Photonics Dictionary: E

The flat or angled surface, usually fine-ground, that limits the aperture of a lens or prism surface.

In image processing, the location of edges by employing templates that respond to the first or second derivative of gray-scale intensity in the neighborhood of each pixel.

In image processing, any operation that strengthens information about the edges of objects displayed. Three types of spatial filtering are used: shift and difference, gradient and Laplacian.

In image processing, a segmentation algorithm for isolating a region in an image by following its edge.

Intensity distribution in the image of an edge. The gradient of the edge-response curve is a measure of the image quality of the optical system under test.

Technique for the precision evaluation of coincidence of a laser beam's center with the edge of the object under study and exact location of that edge by means of a double electronic differentiation...

The maximum variation in thickness of a lens as measured around a diameter centered on the optical axis. The ETD divided by that diameter yields the wedge of the lens.

Process for growth of solar cells that results in rectangular shapes consisting of many interconnected cells in a series or series-parallel arrangement. EFG cells show increased efficiency with...

An edge-emitting light-emitting diode is a type of LED structure where light emission occurs primarily along the edge of the semiconductor chip rather than from the surface. Edge-emitting LEDs are...

A lamp that uses the transmission of an electric current through a gas or vapor to produce illumination. Neon, mercury and argon lamps are examples of electric-discharge lamps.

A device consisting of an airtight quartz tube that holds the material to be analyzed. When a high-frequency electrostatic field, generated by microwaves, is applied to the tube, it emits energy of a...

A panel of photoconductive and electroluminescent layers used as either a positive or negative image intensifier, depending on amplitude and phase of its two power supply voltages. The...

An image intensifier tube that uses a magnetic field for focusing. It yields high-quality images, but its use is limited by its size and weight relative to other image tubes.

A cathode-ray tube that increases the brightness or size of an image or forms a visible image from invisible radiation. The focal plane for the optical image is a large, light-sensitive, cold...

An EMCCD (electron-multiplying charge-coupled device) camera is a type of scientific camera specifically designed for low-light imaging applications that require high sensitivity and fast readout...

An advanced magnetic device used in x-ray lithography to beam x-rays onto the surface of silicon wafers used for semiconductor circuits.

The point at which short-wavelength transmission is cut off.

The effect produced by electrical charges or fields alone, without interaction with magnetic influence.

A nonmagnetic instrument utilizing an electrofocus and deflection tube with a photocathode for imaging purposes. The optical image is converted into a photoelectric output at the photocathode and is...

Information storage on a dielectric medium that represents the data as those spots on the medium having electrostatic charges, forming an observable record of the data.

An image intensifier that uses electrostatics to amplify and focus the electronic image.

In optics, the light ray leaving a medium in contrast to the entering or incident ray.

The maximum to minimum range of temperature, pressure, humidity, vibration and biological conditions under which an optical component or system can function and be stored. The range required depends...

An image, real or virtual, whose spatial orientation is identical to that of the object. The image obtained at the retina with the assistance of an optical system is said to be erect when the...

The lowest anode voltage at which a gas tube can sustain a discharge.

In a waveguide, a change in direction of the axis without deviating from the plane of polarization.

Observed phenomenon of a small developed image with higher density than a larger image because of variation in photographic plate densities with variations in size of opening.

A grating that serves to provide higher resolution and dispersion than the average grating, and still has a greater free spectral range than either the Fabry-Perot etalon or the reflection echelon.

A specialized form of diffraction grating consisting of assembled glass plates of equal thickness that resemble a flight of stairs. The light enters through the largest plate at the end and emerges...

The finishing of the edge of an optical element by grinding.

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,...

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.

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

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

Any lamp whose emission of radiant energy is dependent upon the passage of an electrical current through the emissive medium.

A device that uses four electrodes set in an alternating positive-negative polarity series to focus the beams of charged particles employed in electron microscopes and particle accelerators.

Expression of the length of a transmission medium in terms of wavelengths of the propagating wavelength. In general, electrical length is an expression of physical length in wavelengths, radians or...

The effect whereby a light beam is deflected by a birefringent prism when its polarization is changed by voltage applied to an electro-optical crystal through which the beam passes. The deflection of...