Three Monitors and Three Fresnel Lenses

When I first heard about using 3 monitors with racing sims, I started looking in to how to do it and what was needed. It looked very simple to do, but since I was a huge fan of using a Fresnel lens (F550 from http://www.3dlens.com/), I also wanted to try and use 3 Fresnel lenses with 3 monitors.

To use three monitors I am using the Matrox TripleHead2Go with a resolution of 3074 X 1024 and single GeForce 6800 GT graphics card. Many graphics cards and resolutions are supported (see the Matrox web page for details). Many available video modes of the TripleHead2Go support only up to a 60Hz refresh rate. This is the refresh rate of LCD screens and does not equate to the bad looking 60hz rate when applied to a CRT.

Setting up the TripleHead2Go is straight ahead, you just need enough room. Using 3 Fresnel lenses along with this setup makes thing trickier.

Things to consider when using 3 lenses:

how to mount the lenses to the monitors,
what distance will be best between the lens and monitor,
what distance will be best between you and the lens,
how much space will you need (the monitors will need to be further apart), and
at what angle will the side monitors be positioned?

To make things as flexible as possible I came up with a very simple design to hold each lens and monitor. The monitor sits in the frame with the lens hanging on front (in a dark room there is no need to put a shroud around the lens.) The monitor can be moved back and forth in the frame to adjust distance between itself and the lens. The whole unit can be moved as one piece to position the monitor where you want it. The lens can be moved up and down by the screws that hold them. The top bars holding the lenses can be moved to shift the lens left and right if need be. So I had lot's of flexibility. The only issue was that the lenses would not be able to be removed easily to use the monitors for regular computer work. I previously had decided to just dedicate the monitors to racing sims and the odd computer game I may play. The lack of clarity imposed by the effect of the Fresnel lens is not something you would want to deal with for regular computer work.

When I first used a Fresnel lens, it was with a single monitor. The best distance I found between the lens and CRT was 12 inches. I figured that was probably what I was going to use with the 3 monitors (that's why my lens holders are so deep.) When I first tried 12 inches with the new setup, I realized that the difference of what each eye was seeing on the inner edge of each side lens (the left edge of the right lens and the right edge of the left lens) was so different as to be distracting and physically bothersome to my eyes. I now believe this is due to the way the lenses are cut. Maybe a different cut (if it was available) would cure this (see picture below.)

I found that I could reduce this bad affect on the edge of the side monitors by putting the lens closer to the monitor. Four inches seamed to be a good compromise. Once the monitor was moved up to the lens, I had to move the whole unit farther away from me as the image size got smaller (the down side of moving the lens and monitor closer to each other) as I started to see the edges of the monitors.

I also tried putting thin strips of dark paper over where the lenses meet. This at first seamed counter productive as I was able to get rid of the monitor edges only to put them back in via a different format. The reason why this helped was that it eased the transition between the lenses, not only helping if things where not perfectly lined up, but also helping the distortion caused by the outer edges of the lenses being together.

Here is an attempt at a sketch to show this. The lines in the top and bottom picture are the same, but by dividing them up, they don't look as out of alignment. Pull back from the monitor until the bottom one looks ok and you will see the top one still looks bad. I will continue to experiment with this.

Benefits of 3 Fresnel Lenses

makes the screens look larger
focus is further out than at the face of the monitors
the lens seams to bring out depth (a very subtle 3d effect), and
it gives the ability to position monitors/lens to eliminate the edges of the monitors from between the middle and side monitors.

Problems of 3 Fresnel Lenses

distortion on inner sides of outer monitors
moving your head to the side (like leaning into a turn) changes what you see where the side lenses meet the center lens. Move your head far enough and you will see the monitor edges. This doesn't happen when you turn your head.
the distance between you and monitor and the angle of the side lens/monitor is dictated by the lens and not as flexible as without lenses and
-if you need the side monitors at extreme angles, (let say more than 45 degrees) you will be looking through the lenses at too great an angle.

Recommendations
Three screens work great and give great immersion. I highly recommend this approach. Make sure the sims you want to use support this mode and look into if they have any special views to better support 3 monitors. I am not sure if the Fresnel lens in a 3 monitor setup is worth it due to the issues mentioned above. If you use only one monitor, get a Fresnel lens!

Pictures disclaimer. It is hard to photograph with the lenses. The camera has only one '"eye" so it can't show the depth nor the effect of peripheral vision. The camera is sitting further back than where my eyes would be. This was done in order to see the full width of the lenses. Because of that, the lenses are in the wrong place for the camera and 1) you now see lines between the monitors, 2) you see an exaggerated fish eye view on the far left and right 3) there is way more distortion in the picture and 4) parts of the pictures look washed out and parts look very dark. Non of these things are experienced with ones own eyes. The best thing to take away from viewing these pictures is the larger view of what is around you.

All of these are at 3840 x 1024 resolution. The standard FOV was used. No other changes were made in the sims to accommodate using 3 monitors.

rFactor pictures

rfactor pic

Live For Speed pictures

netKarPro pictures

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