In the early 1990s,verticality and linearity of the elevator guide rail were tested by suspending steel wire rope while their installation and inspection. But the detection of in -use guide rail was a difficult thing. The founders and leaders of the company Liu Hongyun and several optics experts decided to work on this problem unsolved worldwide for long. The technology of laser measurement is the ideal choice for measuring the elevator guiding rail, but they have two difficulties. First, the plumb benchmark cannot meet the high precision requirements. Second, the diffusion of laser beam can lead to errors. Based on literatture data and experimental results, the compensate technology of liquid double optical wedges and the creating technology of non-diffracting ring grating have been introduced for the first time into the fine instruments of laser measurement. In 1993, Dalian Lat Laser Technical Development Co.Ltd was set up in Dalian to follow the dream. Any of the products has its imperfection. Though JZC has been the mecessary instrument to elevator companoes, the manual identification and manual processing are not ideal for some users. LAT started to solve the problem of digital antomatic identification of laser spot center in long distance. There are disadvantages of Position-Seneitive Detector(PSD) that drift, small receiving area,short measuring distance and high price etc. And there is big error in fourquadrant photoelectric receiver sensor. Facing this situation, LAT innovation can only follow our own path.After five years of efforts, LAT worked out the digital identifying technology of laser ring grating and crisscross facula center, improving the precision from 0.2mm of human identifying to 0.005mm and greatly improving the speed of measurement. They have been successfully applied into JZC series products. Over the years LAT establishes the technology system with 3 core techniques, 4 invention patents and 13 independent intellectual properties.</p>