Lcd Filter Design And Testing

Filter is used to transmit spectrum of definitive broad band in the continuous spectrum or to extract certain radiation in the line-spectra. It has an important role in all domains of science and technology. What are especially worth noticing are the applications of the tunable filters.Basing on diversity theory, there are diversified tunable filters.The mechanical tunable grating filter is realized by a grating and a rotary section. The angle between the incident light and grating is the decisive factor of the transmit wavelength. The tunable performance is obtained by rotating the grating. The disadvantages of the mechanical tunable filter are high control voltage, slow response time and big volume.The electric-optic tunable filters are obtained by the alteration of the birefringence of the electro-optic material applied voltage. The tunable performance can be realized by rotating the electro-optic material in electric field.Now with the development of the crystal material science, the electro-optic tunable filters are used widely. Its applicable spectral range is broad.Tunable liquid crystal filters are one kind of electro-optic tunable filters which have been being extensively payed attention to.Tunable liquid crystal filters have two main forms: Lyot tunable liquid crystal filters and tunable liquid crystal F-P filters. Lyot tunable liquid crystal filters are designed, basing on the theory of Lyot filter and electro-optic effect of liquid crystal. Tunable liquid crystal F-P filters, which were reported by Mallision in 1987, use liquid crystal for the medium in the cavity of the filters.It is proved that Tunable liquid crystal filters have many attractive features:(1) Its applicable spectral range is broad. Many liquid crystals have very large birefringence and good transparency in both near ultraviolet band, visible band and infrared band.(2) The tunability is determined by the birefringence of the liquid crystal, alarge birefringence change can be obtained by a small voltage change.(3) The thickness of the liquid crystal and the arrangement of the liquid crystal molecule are flexible, there are no deviation in the outgoing beams.(4) Its used area is wide, its fabrication is simple and its cost is low.Since 2000, the electro-optic quality of liquid crystal filter has been being studied exhaustively and systematically. Articles having been released discussed the birefringence of nematic LC driven by voltage, the transmitted spectrum of Lyot liquid crystal filters, the characteristics of Lyot LC electro-optic wave filter and so on. At the same time, the group lead by T.uchida in the engineering department in Yaogu University in Japan did series of work on multiple tunable liquid crystal filters, and used them in lasers to improve the quality of blue light. However, domestic study on this field is a fat lot.The theme includes four sections. The species of tunable filters are introduced in the first chapter. At the same time quartz crystal tunable filters and liquid crystal tunable filters are described in this part. In the second chapter, the basic knowledge and the electro-optic effect of liquid crystal are described in detail. Theoretical study on tunable multiple liquid crystal filters is discussed in the third chapter and the filters are tested in the forth chapter.Originality innovation of this paper is that The letters reported previously only discussed the theory and the spectral characteristics of the tunable liquid crystal filters, but in this theme three originality innovations are presented. 1. Designing method for tunable multiple liquid crystal filters as optical devices is firstly presented. 2. Optimum designing for band width compression of the multiple liquid crystal filters is made. 3. Although the characteristics of the liquid crystal, dispersion of birefringence and the deflection of the optical axis of the liquid crystal cavity when voltage applied are ignored in the process of designing, the results are still valuable for the preparation for the devices concerned.