Papers by Keyword: Spatial Light Modulator

Abstract: In this paper, a non-mechanical axial zoom scanning method based on a phase only liquid crystal spatial light modulator is proposed. This novel method is to overcome the measurement error caused by moving mechanical parts in the axial mechanical scanning methods in the confocal microscopy system. The modulation on the incident wave front is completed by a spatial light modulator, which provides this scanning method some outstanding advantages including the flexibility of control and the absence of moving mechanical parts, especially suitable for the fixed sample imaging occasions. By simulating the multiple Fresnel lens with LCSLM to generate controllable multi-focal points and thus realizing this method of axial multi-focus scanning to enhance the axial scanning efficiency and the range. Simulations and experiments on the axial scanning features of the axial multi-focus zoom scanning method are carried out. Results of simulations and experiments indicate that non-mechanical axial zoom scanning can be realized with the use of a spatial light modulator in the confocal microscopy system.

Abstract: Due to the special properties of asphere lens, the testing of it is more difficult than that of spherical lens. In this paper, the development of a new method using the liquid crystal spatial light modulator (SLM) to measure the accuracy of an aspheric surface is presented. The surface form was measured using a new component as the compensator lens in conjunction to provide an interferogram representing the aspheric form deviation from the nominal. Interferograms are decoded using a spatial-carrier phase shifting technique. The interferometric data is compared to data obtained using a contact stylus profilometer. The system can be mounted over a polishing machine and used for on-line testing of aspheric mirror surfaces.

Abstract: In this paper, a mode conversion model is proposed to increase the capacity of optical fiber communication systems. In this model, a spatial spectral matching method is used to convert the original mode to the desired mode for mode division multiplexing in optical fibers. A binary phase spatial light modulator is employed on the Fourier plane as a spatial filter. Numerical results show that the original modes can be converted to the desired modes.

Abstract: It is proposed in this paper to use phase only liquid crystal spatial light modulators to realize non-mechanical lateral and axial confocal microscopic laser scanning. With a phase only liquid crystal spatial light modulator used as a scanner to realize laser beam deflection, a confocal microscopic lateral beam scanning system is designed. A zoom illuminating lens is formed by incorporating a liquid crystal spatial light modulator along the confocal illumination light path, and thus the focus of the objective lens is axially shifted to realize the axial non-mechanical scanning. The theoretical analyses indicate that phase only liquid crystal spatial light modulators can be used to realize non-mechanical 3D confocal microscopic laser scanning.

Abstract: This paper presents a novel out-of-plane micro spatial light modulator (μSLM) based on leverage principle. Design principles and analytical models are both developed and verified by Finite-Element-Analysis (FEA). The μSLM consists of four individual actuators, each actuated by electrostatic attractive force to produce a downward displacement, and this displacement is magnified to be a large displacement at the mirror by the lever principle. Compared with conventional electrostatic μSLMs, the stroke of proposed design can be remarkably increased. Then the optimization of the design is also given to produce largest out-of-plane stroke. The mirror is 500μm by 500μm by 1.5μm and the lever is 200μm by 30μm by 2μm. As large as a 4.5μm stroke is obtained by simulation and the resonant frequent is about 4.8 KHz.

Abstract: To correct wave front distortion, a phased only Liquid Crystal Spatial Light Modulator (LCSLM) is used. LCSLM can modulate the phase of the incident beam by changing the electric field applied to the transparent electrodes of a liquid crystal cell. The voltage change causes the refractive index of the liquid crystal change, so a phase shift produces. The distortion of a wave front can be measured by using a wave front interferometer. Since each pixel of SLM may be addressed and controlled independently, so proper voltage is supplied to each pixel to compensate the phase corresponding to the distortion. Before wave front correction, the LCSLM is tested and corrected by employing a Twyman-Green interferometer, which shows the relationship between the applied voltage and the phase value of each pixel. Experiment result shows that after error compensation of LCSLM, the wave front distortion correction accuracy reaches 0.06 λ.

Abstract: Based on the principle of moiré techniques, a new method combined with Electric Addressing SLM technique was proposed. The specimen grating is modulated by the SLM system, and its the frequency can be changed with aid of a 4f Fourier system. The moiré is generated by the overlapped specimen grating and a reference grating in the Fourier system. Typical test is conducted with a polyurethane beam. The successful results verify the feasibility of the method, and show its good potential of further application to the in-plane deformation measurement.

Abstract: When the constitutive elements of photonic crystals (PCs) are magnetic, or even only a defect introduced in PCs is magnetic, the resultant PCs exhibit very unique optical and magneto-optical properties. The strong photon confinement in the bulk of magnetic PCs results in large enhancement in linear and nonlinear magneto-optical responses of the media. Novel functions, such as the band Faraday effect, magnetic super-prism effect and non-reciprocal or magnetically controllable photonic band structure, are predicted to occur theoretically. All the unique features of the media arise from the existence of its magnetization, and hence they are called magnetophotonic crystals providing the spin-dependent nature in PCs.

Abstract: A hybrid correlation system incorporates an optical correlator, spatial light modulators(SLM), digital cameras and a computer. Spatial light modulators and cameras are used to dynamically update the input and the spatial filter. The hybrid correlation system integrates the parallel processing capability of the optical correlator and the flexibility of the digital system. It can be used as a high-speed multi-function information processor. This paper focuses on the design and fabrication of a hybrid optical correlator and how it is used as an intelligent instrument. We address the issues of rigorous requirements for filter registration and matched filtering by proposing practical approaches. We include the analysis and use of intensity filters based on commercial SLMs for real-time pattern recognition. We present the engineering details of a specific hybrid optical correlator for applications to the real-time identification of an aircraft.