Not familiar with one of our terms? This glossary can help.
The failure of a lens to bring all the rays of light to exact focus, causing a blue-red image.
A lens which corrects for chromatic aberration; transmits light that forms images practically free from prismatic colors.
A lens which corrects for spherical aberration and coma.
A defect in which the lens fails to unite rays of light from an external point at a single image point, thus giving an imperfect image or vision.
- chromatic aberration
The inability of a lens to focus light of different colors at a simple point.
A corrected lens, named after its British inventor, Henry Coddington.
The blurred appearance or hazy border surrounding an object
viewed through a lens which is not free from spherical aberration.
Describes a lens surface which is hollowed; interior of a curved surface.
Describes a lens surface that curves or is rounded outward.
A lens or lens system which corrects for aberrations; remedies deviations of light rays from object to eye to produce a clear, sharp image.
- crown glass
Optical alkali-lime glass having a low dispersion and usually a low index of refraction.
- curvature of field
When a plane field is not imaged as a plane, or the outer part of the field is not imaged in the same plane as the center and
therefore appears out of focus; as opposed to flatness of field.
- curvature of lens
The amount of sharpness of curve in a lens surface.
The amount of power in a lens needed to focus parallel light at
The separation of light into its component colors, as in passing through a prism.
That defect of a lens whereby the images of straight lines
- double lens magnifier
A magnifier composed of two single lenses.
- flatness of field
Appearance of the image to be flat; a plane in the object will be imaged as a plane as opposed to curvature of field.
- flint glass
A heavy, brilliant glass containing lead and having a high dispersion and usually a high index of refraction.
The point at which light rays through a lens intersect to form
- Hastings Triplet
A highly corrected magnifier composed of three simple lens elements cemented together to form a single lens.
- highly corrected
A magnifier or lens in which virtually all aberration is eliminated.
The likeness or picture formed by a lens; the optical counterpart of an object.
A crescent-shaped lens—one which is concave on one surface, convex on the other. It may be converging or diverging.
Pertaining to flat; a plano lens surface has no curve.
A lens with one surface flat, the other curved inward. (See concave)
A lens with one surface flat, the other curved outward. (See convex)
- refractive index
The ration of speed of light in a vacuum, or in a given medium to its speed in a different medium.
A magnifier or lens in which only part of the aberration is eliminated.
- spherical aberration
A defect in a lens which causes marginal and central rays to focus at different distances from the lens, producing an image which lacks contrast.