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Thread: Digital Eye Testing Chart

  1. #26
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    TV Feature: displaying images

    Quote Originally Posted by hbvision View Post
    For anyone capable of using FOSS (free open source software) there is this:
    http://radagast.ca/snellen/snellen.html

    I'll be setting it up on a Raspberry Pi with a usb remote. Expect it to cost $250 with monitor, mount, cables, remote.
    I'll write back once I have it tested.
    Most modern televisions - especially large screen televisions - have a USB port. These are typically used for firmware updates. However, it is also possible to place images on to USB drives and have them play on the television. For example, on my very inexpensive LCD TV, I have to change the TV's 'Source' to 'USB' - then I can browse the images on the USB drive using the remote control.

    It would seem that such a solution would work for displaying eye testing charts by displaying the eye charts in whatever software creates them, and then taking screen shots and saving those to the USB drive.

  2. #27
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    Quote Originally Posted by hbvision View Post
    For anyone capable of using FOSS (free open source software) there is this:
    http://radagast.ca/snellen/snellen.html

    I'll be setting it up on a Raspberry Pi with a usb remote. Expect it to cost $250 with monitor, mount, cables, remote.
    I'll write back once I have it tested.
    Did you manage to setup the snellen software? i wanted to try , but did not have a chance ...need to download a copy of linux...i wanted to do it on VMWARE... if u setup...can u tell me other than snellen chart...what other features is in that software other than snellen chart...

    Thanks

  3. #28
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    Quote Originally Posted by danielccn View Post
    Did you manage to setup the snellen software? i wanted to try , but did not have a chance ...need to download a copy of linux...i wanted to do it on VMWARE... if u setup...can u tell me other than snellen chart...what other features is in that software other than snellen chart...

    Thanks
    Question (to anyone): Aside from the Snellen chart, what features would you be looking for?

    I'm a hardware and software developer and have been for nearly 40 years. I can think of a half-dozen much less expensive ways to get this done using off-the-shelf components. Building an entire Linux machine just to show a single graphic seems to be overkill.

  4. #29
    What's up? drk's Avatar
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    Lots of goodies.

    Visual acuity is indeed measured by a Snellen chart, but you have to run a few patients to see what other things would help.

    My setup is programmable, so I can show a series of charts in a certain order.

    There are "line isolation" options, as well as "letter isolation" options.

    There are refracting aids, as well, such as polarized projection (not on an LCD screen, of course) to be used in conjunction with polarized lenses in the phoroptor for special tests, etc.

    It's more involved than...meets the eye!

  5. #30
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    Quote Originally Posted by drk View Post
    Lots of goodies.

    Visual acuity is indeed measured by a Snellen chart, but you have to run a few patients to see what other things would help.

    My setup is programmable, so I can show a series of charts in a certain order.

    There are "line isolation" options, as well as "letter isolation" options.

    There are refracting aids, as well, such as polarized projection (not on an LCD screen, of course) to be used in conjunction with polarized lenses in the phoroptor for special tests, etc.

    It's more involved than...meets the eye!

    Nothing you've mentioned is impossible, let alone difficult, for the platforms I have in mind. I can see this problem being solved for ~$100 in hardware and a fraction of that for the software - and no need to load Linux.

  6. #31
    What's up? drk's Avatar
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    Neat! Make some money.

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