Shanglian Huang

Theoretical analysis of grating light valve

In this paper, the grating light valve (GLV) is presented. A simple method based on multi-beam of light interference theory is put forward to analyze its optical performance. Computer simulation demonstrates that the dimension of its structure and light source have different influence on the diffractive efficiency. According to detecting system, the diffractive efficiency in the OFF state is about 3.8544x10-16 at the wavelength of 0.66um, about 2.8218x10-16at the wavelength of 0.5145um, 1.7846x10-16at the wavelength of 0.488um, which should ideally be zero. The result indicates that such method applied in the analysis of the GLV is agreeable and simpler. In order to gain higher diffractive efficiency, the air gap should be reduced.

A Near-Infrared Spectrometer Based on Novel Grating Light Modulators

A near-infrared spectrometer based on novel MOEMS grating light modulators is proposed. The spectrum detection method that combines a grating light modulator array with a single near-infrared detector has been applied. Firstly, optics theory has been used to analyze the essential principles of the proposed spectroscopic sensor. Secondly, the grating light modulators have been designed and fabricated by micro-machining technology. Finally, the principles of this spectroscopic sensor have been validated and its key parameters have been tested by experiments. The result shows that the spectral resolution is better than 10 nm, the wavelength deviation is less than 1 nm, the deviation of the intensity of peak wavelength is no more than 0.5%, the driving voltage of grating light modulators array device is below 25 V and the response frequency of it is about 5 kHz. With low cost, satisfactory precision, portability and other advantages, the spectrometer should find potential applications in food safety and quality monitoring, pharmaceutical identification and agriculture product quality classification.

Electromechanical Characteristic Analysis of Passive Matrix Addressing for Grating Light Modulator

A Grating Light Modulator (GLM) based on Micro-Electro-Mechanical Systems (MEMS) is applied in projection display. The operating principle of the GLM is introduced in this paper. The electromechanical characteristic of the passive matrix addressing GLM is studied. It was found that if the spring constant is larger, both the response frequency and the driving voltage are larger. Theoretical analysis shows that the operating voltage and the pull-in voltage of the GLM are 8.16 and 8.74 V, respectively. When an all-selected pixel in a m×n array is actuated by a voltage V0, the voltages of the half-selected pixel in row and column are V0(m–1)/(m+n–1) and V0(n–1)/(m+n–1), respectively, and the voltage of the non-selected pixel is V0/(m+n–1). Finally, the experimental results indicate that the operating voltage and the pull-in voltage are 7.8 and 8.5V respectively, and the response frequency of the GLM is about 7 kHz. The crosstalk in a 16×16 GLM array is validated by the experiment. These studies provide a theoretical basis for improving the GLM driver.

Electromechanical characteristics analysis and simulation of grating light modulator

In this paper, a 27um×27um novel grating light modulator supported by cantilevers has been presented, and it can be fabricated using silicon surface-micromachining technology. The structure and basic operation principle of grating light modulator is introduced. The structure is composed of grating plate, address electrode and four cantilevers, the grating plate, which is supported by four cantilevers placed around, is overhung about one wavelength of incidence light from the underlying address electrode, it is actuated like a piston by electrostatic force, and piston-type motion of grating can be used to modulate phase of incident light, therefore, the grating light modulator array is a potential device for projection displays and relevant devices for its intrinsic characteristics. Mechanics model is developed for deducing the deformation equation, the relationship between the electromechanical characteristics of the device and the geometrical parameters and material performance is analyzed, such as pull-in voltage, resonance frequency and step response time. Electromechanical coupled simulation is done by Coventorware, then, more reasonable geometrical parameters are obtained for fabricated in the next step.

Optical and electrodynamic analysis of a novel spatial light modulator

In this paper, a novel spatial light modulator is presented. A pixel of the novel spatial modulator is turned fully OFF when all pixel ribbons form a flat reflective plane and turned ON by electrostatically deflecting alternate ribbons to produce a blazed diffraction grating. According to scalar diffraction theory, the optical performance is analyzed in details. And the influence factors on diffractive efficiency are discussed. Meanwhile, with the application of electromagnetics, electrodynamics analysis is introduced including the relation between threshold voltage and structure material characteristic. Computer simulation on the condition of different incidence light, different duty-cycle is carried on, presenting the relation between diffraction efficiency and wavelength, duty-cycle, etc. There is a promising foreground based on optimization of structure.

