Some Aspects of Analysis of a Micromirror

Micromirror is a very small mirror based on the principle of Micro Electro Mechanical Systems (MEMS). Micromirror application in areas like laser scanning displays, DLP Projection system and HDTV are realized using MEMS technology. In this study, an electrostatically controlled micromirror is designed using COMSOL multiphysics software. The structural and mechanical properties of the actuation mechanism of various shapes of a micromirror will be studied. The base materials used will include Copper, Silicon and Aluminum. To make the cantilever more efficient, the structural steel was introduced along with the base materials listed above so as to obtain the displacement of the mirror. In order to evaluate the mirror further, the analytical formulation for Capacitance and Torque are developed and compared to the calculated theoretical values. The final results are shown as a range of wavelength, which will be obtained taking into consideration the tilting angle obtained from various materials used for the designing of the mirrors.


INTRODUCTION
During the last ten years, the development of Micro Electro Mechanical Systems (MEMS) technology has taken a huge leap in the field of communication and medicine industries, academia and automotive and optical industries.This huge improvement was possible by reduction in the mass and size of various MEMS devices which further help in improving the performance of these devices.Out of all these applications, Optical Coherence Tomography (OCT) for an endoscope, optical switch arrays for communications, Confocal Laser Scanning Microscopy (CLSM) and digital micro-mirror devices for Digital Micromirror Device DMD for Digital Light Process (DLP) Projection, find varied uses in the field of optical industries.Be it the case in the form of a micro lens array where a computer-controlled digital micromirror chip modulates incoming light as it is reflected into a vat of liquid photosensitive polymer (Cuiling and Mehryl, 2014;Van Kessel et al., 2011) or any other application, micro mirrors are here to stay.Digital micro mirror device, or DMD is the core of DLP projection technology (Park et al., 2008;Mamat et al., 2013) and was invented by Dr. Larry Hornbeck and Dr. William E. "Ed" Nelson of Texas Instruments (TI) in 1987.Micromirror devices are based on small mirrors which vary in the range of millimeters.They may be used in projectors inertial sensors.These mirrors used Micro Electro Mechanical System, so that their states (on/off) are controlled by applying a voltage between the two electrodes around the mirror array.Electrostatic forces also controls micro-mirror (Bansal and Singh, 2014;Wei-Hsin et al., 2008a) It is typically quite small and arrays of such devices can be implemented in a projection system.Actuation mechanisms like electrostatic, piezoelectric electromagnetic and electrothermal have been exclusively used in micromirror designs (Wei-Hsin et al., 2008b).For this simulation, we used Solid Mechanics, electrostatic and Electromagnetic Wave mechanism.

LITERATURE REVIEW
A lot of work in the field of MEM micromirror is in the process.Where an ample amount of work has been carried out starting from the MEMS based DLP Processing which is being studied till today (Hornbeck, 1996;Katal et al., 2013).Along with it, a lot of importance has also been given to various applications of a micromirror (Shahid et al., 2014) and its has been further classified as an optical system (Solgaard et al., 2014).But not much work has been has been carried out so as to explain the basic characteristics of MEMS micromirror in detail which has been carried out in this study.

SIMULATION RESULT
The model created uses 3D structural analysis using COMSOL software.Solid Mechanics was design the Micromirror.Its central portion is surrounded and supported by two cantilever beams (Electrodes).One end of the cantilever beam is connected to the central portion while the other end is kept free.The parameters used to design are shown in Table 1.In the table, g represents the air gap taken between the electrode and for aluminum and structural steel-rectangular shape for copper and structural steel-square shape

Simulation of capacitance and torque using
The model was created uses 3D structural analysis using COMSOL software.Electrostatics was used to design the Micro mirror.The parameters used to obtain the models are shown in Table 3.Air was taken the surrounding material in order to calculate Capacitance.Terminal and ground voltage was applied on different parts of the plates.Force Calculation used on the two edges of the plate to obtain the torque.The final comparison of the simulated and calculated values capacitances and torques for all the three shapes -------------------------------------0.5 0.  we can note that the for Fig. 20 to 22, the output is a scattered graph with an uneven display while for Fig. 21 the result is displayed in a rather proper manner.

CONCLUSION
In this study, after a survey of various aspects related to a micromirror, it can be concluded that the combination of Aluminum and Structural steel suffers

RECOMMENDATIONS
For further studies, It is suggested to include more number of electrodes and shaped in place of the ones used so as to get a wide range of idea related to this field.Also, the formulation can be done which is related to the error obtained from the wavelength range in order to minimize it.Apart from the capacitance and torque values obtained more research and study can be carried out on various other factors for e.g., the switching time and the closed loop behavior of the device.
th of the micromirror The width of the micromirror The ratio of the width to the length of the The initial air gap between the micromirror The potential difference between the micromirror and its electrode Equilibrium only occurs in a given range.Beyond this limit, the electrostatic force overcomes the spring force causing the two plates to quickly snap into in effect.It can be = Strain energy in two torsional strings = D, x = 1, m = D-Lsinθ, expression for I in Putting this value in Eq. (3), we get:

Fig. 21 :Fig. 22 :
Fig.21: Copper-circular shape for 300 nm from high deformation and stress for all the three shapes used and the least displacement is obtained by the combination of Silicon and Structural Steel.Out of all the three shapes studied, the capacitance and torque for Aluminum+Structural steel is highest and the least is obtained or of Silicon and Structural Steel which justifies the first conclusion.Also it has been noticed that the capacitance and torque are seen to be high generally for all the square shapes.From the range of

Table 1 :
Parameters for various shapes of a micromirror

Table 2 :
Total displacement for various shapes of a micromirror -

Table 3 :
Parameters used to simulate the values of

Table 4 :
Comparison between theoretical and practical values for capacitance and torque obtained

Table 3 :
Parameters used to simulate the values of capacitance and torque -