Photonics Dictionary: O

An acid-resistant, lustrous volcanic glass, usually black or banded.

A form of high-power microscope objective where the space between the object and the first element is filled with an oil having the same index as that element. This form reduces losses, increases the...

Also referred to as the opposition surge, the opposition effect is a photometric phenomenon in which a rough retroreflective surface appears brighter when illuminated from directly behind the...

The mathematical evaluation of an optical system to determine and quantify its basic optical properties and image quality characteristics.

Optical cements and adhesives are specialized materials used in the assembly and bonding of optical components in optical systems. These materials are designed to provide secure and durable bonds...

A measure of the transmittance through an optical medium. Optical density equals the log to the base 10 of the reciprocal of the transmittance. where τλ is transmittance. In spectroscopy,...

The transmittance of a point on a photographic negative equal to the log to the base 10 of the reciprocal of the transmittance through the negative at that point.

Optical design and engineering services involve the development, customization, and optimization of optical systems and components to meet specific performance requirements and application needs....

Optical design software refers to specialized computer programs used by optical engineers, physicists, and designers to simulate, model, analyze, and optimize the performance of optical systems and...

In dry etching, a method of characterizing the composition of solid materials such as metal. Atoms in the OES technique are excited by energy that comes from a spark formed between the sample and an...

The process by which an atomic system changes from one energy level to another by either the emission or absorption of visible, infrared or ultraviolet radiation.

The element that resembles a lightweight metal, but when very pure, has a very high electrical resistance and is transparent to the infrared between about 0.5 and 15 µm.

A transistor that uses an electro-luminescent source, a transparent base and a photoelectric collector.

The emission of gas or de-aeration due to thermal variations and often occurring in a vacuum. In a cleanroom, contamination from the spontaneous emission of absorbed particles.

A process for the production of optical fibers. A glass bait is rotated in a traversing flame of a reaction burner. Reactants passed through the flame react with oxygen at the high temperatures to...

The figure seen through or imaged by an optical system. It may contain structures, natural or artificial, or it may be the real or virtual image of an object formed by another optical system. In...

A coarse diffraction grating that is used to form a scale of intensities to determine the relative magnitudes of stars. The grating is placed over the objective of a telescope to form a diffraction...

1. A prism used in some instruments to bend light 90° before it enters the objective. 2. A dispersing prism located in front of an astronomical telescope objective to produce spectra of all...

A common technique in microscopy, oblique illumination is one in which the object is illuminated by a light source that is at an oblique angle (on the side) to the optical axis. This technique is...

coma, fifth order aberration with on-axis focal point variation with incident off axis ray height position

A hemispherical covering that is rotatable about a central axis. There is a slit opening along one side wide enough to allow a telescope to be directed at any vertical angle up to 90°.

Refers to the characteristic hue of the ocean according to the presence and concentration of specific minerals or substances, such as chlorophyll. Atmospheric aberrations of color must be corrected...

In optics, an octave typically refers to a range of frequencies or wavelengths that spans a factor of 2. In other words, when dealing with optics, an octave encompasses a doubling of frequency or...

The physical adaption of the eye lens, by means of ciliary muscle contraction, in order to maintain a clear, in focus image of light and other objects and surroundings at a given distance onto the...

The prism used in a rangefinder to bend the lines of sight through the instruments into the eyepieces.

An electro-optical infrared tracker consisting of a beamsplitter, an illuminating source, an image dissector tube and an electronics unit, that automatically acquires and tracks particular eye...

Off-axis paraboloid and ellipsoid mirrors are specialized optical components used in various optical systems, particularly in applications requiring precise focusing, collimation, or imaging of...

The electrical resistance between two points of a conductor when a constant difference of potential of one volt, applied between these points, produces in this conductor a current of one ampere, the...

A polished plano-parallel plate that is contacted to an unpolished glass surface to permit see-through analysis of the material. The plate eliminates effects because of the surface quality of the...

Oleophobic is a term used to describe substances or materials that repel or resist oils. The word oleophobic comes from the Greek words "oleo," meaning oil, and "phobos," meaning fear. Oleophobic...

Opacity refers to the degree to which something is not transparent or translucent, meaning that it doesn't allow light to pass through it easily. It's a measure of how much a material obstructs the...

A material consisting of very small colorless particles imbedded in a clear glass matrix. It is available in two forms: flashed opal and pot opal. The flashed variety consists of a rather thin layer...

An opaque projector is a device used for enlarging and projecting images from opaque objects such as printed pages, photographs, or three-dimensional objects onto a screen or surface. Unlike a...

An interface in an optical network that permits an optical signal to pass without changing the optical signal to an electrical signal and therefore does not limit the signal to a specific protocol.

In morphological image processing, a series of erosions followed by the same number of dilations.

The methods and techniques used to obtain medical photographs of the human eye. To photograph the exterior of the eye, conventional still photographic equipment and procedures are used. Similarly, in...

Ophthalmology is a branch of medicine that focuses on the anatomy, physiology, and diseases of the eyes and visual system. Ophthalmologists are medical doctors who specialize in the diagnosis,...

Also referred to as a funduscope, an ophthalmoscope is a specialized instrument used by ophthalmologists for observing and photographing the fundus (interior) of the eye which includes the retina,...

The capacity of a chiral substance such as a crystal or molecule to rotate the plane of polarized light that is transmitted through it. Any substance that cannot be superimposed onto it's mirror...

A measure of the optical path length for light traveling from the sun or other celestial source through Earth's atmosphere to sea-level relative to the optical path length traveled by light from the...

Optical artifacts refer to undesired or unintended effects that can occur in optical systems, such as microscopes, cameras, telescopes, and other optical instruments. These artifacts can distort or...

An optical assembly refers to a collection of optical components that are carefully arranged and aligned to perform a specific function within an optical system. These components may include lenses,...