Polaroids, in this sense, are sunglasses treated with Polaroid: a material that cuts glare by letting light through in mainly one direction. People say Polaroids the way they say a brand that became a type — a pair of dark glasses for sun and driving, often with the capital letter still sitting on them because Polaroid began as a trademark. Informal English uses the plural for the glasses themselves: put on your Polaroids. Though actually the same name is famous for instant photos, that is a different thing; here we are talking about the sunglasses.

偏光墨鏡（Polaroid；不是拍立得照片）