Glossary: N

NIR (Near Infrared)

The portion of the electromagnetic spectrum from 700 to 1100nm. Definition may differ by application.

Neutral Density Filter (ND)

A type of filter that yields a constant attenuation, or optical density, value over a range of wavelengths (i.e. spectrally flat). It is useful for attenuating, or reducing, the amount of light in a system.


Caused by the unwanted spontaneous emission of light from a laser medium resulting in reduced optical performance.

Noise Equivalent Power (NEP)

The incident light power required to produce a signal on a detector that is equal to the noise. In this case, the signal-to-noise ratio is equal to one.

Non-Polarizing Beamsplitter

A type of beamsplitter that splits the incident light by a specific percentage without altering the polarization state of the transmitted or reflected light.

  See also Polarization , Beamsplitter

Normal Load Capacity

The maximum downward (compression) load or force that can be applied to a mechanical component perpendicular to the mounting surface. The center of force, or the center of gravity, of the load must be located in the center of the mounting surface.

Notch Filter

A type of filter designed to block a pre-selected bandwidth while transmitting all other wavelengths within the design range of the filter. Manufactured using the dielectric stack method, which uses a series of thin layers of dielectric materials of alternating refractive index.

Nth Order

Multiple combinations of wavelength and integer order values that will satisfy any given groove spacing, angle of incidence, and diffracted angle calculated from the grating equation. Gratings are generally specified in terms of first order diffraction since efficiency decreases with higher orders.

Numerical Aperture (NA)

The sine of the vertex angle of the largest cone of meridional rays that can enter or exit an optical system. In other words, it governs the amount of light entering or exiting a system. It is inversely related to the f/#.

Nyquist Limit

The theoretical limit of a camera's resolution or sampling ability, defined as the inverse of twice the pixel size. 

  See also Pixel

Spherical optics, aspheric lenses, prisms, imaging lenses, imaging and laser optics assemblies, and mechanics are just a few of our expertise.

Edmund Optics' engineers are experts in delivering the best solution possible. From stock products to custom designs, EO has the industry and technical knowledge to help meet your needs.

Over 15 regional offices in the Americas, Europe, and Asia to offer local support with world-class service.

Need to contact Edmund Optics? Use any of our fast and friendly services to meet your needs.