Field flattener lens

A field flattener lens is a special type of lens that makes things look flat when you look through it. Imagine you are looking at something far away, like a mountain range. Sometimes, when you look through a regular lens, the edges of the mountains can look blurry or curved. That's because the lens bends the light in a way that makes things look curved or stretched out.

A field flattener lens fixes this problem by bending the light in a different way. It helps to make the edges of the mountains look sharp and straight, so the whole scene looks flat and even. This makes it easier for scientists and photographers to take clear pictures of the things they are studying.

Think of it like ironing out a wrinkled shirt. The field flattener lens smooths out any wrinkles in the light, so everything looks nice and flat (just like a flat, ironed shirt).