| 摘要 |
A system and method for producing an eye safe laser communication system. The system and method detects an interfering object in the optical path and cuts off or reduces the power in the communication beam to safe levels. In one embodiment, a second laser diode transmitter and receiver is installed in each network node. The laser transmitter is pointed at a corresponding network node and the pulses travel in parallel with the communication beam. The pulses are reflected back to the transmitting node where they are detected. Their flight time is measured. When an interfering object is present, in one scenario, the pulses bounce of the interfering object and return to the receiver in the transmitting node, resulting in a reduced flight time. This reduced flight time is interpreted as an interfering object and the beam is shut down or reduced to a safe level. In a second scenario, the interfering object absorbs the detection beam. In another embodiment, a CCD camera is used to capture a reflection from an object in the path of the communication link. In this embodiment the CCD has an overlapping field of view with the communication transceiver's transmit laser. The laser's transmission beam forms a baseline pattern on the CCD. Any pixel to pixel variation from the baseline pattern indicates an interference, thus triggering the system to shut down or reduce the power of the communication link. Another embodiment uses retroreflection of the human eye to detect interference by the human eye and an optical magnification device. In this embodiment, a CCD is used to detect signals bent back by retroreflection of the human eye. When such a signal is detected, the link is immediately shut down. Another embodiment utilizes the communication link itself and a detector in the receiver to detect instantaneous power drops caused by an interfering object. When an interfering object is detected, the system shuts down or reduces the power of the communication beam to an eye safe level. |
