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Strange phenomena involving pinball display

  1. Jan 10, 2014 #1
    I was playing my old pinball machine today when the display started to malfunction. After several minutes, the dot matrix display shows only a horizontal stripe as shown below.

    The interesting thing is that when I move my eyes vertically over the horizontal stripe on the display, I am able to see words as if the screen is working properly! As soon as my eyes stop moving, it collapses back into a single line. It is as if everything is contained within this stripe on the display and somehow moving my eyes over it separates it out. The other interesting thing is that if I move my eyes up, then the words are displayed upside-down and mirror image. If I move my eyes down then the image is right side up... so strange.

    I was able photograph it by moving my camera across the display (ignore the multiple images) but it's difficult to see unless you zoom in. The second attached picture shows the words "free play" upside down and mirror imaged. [remember the display looked like image 1 in reality]

    The third image shows some numbers, again upside down and mirror image but a little more clearly than the previous image.

    I'm assuming this phenomena has something to do with the nature of the display itself. It is an old gas-plasma display but I know nothing of the specifics of the gas. I'm very interested in figuring out how this works. Does anyone have any ideas? :confused:
    Last edited: Jan 10, 2014
  2. jcsd
  3. Jan 10, 2014 #2


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  4. Jan 10, 2014 #3
    I think you are correct. After researching a bit more, the display is a 128x32 matrix where each of the 32 rows is refreshed one at a time starting from the top and working down. When working properly, they appear to be lit up all at once to the human eye due to the high refresh rate (~200hz).

    I think what is happening is that all of the I/O commands for the entire display are being passed through the single row of bulbs in sort of a cycle. Therefore, when moving one's eyes over the display it is acting as a moving "shutter" capturing each of the individual lines and spreading them out over space. The brain is able to put this together as the image!
    (This would also explain why moving one's eyes in the opposite direction causes the image to flip)

    Fascinating :cool:
    Last edited: Jan 10, 2014
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