I'm designing a DIY electronics project using a black water bottle with a small LCD integrated into one section of the outer wall. The upper part would still hold water, while a sealed lower compartment would contain the electronics, possibly including an old Android phone to control the display. The screen should look like an ordinary black section when viewed normally, with simple white text becoming visible only through specially prepared polarized glasses. A tiny Bluetooth input device with a motion sensor and one or two buttons would act as a miniature mouse for navigating the phone or display. I'm mainly looking for advice on whether an LCD and carefully arranged polarizers can make the screen effectively invisible to the naked eye while remaining readable through the glasses, and how best to mount and seal the display in the bottle wall while keeping the assembly compact and reasonably waterproof.
1 Answer
LCDs already rely on polarizing layers to produce a visible image, so the basic idea is optically plausible. One possible approach would be to remove or replace the screen’s outer polarizer and use the polarizing lenses in the glasses as part of the viewing system. The orientation of the glasses would be critical, especially if the display is angled. However, it probably would not be as simple as removing one layer from any LCD: the panel still needs the correct polarizer arrangement, and ambient reflections or light leakage could make the screen visible without the glasses. You would likely need to experiment with a sacrificial LCD, different polarizer angles, and a dark cover layer to get strong contrast. Mechanically, placing the display behind a precisely fitted dark window and sealing the electronics in a separate compartment would be more practical than making the LCD itself part of the bottle’s waterproof wall.
Not necessarily any LCD. Removing the outer polarizer may leave a washed-out or mostly bright panel, and the remaining layers still have to be aligned correctly. Testing several inexpensive panels would be safer than modifying the only display you have.
So could I use nearly any LCD and just remove its existing polarizer, or does the panel need a particular construction?