LCOS-Based Optical Zoom System Research

The optical zoom system is widely used in many applications, such as target detection, video surveillance, electronic equipment, tracking, etc. In order to vary the magnification of the zoom system, the optical zoom system uses a mechanical zoom scheme to achieve the zoom function, where the relative position between the components of the multiple optical elements is regulated precisely and mechanically. However, in order to maintain the imaging plane stationary, the mechanical zoom system requires controlling precisely the relative movement between the lens components. The requirements on the mechanical construction of the zoom system and the degree of precision must be very high, which result in the shortcomings of system, such as large volume, high cost, slow response speed, etc. With the development of optical technology and electronic technology, non-mechanical modulation or active optical components (such as spatial light modulator) are introduced to the optical zoom system. As the result a novel optical zoom system could be build in small size, low cost, fast response, which has drawn an active attention in the current research and application.The liquid crystal spatial light modulator, as a novel active optical device, is currently the only one that can realize amplitude, frequency, phase and polarization state modulation on the real-time incident light wave. With the rapid development of LC technology, the electrically addressed liquid crystal device LCD is widely used as a display device for amplitude modulation, further, the liquid crystal spatial light device used for phase modulation and the associated application are also begun to attract attention. Liquid Crystal on Silicon (LCOS) is marriage of flat-panel display and silicon chip technology, so the benefit from both sides; especially in high-resolution and phase modulation have potential advantages. Combining calculating and the optics, phase modulation on the input light, can achieve the function of the digital lens. LCOS-based optical zoom system outperforms the mechanical optical zoom with the outstanding advantages, such as programmable, high-resolution, lightweight, small size, and low production cost.The work done and results gotten in the thesis are summarized as follows:1. According to the phase transformation principle of the lens, combining the LCOS phase modulation characteristics and computational LCOS thought, the calculation method of the digital lens based on LCOS is proposed to obtain the digital lens phase modulation pattern.2. An experimental verification system using valid LCOS is set up for testing digital lens features. The function of digital lens phase modulation is realized and verified by feeding the2D phase pattern to LCOS.3. The relationship between focal length and lateral magnification of the optical zoom system with digital lens focal length is discussed. Experimental verification using the laser light source and LED light source for LCOS optical device is carried out to verify the feasibility of this approach.It is proved that the work has achieved the function of the digital zoom lens.