Stanford Vision Group : Display System

We're currently using an NEC LCD in a faraday cage with a conductive glass front, and binoculars/mirrors to view the setup.

Here're some notes and resources regarding each component.

1. LCD monitor . We like the NEC display (circa 1999): nice size, resolution, color saturation . The only problem is blur at high tf's. (2/2001: still using NECs)

2. Faraday cage . After making a beta-version of plywood and copper nails, I had a second one built out of ABS material (cheap, strong, easy to cut cousin of everyday acrylic). It's about 30 wide by 20 high by 20 deep (inches). Five sides are easy, the sixth (front w/glass) is a bit tricky.
Top + bottom: flat.
Left + right sides: flat, expect for 2" square holes in top corners for ventilation (see note later in shielding section), these vents are prob optional.
Back: flat, with holes drilled to allow for video In and power supply to run through.
Front: actually a hinged door, so that we can open the box for installation/maintenance. The front is mostly the glass panel with a 1-2" ABS frame that is connected to the hinges on top (ie, the front of the box is actually a top-hinged frame in which we placed the glass).

3. Conductive glass : Call Ian Waterman at Tempest Security (1 937 335 5600) Very nice guy, although note that this company's primary business is supplying air control towers, etc: much larger volume (we're essentially buying scrap and demos from them). We're using a 2-ply (99% filtering at relevant rfs) sheet of conductive glass from them; he called me ~1/2000 to mention that they've improved the specs on their glass, so ask what they've got. The 2-ply sheet we have allows >80% light transmittance (equal across visible wavelengths), so out maximum luminance through the glass is comparable, usually higher, than a CRT.
The glass is coated with a conductive film, and the 2-ply has film on the outside and inside faces of the glass (and the film doesn't wrap around the edge), so we needed to connect (1) the 2 sides of the glass to each other, and (2) the conductive glass surfaces to the rest of the faraday cage (see next).

4. Shielding . For the most part, we just layered the inside of the box with thin copper sheeting (it has a middle layer of some kind of plastic). We found large sheets at a large metal warehouse in the area. It's easy to cut/fold. We connected separate sheets to one another using conductive tape (copper tape from 3M, get the stuff with *conductive adhesive*, NB there is also a version with standard nonconductive adhesive). With the inside fully wall-papered with copper, we needed to connect the glass to the rest of the box, and to be able to pass the video (LCD display) wires out of the box to our computer. I've mentioned that the glass was set in an ABS frame (ie, the front face of the box). When the glass was laid into the frame, we had the guy who made it lay in a strip of copper-sheeting that formed a U (in cross section; ie, ~1" of the outer edge of both sides of the glass is surrounded by copper). This strip extends onto the inside edge of the frame (ie, comes out of the frame and into the box). This inside edge is now covered in copper and has a physical connection to both sides (conductive surfaces) of the glass. So, we need to connect this edge to the rest of the box (the inside). This edge presses against the front of the inside of the box, but to ensure enough contact, we had the manufacturer add an extra 1/2" lip around the front edge of the main box. We extended the copper-shielding from the inside of the box out over and around this lip. To be absolutely sure that we were getting good contact between the copper of the front frame and the copper on the lip, I laid a stripe of silicone under the copper on the lip, so that a little "mush" could occur when the frame/front face edge was pushed against the front lip. Much of the work around edges is done most easily with the copper tape (instead of folding the actual sheeting). We added several plastic clasps around the 3 non-hinge sides of the frame to ensure that the front stays closed but can be opened if needbe.

5. Wiring . Pass the video wires out the back of the box through a brass plate that is connected to the rest of the interior sheeting. Drill an appropriately-sized hole in both the brass and the back of the box. Treat the brass panel as a patch panel; ie, pass the video signal out the box through a set of feed-through connectors (as opposed to just running a continuous wire out a hole).
Pass the power supply through the box by placing an RF/power filter. These are small filters that you can find at an electronics place (or rip one out of an old PC: we had some trouble finding a place with them, and happened to find one lying around our magnet room). Plug the monitor into the filter; attach the filter (in a small metal box) to the interior copper shielding, and have it extend out of the rear of the box; plug the output wire from the filter into a power source.

6. Etc . Other random facts: (1) make sure the top hinge is strong-- that glass is quite heavy (and expensive-- you'll probably pay > $750 / sheet). (2) We added 2" vents on 2 sides of our box for ventilation. I'm not sure how important they are (the box is sig larger than the LCD). If you want to do this, just drill some vents, place aluminum (screen door) mesh over the holes (from the inside), and attach the mesh to the interior copper sheeting with copper tape. (3) We attached the copper sheeting to the box interior using 'liquid nails' or some equally nasty stuff. Ventilate well.

Questions: contact Alex Huk (huk@white.stanford.edu)