Digital Light Processing (DLP) uses a matrix of tiny mirrors (5.4 micrometers
or smaller). Each mirror can be tilted by an electrostatic field. In operation,
the chip reflects light from a bright source to a lens to be focused on a
screen. Each mirror controls one element of the image. To turn an image element
dark, the mirror is tilted to reflect the light to a heat sink coated with a
black light and heat-absorbing material. The brightness of each element is
controlled by modulating the time that the mirror reflects light to the lens as
opposed to the heat sink.
DLP projectors are commonly used in digital Cinema theaters. These
professional systems use three separate DLP chips to create a color image. Each
chip casts its light through an appropriately colored filter (red, green, or
blue) and then through a beam combiner to project out a single lens.
A
professional Cinema DLP projector
Consumer DLP systems use a single DLP chip with the light beam passing
through a rotating filter wheel with three colored filters before arriving at
the chip. This system requires three phases to create the image. Three
monochromatic images (red, green, and blue) are projected in rapid succession to
create the final image.
The mechanism of a single-chip DLP projector. Light from the source
(upper right) passes through the color wheel to a mirror (upper left)
and then to the DLP chip (red arrows). The chip's mirrors reflect the
light either through the projection lens (yellow arrow) or to the heat
sink (blue arrows).
Color filter wheel from a single-chip DLP projector. The colors
appear cyan, magenta, and yellow instead of red, green, and blue because
the filters are dichroic filters.[2]
Each filter reflects the color that is complementary to the color it
passes (as opposed to typical filters that absorb the colors they don't
pass). Thus, the filter that appears yellow in the photo passes blue
light to the DLP chip. The filter that appears cyan passes red light,
and the one that appears magenta passes green light.[3]
Home theatre DLP systems may be open projectors or consoles using rear
projection. The rear projection system requires substantial space to accommodate
the internal projector. These systems are easily recognizable from LCD and
Plasma systems by the bulk of the system behind the screen.
A
DLP television. Notice the prominent bulge in the back that accommodates
the projector.
Consumer DLP front projectors look much like LCD projectors and have similar
features and also have the same high cost of lamp maintenance. DLP projectors
also have higher contrast than LCD projectors
A ceiling-mounted consumer-market
DLP front projector.[4]
Note that the projector is upside down, so the image must be flipped to
appear correctly.
Single-chip DLP systems suffer from the "rainbow effect." There is a slight
delay between the projection times of the three colors that make up the image.
If an object moves, it will appear in a different place in each sub-image. This
causes its image to be broken up into three images of different colors in
different places.
A
hand moving through the beam of a single-chip DLP projector. This causes
the same rainbow effect seen with a moving object in a projected image.
