An anticounterfeiting device comprising a surface relief structure having both
diffractive and polarizing properties. Polarization of reflected light is controlled
by the orientation and composition of a fine grating structure whose shortest period
is substantially smaller than the wavelength of visible light; and diffraction
is controlled by a longer period component of the grating structure having a second
orientation. Presence and arrangement of the polarizing properties of the device
are detected by illuminating the device with polarized light and viewing the reflected
light, or by illuminating the device with unpolarized light and viewing reflected
light through a polarizer. Because such a device is difficult to copy or reverse
engineer precisely, the authenticity of the device can be judged by the presence
and arrangement of the polarization properties and the diffraction properties in
the device.