This document defines and describes different types of optical distortion. It explains that distortion is a deviation from rectilinear projection where straight lines in a scene remain straight in an image. The most common distortions are radially symmetric and include barrel distortion where magnification decreases with distance from the optical axis, pincushion distortion where magnification increases with distance, and moustache distortion which is a mixture of both. The document also discusses causes of distortion and where different types typically occur, such as in wide-angle lenses.

1. DISTORTION(OPTICS) IN
ABERRATION

2. DEFINITION
• Distortion is the most easily recognized optical
aberration .It is deforms the image as whole.
In geometric optics and cathode ray tube (CRT)
displays, distortion is a deviation from rectilinear
projection, a projection in which straight lines in a
scene remain straight in an image. It is a form of
optical aberration.

3. RADIAL DISTORTION
• Although distortion can be irregular and
follow many patterns.
• The most commonly encountered distortions
are radially symmetric or approximately so.
1 2
3

4. CLASSIFICATION OF RADIAL
DISTORTION IN OPTICS
The radial distortion classified in three types:-
1. Barrel Distortion
2. Pincushion Distortion
3. Mustache Distortion

5. BARREL DISTORTION
• In Barrel Distortion, image magnification decreases
with the distance from optical axis.
• The apparent effect is that of an image which has
been mapped around a Sphere or Barrel.
• Straight lines running through the image centre
remain straight and a circle concentric with the
image centre remains a circle, although its radius is
affected. It is actually a diminished radius mapping
for large radii in comparison with small radii.
1 2

6. PINCUSHION DISTORTION
• In pincushion distortion, image magnification increases
with the distance from the optical axis.
• The visible effect is that lines that do not go through
the centre of the image are bowed inwards, towards
the centre of the image, like a pincushion. It is actually
simply an exaggerated radius mapping for large radii in
comparison with small radii.
1 2

7. MOUSTACHE DISTORTION
• A mixture of both types, sometimes referred to
as Moustache Distortion (moustache distortion)
or complex distortion, is less common but not
rare. It starts out as barrel distortion close to the
image centre and gradually turns into pincushion
distortion towards the image periphery, making
horizontal lines in the top half of the frame look
like a handlebar moustache.

8. Moustache Distortion

9. ORIGIN OF ABERRATION
• A common cause of distortion is the
introduction of a aperture stop in a system of
thin lenses to reduce spherical aberration.
• The position of such aperture stop determines
the amount and sign of the distortion

10. The influence of stop position on distortion. Note that the image size h differs for a constant object size y.

11. OCCURRENCE
• In photography, distortion is particularly associated with zoom
lenses, particularly large-range zooms, but may also be found
in prime lenses, and depends on focal distance – for example,
the Canon EF(Electro Focus) 50mm
• Barrel distortion may be found in wide-angle lenses.
• Moustache distortion is observed particularly on the wide end
of some zooms, with certain retro focus lenses, and more
recently on large-range zooms such as the Nikon 18–200 mm.
• A certain amount of pincushion distortion is often found with
visual optical instruments .Ex -binoculars.

12. REFERENCES
• http://en.wikipedia.org/wiki/Distortion_(optic
s)
• www.google.com
• http://toothwalker.org/optics/distortion.html