Physical And Optical Chara Of Ophth Lenses Flashcards
Relating to the eye, this refers to the interval surrounding the retina in which an eye sees an object in focus
Depth of focus
Short focal length leads to _______ depth of field
Large
The interval surrounding the fixation plane in which an object can reside and still be in focus
Depth of field
An increase in aperture size and depth of field
Decreases depth of field and depth of focus
Create optical distortions in image quality or a deformation of the image plane
Aberrations
Two types of aberrations
Monochromatic and chromatic
Wavelength independent aberrations
Monochromatic aberrations
Monochromatic aberrations that distort image quality
Spherical
Coma
Radical astigmatism
Monochromatic aberrations that deform the image plane
Curvature of field
Distortion
Chromatic aberrations
Longitudinal
Transverse
An aberration that occurs when peripheral rays focus at different points on the optic axis than the parasail rays
Spherical aberrations
Length of a blur circle
Longitudinal SA
Area size of blue circle
Lateral SA
What is the basis for SA
Paraxial approximation is not always valid
Increase in pupil size leads to a _____ in quality of image due to _______ aberrations
Decrease
Increased
Point of focus of a beam of light is dependent on where the light stroked the optical system
Longitudinal SA
Marginal rays focus to a different location compared to parazial rays
Longitudinal SA
-a point object is no longer forming a point image (the image is blurred)
Results from the fact that mag is varied as the height of incident rays above the axis varied
Coma
- asymmetric comet-shape patch
- only in off-axis point sources
Relevance of SA and coma
Largely irrelevant to ophthalmic optics because the small pupil size only accepts paraxial rays
-very high powered lenses-necessary to compensate for spherical aberration by using aspheric lenses
Two factors that influence the effective power of a lens
- Increase in vertex distance for peripheral viewing resulting in a positive shift in effective power for plus and minus lenses
- light rays strike at an oblique angle inducing astigmatic and spherical error
Spherical error
Field curvature
Cylinder error
Oblique astigmatism
Other terms as oblique astigmatism
Radical astigmatism or marginal astigmatism
Due to rays hitting the lens obliquely causing the power to be altered by this tilt of the lens
oblique astigmatism