一、引言俗话说:“百闻不如一见”,据有人估计,人从外界获得的知识60～80%是通过眼睛这一感官摄取的。可见,眼睛对人来说是多么重要。可惜,不管在空间上还是在时间上,人的眼力都是十分有限的。所以自古以来人们就渴望扩大眼界,提高视力。电视技术出现之后,使这种愿望逐渐得以实现。但是,大约在一个世纪之前,电视仍旧是渺茫而不可思议的,仿佛那只不过是魔术的王国。从19世纪70年代开始,才出现了一些较有科学根据的想法。随着电子技术的发展,逐渐使电视有了实际可能性。于是,进入了机械电视阶段。20世纪20年代,制作表演了无数精巧的机械扫描电视装置,涌现出一些电视台,提供了可视娱乐,与高度成功的声音广播电台展开了竞赛。但这种媒介对公众的吸引力仍旧 I. INTRODUCTION As the saying goes: “It is better to see everything in one hundred.” According to estimates, 60-80% of the knowledge people get from the outside world is absorbed through the eyes. Visible, how important it is to the eye. Unfortunately, people’s eyesight is very limited both in space and in time. So since ancient times, people are eager to expand their horizons and improve vision. After the advent of television technology, this desire was gradually realized. However, about a century ago, television was still slim and incredible, as if it was just a magic kingdom. Since the 1870s, there have been some more scientific-based ideas. With the development of electronic technology, there is a real possibility of television. So, entered the stage of mechanical television. In the 1920s, there were numerous incredibly sophisticated mechanical scanning television installations, some television stations emerged, visual entertainment provided, and contests with highly successful sound radio stations. However, this medium is still attractive to the public