In imaging optics, a field lens is a positive-powered lens or group of lenses that comes after the

objective lens In optical engineering, the objective is the optical element that gathers light from the object being observed and Focus (optics), focuses the ray (optics), light rays to produce a real image. Objectives can be a single Lens (optics), lens or mirr ...

and before the

image plane In 3D computer graphics, the image plane is that plane in the world which is identified with the plane of the display monitor used to view the image that is being rendered. It is also referred to as screen space. If one makes the analogy of taking ...

or the

eyepiece An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is named because it is usually the lens that is closest to the eye when someone looks through the device. The ...

, serving to change the size of the image or to provide image-space

telecentricity A telecentric lens is a special optical lens (often an objective lens or a camera lens) that has its entrance or exit pupil, or both, at infinity. Telecentric lenses are often used for precision optical two-dimensional measurements or reproductio ...

. It is used for the reduction of detector size and, in instances needing high optical gain factor, it can correct aberrations through its several elements. Optical systems that feature multiple image planes are at risk of a potential problem, which involves the inability on the part of succeeding

relay lens In optics, a relay lens is a lens or a group of lenses that receives the image from the objective lens and relays it to the eyepiece. Relay lenses are found in refracting telescopes, endoscopes, and periscopes to optically manipulate the light ...

es to capture a cone of light from the primary objective lens. The field lens - by behaving as a variably angled lens - solves this problem by bending or refracting the cone of light back into the succeeding relay lens. In

X-Ray microscopy An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations. Unlike visible li ...

, the field lens is used to produce parallel and homogeneous illumination of the

stencil Stencilling produces an image or pattern on a surface, by applying pigment to a surface through an intermediate object, with designed holes in the intermediate object, to create a pattern or image on a surface, by allowing the pigment to reach ...

References

{{optics-stub Lenses Microscope components