NLS-Glossary

The distance between the maximum and minimum surface in which a scanner is capable of reading bar codes of a specified X dimension.                                                           

Dichroism is a phenomenon in which the optical absorption in a substance depends on the direction of propagation and the state of polarization of the light beam. A dichroic crystal is an optically anisotropic crystal in which either the e-wave or the o-wave is heavily attenuated (absorbed).

Dielectric is a material in which energy can be stored by the polarization of the molecules. It is a material that increases the capacitance or charge storage ability of a capacitor. Ideally it is a non-conductor of electrical charge so that an applied field does not cause a flow of charge but instead relative displacement of opposite bound charges and hence polarization of the medium.

Dielectric loss is the electrical energy lost as heat in the polarization process in the presence of an applied ac field (an alternating electronic field). The energy is absorbed from the ac voltage and converted to heat during the polarizations of the molecules. It should not be confused with conduction loss ${\mathbb{E}}^{2 }$
or ${\mathbb{v}}^2$/$\mathrm{ℝ}$. See complex relative permittivity.

Dielectric mirror is made from alternating high and low refractive index quarter-wave thick multilayers.

Such dielectric mirrors provide a high degree of wavelength selective reflectance at the required free space wavelength if the thicknesses of alternating layers ${\mathbb{d}}_1$ and ${\mathbb{d}}_2$ with refractive indices ${\mathbb{n}}_1$ and ${\mathbb{n}}_2$ are such that  ${\mathbb{n}}_{1 }{\mathbb{d}}_1+{\mathbb{n}}_{2 }{\mathbb{d}}_{2 }=\frac{1}{2\mathrm{\lambda }}$ which then leads to the constructive interference of all partially reflected waves at the interfaces.

Dielectric strength is the maximum field (Ebr) that can be sustained in a dielectric beyond which dielectric breakdown ensues, i.e. there is a large conduction current through the dielectric shorting the plates.