Features: Laser head move outward from center movement in the region of the Table-of-Contents, find location on the disk by emitting laser, induced resistance to accept to the reflected signal output into electronic data. Laser head is a the essential part of CD drive, and also is the most sophisticated part.It is mainly used for data reading, so take special care when cleaning drive inside. Laser head mainly includes laser generator (also known as laser diode), semi-reflective prism, objective lens, lens and photoelectric diode. When laser head reads the data on disc, the laser light from laser generator goes through semi-reflecting prism and converges on the objective lens; lens will make laser into extremely tiny points on CD. Because of the reflection material on the disc, light will reflect back, through the objective lens, then illuminate on semi-reflecting prism. Since prism is semi-reflecting, light beam can not goes through it completely, but reached the photo-diode through the lens. Due to the disc surface is uneven point to record data, so the reflected light will be in different directions; people define different direction of signal as "0" or "1", light-emitting diodes gets the data of "0", "1", and ultimately resolve them as the data we need. Specifications: Model: PVR-802W KHM430G Excitation Mode: Electric excitation Operation Mode : Continuous Wavelength Range: Visible light Length: 4.8cm/1.88in Weight: 20g(approx.) Package Includes: 1 x Laser Head .