The Hektor lens is a series of camera lenses produced by the German manufacturer Leitz (now known as Leica). Introduced in the 1920s, Hektor lenses were known for their quality and performance, especially in the field of portrait and general photography. They were designed for use on Leica cameras and feature a classic design with a strong emphasis on optical quality.

A hot mirror is an optical filter designed to reflect infrared (IR) radiation while allowing visible light to pass through. It is often used in various applications, including photography, projector systems, and thermal imaging. Hot mirrors are constructed using a thin film coating on a glass substrate, which selectively reflects infrared light (typically wavelengths longer than 700 nm) and transmits visible light (approximately 400 to 700 nm).

Hyperpolarizability is a measure of a material's non-linear optical properties, specifically its response to an applied electric field in a way that goes beyond the linear (first-order) response. In simpler terms, while linear polarization relates to how a material's electric dipole moment changes in proportion to an applied electric field, hyperpolarizability describes how the dipole moment changes in response to higher-order terms of the electric field.

An injection seeder is a device or system used in the context of seed germination and agricultural practices, primarily for the purpose of planting seeds in a controlled and efficient manner. The term can refer to various types of equipment or mechanisms that inject seeds into the soil at specified depths and intervals, ensuring optimal growth conditions. In detail, injection seeders operate by embedding seeds directly into the soil, often utilizing a pneumatic or mechanical system to deliver seeds accurately.

Intrinsic hyperpolarizability refers to a property of nonlinear optical materials, specifically in the context of their response to external electric fields. It quantifies how the polarization of a material changes in response to the electric field beyond the linear approximation. While the linear response of a medium to an electric field can be described by its linear polarizability, hyperpolarizability is the next level in the series expansion of the polarization with respect to the electric field.

The Jamin interferometer is an optical device used to measure the refractive index of materials and to perform precision measurements in various fields such as optics and metrology. It is named after the French physicist Émile Jamin, who developed this interferometric technique. The basic configuration of a Jamin interferometer consists of two beam splitters and two mirrors, arranged in such a way that two beams of light are generated from a single coherent light source.

Kleinman symmetry arises in the context of many-body quantum systems, particularly in the study of non-equilibrium dynamics and quantum statistical mechanics. It is associated with the spectral properties of certain operators that describe the system. In mathematical terms, Kleinman symmetry refers to a specific property of the Green's functions (or correlation functions) in quantum many-body systems, where the matrices that represent these functions exhibit a symmetric structure.

The Journal of the Optical Society of America (JOSA) is a peer-reviewed scientific journal published by the Optical Society of America (OSA). Established to advance the field of optics and photonics, the journal covers a wide range of topics related to optical science and technologies. This includes, but is not limited to, areas such as light-matter interactions, imaging, optics materials, lasers, and optical systems.

Knapp's Model of Relational Development, often simply referred to as Knapp's Rule, is a communication theory proposed by sociologist Mark Knapp in 1972. The model outlines how relationships develop and dissolve through a series of stages, categorized into two main phases: the coming together phase and the coming apart phase. ### Coming Together Stages: 1. **Initiating:** This initial stage involves the first interactions and the presentation of oneself. Individuals assess each other for potential compatibility.

Laser detuning refers to the difference in frequency between a laser light and a specific transition frequency of an atom, molecule, or other system. In the context of atomic or molecular physics, this concept is often encountered when discussing laser cooling, optical pumping, or coherent control experiments. ### Key Aspects of Laser Detuning: 1. **Definition**: - It is the frequency offset of the laser light from the resonance frequency of the atomic transition.

Lasing without inversion (LWI) is a phenomenon in quantum optics that refers to a mechanism of producing coherent light (laser light) in a system where the usual requirement for population inversion is not met. Normally, in traditional laser operation, a population inversion is necessary, where more atoms or molecules are in an excited state than in a lower energy state. This population inversion is essential for achieving stimulated emission, the fundamental process that amplifies light in a laser.

The least distance of distinct vision, also known as the near point, refers to the closest distance at which the human eye can focus on an object clearly. For a typical, healthy human eye, this distance is generally around 25 centimeters (10 inches). However, this value can vary among individuals, especially as people age or have certain vision conditions. Within this range, objects can be seen clearly without straining the eyes.

Lens sag refers to the phenomenon where a lens—typically in optical systems such as telescopes or cameras—experiences a distortion or bending due to its own weight or the support structures used to hold it. This sag can affect the performance and optical quality of the system. In practice, lens sag occurs when a large lens is supported at points that don’t evenly distribute its weight. The center of the lens may dip or deform, leading to issues in focusing light accurately.

A lenslet is a small lens that is typically used in optical systems such as plenoptic cameras, light field sensors, and displays. Lenslets are part of arrays of lenses that help capture or manipulate light in specific ways, enabling features like depth sensing and 3D imaging. In the context of light field technology, for example, lenslets are arranged to capture multiple perspectives of a scene simultaneously. This allows for post-capture changes in focus or perspective.

Lindberg is a Danish eyewear brand known for its high-quality, minimalist designs and innovative materials. Founded in 1985 by Hans D. Lindberg and his wife, the company has gained a reputation for its luxury glasses that combine style, functionality, and comfort. Lindberg offers a wide range of eyewear, including prescription glasses and sunglasses, characterized by their lightweight construction and customizable features.

The Lummer-Gehrcke interferometer is a type of optical device used for precise measurements of wavelengths and other optical properties. It operates based on the principle of interference and utilizes thin film optics. The device typically comprises two highly reflective mirrors separated by a thin air gap or a thin film, creating a set of parallel surfaces.

The Martin–Puplett interferometer is an optical device used for measuring the interference of light waves, typically in the infrared and millimeter wavelengths. It is particularly useful in spectroscopy and in the analysis of thermal radiation. The interferometer consists of: 1. **Beam Splitters**: It features two beam splitters that divide the incoming light beam into two paths. The split beams travel along different paths before being recombined.

The material dispersion coefficient is a key parameter in the field of optics and fiber optics that quantifies how much different wavelengths of light travel at different speeds through a material. This phenomenon occurs because the refractive index of a material changes with the wavelength of light, causing various wavelengths to experience different propagation velocities. In optical fibers, material dispersion contributes to pulse broadening as light pulses travel down the fiber.

A mechanical splice is a method used to join two optical fibers together, enabling the transmission of light signals from one fiber to the other. This type of splice does not require fusion (melting the fibers together) but instead uses a mechanical device to align and hold the fibers in place.

The Michelson stellar interferometer is an astronomical instrument used to measure the properties of celestial objects, particularly their angular diameters and surfaces. It is based on the principle of interference of light waves, originally developed by Albert A. Michelson in the late 19th century. The design consists of two main parts: two mirrors and a beam splitter. ### Key Components: 1. **Beam Splitter**: A device that divides incoming light from a star into two separate beams.