Wide-angle Lighting Rainbow Hologram

Researches on making rainbow holograms with large illumination angles and applying such holograms to compact display systems are presented in the essay.Theoretical analysis shows that rainbow holograms have least image blur compared with other kinds of holograms when illumination angles are very large. So rainbow holograms are adopted in the research. The parameters used in the hologram recording geometry are calculated and applied to the experiments. The experimental results meet the expected effects made by the theoretical design.The experimental data and theoretical analysis verify that harmful interference fringes in the holograms with large illumination angles are fringes of equal inclination, which are generated by irradiating an divergent beam to a parallel plate. According to the fringe formation mechanism and the factors which affect the fringe interval and contrast, three methods have been developed to eliminate such fringes in rainbow hologram recording: 1 .let the glass side of the recording plate face the reference beam; 2. Attach a piece of black paper on the surface of glass substrate of the recording plate; 3 .Use collimated reference beam for recording. Each method has its own advantages and shortcomings and can be selected according to the application situation. The harmful interference fringes are effectively eliminated by use of these methods so that the quality of the hologram is greatly improved.High quality rainbow holograms with large illumination angles have been used in making holographic palace lanterns and table lamps. Good viewing effects have been achieved---tlie holographic images are clear and colorful, and there is almost no impact of harmful fringes on the holograms.Three step rainbow hologram recording process was adopted forfurther improving the quality of the holograms illuminated by divergent light sources very close to the edges of the holograms. A compact hologram display system has been obtained by assembling the hologram and the light source in the same unit. The reconstructed holographic image is clear, without distortion, which fulfils the objective of the research project.