Photonics Dictionary

Reflectance spectroscopy is a technique used to analyze the reflective properties of materials across various wavelengths of the electromagnetic spectrum. By measuring the reflectance of light from a...

The term reflective is an adjective that describes the ability of a surface or material to reflect light or other forms of radiation. It implies the capability of bouncing back or redirecting...

A lamp used in projection that is made with a reflector built into the bulb, normally by coating a portion of its interior with a reflective material to ensure the reflector's optimum position in...

A light ray that has had its direction altered because of its traversing an air-to-glass interface at some angle. In an optical waveguide, a ray that is refracted from the core into the cladding.

A figure of merit corresponding to the amount of light seen by a viewer through binoculars. A higher number indicates a brighter image in low-light situations. The relative brightness value is...

The ratio of the velocities of light in two adjacent media, neither of which is air.

The discernment of depth or apparent difference in distance that causes the object to stand out from its background because of stereoscopic vision. The impression of relief can be obtained from the...

A device employed to identify toxic agents lingering on the ground or in the air from up to three miles away, by using laser beams to detect infrared light-absorption patterns that can be analyzed to...

Remote sensing is a method of data collection and observation where information about objects, areas, or phenomena on Earth's surface is gathered from a distance, typically using sensors onboard...

The optical phenomenon in which white light dispersed by small particles in suspension appears blue when viewed through a suitable Nicol prism.

The fluorescent emission spectrum emitted by certain substances following the irradiation of one of these substances with light that is of the same wavelengths as its fluorescence.

A resonator is a device or system that exhibits resonance, which is a phenomenon that occurs when an external force or stimulus is applied at a specific frequency, causing the system to oscillate...

The gain that occurs between light intensity incident on a CCD given by the photocurrent produced.

The degree of angular shift in the phase of incoming polarized light.

A device that uses nematic liquid crystals sandwiched between fused silica substrates to change the phase of polarized light. The cell is tunable from half-wave to zero retardation because variation...

A reticle, also known as a reticule or graticule, is a pattern or set of markings placed in the focal plane of an optical instrument, such as a microscope, telescope, riflescope, or camera, to...

The retina is a light-sensitive tissue layer located at the back of the eye, opposite the lens. It plays a crucial role in the process of vision by converting light into neural signals that are sent...

A special-purpose camera used by ophthalmologists to photograph the retina of the eye. The optical system operates through the eye pupil, and the illuminant must be able to send light into the eye...

Two lenses, separated by a distance equal to the sum of their focal lengths, and retroreflecting mirror assemblies, one of which is coaxial with the lenses and the other slightly translated off-axis.

Retroreflection is a phenomenon in optics where light is reflected back toward its source, typically in a direction nearly parallel to the direction from which it originated. This occurs due to the...

Retroreflectivity refers to the property of a surface or material to reflect light back to its source, regardless of the angle of incidence. Unlike most surfaces that scatter light in various...

A retroreflector is an optical device or structure that reflects incident light or electromagnetic waves back to their source, regardless of the direction from which the light approaches. Unlike...

A prism made of two elements cemented together that, depending on its orientation, inverts or reverts an image. It may be used in converging or diverging light. Sometimes referred to as a K prism.

Rhodamine refers to a family of fluorescent organic dyes that are widely used in various fields, including biology, chemistry, medicine, and materials science. These dyes are known for their bright...

A photodiode having a conducting grid that covers the surface of the photodiode junction and intercepts and wastes some of the light. In this way, efficient optical- and microwave-frequency design...

A type of 45-90-45° prism used to bend a beam of light through a right angle with the surfaces forming the 90° angle acting as transmitting faces.

A ring laser gyroscope (RLG) is a type of gyroscope that uses laser light to detect and measure changes in orientation. It operates based on the Sagnac effect, which is a fundamental principle of...

A Risley prism, also known as a Risley prism pair or Risley rotating prism, is an optical device used for controlling the direction of a laser beam or other optical beam by independently rotating two...

The light-sensitive cells on the retina of the eye that are responsible for low-resolution, peripheral vision.

A structured light device using a rapidly rotating laser to project a beam of light that appears to the human eye as a continuous circle; used as a reference marker on walls or landscape for...

A disc composed of a series of holographic optical elements that diffract light at various angles. When spinning, a raster scan may be generated.

A circular optical wedge (prism of small refracting angle) mounted to be rotated in the path of light rays to divert the line of sight to a restricted degree.

A roughening laser is a laser-based surface modification technique aimed at altering the surface texture of a material to achieve specific properties such as enhanced adhesion, light diffusion, or...

A Rugate filter is a type of optical filter that is designed to have a continuously varying refractive index profile throughout its thickness, rather than the discrete layers found in traditional...

A ruticon is an opto-electronic device in which light going through it can be modulated by an electric field. The intensity distribution of the resulting image can be precisely controlled....

The reversal of a developed image due to the exposure of the partially developed image to actinic light.

Sagnac interferometry is a technique used to measure rotation or angular velocity based on the principle of interference. It relies on the Sagnac effect, named after the French physicist Georges...

Sapphire optical fiber is a type of optical fiber made from single-crystal sapphire, which is a form of aluminum oxide (Al2O3) that is highly transparent in the infrared region of the electromagnetic...

A sapphire window refers to a transparent optical component made from sapphire crystal. Sapphire is a single-crystal form of aluminum oxide (Al2O3) that is highly prized for its exceptional optical...

Sapphire refers to a crystalline form of aluminum oxide (Al2O3) that is used in various optical and photonic applications due to its exceptional optical, mechanical, and thermal properties. Sapphire...

A saturable absorber is a type of optical device that exhibits variable absorption properties depending on the intensity of incident light. In essence, it becomes less absorbent as the light...

A double-plate device used to transmit polarized light and form interference fringes of the light, thus indicating its presence. It consists of two calcite plates of equal thickness, cut parallel to...

1. A polariscope consisting of a Savart plate and a tourmaline plate analyzer, and used to produce parallel color fringes by transmitting polarized light. 2. A polariscope composed of an analyzing...

Scalar diffraction theory is a simplified approach used to describe the propagation of electromagnetic waves, particularly light, as they encounter obstacles or apertures. It is termed "scalar"...