An optical device includes a non-transparent substrate. The optical device
further includes a first optical layer which is at least partially
transmissive and at least partially reflective to incident light. The
optical device further includes a second optical layer which is at least
partially reflective to incident light. The second optical layer is
spaced from the first optical layer. At least one of the first optical
layer and the second optical layer is movable between a first position
with a first distance between the first and second optical layers and a
second position with a second distance between the first and second
optical layers. Movement of the at least one of the first optical layer
and the second optical layer between the first and second positions
modulates the reflectivity of the device.