30-07-2012, 04:39 PM
Digital Light Processing and MEMS: Timely Convergence for a Bright Future
115_Digital_Light_Processing_MEMS_Timely_Convergence.pdf (Size: 1.42 MB / Downloads: 89)
Introduction
The world is rapidly moving to an all-digital communications and entertainment infrastructure.
DMD and DLP technologies are introduced in the context of that infrastructure.
1.1 The Final Link
In the near future, most of the technologies necessary to achieve an all-digital communications
and entertainment infrastructure will be available at the right performance and price levels. This
will make an all-digital infrastructure chain such as the one shown in Figure 1 commercially
viable.
The All-Digital Infrastructure
The links in this chain include capture, compression, transmission, reception, decompression,
hearing, and viewing. But the final link is missing-an all-digital display. Digital images received
today must be translated into analog signals for viewing on today's analog televisions.
The digital display block shown in Figure 1 accepts a digital signal, but unlike analog displays of
today, it outputs to the eye of the viewer an optical signal that is also digital. The viewer
perceives the digital signal as an analog signal, in essence performing the digital-to-analog (D/A)
conversion physiologically. An all-digital display possesses a degree of image stability and noise
immunity that is inherently attributable to its digital nature.[1] Consider a digital word that is
input electronically to the display. That word is converted into an optical word that is nearly
immune to environmental, aging, and manufactur ing influences.
Historical Context
One of the remarkable aspects of DLP technology is the timely convergence of market needs and
technology advances, resulting in significant business opportunities for this all-digital projection
display technology. The left vertical axis of Figure 3 shows recent market needs that are best
served by an all-digital connection.
The Mirror as a Switch
The address circuit and electromechanical superstructure of each pixel support one simple
function, the fast and precise rotation of an aluminum micromirror, 16 μm square, through angles
of +10 and p;10 degrees. Figure 4 illustrates the architecture of one pixel, showing the mirror as
semitransparent so that the structure underneath can be observed.
DMD Cell Structure
To provide a thorough understanding of the DMD
pixel structure and how it is addressed, we employ
several figures involving exploded views, cutaway
views, and an electrical schematic diagram. Figure
6 shows the pixel structure of Figure 4 in an
exploded view illustrating how the various layers
interrelate, including the underlying static random
access memory (SRAM) cell that is used to address
the pixel. Figure 7 shows a progressive cutaway
view of a 3 x 3 array of pixels. Figure 8 depicts
how each layer is electrically interconnected and
defines the bias and address voltages that must be
applied to the pixel for proper switching action.