Definitions

The size of the field of view in the object space of an optical system as differentiated from that in the image space (apparent field).

Any form of laser; e.g., a dye laser, having an output that can be adjusted over a wide range of wavelengths. Normally the range is about 70 nm wide.

Turbidity is a measure of the cloudiness or haziness of a fluid caused by the presence of suspended particles. These particles can include sediment, silt, clay, plankton, and other microscopic...

Simulation of atmospheric turbulence for laboratory experimentation purposes, achieved by creating an unstable vertical gradient temperature in a tank filled with water.

A defect of natural quartz crystals in which both the right and left quartz are in the same crystal.

Characteristic of an acousto-optic modulator, defined by the overlap integral of the incident light and sound field profiles; similar to a convolution operator.

Two-photon excited fluorescence (TPEF) is a nonlinear optical method that allows imaging of biological cells and living tissue. The advantage of TPEF in comparison to conventional fluorescence...

This results from the simultaneous absorption of two photons, each having half the energy needed for excitation and requiring a high spatial and temporal concentration of photons. The ensuing...

Two-photon polymerization (TPP) is a technique used in additive manufacturing, specifically in the field of 3D printing. It involves using a focused laser to polymerize a photosensitive material in a...

A testing device that provides a contour map of the emergent wavefront for the observer in terms of the given wavelength of the light.

Twyman-Green interferometry is a technique used in optics to measure the flatness or surface profile of optical components with high precision. It is based on the principles of interference of light...

A system used to measure very small displacement by electrical means.

A dark-field microscope used to view extremely small objects. These objects are suspended in a gas or liquid in an enclosure having a black background. A convergent pencil of bright light enters from...

The rays (such as ultraviolet rays) lying past the visible region of the spectrum.

A highly accurate cathode-ray tube used to display information with the utmost efficient stability and resolution. The information is viewed as a series of points, particularly suited for...

A laser capable of generating light pulses that last only a few femtoseconds. This can be achieved by nonlinear filtering to increase bandwidth and compress the pulse or by passive mode-locking or...

A device that uses a piezoelectric crystal to convert ultrasonic sound waves, transmitted through a subject, into a voltage that modulates the electron beam of a cathode-ray tube.

Ultrasound used in the cleaning of metal and optical parts by virtue of its vibration rates. Large acoustic forces break off particles and contaminants from surfaces.

An instrument with a fluid that modulates a light beam traversing it because of the effect of ultrasonic waves passing through the fluid.

Ultrasonic refers to sound waves with frequencies higher than the upper audible limit of human hearing, typically above 20,000 Hz. These waves are termed ultrasonic because they are beyond the range...

Ultraviolet-C (UV-C) refers to a specific range of ultraviolet radiation with shorter wavelengths than those of visible light. UV-C radiation spans the electromagnetic spectrum with wavelengths...

Ultraviolet (UV) fiber optics refers to optical fibers that are designed and optimized for the transmission of ultraviolet light, which is electromagnetic radiation with wavelengths shorter than...

A lens intended for use with wavelengths shorter than about 380 nm. It must be made of quartz, calcium fluoride, lithium fluoride or some other material transparent to ultraviolet radiation, as glass...

The study and photographing of microscope specimens in ultraviolet light; using an optical microscope containing fluorite and quartz components to efficiently image wavelengths much shorter than the...

A technique for measuring the energy spectrum of electrons emitted during the absorption of ultraviolet radiation. This spectrum reveals the characteristic ionization energies of the molecules and...

Ultraviolet reflectance refers to the ability of a material or surface to reflect UV light. Ultraviolet light is electromagnetic radiation with wavelengths shorter than those of visible light,...

That invisible region of the spectrum just beyond the violet end of the visible region. Wavelengths range from 1 to 400 nm.

A connection, typically made up of one or more cables, between a laser head and a separate power supply. Flexible pipes or hoses are sometimes used to protect and stabilize multiple cables.

The field of photography concerned with the recording of subjects beneath the water with a watertight, water-resistant camera system.

A color space in which equal distances represent equal visually perceived color differences.

A piezoelectric transducer made of a thin strip of piezoelectric material bonded to a strip of metal.

Refers to the transistors in which the working current flows through only one type of semiconductor material, either P-type or N-type. In unipolar transistors, the working current consists of either...

A system by which consumer products are assigned a bar code that is read by a scanner at a cash register, enabling computerization of pricing and inventory records.

One of the four functions that allows the computation of a transparent medium's index of refraction, provided the index has been identified for four standard wavelengths.

An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without a human pilot onboard. UAVs are remotely controlled or autonomously operated, and they can be used for various...

A multilayer antireflective thin-film coating, so called because its reflectance rises steeply at wavelengths above and below a narrow band at zero. The v-coat is particularly useful in high-power...

A V-shaped channel pressed or etched into a substrate, in which, for example, optical fibers may be placed to create an integrated optical component.

In an ionic crystal, the region in the crystal lattice where the ion, predicted to be present, is absent.

In optics, the term vacuum typically refers to a space devoid of matter, including air and other gases. However, in practical terms, achieving a perfect vacuum, where there is absolutely no matter...

Equipment dependent on the effects of a vacuum. The principal applications in optics are in the coating of lenses and substrates and the fabrication of multilayer interference filters.

A valve that serves to release air into an evacuated system.

A vacuum chamber is a sealed enclosure from which air and other gases are removed to create a low-pressure environment, typically close to or at a complete vacuum. These chambers are often...

A gauge designed to measure the degree of vacuum in an evacuated vessel. A simple U-tube containing mercury is adequate for low vacua, but for high vacua other methods must be employed. See McLeod...

Any source that emits radiation of wavelengths between 100 and 300 nm. Instruments used to study these sources must be evacuated, as vacuum ultraviolet does not travel freely in air.