Optical Systems Of Novel Holographic Sight-Design And Fabrication

Holographic sight is a new type of aiming device developed at the end of the 20^th century. Holographic, electronic and mechanical techniques are adopted to fabricate holographic sights. Through certain combination of the optical, electronic and mechanical components, the aiming target and the reproduced reticle pattern can be observed at the same time from a holographic sight, realizing precise aiming. Holographic sights are widely used for military and shooting competitions, due to their advantages of high aiming speed and precision, wide vision field, and concealing capability. However, presently the designs of such device, both at home and abroad, use traditional optical elements to realize collimating and deflection functions, which leads to complexity of the device and high cost in manufacture. To achieve compact and low-cost holographic sights, the thesis proposes a new design that uses holographic optical elements as the key components. Due to their advantages of good performances, lightweight, low cost, simple production processes and the capability of integrating several optical functions, holographic optical elements play a role that can not be replaced by ordinary optical ones. In the project, using holographic optical elements as the main components in the optical system was studied. Two kinds of design, including a reflection system and a transmission system, were implemented. The prototype of the sight based on the design has been produced. The experimental results demonstrate that the prototype has the advantages of simplicity and compactness in construction, low cost and advanced performances. In the thesis the thorough study of the fabrication of holographic sight is presented, including design of the optical system, theoretical analysis and experimental schemes. The main research works and results of the thesis are as follows:1. The merits and short comings of the existing sights made home and abroad are analyzed. The utilization of a holographic matching filter as the key element in the optical system of the sight is proposed. Two kinds of optical systems, including reflection and transmission systems, are designed. The proposed holographic matching filter has the functions of filtering, matching, collimating and deflection, thus forming the optical system with the advantages of simplicity, compactness and low cost, and at the same time achieving advanced performances.2. To solve the problem of reproduced image deviation caused by fluctuation of the wavelength of the laser diode, the system consisting of bi-holographic optical elements is proposed. The validity of the system to eliminate the image deviation caused by fluctuation of the wavelength has been proved by both theoretical analyses and experimental results.3. Aberration compensation theory is used to analyze the spacial frequency and position of the hologram and the holographic matching filter. The result indicates that the two elements must be positioned in parallel and the illuminating light beam must be collimated so as to compensate the drift of the wavelength. Concerning the relation between the hologram and the holographic matching filter, as well as the designed optical system, the parameters in the optical setups for recording hologram and holographic matching filter are theoretically analyzed.4. The diffraction efficiency of holographic optical elements is analyzed using rigorous coupled-wave theory. The result shows that the diffraction efficiency of the optical elements is related to the groove depth, structure period, light incident angle, polarization direction, wavelength and the refractive-indexes of the two media. The optimal groove depth for high diffraction efficiency has been obtained.5. Embossing technique is used to replicate relief structure of the holographic matching filter onto PC thermoplastic material. The technique can lead to rapid mass replication, and therefore, low cost and high efficiency.