Grating light modulator for projection display

A novel grating light modulator for projection display is introduced. It consists of an upper moveable grating, a bottom mirror, and four supporting posts between them. The moveable grating and the bottom mirror compose a phase grating whose phase difference is controlled by the actuating voltage. When the phase difference is 2k\pi, the grating light modulator will switch the incident light to zero-order diffraction; when the phase difference is (2k-1)\pi, the grating light modulator will diffract light to first-order diffraction. A 16\times16 modulator array is fabricated by the surface micromachining technology. The device works well when it is actuated by a voltage with 1-kHz frequency and 10-V amplitude. The fabricated grating light modulator can show blackness and brightness when controlled by the voltage. This modulator has potential applications in projection display system.

Analysis of a Hadamard transform near-infrared spectrometer based on grating light modulator

This paper proposes a novel Hadamard Transform near-infrared spectrometer based on MOEMS(Optical micro-electro-mechanical system ) grating light modulator. A new method that grating light modulator combined with a single near -infrared detector to detect spectrum is applied. The programmability of the grating light modulator linear array is used to implement a Hadamard Transform encoding masks. Firstly, optics theory has been used to analyze the essential principle of the spectrometer and the optical principle of grating light modulator. Then, It is theoretically proved that the Hadamard Transform near-infrared spectrometer can reconstruct spectrum effectively and have a high signal noise ratio. Finally, a new structure of the grating light modulator is given. Results of the software simulation show that 5.5V maximum actuating voltage and 5 kHz response frequency are suitable for a miniature, portable, cost-efficient spectrometer.

Characteristic analysis and study of an active matrix addressing for grating light modulator

Grating Light Modulator(GLM) based on MEMS is applied in projection display. In order to eliminate crosstalk of GLM array, a monolithic integration device of GLM and active matrix is presented with post-CMOS process. The operating principle of monolithic integration device is introduced. Active matrix unit is composed of a NMOS transistor and a capacitor. The bottom electrode of GLM is connected to the electrode of the capacitor by via, so the voltage of GLM equals to the voltage of capacitor. Every GLM unit is controlled by sole active matrix unit, so crosstalk can be eliminated, which improves optical contrast and optical utilization ratio. And, the monolithic integration process of active matrix and GLM is designed. Then the key indexes and parameters of active matrix which influences the performance of monolithic integration device are analyzed in detail. Its indicated by analysis that storage capacitor and width-length ratio of transistor influence the holding-voltage property and switch speed of monolithic integration device. Finally, with 0.18µm process design kit(PDK) of SMIC and Cadence software, layout of monolithic integration device is designed. The simulation results validate the correctness of the analyzed theory and the designed circuits. The monolithic integration device designed can be applied in projection display which has 1920×1080 resolution, 30Hz frame frequency and 256 grayscales.

Analysis and optimization for effective diffraction area of grating movable light modulator

GMLM (Grating Movable Light Modulator)is a novel light modulator based on MOEMS technology which can be used in fields of display and print. But present design has only 30% effective diffraction area, which can deeply influence the key parameters such as pixel-filling-ratio and contrast. An electromechanical model of the device was established, and the effective spring constant of GMLM was deduced by energy method. According to that the relation between structure parameters and effective diffraction area was analyzed theoretically. Then optimized structures were simulated and validated by FEM software Coveter Ware. Simulation data shows that the optimization device model can enhance the effective diffraction area to about 90% from less than 30% before optimization.

Progress of optical sensor system for health monitoring of bridges at Chongqing University

With decades of research experience on optical sensors, Optoelectronic Technology Lab of Chongqing University (OTLCU) has studied on a variety of sensors system designed for practical use in health monitoring. In OTLCU, embedded and surface mounted fiber Fabry-Perot strain sensor has been developed for monitoring the local strain of both concrete and steel truss bridge. Optoelectronic deflect meter, with a group of optical level sensor in a series connected pipe, was developed for deflection monitoring and line shape monitoring of the bridges. Laser deflect meter, with a laser pointer and a sensors array, has been also developed for a dynamic deflection monitoring of the bridges. To monitoring the 2-Dimentional displacement of the bridge, a self-calibrating imaging system was developed. All these sensor systems have been applied in different bridges successfully. This paper briefly describes principle of these optical sensing systems, and also gives some representative results of the system in practical application of bridges.