Photonics Dictionary

An image-forming system having curved mirrors in place of transparent glass components. Mirror lenses are commonly used for astronomical purposes as well as cheap solutions for very long focal length...

A molded lens is an optical lens manufactured using a molding process, typically involving the shaping of a material, such as glass or plastic, into the desired lens shape. This process involves...

An array of refractive microlenses that are round, square and hexagonal and as small as 15 µm. They are used for Hartmann testing, laser diode collimation and other applications that require...

A lens with internally adjustable elements to produce a range of focal lengths. Unlike a true zoom lens, a multifocal lens must be refocused each time the focal length is changed. See variable-focus...

A block that can hold more than one lens or blank.

A camera that uses a rotating mirror to project sequential images onto lenses that are arranged in an arc. The reflected images can then be recorded on stationary film. By using an 8-mm frame format,...

A lens used in the optical testing of an aspheric surface. It converts a spherical wavefront into one that precisely matches the surface under test. When the wavefront is reflected from that surface,...

A lens system that is capable of producing a 360° image, or one that is very close to that. In recording, the image may be formed on a curved strip of film surrounding the lens, resulting in a...

Lenses that have identical flange focal distances and can be interchanged.

A theoretical, ideal lens capable of producing perfect images. Used as a lens design and analysis tool to image collimated output from an afocal system.

Two simple meniscus lenses arranged symmetrically on either side of the aperture stop, providing reduced coma, lateral color and distortion.

A high-speed, narrow-field lens consisting of two achromats spaced about the aperture stop. Its uses include portrait photography and motion picture projection.

A lens with one plane surface and one concave surface.

A lens that has one plane surface and one convex surface.

A lens made from transparent plastic material. Lenses over 31/2 in. in diameter are usually machined, ground and polished. Smaller lenses are usually injection molded, the mount surrounding the lens...

A lens that is symmetrical and designed to work between 1:1 and about 4:1. It covers a field of about ±20° at f/8 or f/10, and may have a focal length up to about 30 in., although the usual...

A device used in electron microscopes and particle accelerators to focus electron beams by the arrangement of four electrodes of alternating signs around the electron beam.

A double meniscus system in which two achromatized meniscus lenses are arranged symmetrically on either side of the aperture stop, reducing or eliminating distortion, coma and lateral color.

A lens or lens system used to transfer a real image from one point within an optical system to another, with or without magnifying it.

Also known as reversed telephoto lens. A lens consisting of an ordinary objective with a negative component near its front focal point. Thus, the back focus is large, relative to its focal length....

A sequential scanning device, utilizing a revolving lens, in which the cathode-ray tube image is transformed into a circle of fibers. The rotating lens focuses each fiber successively on a multiplier...

A toric lens generated by rotating a specific cross section about an axis beyond its area and used in the formation of annular images.

A corrective lens system that is placed near the focal plane of a Newtonian telescope to increase its effective field of view by correcting for coma formed by the telescope's paraboloidal mirror.

A lens designed for projection of color transparencies.

A lens that exhibits spherical aberration when used at large aperture settings, and that forms an image with a slightly blurred outline.

A photographic objective that uses the thick meniscus principle to obtain its power. It is designed to photograph small fields at large apertures.

A spheric lens, also known as a spherical lens, is a type of optical lens with at least one surface that is part of a sphere. This means that the lens surface is curved in a symmetrical manner,...

A tiny lens (as small as 100 µm in diameter) used to focus light on charge-coupled devices, formed by heating a photosensitive material exposed through a mask, leaving a pattern of raised...

A close-up lens, semicircular in shape, that is mounted in front of a conventional lens focused at infinity. The result is an image made up of two sections; one focused through the split lens on near...

The interference of the two real images formed by a Billet split lens.

A lens derived from the Cooke triplet anastigmat, but with one of the crown elements split in two, resulting in improved speed and correction of aberrations.

A lens whose focal length is roughly equal to the diagonal of the negative format of the camera on which it is mounted.

A meniscus that is often fitted before a camera lens to permit focusing on near objects.

A lens system made up of two sets of similar lenses, each of which compensates for many of the aberrations produced by the other. The lens sets are arranged symmetrically on either side of the...

There are three types of telecentric lenses: -Image-space telecentric lenses are those in which the aperture stop is located at the front focus, resulting in the chief rays being parallel to the...

A compound lens so constructed that its overall length is equal to or less than its effective focal length.

A telescope lens is a primary optical component of a telescope system that gathers and focuses light to form an image. It is typically a curved, transparent piece of glass or other optical material...

A lens similar to the Cooke triplet anastigmat, with the rear crown achromatized for improved coverage and definition. It is used in medium-speed cameras and enlargers.

Distortion of an optical component as a result of heat, which can influence the divergence and the mode quality of a beam passing through the component.

A lens with an axial thickness adequate to make it producible.

A concept used for purposes of preliminary calculations and analysis. In theory it is a lens whose axial thickness is zero.

Formulas designating the relationships between image distance, object distance, focal length, refractive index, etc., of a thin lens.

A symmetrical, very wide-angle lens. Well-corrected for spherical aberration and color, the Topogon can cover fields up to 90° at speeds from f/11 to f/6.3.

A lens having one or more toric surfaces. A toric surface is one having a maximum power in one meridian and a minimum power in a perpendicular meridian. In ophthalmic optics, toric lenses are used to...