An optical axis is an imaginary line that passes through the geometrical center of an
optical system such as a
camera lens
A camera lens, photographic lens or photographic objective is an optical lens (optics), lens or assembly of lenses (compound lens) used in conjunction with a camera body and mechanism to Imaging, make images of objects either on photographic film ...
,
microscope
A microscope () is a laboratory equipment, laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic ...
or
telescopic sight.
Lens elements often have
rotational symmetry
Rotational symmetry, also known as radial symmetry in geometry, is the property a shape (geometry), shape has when it looks the same after some rotation (mathematics), rotation by a partial turn (angle), turn. An object's degree of rotational s ...
about the axis.
The optical axis defines the path along which light propagates through the system, up to first approximation. For a system composed of simple
lenses and
mirror
A mirror, also known as a looking glass, is an object that Reflection (physics), reflects an image. Light that bounces off a mirror forms an image of whatever is in front of it, which is then focused through the lens of the eye or a camera ...
s, the axis passes through the center of curvature of each surface, and coincides with the axis of
rotational symmetry
Rotational symmetry, also known as radial symmetry in geometry, is the property a shape (geometry), shape has when it looks the same after some rotation (mathematics), rotation by a partial turn (angle), turn. An object's degree of rotational s ...
. The optical axis is often coincident with the system's mechanical axis, but not always, as in the case of
off-axis optical systems.
For an
optical fiber
An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...
, the optical axis is along the center of the
fiber core, and is also known as the ''fiber axis''.
See also
*
Ray (optics)
*
Cardinal point (optics)
*
Antenna boresight
References
*
*
Geometrical optics
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