A diffractive optical MEMS device for spatial and temporal light modulation is described that is capable of high-speed digital operation. The device contains electromechanical ribbons suspended flat above a silicon substrate by a periodic series of intermediate supports. When actuated electrostatically, the ribbons conform around the support substructure to produce a grating. The device has optical switching times of less than 50 nsec, sub-nanosecond jitter, high optical contrast and efficiency, and reliable actuation in contact mode. The fine gray levels needed for digital imaging systems are produced by pulse width modulation.

Conformal grating electromechanical system (GEMS) for high-speed digital light modulation

Time-dependent deformation (creep) behaviors of piezoelectric microactuators have been investigated. Position (or gap height) drift of microbridged actuator beam and its displacement amplitude change with time could be attributed to the anelastic behavior of the driving unit itself based on lead zirconate titanate (PZT) in the actuator, and as well as to the mechanical stress states established in the microactuator beam after the surface release of the micromachined actuator structure. From creep analyses of a simple microcantilever and microbridge beam structures, it was turned out that the overall creep behavior in microbridged piezoactuator structure was mainly dependent on the actuator beam initial deflection configuration governed both by residual stress of the actuating part Pt/PZT/Pt stack and the stress gradient through the silicon nitride (SiNx) microbridge beam.

Creep behavior of undoped and La–Nb codoped PZT based micro-piezoactuators for micro-optical modulator applications

Speckle noise is a major obstacle for the application of laser light sources in projection displays and illumination. In this paper, a method for speckle reduction using a Micro-Electro-Mechanical Systems (MEMS) diffuser device is presented. The MEMS device consists of a random reflective pattern on the top surface of a moving mass that is vibrated in-plane by an electrostatic push-pull comb drive. The harmonic in-plane motion of the MEMS diffuser creates time-varying speckle patterns that are averaged by the camera or the eye, thus reducing speckle noise. The device is fabricated using Silicon-On-Insulator (SOI) technology. The measured device shows good agreement with analytical calculation and simulation. Using a red He-Ne laser, speckle contrast is measured both for free space geometry and for light pipe geometry. Speckle contrast reduction up to 43.08% for the free space geometry and 26.8% for the light pipe geometry is achieved.

Design, Modeling, and Characterization of a Microelectromechanical Diffuser Device for Laser Speckle Reduction

A small sized, low power consuming, shock proven optical scanner with a capacitive comb-type rotational sensor for the application of mobile projection display is designed, fabricated, and characterized. To get a 2-D video image, the present device horizontally scans a vertical line image made through a line-type diffractive spatial optical modulator. To minimize, device size as well as power consumption, the mirror surface is placed on the opposite side of the coil actuator. To prevent thermal deformation of the mirror, the mirror is partially connected to the center point of the coil actuator. To be shock proof, mechanical stoppers are constructed in the device. The scanner is fabricated from two silicon wafers and one glass wafer using bulk micromachining technology. The packaged scanner consists of the scanner chip, a pair of magnets, yoke rim, and base plate. The fabricated package size is 9.2×10×3 mm (0.28 cc) and the mirror size is 3×1.5 mm. The scanner chip receives no damage under the shock test with an impact of 2000 G in 1 ms. In the case of a full optical scan angle of 30 deg at 120-Hz driving frequency, linearity, repeatability, and power consumption are measured at 98%, 0.013 deg, and 60 mW, respectively, which are suitable for mobile display applications.

Slow scanning electromagnetic scanner for laser display

A method for speckle suppression based on Barker code and M-sequence code diffractive optical elements (DOEs) is analyzed. An analytical formula for the dependence of speckle contrast on the wavelength of the laser illumination is derived. It is shown that speckle contrast has a wide maximum around the optimal wavelength that makes it possible to obtain large speckle suppression by using only one DOE for red, green, and blue laser illumination. Optical schemes for implementing this method are analyzed. It is shown that the method can use a simple liquid-crystal panel for phase rotation instead of a moving DOE; however, this approach requires a high frequency of liquid-crystal switching. A simple optical scheme is proposed using a 1D Barker code DOE and a simple 1D liquid-crystal panel, which does not require a high frequency of liquid-crystal switching or high-accuracy DOE movement.

Optical schemes for speckle suppression by Barker code diffractive optical elements

A diffractive optical modulator has been fabricated based on a micromachining process. Novel
properties of its fast response time and dynamics were fully understood and demonstrated for the
strong potentials in embedded mobile laser display. Bridged thin film piezo-actuators with so called
open mirror diffraction structure has been designed. Optical level package also was achieved to
successfully prove its display application qualities. Display circuits and driving logic were developed
to finally confirm the single-panel laser display at a 240Hz VGA (640×480). With its efficiency of
more than 75% and 13cc volume optical engine with the MEMS-based VGA resolution SOM
showed 7 lm brightness at a 1.5W electrical power consumption. Detailed design principle,
fabrication, packaging and performances of the invented SOM are described.

A novel diffractive micro-optical modulator for mobile display applications

This paper deals with the development of prediction method of deployment performance of a inclined forward folding wing. It uses the inclined forward folding wing mechanism, whose motion is three-dimensional. Within the analysis axis, this motion is well described and the governing equation can be well established. External moments, such as the deploying moment due to torsional spring, friction moment, aerodynamic moment, and gravity moments are well modelled and the governing equations is solved numerically. Thus the deployment performance of a inclined forward folding wing can be predicted successfully. 

Analysis of deployment modeling of a inclined forward folding wing

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A novel diffractive micro-optical modulator for mobile display applications

Analysis of deployment modeling of a inclined forward folding wing