Photonics Dictionary

An achromat, in the context of optics, refers to a type of lens or lens system designed to reduce chromatic aberration. Chromatic aberration is an optical phenomenon where different colors of light...

An optical system with object and image points at infinity. Literally, "without a focal length."

The angle formed between a ray of light striking a surface and the normal to that surface at the point of incidence.

Aplanatic points refer to specific points in an optical system where certain aberrations, such as spherical aberration or coma, are minimized or eliminated. In an optical system, aberrations are...

An apochromat, often referred to as an apochromatic lens or apochromatic objective, is a type of optical system designed to minimize chromatic aberration. Chromatic aberration occurs when different...

A point source of light used for the test and evaluation of image quality. May be a backlit pinhole in an otherwise opaque sheet placed at an appropriately large distance from the lens being tested.

A cylindrical lens that may be rotated to distort a bundle of light originating at a point source, to form a line image.

An astronomical mirror, also known as a telescope mirror or primary mirror, is a key component of a reflecting telescope. It serves as the primary optical element responsible for gathering and...

An astronomical telescope is a type of optical instrument designed to gather and magnify light from distant celestial objects for observation and analysis. It typically consists of two main optical...

An optical device that produces a line image lying along the axis from a point source of light; therefore, it has no definite focal length. A lens with a weak conical surface on one face.

Azimuthal polarization refers to a specific polarization state of light where the electric field vector of the electromagnetic wave points along the azimuthal direction (around the propagation axis)....

The distance from the final optic within a system to the rear image point of the system. See focal length.

The degree to which a pixel in a digital image represents the analog brightness of the corresponding point in the original image. It is dependent largely on the number of bits devoted to representing...

Focal, nodal or principal points of a lens. If the respective distances of the object and image are measured from the cardinal points, all thin-lens equations are applicable to thick lenses.

Chromatic aberration is an optical phenomenon that occurs when different wavelengths (colors) of light are refracted by a lens or optical system, leading to a failure to focus all colors to the same...

The image of a point source that appears as a circle of finite diameter because of defocusing or the aberrations inherent in an optical system.

Best point of focus for an image in a beam of light at the smallest cross section of the beam.

Circular dichroism (CD) is a spectroscopic technique used to study the structural characteristics of chiral (asymmetric) molecules, particularly biomolecules like proteins, nucleic acids, and certain...

A colorimeter is a device used to measure and quantify the color characteristics of an object or a light source. It provides objective and standardized color information, typically expressed in terms...

A lens aberration, resulting from different magnifications in the various lens zones, that occurs in that part of the image field that is some distance from the principal axis of the system....

Computer vision enables computers to interpret and make decisions based on visual data, such as images and videos. It involves the development of algorithms, techniques, and systems that enable...

A computer-generated hologram (CGH) is a holographic image produced using computational methods and algorithms, rather than traditional optical techniques. CGHs are generated entirely in digital form...

Concave and convex spherical mirrors are types of curved mirrors that have surfaces shaped like segments of spheres. These mirrors are commonly used in optics for various applications, including...

1. A solid figure whose base is a circle and whose sides taper upward evenly to a point or apex. Light rays diverging from or converging upon a point are sometimes referred to as a cone of light. 2....

A confocal resonator, also known as a confocal cavity or confocal laser resonator, is a type of optical resonator configuration used in laser systems. The term confocal in this context refers to the...

A system that determines whether an image is in or out of focus by means of a source of illumination at the conjugate focal point, which reflects off the target; the return beam is mediated by masks...

The two points on the principal axis of a mirror or lens so positioned that light emitted from either point will be focused at the other, i.e., object and image points.

The ratio between the object distance and the image distance measured along the principal axis of a lens or mirror. An object at the focal point of a lens has an infinite conjugate ratio; an object...

A formula indicating that, for an imaging lens system, the image brightness for off-axis points will fall off at a rate proportional to the cos4 of the off-axis field angle.

On a display monitor, a small, mobile rectangle, cross-hair or pointer that locates a feature in an image that is the object of attention, or indicates where the next character will appear in word...

A cylindrical lens is an optical component that has different curvatures along its two orthogonal axes, resulting in a shape resembling a cylinder. Unlike spherical lenses, which have the same...

A condenser that forms a hollow cone-shaped beam of light with its focal point in the plane of the specimen. If it is used with an objective having a numerical aperture lower than the minimum...

A flanged or plain ring with a restricted aperture, located in an optical system at any of several points, that cuts off marginal light rays not essential to image formation. Diaphragms are used as...

A digital camera is a device that captures and records still images or video in digital format. Unlike traditional film cameras, which use photographic film to capture and store images, digital...

The technique by which an analog image is converted by any of several means into a finite array of points, each represented by some numerical value. Once created, this array can be the basis of a...

A diode laser is a type of laser that uses a semiconductor diode as the active medium to generate coherent light. Semiconductor diodes are electronic devices that conduct electricity primarily in one...

A diverging lens is a type of lens that causes parallel rays of light to spread out or diverge. It is thinner in the center than at the edges and is commonly referred to as a concave lens. The most...

1. The use of an electronic microdensitometer to measure points of equal density on a photographic deposit. 2. A technique that simplifies a picture's density pattern by making a single isodensity...