For Theoretical And Experimental Study Of The Polarization Optics Devices Lcos Projectors

Chapter 1 gives a brief review of the thesis. This thesis mainly discusses the devices based on crystal optics and polarization,which includes Polarization Interference Filter (PIF) used in the separation and combination systems of LCOS,achromatic wave plates based on the similar principal of PIF and the crystal polarization beam splitter.Chapter 2 reviews the properties of birefringent crystals. They are basic foundations of this thesis because PIF,achromatic wave plates and polarization beam splitter have indivisible relationship with the properties of birefringent crystals.Chapter 3 introduces the theory of PIF. PIF is composed of two polarizers and a series of birefringent crystals between them. When light travels through this system perpendicularly,the light after the first polarizer will divide into orthogonally polarized ordinary and extraordinary impulses. Because of the difference between the extraordinary and ordinary indices of refraction of the crystal,after passing the crystal,the two orthogonally polarized impulses will be different in phase. Later in the second polarizer,the light will again project to the transmission direction of the polarizer and interfere with each other. Because the thickness is uniform in every crystal,the value of the difference of phases is only determined by the wavelength. Specifically,the interference strengthens the magnitudes in some wavelengths,thus the color of that wavelength will be displayed;on the contrart,in other wavelengths,the interference attenuates the magnitudes,thus the color of that wavelength will disappear.Chapter 4 uses optimization methods to figure out the orientations of the crystals. Using the phenomenon presented in Chapter 3,our aim now is to find out the orientations of the crystals so that the combination of these crystals will have an output of certain distribution in the wavelength domain. In realizing this,two important factors must be determined:the thickness of the crystals and the orientations of the crystals. Concerning the first factor,our aim is to let the desired curve 'travel through' our considered wavelength domain. In regard to the second factor,we use genetic algorithm (GA) and conjugate gradient method (CG) to obtain the orientations of the crystals.Chapter 5 presents the experimental setup of PIF and considers related errors. The first important thing in experiment is the material we choose. We use quartz and stretched polymer retarder sheets in our experiment. Secondly,we should consider the dispersion of the material to redesign the PIF because dispersion will move the filtering curve in spectrum domain. Moreover,we should find ways to calibrate the thickness and orientations of the birefringent crystals precisely.Chapter 6 discusses the designing method of achromatic wave plates,which is an expansion of the design method of PIF. The differences between achromatic wave plates and PIF include:- that the achromatic wave plates do not have the polarizers and the desired function. The objective of PIF is to realize a certain distribution of interference spectrum,while that of the achromatic wave plate is to realize the retardation by using several crystals to modulate the input beam. Despite of those differences,their basic things are the same:through modifying the length and orientations of crystals to modulate the input beam so as to realize certain kind of complex amplitude distribution. As the experimental realization of achromatic wave plates is somewhat the same as that of PIF,this thesis will not discuss it.Chapter 7 gives a brief conclusion to this thesis and predicts room to improve the design and fields to apply this design.