VGA projection display using electromagnetically actuated steel micromirrors

Abstract

Projection display in VGA display format, which is 640x480 pixels in resolution, is aimed to be achieved using electromagnetically actuated steel micromirrors. In the work, the focus is the projection display control system but not the micromirrors. A projection control system, which is capable to control the actuation of the micromirror whose speci cations meet the VGA display format requirements, is designed, simulated and realized. The projection control system is capable to generate a superimposed current signal consisting of sinusoidal signal at frequency of 16 kHz and saw-tooth signal at frequency of 60 Hz and it can modulate the laser at frequency of 18.5 MHz to form an image in VGA resolution. Micromirror actuation is controlled by controlling the actuating electro-coil current. In order to control the coil current, linear closed loop current control technique with four-quadrant non-simultaneous complementary PWM switching is used. Simulation of the closed loop current control is done for signals in di erent waveforms and at di erent frequencies. Realization of the projection display control system is based on a digital signal controller. Closed loop current control algorithm runs on the digital signal controller. Modulation of the laser is also done with the digital signal controller. The steel micromirror used in the work does not meet the VGA display format requirements but it is the scanner whose performance is the closest to VGA requirements among the micromirrors we have. The fast scan frequency of the micromirror is 11271 Hz and the slow scan frequency is 285 Hz. The projection display control system is adjusted to work with this micromirror. Experiments were done with the control system and the micromirror. Images with 20x40 resolution in pixels were achieved as the results of the experiments.