Study On Laser Scan Unit Based On ARM

Laser Scan Unit is one of the important parts of digital copier. It's the actuating element for image printout. Whether a copier has a high performance is partially determined by the operating efficiency of LSU. This thesis is aimed at designing a more available and stable LSU. Via a detailed analysis of RICOH 1045 Copier's LSU, a new controlling scheme based on the embedded operating system is proposed .The following are the primary work of this paper. At first, according to the LSU's requirements for control, Linux RTOS is transplanted to embedded system based on the control circuits of microchip S3C2440. Circumfusing the above system, a direct coupled differential circuit is designed for laser pulse modulation output. Furthermore in the design of circuit, a circuit simulation software PROTEUS is used for confirming the feasibility of the modulation model. Requirements for driving the six sided mirror is concluded through the analysis in the process of printout. Then a circuit for driving the brushless DC motor is designed based on the polygon mirror motor driver IC LB1875, which contains over-current and under-voltage protection. PWM signals for each phase are captured, which confirmed the feasibility of the design. An Incremental-PID feedback control algorithm is proposed based on the detailed analysis in the working features of semiconductor laser diode. Also, a hardware circuit is designed for feedback control based on the A/D converting with power measurement and the D/A converting with voltage feedback. In the aspect of the soft design, driver program is compiled under Linux embedded system for modulation circuit and brushless motor circuit. In the end of this thesis, a scheme for testing designed LSU is proposed based on the embedded system.