Electro- and photo-controllable spatial filter based on a liquid crystal film with a photoconductive layer

• Published in: Applied physics. B, Lasers and optics Lasers and optics, 2009-12, Vol.97 (4), p.749-752
• Main Authors: Huang, S.-Y., Wung, T.-C., Fuh, A. Y.-G., Yeh, H.-C., Huang, C.-Y., Ma, C.-M., Huang, S.-C., Mo, T.-S., Lee, C.-R.
• Format: Article
• Language: English
• Subjects: Controllability; Engineering; Exact sciences and technology; Filtering; Filtration; Fourier analysis; Fundamental areas of phenomenology (including applications); Image reconstruction; tomography; Imaging and optical processing; Lasers; Liquid crystals; Optical Devices; Optical materials; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Quantum Optics; Rapid Communication; Stability; Voltage
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-009-3788-1

This work presents an electro- and photo-controllable spatial filter that is based on a liquid crystal (LC) film with a photoconductive layer. The controllable spatial filter can be formed because of the controllability of the photoelectro-induced screen effect of the space charge in the LC cell. An applied dc voltage or incident pumped intensity can be controlled to enable different spatial distributions of the diffraction pattern of the target object to be selected for filtering by the LC cell, such that various reconstructed images can be obtained. A simulation using Fourier analysis is developed, and its results agree closely with experimental results. Additionally, the LC spatial filter has the extra advantage of controllable low or high filtering functions: they are controlled by switching the configuration between normally black and normally white modes.