17.2.1 Spatial Light Modulator
A particularly versatile type of mask is the spatial light modulator (SLM). This
is an array of pixels that allows modulation of the phase or intensity of the light
over specific microscopic regions. Spatial light modulators are available in both
transmittance and reflectance modes. They are based on a variety of technolo-
gies, including microarrays of liquid crystals, mirror arrays, and light-emitting
diodes. For example, a micro-pixel array of light-emitting diodes has demon-
strated effectiveness for structured illumination [9]. For our purposes the
important feature is that generating a mask with the SLM is no more difficult
than displaying a bitmap image on a computer monitor. The flexibility and
precise pixelwise