Chromatic Aberration I
Dispersive power equation
(Shortest-longest)/(middle-1)
The mean magnitude for foveal tca for read and blue light is
0.82 arcmin
Dispersion of water is not contant, but varies amongst ____ % of the visible spectrum
1%
LCA range is how many diopters in human eyes
2.1 D
The reciprical of dispersive power is called the
Abbe number
Which wavelength is less magnified
Blue is less than red light
The variation of position within wavelength for TCA is referred to as
Chromatic difference of position (y axis) Chromatic difference of magnification
How do we measure chromatic aberration in the eye?
Chromatic difference of refraction (object space)
Lower order aberrations vs higher order aberrations
Defocus and astig: LOA SA, coma and trefoil: HOA
Chromatic aberrations occur when a mixture of
Different wavelengths of light vs monochromatic aberrations are produced with a single wavelength of light
Higher the dispersive power, the higher the
Dispersal
As the abbe number increases
Dispersion decreases
How would you correct a singlet lens that has chromatic aberration?
Diverging lens (-), because it will push the blue convergence point back to meet with the red
Excessive lead vs lag in regulars to wavelength positions
Excessive lead= focus longer wavelengths on retina since eye doesn't need to accommodate Lag= near work= accomodation is needed so shorter wavelengths are in focus
What does a decentered pupil cause
Fovea longitudinal chromatic aberration
TCA varies in magnitude with increasing field angle
Linearly
Which wavelengths are in focus on the retina
Long wavelengths are in focus for low accommodation (relaxed) and short wavelengths are in focus for higher accommodation
How to correct the human eye being more myopic for shorter wavelengths
Negative spectacle lens bc the shorter the wavelength the higher the power
What is dispersive power
Quantifies the amount of dispersion produced by an optical element bc as it increases, the dispersion of the optical element (prism or lens) also increases
Each optical element is selecetd based on two factors
Refractive index Abbe number
The eyes chromatic aberration is determined by the dispersion of the media and not the
Refractive index since the RI changes
what is chromatic dispersion
Separation of white light (polychromatic light) into its component elements
What is the chromatic difference of power?
The chromatic aberration and dispersion of light in image space and on retina
What is longitudinal (axial) chromatic aberration (LCA)
The chromatic difference of focus occurring when blue rays formed in front of the image formed by the red rays -diopter and it's the distance between the image planes
What type of aberration is off axis and is a chromatic aberration
Transverse chromatic aberration , measure by angle
What is transverse chromatic aberration
Variation of position of the image on the retina with wavelength Variation of mag with wavelength
What is the chromatic difference of refraction
Vergence of source for which the source is focused at the retina for a range of wavelengths- at object space which is the easiest to measure
The angle between what two axises is usually only a few degrees and is essentially zero
Visual and achromatic axis
What does the transmission speed of light within a refractive medium depend on
Wavelength bc the shorter wavelengths of light refract more than the longer wavelengths
The average TCA across population is
Zero
How is the TCA specified
by the angle between the chief rays for different wavelengths
