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High-dynamic range projection using a steerable MEMS mirror array

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Title: High-dynamic range projection using a steerable MEMS mirror array
Author: Hoskinson, Reynald
Degree Doctor of Philosophy - PhD
Program Electrical and Computer Engineering
Copyright Date: 2009
Publicly Available in cIRcle 2010-01-08
Abstract: This thesis describes a novel way to improve the contrast and peak brightness of conventional projectors by directing the light from the lamp away from the dark parts of the image towards the light parts before it reaches the projector's primary image modulator. A Microelectromechanical Systems (MEMS) micromirror array is inserted into the optical path between the lamp and the image-forming element. Each element of the array can be tip/tilted to divert portions of the light from the lamp. By directing these mirrors on an image-dependent basis, we can make the dark parts of the image darker and the bright parts brighter. In effect, this method will produce a low resolution approximation of the image on the image-forming element. The micromirror array will allow the projector to adapt its light source to the image being projected in order to maximize peak brightness, contrast and efficiency. Employing such an mechanism within a projector's display chain requires contributions to a number of different fields related to displays. Tradeoffs between the distance on the screen that a light spot from a mirror (mobile light, or ML) could be moved, and its spatial extent were established. Micromirrors suitable for this application were designed, simulated and fabricated. A novel way of optimizing the tradeoffs between tilt angle, mirror size, and mirror resonance frequency by splitting the mirrors into smaller functional subsections was employed. We developed several algorithms that determine favourable placement of the mobile lights from each of the micromirrors in the array, in order to best improve the image. From simulations, the projector average brightness could be increased by a factor of 1.4 if micromirrors were available that could be tilted to 3.5 degrees with the addition of this technology, without changing the projector lamp. If the requirement for perfect image reconstruction is relaxed, the improvement factor increases to 2.5. A prototype was system was developed that allows for fast control of mirror elements, and the positive effect of employing adaptive light distribution in this manner was demonstrated.
URI: http://hdl.handle.net/2429/17758

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