Research On Holographic Screen Fabricated With 2D Hexagonal Lattice Pattern

Techniques of 3-dimensional (3D) display have attracted many investigations around the world. Among various investigations, fabrication of the screens content for 3D color image projection has key importance. In the researches of screen fabrication, holographic screens show distinct advantages of high transparency, high image brightness and contrast, and low fabrication cost. An ideal screen must also provide large viewing zone and be able to display color images. However, so far, reported holographic screens have very small viewing zone and can only display single-color images.This dissertation presents the investigation of a novel holographic screen with 2-dimensional (2D) hexagonal periodic structure. Theoretical analysis and experiments on screen fabrication and applications are described in detail. The screen is fabricated with 3-beam interference holographic approach. In the optical system for screen fabrication, a holographic optical element (HOE), which had been specially designed and fabricated, was adopted. The HOE contains three identical gratings with 120o between each other. Under the illumination of an expanded and collimated laser beam, three first-order diffracted beams of the three gratings interfere, forming a 2D hexagonal lattice pattern. The pattern was recorded in photoresist with small size then used as the template to produce large-size plastic screen via hot-embossing method. The whole screen fabrication process is rapid, manageable and with low cost. Because 2D hexagonal structure has multiple diffraction orders spreading in two dimensions, the images projected on the screen can be observed with large viewing angle so that many people can view the image simultaniously. Theoretical analysis indicates that the screen with larger lattice periods is possible to provide larger viewing angle and brighter image.Two screens with different periods were fabricated for comparison. 3D holographic image and 3D color image were projected on the screens respectively to test the display effects of the screens. Images with large viewing angle and true-color have been observed on both screens. Experimental results demonstrate that for transmission-viewed image the screen with larger period has 65o viewing angle, 10o larger than that with smaller period, and can display brighter image.The image brightness and 3D effect of the screen still need improvement before such screen can be practically used. At the end of the dissertation, the existing problems of the project are pointed out and the suggestions for further work are proposed.