针对实时视觉通信的图像序列自动提炼

本文提出了一项新技术,它可以实现从任意的图像序列中自动提炼出简洁的表达方式,以便进行高效的视觉通信.我们认为,视觉通信的全过程可分为视频数据的传输和人眼对视觉信号的理解两个阶段.因此,本文以心理学中人对图像的认知规律的相火理论为指导,专注于研究如何同时提高图像的可压缩性和可理解性.我们借助一个缘提取算法来保留对人的视觉系统最为敏感的物体边界,再用一个非线性扩散算法减弱无足轻重的细节信号.为了使最终生成的动画保持时间上的一致性,本文的技术方案是在骼个时空域上没计的.而我们依然能够保持实时的处理速度,因为该方法可以方便地使用GPU作并行计算.为了演示新技术的实用性,我们还建立了一个以本文算法作为处理内核的完整的视觉通信系统并在该系统进行所有实验.统计数据表明,本文方法不仅可以明显地降低传输带宽,而且提高了图像序列的可理解性.

Measurement of the wavefront of a laser diode system for intersatellite communication by a Jamin double-shearing interferometer

The frame of a laser diode transmitter for intersatellite communication is concisely introduced. A simple, novel and visual method for measuring the diffraction-limited wavefront of the transmitter by a Jamin double-shearing interferometer is proposed. To verify the validity of the measurement, the far-field divergence of beam is additionally rigorously analysed in terms of the Fraunhofer diffraction. The measurement, the necessary analyses and discussion are given in detail. By directly measuring the fringe widths and quantitatively interpreting the interference fringes, the minimum detectable wavefront height (DWH) of the wavefront is only 0.2 gimel (the distance between the perfect plane wavefront and the actual wavefront at the transmitting aperture) and the corresponding divergence is only 65.84 mu rad. This indicates that the wavefront approaches the diffraction-limited condition. The results show that this interferometer is a powerful tool for testing the semiconductor laser beam's wavefront, especially the diffraction-limited wavefront.