Holographic Display Technology Based On The Liquid Crystal On Silicon Device

Holographic display technology is able to completely retain the object information, so that the human can see the scene more close to that in life without any wearable devices which can bring the visual fatigue. Therefore, holographic has increasingly become focus among scientific researchers, the perfect 3D display effect has made it an ideal scheme for 3D display.Recording and reproducing the light information are the two main parts in optical holography. Recording is a process that the interference fringes the object and reference light engendered on the hologram surface is exposed to the photosensitive material. Reproduction is the reconstruction of optical information. In this process, the optical system must be stable enough. High coherent coefficient between object light and reference light is also required to obtain a clear interference fringes. Those difficulties have made the holographic researchers turn the attention to computer generated hologram (CGH) gradually. In CGH, the construction and transmission of object light, along with the calculation of hologram’s transmissivity, are all accomplished by computer, so it can avoid all sorts of harsh requirements which can happen in optical holography. The traditional CGH is made on a film by controlling a plotter which obviously has the time-hysteresis quality, and once finished, the hologram material can’t be used again.With the invention of the spatial light modulator, the researchers no longer need to make a real hologram in holographic experiments, but just need to generate a digital image in accordance with the hologram’s transmissivity. So using the spatial light modulator to reproduce hologram is a good way to avoid the difficulties in the experiment of the wave-front recording and reconstruction.CGH requires mathematical description of objects, but for holographic recording of real object, the mathematical description can’t be measured directly. The high frequency characteristics of light makes the existing detecting instruments can’t directly obtain phase distribution, so using numerical iterative algorithm restricted by intensity information to obtain the light wave phase distribution has become one of the main thinking, and widely been applied to what in practice.In this paper, based on the theory analysis of the holographic, we combined the numerical iterative phase recovery algorithm with modified off-axis reference light CGH and provided a method to produce CGH for real objects. We also build the holographic display system with the core of LCOS to reproduce the object wave. Here are our main work and innovation points:1. Analyze the basic theory of holographic display. In optical holography, brief analysis was made for the basic realization principle of Fresnel hologram and phase hologram. In CGH, the production process and two typical coding methods including Roman detour phase coding and modified off axis reference light CGH are analyzed in detail. The computer programming simulation is also carried to generate hologram with method above.2. Expounded the basic concepts and parameters of spatial light modulator, and discussed the LCOS-SLM’s optical phase modulation theory, the pixel structure of LCOS, and simple introduced parameters and characteristic of our LCOS-SLM used in our study. Also, how to use the client software is explained in detail, and holographic display platform based on LCOS is built to reconstruct the object wave.3. Researched iterative phase recovery algorithms, including the GS algorithm, ER algorithm, multiplane iteration and other numerical iterative algorithm. A novel iterative algorithm with multiple pure phase modulations to obtain the phase information is analyzed in detail, and we also combined the numerical iterative algorithm with the modified off-axis reference light CGH——using the iterative phase recovery algorithm to obtain the mathematical description of the object and using the off-axis reference light CGH to generate the hologram. Finally, the object light is reconstructed on the holographic display platform as the core of LCOS.