Types of spherical converging and dispersing lenses
Spherical aberration is also called aperture error or spherical shape error. This error occurs in (normal) spherical lenses with a fixed radius.
They have different focal lengths at the centre and edge, with light rays passing through the edge of the lens having a longer focal length than the more central rays and being focused in front of or behind the sensor.
Lenses with significant spherical aberration produce a soft and slightly blurred image, as the sharp centre image is superimposed by an out-of-focus image.
This can be reduced by stopping down the lens or using aspherical lens elements.
However, these are much more expensive to produce due to the different radii of curvature on the glass surface and usually need to be machined individually on CNC machines.
Principle of spherical aberration
Important for Machine Vision
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