Questions with Answers on Optical Aberrations PDF

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Questions with Answers on Optical Aberrations...

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Questions with ANSWERS on Optical Aberrations Which aberration does not occur in monochromatic light? Chromatic aberration How does spherical aberration get worse? As light rays become further away from the optical axis (non paraxial rays) How does spherical aberration affect lenses and mirrors? By reducing the quality of the image What is one way spherical aberration can arise in a telescope for example? Manufacturing errors in the curved focusing mirror What is the longitudinal chromatic aberration (LCA)? The spread of the spectrum along the optical axis ( white light into spectrum=dispersion) What factor depends upon the lens producing LCA? Its material Does chromatic aberration increase with pupil size? Yes so the duochrome test for example is best in the dark What would a hyperope see more clearly on the duochrome? The black rings on the green What would a myope see more clearly on the duochrome? The black rings on the red What is transverse chromatic aberration(TCA)? The spread of the spectrum perpendicular to the optical axis What is a coma and how is it produced? It is similar to spherical aberration but produced by oblique rays of light In comparison to oblique paraxial rays and perpherial oblique rays... They focus closer to the optical axis and produce a larger blur so as the distance increases from the optical axis it becomes blurry What is oblique astigmatism? Parallel rays of light entering the lens obliquely to come to a focus away from the optic axis creating an astigmatic image What is the tangential focus? An image focus produced by the rays travelling in the plane of the obliquity What is the sagittal focus? The other image focus that is 90 apart from the other image focus In human eyes , the sagittal focus forms...

the more hyperopic image shell In human eyes , the tangential focus forms... the more myopic image shell In human eyes , the circle of least confusion lies between... the sagittal and tangential focus How does the image form on a Petzval curved surface than a plane surface? As light rays coming from different points of the object causes variations in object and image distance. This is called the curvature of field aberration How does distortion occur? Because the focal length on a Petzval surface varies causing variations in transverse magnification of the image. It doesnt modify the colors or sharpness , just the SHAPE of the image. Barrel (positive) distortion Occurs when we look through a negative lens Pincushion (negative) distortion Occurs when we look through a positive lens How do aberrations occur in the eye specifically on the axis? As the cornea is sometimes tilted it causes coma and spherical aberration at the fovea , this usually affects the fovea How do aberrations occur in the eye specifically off the axis? Oblique astigmatism effects the monochromatic retinal image also distortion effects the image but the brain adapts to the new patterns that occur therefore is compensated by the brain....