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一谈到窃听,人们就会想到安放在电话、饰物等物品内,被做成形态各异的电子窃听器,而绝对想像不出可以用光来搞窃听。实际上,在秘密战线上,光已经被利用制成间谍活动的窃听设备——激光窃听器。现在,有些国家的谍报机关都广泛应用激光窃听器对外国大使馆、领事馆及戒备森严的外事机构进行窃听活动。激光窃听器,就是用激光发生器产生的一束极细的红外激光,射到被窃听房间的玻璃上。当房间里有人谈话的时候,玻璃因受室内声音变化的影响而发生轻微的振动,从玻璃上反射回来的激光包含了室内声波振动信息。人们在室外一定的位置上,用专门的接收器接收,就能解调出声音信号,用耳机监听室内人的谈话。由于激光本质上是一种频率极纯、极高的电磁波,加上其方向性好,照射和反照射的能量集中,所以解调并不困难。解调反射激光的基本原理与收音机收听广播的原理是相似的。激光窃听法的最大优点是,不需要在窃听的房间里安装任何窃听器就可以实现窃听。这就克服了对无法进入房间安装窃听器的困难,同时也避免了因窃听器被查获而被抓住把柄的危险性。
When it comes to eavesdropping, people will think of placing them in telephones, accessories and other items and making electronic eavesdropping devices of different shapes, and absolutely can not imagine that they can use light to eavesdrop. In fact, on the secret front, light has been exploited to create a spyware eavesdropping device - a laser bug. At present, intelligence spying agencies in some countries widely employ laser bugging devices to eavesdrop on foreign embassies, consulates and heavily guarded foreign affairs agencies. Laser burglar, is a bunch of very thin infrared laser generated by the laser generator, eavesdropping on the glass was eavesdropping on the room. When someone in the room was talking, the glass vibrated slightly due to changes in the sound of the room. The laser light reflected from the glass contained information about the sonic vibration in the room. People in a certain outdoor position, with a special receiver to receive, you can demodulate the sound signal, with headphones listening to indoor conversation. As the laser is essentially a very pure frequency, high electromagnetic waves, coupled with its good direction, irradiation and anti-radiation energy concentration, so the demodulation is not difficult. The basic principle of demodulating reflected laser and radio listening to the principle of broadcasting is similar. The biggest advantage of the laser eavesdropping method is that eavesdropping can be achieved without installing any bug in the eavesdropping room. This overcomes the difficulty of not having access to the room, and also avoids the danger of grabbing the handle when it is seized.