Miniaturization Of Laser Projection Display Based On Lissajous Scan Pattern

Pico laser projector is a great development trend of projection display in future, whichpossesses the advantages of laser technology and MEMS technology, such as excellentcolorperformance, high brightness, long life, small volume, light weight and low powerconsumption.According to the different methods of projection, pico laser projector is mainlydivided intoarray modulation mode and scan mode.Compared with the former, the latter couldprovide system more simple and compactstructure, which is very suitable for developing theportablepico laser projectoror being integrated into other electronic equipment.Therefore thepico laser projector based on scan modehas becomeresearch focus of micro laser projectiondisplay.In this paper, the miniaturization of laser projection display based on lissajous scanning wasfocused on and the projection theory was deeply researched. In order to realize QVGAresolution and higherrefresh ratethan30Hz, the scanning mirror, as the core element,wasdesigned and fabricated by using silicon-on-insulator (SOI) process. Then, the realizingtechniques of laser projector adopting the device sample were investigated.The specificresearch aspects are as follows:On the basis of lissajous motion, the principle of laser projection display based on lissajousscan pattern was analysed, and a number of techniques concerning the pixel definition,calculation of refresh rate and resolution, selection of operating frequency were studied indetail. Besides, an image processing algorithm was investigated to convert the storage style oftraditional image from raster mode to lissajous time mode, and the image conversion withQVGA resolution was successfully simulated by using this algorithm.A two-dimensional resonant scanning mirror employing electrostatic comb drives wasdesigned, and the relationship between structural parameters and operating frequency wasalso reaserched for determining the structure size according tothe requirement of laserprojector with QVGA resolution. In order to realize the performance of scanning mirror inaspects of optics, machinery and electric, a series ofimportant propertieswere analysedincluding electricalcharacteristics,nonlinear dynamics, impact properties, torsional properties,dynamic deformation and optical characteristics. According to the structural characteristics of resonant scanning mirror, the photolithographicmask was designed and the SOI machining process was investigated, analysed and furtheroptimized. Then, the scanning mirror was successfully fabricated and the sample was testedfor performance evaluation.The realizing techniques of laser projector adopting the device sample were investigatedincluding hardware and software. In order to increase the projected imagesize, the optical lenswas designed for enlarging the scanning angle. Finally, a prototype of laser projection basedon lissajous scan pattern was build and realize the projection with QVGA resolution, whichcould prove the correctness and feasibility ofthetheory on laser projection display discussed inthis paper.