Study On The Realization Of The Scanning System In Laser TV

Laser TV system is a kind of TV that substitute the conventional Cathode-ray tube color TV with the laser displaying system. The red, green and blue lasers were used as the lamp-house, after video modulation and scanning, the TV picture was displayed on the screen. This technology is a new kind of TV display technology arose from the late 20th century. Owing to the potential scientific value and industrialization foreground, it has been drawn more interests of the scientists and TV companies over the world.This paper mostly focused on the scanning system in Laser TV. Adopted mechanical scanning mode, the polygonal mirror which driven by the direct current brushless electromotor was used to do the line scan, the galvanometer which driven by the step electromotor was used do the field scan. The paper gives the design parameters of the line and field scan system,and the analysis of the circuit design. By the scanning system designed, the TV picture was showed on the screen already.But as the mechanical scanning system was working, some scanning light lines were appeared on the TV picture. By analysis, we reckon that this is from the galvanometer's mechanical inertia. When the galvanometer was librating, the mechanical inertia resulted in that the odd and even field signals can't be inlaid equally. To solve this problem, the paper gives a design which changes the interleaved scan turning into single line scan. The SAA7111 was used to change the TV signals from analogy to digital mode, the digital TV signals were sent to the AL251 and changed from interleaved signal to the single line signal. After DA change, the single line signal is output from AL251 and modulates the tricolor laser. At the same time, the line synchronal signal's frequency was doubled and output from the AL251 to control the line scan motor. The SAA7111 and the AL251 were both controlled by the 89C51 microprocessor via I2C Bus. The paper gives the hardware design and the software flow Chart.