So topic for today is aberrations in lenses, which is the defect caused in the lenses due to which blur images are developed.It is just an overview of the following topic.
The deviations in dimensions of position and colour in the image produced by a lens in comparison with the actual object is known as “lens defect or aberration’’.
Also, In an optical system
All rays of light from a point in the object plane would converge to the same point in the image plane, forming a clear image. The influences which cause different rays to converge to different points are called aberrations.
There are two main types of aberrations:
1) Spherical aberrations.
2) Chromatic aberrations.
1) Spherical aberrations: The refracting angle of prism near the axis is different than near the edges or periphery of lens. Therefore, when a monochromatic light is incident on the lens, the rays incident near the periphery and parallel to the axis are called “Marginal rays”. The rays, incident near and parallel to axis of the lens are called “Paraxial rays”. They suffer least deviation.
2) Chromatic aberrations: This defect is due to the prismatic action of lens. When a parallel beam of white light or a composite beam of light is incident on the lens, the beam is not only deviated: but also dispersed into it’s constituent colours; at different focus to form a chromatic aberration.
- Methods to reduce spherical aberration:
Methods to reduce chromatic aberration:
Difference between spherical and chromatic aberration:
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