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Spatial Light Modulation and
Applications
Chaunee McKay
Katherine Ballman
MSI Industrial Internship- Optics Track
8/12
Content
• Conversion of a Sharp XG-NV2U LCD Projector
to a SLM
• LCD Basics
• Uses: Optical Vortices, Fourier Optics
• Benefits: Accessibility, Cost
• References
Sharp XG-NV2U LCD Projector
• Donated from fellow department, also available
on ebay, or government auction sites ($40.00).
• Top casing must be removed in order to gain
access to the circuit board, power supply, and
LCD panels.
• The control panel is attached to the top case by a
ribbon cable which clips into the top circuit
board.
• For the SLM to function we need access to the
LCD panels, but still want the projector to
communicate with a computer.
Parts Removal
The metal halide lamp
can be accessed
through a panel on
the bottom of the
projector.
The cover for this
access panel must be
in place for the
projector to run or
both lock
mechanisms must be
depressed.
Lamp Removal
• The power supply, which connects to the lamp, can be traced back to
the main circuit board of the projector to a 24 pin ribbon cable.
• The power supply has a metal casing around it. The lid of the casing
must be bent back after the screws have been removed from the
sides in order to access the wires (note: don’t be afraid to be a little
rough with the metal casing).
• Three wires on this cable communicate the status of the lamp.
A
C
B
Lamp Removal
• When the projector is on, pins A,B, and C all
read 23 V. However, when the lamp is not
connected, pins A and B read zero.
• In order to send a false OK signal to the board,
cut and strip all three wires, then solder A and B
to C, so that A and B constantly read 23 V, hence
sending a false OK.
Fan Removal
• The back fan (used to cool the halide lamp), can now also be removed.
• The resistance of the fan was measured using a Multi-Meter, and then
replaced with an equivalent 6K ohm resistor.
• The three wires communicating the status of the fan to the projector, In
(red), Out (black), and Monitor (yellow), can be traced back to the main
circuit board.
• The resistor was then twisted into place and soldered. (Note: The monitor
wire has to be on the same side of the resistor as the out wire)
Lens Removal
• The lens must be
removed in order to
gain access to the
screws needed to
remove the LCD
panels.
• In order to remove the
lens, the lip of the
casing surrounding the
lens must be cut away.
• After the lip has been
cut, the four screws
attaching the lens to
the optical path can be
removed.
• Take the lens out.
LCD Panel Removal
• Removing the
LCD panels
requires the
temporary
displacement of
the circuit
boards in order
to gain access to
the LCD panels
• This must be
done with care!
LCD Panel Removal
• All screws holding down the boards should be
noted before removal so that the boards can
later be put back into place.
LCD Panel Removal
• Once the circuit
boards are removed,
three ribbon cables
attached to the LCD
panels can be seen.
• The remaining
screws can be
removed, and the
panels disconnected
and pulled free.
LCD Panel Removal
• Inside the positioning
casing holding the three
LCDs will be three color
filters, and one large
polarizing crystal (not
shown in picture) along
with the LCD panels.
• Disconnecting the panels
from the polarizing crystal,
each panel can now be
removed.
• The screws on the bottom
can now be accessed and
the polarizing crystal
removed.
• The color filters are slid
into place and held by
epoxy. Using a razor, you
can scrap away the epoxy,
and use pliers to remove
the filters.
SLM Set Up
• For this setup, we
connected one
LCD panel into
the green input.
• The projector will
still run
regardless of
whether the
other LCD panels
are connected.
• The remaining
panels can be
stored as
replacements.
LCD/Computer Interface
• Clicking the “Input Select” button on the control
panel directly displays on the LCD panel which
picture input the projector is communicating to.
• Once RGB 1 is selected it is then possible to
connect a computer to the projector through
output RGB 1, and display the computer screen
to the LCD panel directly.
How our LCD panel works
• Translucent
Twisted
Neumatic
Liquid Crystal
Display
• Drive methodThin Film
Transistor
Active Matrix
Panel
http://en.wikipedia.org/wiki/Twisted_nematic_field_effect
Pixel Layout
Communication to a
particular pixel is
accomplished by sending a
charge down the column
containing that pixel. The
row containing that pixel is
concurrently activated as
ground, and so only the
desired pixel receives the
charge.
http://en.wikipedia.org/wiki/TFT_LCD
Holoeye Spatial Light Modulator
• LC 2002: Translucent Spatial Light
Modulator
For only $6248.43
http://www.elliotscientific.com/307/Spatial-LightModulator-60-Hz-SVGA/#
Commercial
Pixels
Pixel Pitch Panel Size
Formats
Frame Rate
800 x 600 32 µm
21.0 x 26.0 mm VGA - SVGA Resolution
60 Hz
Ours
Pixels
Pixel Pitch Panel Size
832 x 624
33 µm
19.8 x 26.4 mm
Formats
VGA - SVGA Resolution
Frame Rate
60 Hz
Optical Vortices
Experimental Set Up for Fourier Optics
• The light source used in this set up (white light) was such
high intensity that it was necessary to utilize apertures,
beam splitters, neutral density filters, and mirrors to
diminish the beam.
• The CCD camera used was extremely sensitive to the
light intensity produced by the beam, and initially many
of the images produced by the camera were washed out.
• Even though the focal length of the collimating lens was
known, fine tuning was necessary to ensure we were as
close to the focus of the lens as possible.
• Due to limitations in space, a short focal length
collimating lens was used.
Fourier Optics Set Up Schematic
Fourier Optics
• CCD Image,
with focus at
focal length of
the imaging
lens.
• White screen on
LCD
Vertical Cross Hatch
Above: Replica of diffraction
pattern displayed on LCD
Right: CCD Image, with focus at focal
length of the imaging lens.
The above diffraction pattern was
displayed on the LCD screen.
Horizontal Cross Hatch
Above: Replica of diffraction
pattern displayed on LCD
Right: CCD Image, with focus at focal
length of the imaging lens.
The above diffraction grating was
displayed on the LCD screen.
Suggested Improvements
• Optical Rail to fine tune the focal distances, and
assuring that the LCD panel is located in the
transform plane.
• For ease of access, extend the ribbon cable which
connects the LCD to the projector.
• Reduce stray light by better containment of the
light source.