||Liquid crystal display (LCD) device utilizes the change of the tilted angle of individual liquid crystal molecules, controlled by the applied voltage, to change the shape of index ellipsoid. Our research uses this change to control the relative phase shift of the incident wavefront and then the phase-modulated light produces a 3-D Fresnel image. |
The characteristics of every liquid crystal display, such as direction of extraordinary axis, twisted angle and tilted angle of liquid crystal, are generally different. At first, we utilize several lights of particular polarizations and particular wavelengths to determine all the above parameters. Then, we use these parameters to establish a phase shift versus gray level table. Finally, base upon this table, we draw a picture of size 1024x768 pixels on the LCD to modulate the phase of the incident light.
The LCD we use for our research is the type EPSON L3P10X, which can only produce relative phase change for incident wavefront up to 180 degree. Therefore, we use root-mean-square error to choose the proper range of phase modulation. Since our LCD can’t control the phase as well as the amplitude of incident wavefront simultaneously, we then adopt the method of one-dimensional zone plate to generate the desired 3-D image. By dividing the hologram plane into many sections and addressing proper information on each section, the distance of the 3-D image from the LCD device can be shortened. With a series of 3-D images of different viewing angles in hand, we then use “persistence of vision” to demonstrate the animation of a rotating cube.
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