Definitions

In an optical system, the gradual reduction of image illuminance as the off-axis angle increases, resulting from limitations of the clear apertures of elements within the system.

The product of the actual base or baseline of a rangefinder or heightfinder, and the power or magnification of the instrument.

Virtual histology refers to the use of digital technology and computational methods to simulate or recreate histological images and structures without the need for traditional physical slides and...

An image that is formed when rays emerging from an optical system are diverging from the optical axis. The virtual image is formed where the bundle of diverging rays appear to intersect each other...

Virtual reality (VR) is a computer-generated simulation of a three-dimensional environment or experience that can be interacted with and explored by an individual using electronic devices, such as a...

The use of miniature scanners to project raster-scanned video images directly onto the surface of the human retina, eliminating the need for a projection surface.

The maximum distance at which the eye can perceive and evaluate objects.

1. An instrument used to determine the visual range in an environment. 2. A type of photometer that artificially reduces an object's visibility to threshold limits and records the quantity of...

That region of the electromagnetic spectrum to which the retina is sensitive and by which the eye sees. It extends from about 400 to 750 nm in wavelength.

That term pertaining to the spectral region that can be perceived by the eye.

An instrument that uses an erbium:glass laser to determine cloud height from the ground.

The processes in which luminous energy incident on the eye is perceived and evaluated.

The angle subtended by an object at the point of observation.

An imaginary line between the object, through the nodal point of the eye, and the fovea, or point of finest retinal acuity.

A pair of stars (double star) that can be seen separately with a telescope, generally by setting a filar micrometer for the separation and position angle. Observation of visual binaries improves with...

Visual detection and ranging (ViDAR) is a technology that utilizes optical sensors, such as cameras or other imaging devices, to detect and track objects in the surrounding environment. Unlike...

A device that enables visual tracing of a fiber optic cable to check for breaks and defects by coupling visible light into the cable. Also called fiber tracer.

The angular field of view that is seen by the eyes when fixed on a point straight ahead. The normal binocular visual field is approximately 130° in diameter.

A photometer that permits visual comparison of the luminance of two surfaces.

The value of the expanse of b-particles in an absorber, evaluated by visual examination of breaks in the absorption curve.

An electron tube that stores and visually displays information by means of a cathode-ray-beam-scanning and charge-storage mechanism.

A series of high contrast block letters or similar objects arranged to permit the evaluation of eyesight in humans.

A visual system including a tiny television tube and imaging optics, all contained in a helmet to be worn by pilots in flight simulator training.

Having the characteristics of glass.

The transparent fluid that fills the portion of the eye between the eye lens and the retina (the posterior chamber).

A blank area (caused by insufficient inking of the paper) that falls within the range of an intended character stroke in an optical character-recognition system.

The induced birefringence in isotropic gases that results when the gases are placed in strong fields.

A nondestructive testing method for very large scale integration circuits, using a scanning electron microscope to monitor changes in the electronic state of the chip as it is fed test voltages while...

A device that converts alternating voltage to direct voltage, while at the same time increasing its amplitude.

An electric cell having two electrodes of unlike metals immersed in a solution that chemically affects one or both of them, thus producing an electromotive force.

Volume Bragg gratings (VBGs) are specialized optical elements that consist of periodic variations in refractive index throughout the volume of a transparent material, typically a photosensitive glass...

A three-dimensional hologram.

Volumetric imaging refers to the capture, visualization, and analysis of three-dimensional (3D) information from a volume of space. Unlike traditional two-dimensional (2D) imaging, which provides...

A vortex phase plate is an optical device designed to impart a phase singularity, commonly referred to as a vortex or phase vortex, onto a light beam. This singularity results in a phase profile...

An element within a three-dimensional data set image.

A system used for gratings that consists of a concave mirror, a grating and a plate holder mounted normal to the grating to reduce astigmatism and spherical aberration. The mounting yields a...

In the context of electronics and semiconductor manufacturing, a wafer refers to a thin, flat disk or substrate made of a semiconducting material, usually crystalline silicon. Wafers serve as the...

An image intensifier tube in which the photocathode and the output of the microchannel plate are proximity-focused on the microchannel plate input and output phosphor screen, respectively.

A standard of luminous intensity evaluated as the luminous intensity of 1 cm2 of a blackbody at the melting point of platinum.

A solution containing colloidal silica particles.

The power that gives rise to the production of energy at the rate of 1 joule per second.

1. An undulation or vibration; a form of movement by which all radiant energy of the electromagnetic spectrum is estimated to travel. 2. A type of surface defect, usually due to improper polishing.

In quantum mechanics, a wave function (often denoted by the Greek letter Ψ, psi) is a mathematical description that represents the quantum state of a particle or a system of particles. It...

The frequency of a wave divided by its velocity of propagation; the reciprocal of the wavelength.

Also referred to as physical optics - the area of optics in which the wave nature of light is essential when defining its propagation. To exploit the wave phenomena of light, one must interact light...

An optical element having two principal axes, slow and fast, that resolve an incident polarized beam into two mutually perpendicular polarized beams. The emerging beam recombines to form a particular...

Any type of interference produced by a beamsplitter.