According to [Kelsey], transparent displays are guaranteed to make “everything feel like the future.” Unfortunately they’re hard to find, and the ones typically available are OLED and can’t make solid black colors. But as luck would have it, it’s possible to repurpose a common LCD to be sort of transparent.
A LCD uses nematic crystals that can polarize light, with the amount of polarization changing based on the electric field applied to the crystal. Light enters the front of the panel through a polarizing film, passes through the display, and then bounces off a reflective back coating. The display itself usually polarizes light in a way that matches the front polarizer. That means if you do nothing you get reflected light. However, if a part of the LCD gets an electric field, it will repolarize in such a way as to block the reflected light making the display look black in that area.
[Kelsey’s] trick is to peel off the reflector and replace it with polarizing film taken from another display. The new polarizer needs to be bigger than the display for one reason: you need to match the polarizing angle of the front film with the new back film. That means if the new film is exactly the right size, it won’t be able to rotate without leaving gaps. By starting with a larger piece, you’ll be able to rotate for maximum transparency before you stick it on.
We’ve seen some homemade transparent numeric displays. The transparent wood, though, has usually left something to be desired.
Though [Connor] labels it as a work in progress, we’re pretty impressed with how polished his transparent 7-segment display looks. It’s also deceptively simple.
The build uses a stack of seven different acrylic panes, one in front of the other, each with a different segment engraved onto its face. The assembly of panes sits on a small mount which is placed over seven rows of LEDs, with 5 LEDs per row. [Connor] left an air gap between each of the seven individual acrylic panes to clearly distinguish which was lit and to match the separation of the LED rows. To display a number, he simply illuminates the appropriate LED rows, which scatter light across the engraved part without spilling over into another pane.
You can find a brief overview and some schematics on [Connor’s] website, and stick around for the video demonstration below. We’ve featured [Connor’s] work before; if you missed his LCD data transfer hack you should check it out!
Continue reading “A Transparent 7-Segment Display”
Just about every engineer needs to take a drawing class, but until now we surprisingly haven’t seen electronics thrown into rulers, t-squares, and lead holders. [Anirudh] decided to change that with Glassified. It’s a transparent display embedded in a ruler that is able to capture hand drawn lines. These physical lines can be interacted with or measured, turning a ruler into a bridge between a paper drawing and a digital environment.
For the display, [Anirudh] mounted a transparent TOLED display with a digitizer input into a ruler. The digitizer captures the pen strokes underneath the ruler, and is able to interact with the physical lines, either to calculate the length and angle of lines, or just to bounce a digital ball inside a hand-drawn polygon.
There’s no word on how this display is being driven, or what kind of code is running on it. [Anirudh] said he will have some schematics and code available up on his website soon (it’s a 404 right now).