Geiger-mode Avalanche Photo Diode(Gm-APD) Ladar is a probabilistic device outputting three dimensional(3D) images based on the multi-frame imaging statistics, which makes the 3D recovery algorithm one of the key techniques of imaging system. Besides, performance of algorithm plays a crucial role in improving recovery quality of 3D images. This paper researches three 3D algorithms based on histograms, containing peak-selecting algorithm, range-selecting algorithm and Gaussian fitting algorithm. Firstly, the triggered model of Gm-APD is analyzed based on the work timing sequence and imaging theory of Gm-APD Ladar. Meanwhile, the recovery principles of three algorithms are analyzed and clarified. Secondly, two evaluation criterions, average range error and accuracy of range recovery, are raised to evaluate range accuracy. Finally, range images are obtained with above three algorithms in statistics of different frames, based on original data obtained from 64 × 64 Gm-APD Ladar imaging experiment. With the three construction algorithms, the result shows that the range accuracy of recovery range images improves and converges to 0.2~0.3m with the increment of number of frames participating in the statistics, and the accuracy of range recovery can be up to 90%. In low frame numbers, the range accuracy of recovery range profile is worst with peak-selecting algorithm, and the average range error with rangeselecting algorithm performs best while accuracy of range recovery with Gaussian fitting algorithm is highest among all algorithms. The result has important guiding significance for the choice of recovery algorithm under different requests.
To solve the geometric distortion problem of large FOV linear array whiskbroom image, a model of multi center central
projection collinearity equation was founded considering its whiskbroom and linear CCD imaging feature, and the
principle of distortion was analyzed. Based on the rectification method with POS, we introduced the angular position
sensor data of the servo system, and restored the geometric imaging process exactly. An indirect rectification scheme
aiming at linear array imaging with best scanline searching method was adopted, matrixes for calculating the exterior
orientation elements was redesigned. We improved two iterative algorithms for this device, and did comparison and
analysis. The rectification for the images of airborne imaging experiment showed ideal effect.
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