I got a lot of my ideas [and parts] from LL and its members, and I finally got some good pictures, so it is time to share.

I am using the techbench 15 Samsung LCD monitor. I have progressed through the short throw lenses to the long throw lenses.

Here is a picture of the back side of the box where I have a back-and-forth shaped air cavity that blocks the light. The light switch activates the sodium retrofit Ushio, and I have the LL electronic ballast. That is a radioshack 120v fan.

Here is a picture of the 80mm triplet in the original setup. The spousal unit did not like the pj in the middle of the room.

I have it on there backwards in this picture. I moved the box back 3 feet and did not want to mess up my focus board, so I just flipped the triplet in the focus board.

The internal parts. I used a clothes hanger to hold the field lens. I ran a little transparent tape down the side, folded the tape, and used 1/4 inch binder clips to attach the fresnel to the hanger. My box is 15.5 inches from left to right, so I snipped off the hanger and it fit snug on the box.

The infamous light caddy. I made mine with the thin sheets of board binding sheets from HomeDepot. I sliced out the metal between a couple holes to allow it to slide left and right, then mounted that on L shaped corner braces, and then mounted my lamp and reflector on it.

Since then, I added a condenser and IR shield. I also mounted the ladel-reflector onto a fan guard so that I could line it up better to make it point the right direction.

The final design used a 6mm machine screw that ran the whole way through it so that all the pieces lined up.

[I replaced that 8mm screw that you see holding on the reflector that is running up to the condenser with a shorter 6mm screw]

The upgrade. I added an extension onto the box and added the 450-500 varifocal. I had so much trouble making the extension piece one square, that for the second extender piece I made a loosely fitting box that fit on the outside. It is 1/4 inch plywood, with a couple strips of mdf in there to give me a locking mechanism to prevent the outter-addon from coming off.

The front of the newest setup with the varifocal.

The little accessories box on the side. When I first got the parts, I thought the wires from the backlight had some significance, so I ended up putting this on the wrong side of the box.

The holder for the plugs is a computer slot cover that I drilled out to hold the S-video, RCA, and coaxial jacks. The base of the extension is part of the floor of the box that I cut around, so it is not screwed on as a separate box.

One last shot. This is top-down. I used 1/2 inch C channel from HD to mount the LCD. I made a large U, slid the LCD down into it, and then capped it with more C channel. I cut the top part so that it rested on the top of the box.

The edge of the top C channel where I cut out a bit [one last one more picture]

Last weekend's football. The screen is 100x80. 100 pounds of black lab in front of the screen

Realize I am using a 1/4 megapixel [640x480] camera here, so it is not a real good shot

thanks for sharing the pics, interesting design in that ballast enclosure area. Looks like good results in a relatively bright room

Design two has been completed. This uses two mirror to reduce the depth into the room the case hogged up. It sits sideways and allows me to 'zoom' by just moving the last mirror in the system closer to or further from the triplet.

The little line on the bottom left is where the lamp ARC would go. I had a little incident with Lexan melting on my lamp and breaking it in half, so the lamp is sort of missing from my picture.

The big old square of wood with the lexan in the middle of the box is where the LCD goes. The fresnel are in the center of that box, and air goes left and right and left between the LCD-fresnel-lexan.

Here is the outside-front. The control button panel and remote receiver are under the triplet. The handle is approximately centered under the weight of the whole device.

I can aim the image with the small mirror on the top of the image, and I can perform keystone correction with the long mirror that runs up the left side of the image.

I built little insertable-holders for my power supply and ballast. They are mounted in their holders, and then insertion or removal only requires the use of a single bolt and nut to secure the holders.

The man here claims he can get keystone correction with mirrors, and he insists that it works.

I'm clueless.

Perhaps his definition of keystone is slightly different from the rest of us.

Could you clarify what you mean by keystone correction (Is it simply pointing it at a lesser angle?), as well as perhaps give us a scale top-down diagram of your layout? It looks terribly interesting, but I'm having a slight problem with grasping the exact scale.

I do not know what you are clueless about? Or is that just an invitation?

My definition of keystone correction is the same as yours, to stretch or compress sides or corners or both to make an off-square image square again.

Here is a picture of how I learned about it. I took this while I was designing what I made [in case I changed something and could not get back to where I started]. The only diagram would be the lines on the floor of the projector to mark where things go. You can set it up for yourself in a few minutes and see for yourself with two mirrors, a triplet, a 100 watt light bulb, and a plastic grocery bag.

I taped the fresnel/image to hold them up, and the fresnel/image and light source are not going to be moved. The angle will need to be closer to 30 degrees than 45. As stated above, you move the long mirror that runs down between the triplet and LCD and it changes keystone shape. [if you change the long mirror too much, you will then have to compensate by moving the small mirror, but the small mirror just directs the image to the triplet, it does not change the keystone shape]

samples of correction

bottom right in

squared

those are probably not so helpful when on separate pages of the thread, so I linked the one on the prior page here

Doesn't make any sense at all. The camera obviously isn't so great. Probably the brightness.

But anyway. What degree of correction does it allow and is there any distortion in the image quality?

Image quality of course gets distorted when either mirror is moved too far [i.e. the image on the big mirror is deflected away from the small mirror], but it can be remedied by moving the small mirror. That kind of quality problem generally only comes about when the long mirror has the left or right side moved forward or back [as opposed to moving top or bottom]. This distortion seems to be simply a result of focussing length. The remedy is to move the small mirror forward and back [closer to, or further from, the triplet].

Remember, the real goal of keystone correction is to fix the image, so there is already some non-uniform distance in your projector-to-screen measurements. Yes, changing the angles of the mirror cause the image coming out of the triplet to be crooked, but that is the goal, is it not? It comes out crooked because that is what is needed to make the image appear square on the screen.

I have no tools for measuring angles of correction [and I have no idea how to do it either], but it is likely no more or less than fresnel tilting. If you get too far, then the mirrors will send the image into the box's wall instead of the triplet. Perhaps if I had built this just for keystone correction [for a horizontal lamp, it looks like you should be able to get a full range of movement in a 24"x24" box], I could do miraculous things, but I built it for a specific box shape.

My keystoning was simply a result of what I did giving me that ability. I did not build this just to get keystone correction: I built it like this so that the box would not protrude in the headspace over the couch [it got hit a few times by waiving arms and bouncing puppies]. It also took the other end of the box out of the dining room. I used two mirrors because I refuse to bend the edge connectors running into the LCD [which eliminated the one-mirror design].

If you want to build your projector this way, do what I posted above with the drag light and plastic bag, get your angles and dimensions, and build around it. That is what I did. If you do not have a drag light, you could also use a desk lamp with a direction-controlling shade.

How much correction does this allow?

third paragraph