislocation glide dynamics in the metamorphic GaAsyP1-y buffer system is demonstrated by the evolution
of new epitaxial tilt characteristics.
Image sequences is introduced and used to aircraft pose measurement, with the combination of gereralized
point photogrammetry theory and contour matching, image matching algorithm based on Hausdorff distance and
Generalized point is put forward, Generalized point theory error model is established. At first according to OpenGL
imaging mechanism photoelectric theodolite simulative imaging system is built to simulate aircraft image of different
flying pose, and actual image is regard as standard image to calculate aircraft pose initial value on known exterior
orientation parameters to drive simulative system to create image which is consistent with standard image contour, then
simulative and standard edge is extracted and difference of edges is measured, Hausdorff distance method is used to
adjust dynamically edge of simulative image to realize fast matching; Generalized point theory error model is used to
correct aircraft pose to advance accuracy of aircraft pose of image sequences. Simulative experiment of 3Km and 5Km
rocket pose of (45°,30°, 50°) is done, the result indicate the method is feasible and effective, the measurement
accuracy of aircraft pose after correction is better than previously and measurement accuracy of aircraft pose is less than
0.1°.
In order to meet requirement of real-time and high accuracy in image matching aided navigation, a fast and
effective algorithm of remote sensing image matching based on corner detection is put forward. With the combination of
rough and fine match, wavelet transform is used to acquire low frequency component to realize image compression to
decrease calculation work and increase matching speed. Harris corner detection algorithm is used to detect corner of
remote sensing image and template image and energy of every corner is calculated; SSDA algorithm is used to match
remote sensing image and template image coarsely, when the matching result is bigger than one to count absolute value
sum of energy difference of characteristic point energy to realize fine match of remote sensing image and template image
to locate the position of template image in remote sensing image accurately. Simulation experiment proves that the
matching of a remote sensing image resolution of 1018*1530 and a template image resolution of 150*90 can be fulfilled
within 2.392 second, the algorithm is robust and effective, real time image navigation can be achieved.
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