Photonics Dictionary

A device having a pair of decentered lenses, one for each eye, that focuses on a single object as a magnifier. It is often supplied with a forehead fixture or an elastic headband to leave the hands...

1. An eyepiece or magnifier with a scale at its image plane. That scale is placed in contact with an object, permitting direct measurement of its size. 2. Also called traveling stage and traveling...

The near-point distance of the normal eye. The value of 10 in. or 25 cm is normal. This value is used in evaluating the designated magnification of a simple magnifier or eyepiece.

Also known as ocular. The lens system used between the final real image in a visual optical system and eye. It acts as an image magnifier. Many types of eyepieces are known; e.g., the Huygens used in...

A Fresnel lens is a type of optical lens that consists of a series of concentric grooves or steps carved into a flat, thin piece of transparent material, typically plastic or glass. This design...

A magnifying lens fitted with a battery-operated lamp by which an object can be conveniently illuminated during observation.

A low-power (2x to 10x) magnifier consisting of a single positive lens assembly.

A lens or lens system that produces an enlarged virtual image of an object placed near its front focal point.

A small low-power microscope or magnifier with a scale that is used to measure the exit pupil diameter and eye relief on visual instruments. Optical dynameters are often used to measure the...

A low-power magnifier that usually has a large diameter.

A short focal length (less than five inches) positive lens used to produce a magnified image of the object being viewed. While a single element will function, an achromat or multielement assembly...

An instrument used for viewing in low levels of illumination by means of infrared radiation. A high-aperture lens forms an image of distant objects on the photocathode of an infrared-sensitive image...

An eyepiece or magnifier capable of covering a field of view that is greater than 50°.