Definition of laser:
"laser" is the transliteration of English laser in China, Taiwan Province Province and Hongkong. Laser is an acronym for stimulated emission amplification, which is translated as "laser" in Chinese mainland. Laser disc is a kind of movie disc. The recording and storage system of optical disc uses laser technology. Its principle is to cover the surface of a small-diameter optical disc with a metal film, burn a series of tiny pits on it with a laser beam, and store digital data in this way. The information on the magnetic tape is encoded and stored on the master disk, and then copied by molding. When reading information, low-intensity laser is emitted to the surface, and the reflected light signal (whether there are pits or not, the light received by the photodiode is different) is converted into digital information through the circuit, and then converted into analog information, which is displayed on the screen. Therefore, there is no chemical element radium on DVD, so it will not cause harm to human body.