Research On LC-based Spectral Imaging Technology And Its Applications

LC-based spectral imaging technology and its applications are widely and continuously focused on due to its high resolving power in both spatial and spectral dimensions. LC-based spectral imaging technology is also capable of small scale, light weight, low power consumption and more flexibility of spectrometers. But the pity is there is a great gap between the level of domestic research on the key technologies of LC-based spectral imaging and that of in USA and Japan. The researches on LC-based spectral imaging technology application are mostly depending on the imported LCTFs, on which the technological breakthroughs are expected to be made in the last decade. In addition, those researches cannot give full play to the technology’s advantages with respect to the application area, the application styles and the application effects, due to the limit of performance index, export permission and further development on the imported LCTFs.Using Frank’s continuum elastic theory, the director distribution of liquid crystal under applied electric field is simulated by means of the variational principle and the difference iterative method. The angular distribution of oblique-incidence transmission is calculated based on the established light-transmitting model of LC device. And the angular field of view of the LC device is analyzed afterwards. The structure of improved Lyot type LCTF is then presented in order to increase the field of view and equalizing the photoelectric performance of LCTF. The transmitting characteristics of the filter, emphasizing the symmetrical characteristics, are evaluated by numerical calculations.LCTF operating on the visible region and the visible to near infrared region are developed according to the improved Lyot type structure. The driving voltage equations of LCTF are obtained by the least squares fit to the calibrated datum of driving voltages. The driving voltage equations enable the LCTF to randomly select the operating spectrum and the spectral scanning step-size, which make the LCTF more flexible and more convenient consequently. A universal LC-based spectral imaging system is established using the improved Lyot type LCTF. Spatial resolution test, ambient temperature adaptability test and the static spectral imaging test are carried on to verify the key qualifications, the general performance and the reliability of the system. The system is integrated onto planes to proceed the airborne remote sensing application studies. The reliability and the performance of this system are further investigated by means of serial airborne spectral imaging experiments. The results indicate that this system can adapt itself to the airborne environment such as vibration, rapid movement, low temperature and sharp temperature fluctuations. This system can obtain the spectral images of the objects in its field range, and has been proved to have a stable and reliable ability to classify and identify the ground objects using the algorithms for spectrum information extraction and object classification.By the exploratory researches in this article, we have gradually mastered the key technologies in LC-based spectral imaging and have solved the main problems in engineering, which is sure to be the foundations of the applications’extension activities.