光无线局域网上行链路中的光束对准设计

Beam Pointing Design for the Uplink of Optical Wireless LANs

光链路是无线局域网安全性的物理层解决方案,其中上行链路为便携式终端设备设计的LD发射光束对准是关键问题之一。在Windows平台上展示了一种自动对准的软硬件控制方法,利用Windows中的Direct Show函数库,对激光光斑与目标的对准情况进行视频信号采集和图像识别,为简化识别算法,以蓝色为特征颜色并以一个特定的形状来标识对准目标,以650 nm红色LD为识别导向光束。使之位于红外传输光束中心位置左右,通过识别LD红色光斑与蓝色目标并判断它们之间偏差的方位和距离,将数据输出到下位机控制的微型云台,在二维方位上校准光斑与目标的偏差,同时通过红外LD实现了发送端到接收目标的光信号传输。

Optical link is a solution on the physical layer for the security of wireless local area network （WLAN）, where the beam pointing of the emitting laser diode （LD） designed for the portable terminals is one of the key problems. The present work demonstrates a set of software and hardware techniques for automatic pointing on the windows platform. The video acquisition of the status of the laser spot to the pointing target was performed by windows direct show library and thereby image recognition was carried out. To simplify the recognition algorithm, the pointing target is marked by the featured blue color and a specific shape, and a 650 nm red LD as the guiding beam, which was set around the center axis of the infrared transmission beam. The offset between the red spot and the blue target including orientation and distance was recognized, and the resulted data was output to the MCU controlling pan tilt run by two stepping motor to adjust their offset in 2-dimenssions. The optical signal transmission was achieved via the infrared LD＇ s beam from the sender to the receiving target.