Inkjet transparency sheets like you'd find at your local office supply store [0] are polarized; you may not have to order polarizing film.
I used to own a car that had an LCD display where the orientation of the polarization was perfectly set so if I was wearing my polarized sunglasses, the screen was blank. I cut out a little overlay made out of an overhead transparency and fixed the problem.
Most thin sheets of polyester actually function as retarders (not necessarily quarter wave plates) due to the way their molecules are aligned during manufacturing. Here's one of the better cites on the topic, it includes some math to design any desired retarder:
Using a linear polarizer does change the polarization. If he puts his polarizer halfway between the incident angle and the desired angle, he'll get cos⁴(theta/2) of the original intensity in the desired polarization.
If you have two perpendicular polarizers, no light will pass through both. But, if you insert a polarizer at a 45 degree angle to both of them inbetween, some light will pass through. Am I wrong?
I used to own a car that had an LCD display where the orientation of the polarization was perfectly set so if I was wearing my polarized sunglasses, the screen was blank. I cut out a little overlay made out of an overhead transparency and fixed the problem.
0: http://www.officemax.com/office-supplies/presentation-equipm...