0
\$\begingroup\$

Though the question may sound naïve at first, I still wonder if it would somehow be possible to use an LCD/TFT/OLED or other Panel as an image-sensor.

From my understanding of how these kinds of displays work I’d imagine it would at least need a totally different type of controller to read out possible light exposures of the display pixels.

I guess a TFT would not work, but are there other types that could work, even monochrome?

I’d appreciate if someone who is into this kind of technology would like to elaborate on this.

\$\endgroup\$
  • \$\begingroup\$ I would hazard that you would not be able to do it. I expect that any transistors and LEDs would be designed to be resistant to light effects to avoid sensitivity to ambient changes. You could use it as a 'flying spot' scanner to scan a large format negative I suppose if you had a photomultiplier or other sensitive detector and scanned a white dot on a backlit screen behind a negative. \$\endgroup\$ – KalleMP Nov 13 '14 at 9:10
  • \$\begingroup\$ edn.com/design/led/4363842/Use-LEDs-as-photodiodes \$\endgroup\$ – Andy aka Nov 13 '14 at 9:15
  • \$\begingroup\$ So a rewired monochrome LED diplay could work? \$\endgroup\$ – Alexander Rutz Nov 13 '14 at 9:29
  • \$\begingroup\$ If you can find a monochrome LED display, and it doesn't have per-pin transistor wiring that will get in the way, and you can extract information despite the row/column wiring, maybe. It's going to be far easier to get hold of a CCD for this. \$\endgroup\$ – pjc50 Nov 13 '14 at 11:11
3
\$\begingroup\$

Individual LEDs can be used as light sensors: they behave like photodiodes. OLEDs are potentially capable of behaving like this as well (they're also semiconductors), but I can't find reports of anyone having tried it. It's probably extremely inefficient.

LCDs cannot: they operate by applying a field to twist the crystals, and there's no photosensitivity in this process.

Note that unless you optically focus and project an image onto the screen, you won't get a usable image even if you do manage to read out of an OLED screen. You'll just get the average of the incident light.

\$\endgroup\$
  • \$\begingroup\$ Interesting, thanks. I’d imagine using a lens to project an image to the display. A large format camera could be a nice starting point. \$\endgroup\$ – Alexander Rutz Nov 13 '14 at 9:22
1
\$\begingroup\$

It can't work, unless the display has a light sensor to regulate the luminosity, like you have on smartphones.

  1. Physically, an LCD doesn't react to incoming light, and if it does, not to a significant extent. It may react to heat though.

  2. The interface of a display is not made to output data, so you would need a significant amount of hacking to get to the analog pins.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.