Glossary

V

viewing angle
see visual angle
viewing tube
see observation tube
viewing tube flange
see eyepiece-locating observation tube flange
violet corrected objective (VC)
A type of specialized objective that features chromatic aberration correction and high transmission down to ~405 nm in the violet range. This is especially convenient for use with widespread 405 nm laser lines available on confocal systems and for applications such as photostimulation.
See also: objective, photostimulation, chromatic aberration
virtual image
An image formed by back-tracing diverging rays projected by a lens, it is not real and cannot be detected using a detector in the plane of the virtual image. It usually arises due to the object (or image thereof) being located less than one focal length away from the lens. Virtual images and images at infinity can be perceived by the human eye since it contains a lens that converge the rays.
See also: real image, ray tracing, geometric optics
visible light
see light
visual angle
The angle subtended at the observer's retina by the image of an object. It is usually provided in terms of degrees of arc.
Synonyms: angular size, viewing angle
volumetric image
see 3D reconstruction
voxel
A three dimensional pixel. With most optical methods its dimensions are longer along the Z axis due to lower axial resolving power.
See also: pixel, confocal volume