HP Color LaserJet CM4730 Service Manual - Page 181

Laser/scanner system The laser/scanner system forms the latent electrostatic image on the photosensitive drum according to video signals sent from the formatter. The main components of each laser/scanner assembly are the laser driver, scanner motor, mirrors, and focusing lenses. Each color has its own laser/scanner assembly unit, which is controlled by the DC controller. Figure 4-13 Laser/scanner assembly The laser/scanner system uses two laser diodes in one scanning operation to write two lines simultaneously for high-speed laser scanning. The process is summarized below: 1. After receiving the print command from the formatter, the DC controller activates the scanner motor to rotate the six-faced scanner mirror. 2. When the scanner motor starts to rotate, the DC controller allows the laser to emit light and maintains the scanner motor rotation at a constant speed. 3. When the scanner motor reaches its specified speed, the formatter sends video signals to the laser driver PCB through the DC controller. The laser driver emits two laser diodes according to these signals. 4. The laser beams pass through the collimator lens and the cylindrical lens, and enter the sixfaced mirror that is rotating at a constant speed. ENWW Laser/scanner system 161