电梯投影仪，在使用过程中，需要判定电梯门的开和关。SK-Z-5激光测距传感器可以有效解决这个问题。
根据CTR数据显示，2017年第一季度-第三季度电梯电视（楼宇视频）月度刊例收入同比增长19.8%。楼宇广告实现价值回归，增速超过互联网营销（互联网广告增长率9.8%），成为推动行业增长的主要动力之一。
由此可见，电梯视频广告正在悄悄地获得消费者注意力。
According to CTR data, monthly revenue from elevator television(building video) in the first quarter of 2017 to the third quarter increased by 19.8 % year-on-year. The return of value to building advertising has outpaced Internet marketing(9.8 per cent growth rate of Internet advertising) and has become one of the main drivers of growth in the industry.
Thus, elevator video advertising is quietly gaining consumer attention.
但是电梯内空间有限，相较于在电梯内安装电视，电梯投影仪无疑成为更节省空间的方案。将电梯投影仪安装在电梯内最上方，通过监测电梯门开关，实时将广告投放到电梯门位置，无需利用额外空间。
However, the space in the elevator is limited. Compared with the installation of televisions in the elevator, the elevator projector has undoubtedly become a more space-saving solution. The elevator projector is installed at the top of the elevator and the advertisement is placed in the elevator door position in real time by monitoring the elevator door switch, without taking advantage of additional space.
需求分析：
1、当天梯们关闭，广告精准投放到电梯门位置；
2、有效判断电梯门开关时间节点，保证广告有效时长；
3、光源必须对人眼安全；
4、响应时间快；
