Holographic Optics Tweezers Based On TFT-LCD

Optical tweezers is a technique of non-invasively trapping and manipulating micro-particles. It is an important implement of studying life process on molecular scale. Optical tweezers has vast application prospect in the fields of study and application which relate to micro-particles such as atmospheric physics, material science and precise measurement. It has now been one of the hot researching topics in new methods and instrumentation.The objective of this thesis is to fabricate a system of holographic tweezers based on TFT-LCD. We completed the system and applied it to the experiment of trapping yeast cell. The tweezers system based on TFT-LCD has advantages both in producing the light trap with an arbitrary distribution of light intensity and realizing satisfying manipulation of captured yeast cell. In contrast with using a 2D rotating mirror controlled by stepping ultrasonic motor or using a sound-optic deflector mirror, it is more convenient and rapid to control the trap's position in our tweezers system, and the cost of the system is reduced. This provides new means for the development of optical tweezers.The thesis introduces the origin, development and fundamental theory of the optical tweezers, and the theoretical calculation of optical trap force. It analyzes the optical characteristics of Liquid Crystal, its electro-optical effect and the configuration and working principle of the Liquid Crystal Display (LCD). The paper also studies the application of TFT-LCD in Computer-Generated Holograms (CGH), according to the theory of Fourier-CGH. Meanwhile, we measured the diffraction light intensity and analyzed the impact of incidence light polarization direction over diffraction light intensity. In this system, the transmittance of the CGH is maximal when there exists an angle of ninety five degrees between the incident beam's polarization direction and the erect direction and there is no polarimeter at the back of TFT-LCD. In this thesis, we have focused on the construction of a TFT-LCD system and give a detailed explanation on the principles of choosing apparatus. Here, the hollow trap is experimentally achieved by using diffraction on TFT-LCD when it is displaying the dislocation fringes. And the hollow trap can stably capture the yeast cell. Furthermore, the holographic optical tweezers is successfully achieved in experiment based on R-CGH-LCD (reconstruction of CGH based on TFT-LCD). And the holographic optical tweezers can easily manipulate the captured yeast cell.