Discuss Chromatic aberration in a lens.
Chromatic Aberration is an optical issue which occurs when a lens either focuses wavelengths at different positions in the focal plane or cannot converge all wavelengths of color to the same focal plane. It is caused by dispersions of the lens, with different wavelengths of light passing through the lens at different speed. Consequently, the image appears blurred or may have noticeable colored edges (Smith, 20).
– Main Body
A perfect lens would direct all light wavelengths into one focal point. In real situations, each wavelength has different refractive index in lenses, hence resulting into two types of Chromatic Aberration- Longitudinal and Lateral.
– Longitudinal Chromatic Aberration
It is also called both fringing. It takes place when different wavelengths fail to meet at the same focal point after penetrating a lens. Lenses that have this problem can give images that show fringes of red, blue, green or a combination of these colors around objects throughout the image, even at the center. You can get rid of it by stopping down the lens (Smith, 23).
– Lateral Chromatic Aberration
This problem is also called transverse chromatic aberration. It takes place when the lens focuses different wavelengths that are incidental at an angle, along the same plane of focus, but at different points.
Unlike the longitudinal, lateral chromatic aberration is not visible in the center but show up towards the edges of the image in high-contrast regions. Wide-angle and low-quality lenses commonly give rise to blue and purple fringing.
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Both lateral chromatic aberration and longitudinal chromatic aberration occur in simultaneously in many lenses. Longitudinal Chromatic aberration takes place when different wavelengths fail to meet at the same focal point after penetrating a lens. Lateral Chromatic aberration takes place when the lens focuses different wavelengths that are incidental at an angle, along the same plane of focus, but at different points.
These problems can only be reduced stopping down the lenses (for Longitudinal) and applying post-processing software (for lateral).
Smith, Warren J. Modern Optical Engineering: The Design of Optical Systems. 3rd ed. New York: McGraw Hill, 2000. Print.