Photonics Dictionary: E

A color filter, generally used in photography, to emphasize certain color tones and to modify others in a picture for a more dramatic image. A blue effect filter, for example, darkens red and yellow,...

For a lens with an obscured or noncircular aperture, the focal length divided by the effective aperture.

1. That portion of the aperture that functions to collect energy and deliver it to the final system detector. 2. For an obscured or noncircular aperture, the equivalent nonobscured, circular aperture.

In photoelectric sensing, the portion of the transmitted beam that actually functions in the system; the diameter of the beam that determines the presence or absence of an object by being blocked or...

The color of an object when it is illuminated by a nonisophotic source.

A characterization of the throughput performance of data storage systems; the EDR is the total of data retrieved divided by the total time it takes to retrieve it, expressed as megabytes per second.

The real numerical aperture (NA) of a fiber when the computed NA is not valid because of change in the glass indices during drawing and fusion.

As applied to a device or machine, the ratio of total power input to the usable power output of the device.

A weight reducing method whereby material from the rear of a reflector is removed leaving a pattern of ribs normal to the surface in an egg-crate pattern.

A scale attached to a microscope eyepiece that is seen superimposed on the image and that is used to measure the dimensions of the viewed object.

A unit of energy equal to the amount of energy absorbed by one molecule of material undergoing a photochemical reaction, as determined by the Stark-Einstein law.

Three proportional coefficients labeled Am, Bmn, and Bnm, that respectively characterize the rate of spontaneous emission, induced emission, and absorption of radiation by an atom, ion or molecule.

A shift in the direction of the red in the spectral lines of light which, defined by the relativity theory, will have decreased frequencies upon emerging from a highly gravitational field.

Scattering caused by the interaction between ingoing and outgoing particles of the same type, with no loss of kinetic energy.

A change in the refractive index of an optical fiber caused by variation in the length of the fiber core in response to mechanical stress.

Any material of a macromolecular nature that can stretch at room temperature to more than twice its length and return to approximately its original shape when stress is released.

The organic inclusion in quartz crystal that forms delicate films and microspheres and that shows a maximum absorption at 450 nm.

A refracting telescope that uses a prism to bend the line of sight 90°.