Glossary: V
Varifocal
Low magnification lens which has a variable focal length, but which requires refocus with adjustment.
Vernier
For rotary stages, a scale measuring the amount of angular movement by the drive. Vernier values of resolution are the smallest angular movement that can be measured by the scale.
Vibration Rating
Measure of the vibrational durability of a component within a certain range of frequencies, expressed in units of acceleration (G).
Viewing Angle
For light control film, the full angle through which the film will transmit light. This value is centered about the louver angle of the film.
See also
Louver Angle
Vignetting
A fall-off in illumination of the image. This can occur when the sensor is larger than the specified maximum sensor size of the lens is used or can naturally occur due to limitations of the geometry of the system.
VIS Coating
BBAR coating optimized for use in the visible spectrum between 425 nm and 675nm. Does not transmit NIR efficiently.
VIS/NIR Coating
BBAR coating optimized for use from 425nm to 900nm with good transmission out to 1000nm.
Viscosity
A measure of a fluid's resistance to flow, or the ratio of shearing stress to the velocity gradient. Water is a low viscosity fluid while peanut butter has a high viscosity.
Visible Spectrum
The part of the electromagnetic spectrum from approximately 400 - 750nm.
