Photonics Dictionary: L

A device used for measuring the height of clouds from a position on the ground. Measurement technique uses a vertically directed beam stably positioned such that scattered radiation may be detected...

Device which determines particle velocity through the measurement of scattered interference of a beam pair from a single source. The measured light is Doppler shifted which provides information...

Means of determining the relative motion of a (seismic) mass or acceleration body from a stable laser operated system.

An interferometer that uses a laser as its light source. The purely monochromatic nature of the laser results in improved efficiency and overall performance.

Laser parameters are the characteristics that define the behavior and performance of a laser. These parameters can be categorized into several groups: spatial, temporal, spectral, and operational. ...

An instrument usually consisting of a very long interferometer, 3 to 800 m, and a laser light source for the study and measurement of strain, such as those formed by earth tides and gravitational...

A system that uses a continuous-wave laser to measure the velocity of an object by focusing the laser beam on the object, perpendicular to its direction of motion. An optical grating receives...

The variation of the electronically detected signal with respect to the scaled version of the classical optical signal incident on the photomultiplier tube.

A scattering photometer using scattered light in the solid angle 4.51+0 19° with respect to the forward direction, and an impactor with a rectangular jet. Scattered light intensities of entering...

An extensometer used to measure deformations in the thickness of a plate caused by tension, compression or other stress.

A lateral shearing interferometer is an optical device used in interferometry to measure phase differences between two beams of light. Interferometry is a technique that combines and analyzes...

A Laurent polarimeter is an instrument used in optics for measuring the rotation of plane-polarized light caused by optically active substances. Optical rotation, also known as optical activity, is a...

An ophthalmic instrument used to measure the magnitude and direction of the maximum and minimum powers of a spectacle lens, and mark the optical center of the lens by an ink dot. When the lens to be...

Any device that is used to sense and measure light. See exposure meter; photoelectric exposure meter; photoelectric photometer; reflected light meter.

A subtractive colorimeter that expresses a liquid's or object's color as a combination of three colors. These colors are developed through viewing the specimen object through three series of slides,...

A type of photometer calibrated in luminance units (candles per square unit, or lamberts). In photography an exposure meter contains a luminance meter to record the average luminance of a scene.

An illuminometer designed to measure illumination in terms of luxes.

A unit of luminance equal to 1/p candela per square centimeter. (l).

A broken circle used as the test object in distinguishing visual acuity. The width of the gap in the circle is equal to the breadth of the black line and one-fifth the circle diameter. Also known as...

Lapping and polishing services involve specialized processes used to improve the surface finish and dimensional accuracy of components to meet specific requirements or standards. These services are...

Laser ablation is a process that involves the removal or erosion of material from a target surface using laser energy. This technique is widely used in various scientific, industrial, and medical...

The laser damage threshold refers to the maximum level of laser intensity that a material can withstand without experiencing damage. It is a critical parameter in laser applications and is...

A laser diode module is a compact device that incorporates a laser diode, optics, and often other components into a single package. These modules are designed to provide a convenient and efficient...

Laser optics refers to a broad category of optical components and systems designed for manipulating and controlling laser light. Laser optics play a crucial role in shaping the characteristics of...

Laser shock peening (LSP) is a surface treatment process used to enhance the mechanical properties and durability of materials, particularly metals. It involves the use of high-energy laser pulses to...

A method of analysis in which a pulsed laser beam is used to heat a particle, producing a plasma, or laser spark. As the plasma cools, optical energy characteristic of the elements in the plasma is...

Laser surgery refers to a medical procedure in which a laser, or focused beam of light, is used as a precision tool to cut, vaporize, coagulate, or otherwise modify tissues for therapeutic or...

The circle of confusion is a defocused or aberrated image of a point. Focus is generally set where the diameter of this circle is minimized or least.

A lens blank is a piece of optical material in a raw, unfinished state, typically in the form of a disk or block, from which lenses are eventually fabricated. Lens blanks are made from various...

A rotating disc that holds several lenses of differing focal length about a diameter. Used to switch lenses in a system while maintaining focus.

A tool used to determine the curvature of a lens surface in terms of dioptric power. See lens watch; spherometer.

Also known as f number, lens speed is commonly represented as the ratio of the focal length to the diameter of the lens. Lower f numbers produce brighter images.

Lens testing equipment refers to a range of specialized tools and instruments used to evaluate the optical performance, quality, and characteristics of lenses. These instruments are essential for...

Phenomenon caused by an ultrashort and ultra-intense light pulse propagating in a Kerr medium, such as air or water. When the pulse's power exceeds the critical power (approximately 3 GW in air),...

The electrical power used to stimulate any light source. Power supplies may be step-up or step-down transformers; rectifiers to convert AC to DC; ammeters and voltmeters to observe the input to the...

A linear positioning stage, also known as a linear stage or translation stage, is a precision mechanical device used to accurately move and position objects along a linear axis. These stages are...

Linewidth, also known as spectral linewidth or line width, refers to a measure of the width of a frequency spectrum of a signal or a resonance. It indicates the range of frequencies over which the...

A small half-shade analyzer placed in the eyepiece of a polarimeter to determine the character of the polarized light emitted by the instrument. It consists of a Nicol prism situated so that it...

A lock-in amplifier is a specialized electronic instrument used to extract and measure small signals embedded in noise or interference. It is particularly useful in fields such as spectroscopy,...

Long-wave infrared (LWIR) refers to a specific range of the infrared spectrum. Infrared radiation is divided into three main categories based on wavelength: near-infrared (NIR), mid-wave infrared...

Low Earth orbit (LEO) refers to a region in space that is relatively close to Earth's surface, typically characterized by altitudes ranging from approximately 180 to 2,000 kilometers (112 to 1,242...

An interference microscope that uses a light beam originating from a low-coherence light source. The sample is placed in one interferometer arm, and the other arm provides a reference beam. The...

A high-resolution spectroscopic device commonly used in the early 20th century as a component of double-beam interferometers. Light introduced at one end of the plane-parallel glass plate will be...

SI unit of luminous incidence or illuminance, equal to 1 lumen per square meter.