An experiment is designed to validate the visible imaging system′ s performance through analyzing the effects of resolution, contrast and the illumination. The effective targets at a distance of about 4.5 km are tested instead of 20 km. Under conditions of 11 km visibility, the equivalent detection range is figured out by means of contrast and illumination. If the target′ s illumination is not less than 300 lux, the system can identify the target with 0.253 contrast, but it is not sure when the contrast is between 0.2 and 0.253. With special image processing, the result is significantly improved. Experimental results show that the system′ s performance can meet the special requirements.
Direct wavefront gradient algorithm directly establishes correspondence between measurands of the wavefront sensor and response characteristics of the deformable mirror. The voltage can be directly calculated by the algorithm. We use Hartmann wavefront sensor with 64 sub-apertures to detect the distorted wavefront. Based on the hypothesis that of deformable mirror is the weighted addition of the influence function, each of the voltage values applied on the drive is solved by the algorithm. The simulated 32 units of deformable mirror can be controlled and then distorted wavefront can be restored. The simulation result shows that direct wavefront gradient algorithm can effectively adjust the distorted wavefronts.
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