I'm designing a DIY electronics project using a black water bottle that should still look ordinary from the outside. A small LCD would be integrated into one section of the bottle wall, while the upper section would remain available for water and the lower section would be sealed off for electronics.
The goal is for the display area to appear completely black or otherwise indistinguishable from the bottle when viewed normally. White text should become visible only through specially modified glasses. My initial idea is to use an LCD with its polarization layers arranged so that the glasses provide the viewing polarization.
An old Android phone could serve as the controller, connected by a short cable to the small display. A tiny Bluetooth input device with a motion sensor and one or two buttons could act as a miniature mouse for navigating the phone or displayed content. The screen would mainly show simple white text on a black background.
I'm looking for advice on whether this optical arrangement is practical. Could removing or rearranging the LCD's polarizer make the image effectively invisible without the glasses while still producing readable white text through them? Would the result depend on the viewing angle or the orientation of the polarizing filters? Would another display or filter arrangement work better?
I'd also appreciate suggestions for mechanically integrating a small display into the bottle wall, routing its cable through a minimal opening, and keeping the electronics section compact and reasonably waterproof. I want to build the system myself rather than use a ready-made product.
1 Answer
The basic idea is technically plausible because LCDs already rely on polarizers to create a visible image. In principle, you could remove the LCD’s output polarizer and use the polarized lenses in the glasses as the viewing filter. The glasses would need to be aligned with the polarization direction required by the panel, and the result could change noticeably if the screen or glasses are rotated or viewed at an angle.
Not necessarily. Different panels use different optical stacks, and removing a polarizer can damage the panel or leave poor contrast. It would be best to experiment with an inexpensive spare LCD first and test the panel’s brightness, viewing angle, and polarization direction before trying to integrate it into the bottle.
So would this work with any LCD if I carefully removed its existing polarizer?