Micro-optical elements with their own scale of a few to
several hundred micrometers are extensively applied to optical
devices using MEMS technology to collect, distribute
and modify optical radiation. In general, micro-optical elements
can be roughly grouped into three generic areas; one
is refractive, another is diffractive and the other is reflective.
Refractive elements used in photoelectric systems are usually
more popular than reflective ones. But reflective optics
is useful for packaging an optical system into a smaller space