MEMS SLM along the optical axis. For most applications, the resolution specifi-
cations require the height to be much larger than the height of practical MEMS
structures by themselves, so grazing incidence and large diffraction angles are
necessary. Early MEMS-diffract ive filters that were designed for normal incidence
[142] are therefore useful only for low-resolution applications. Better resolution
can be obtained by adding another diffractive eleme nt [143], or by creating a
diffractive structure with high diffraction angles [144].
The third characteristic of diffractive filters that is illustrated by Figure 19.24 is
that the loss of the filter is proportional to its complexity. The inciden t light is split
into N spatially separate channels