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 method-Thin Film Transistor Active Matrix Panel http://en.wikipedia.org/wiki/Twisted_nematic_field_effect

Pixel Layout

http://en.wikipedia.org/wiki/TFT_LCD

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.

Holoeye Spatial Light Modulator

• LC 2002: Translucent Spatial Light Modulator

Pixels Pixel Pitch Panel Size Formats Frame Rate 800 x 600 32 µm 21.0 x 26.0 mm VGA - SVGA Resolution 60 Hz

For only $6248.43

http://www.elliotscientific.com/307/Spatial-Light-Modulator-60-Hz-SVGA/#

Pixels Pixel Pitch Panel Size Formats Frame Rate 832 x 624 33 µm 19.8 x 26.4 mm VGA - SVGA Resolution 60 Hz

Commercial

Ours

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

Right: CCD Image, with focus at focal length of the imaging lens. The above diffraction pattern was displayed on the LCD screen.

Above: Replica of diffraction pattern displayed on LCD

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.