PurpleSquirrels

DSI Multitouch construction – Part 8

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by

Ben Foster
in ,

In the never ending quest to get better blob tracking on my touch screen I decided to add more cameras. A few months ago I added a second camera but they didn’t quite cover the whole screen – there was about an inch gap in the centre of the screen. I didn’t want to use wider lenses because of the distortion so I decided to add two more camera to bring the total to 4, with each camera tracking a quarter of the screen.

I was trying to think of a good way to mount the cameras so that they were evenly spaced and I came up with the idea of using a piece of wood with a routed cavity to sit each camera in. The problem with this was that the wood would have to sit above the backlight of the LCD and so it would block some light. Then I remembered I had a spare piece of 10mm acrylic from my old 19″  FTIR touch screen. So instead of using wood I cut and routed the piece of acrylic so that the cameras had transparent mounting plates.

Here are some photos of my process…

Left: Acrylic measured so that the lense of each camera is perfectly spaced; Right: Testing routing the acrylic – I had to use the slowest speed and keep moving so the router bit didn’t gum up with melted plastic. Super messy!

Left: Routing the first cavity, very rough but it doesn’t matter; Right: All cavities routed and the mess from just one.

Left: Cleaned up; Right: New jigsaw, my old one was crap.

Left: Mess from cutting, this called for vacuuming the yard; Right: The two plates routed and cut.

Left: Cameras mounted with Blu-Tack; Right: All four cameras mounted and sitting in place – nice and evenly spaced!

That is all for now.

Comments

6 responses to “DSI Multitouch construction – Part 8”

  1. Robert Foster Avatar
    Robert Foster

    hey,
    Just wanted to ask how you resolved the problem with the backlight giving off IR? It looks like you’re still using the original backlight in these pictures where an earlier post mentioned you would have to replace it?

    Thanks,
    Rob.

    1. Ben Foster Avatar
      Ben Foster

      Hi rob
      I am still using the original backlight. It didn’t end up being as big of an issue as I first thought. I am getting plenty of illumination from my LEDs which is much stronger than the backlight.

      I also read that it can be difficult to hook up a different backlight and the screen may not function without the original connected.

      Cheers
      Ben.

  2. Robert Foster Avatar
    Robert Foster

    Cool! good to know – I’ve just pulled apart a 42″ Kogan (Samsung LCD apparently), and ordered the necessary bits from the US, now to design a cabinet for it all…

  3. Phidgets Inc Avatar
    Phidgets Inc

    How’d this go? Haven’t seen anything in a while and would love to see the completed project.

  4. Erdem Erciyas Avatar
    Erdem Erciyas

    Have a good day… i have a problem about backlight. i am runing lcd but i saw other object under the lcd panel.

    1. Ben Foster Avatar
      Ben Foster

      Are you using a backlight diffuser? It is required to blur the light coming from behind the LCD, otherwise you will see through it. I sandwiched the diffuser between to pieces of clear perspex and sat the LCD on top, and used tracing paper as the diffuser instead of the original one from the LCD which allowed more IR light to pass through.

      — Endlighten
      — LCD
      — Clear perspex
      — Diffuser (tracing paper)
      — Clear perspex
      |
      |
      |
      —- Backlight

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