Optics: Chromatic Aberrations 2 Flashcards
What does the significance of chromatic defocus depend on?
Luminance
Difference (in diopters) between blue and red wavelengths?
About 2.1D
When the peak of the luminance spectrum is in focus, most of the light is less than ____D out of focus
Less than 0.25D
Visibility of a target will be dominated by wavelengths that are …
Only slightly defocused
What is the chromatic difference of magnification of two wavelengths proportional to?
The axial distance (z) from the pupil to nodal point
The magnitude of the difference in magnification depends on the ___________
Axial distance
When is chromatic differences in magnification (CDR) important?
When viewing through an artificial pupil or optical instrument that moves the entrance pupil outside the eye
Does CDM less than 1% have dramatic effects on depth perception?
Yes because the visual system may interpret the different size and cause distorted perception
What is the chromatic difference of position (CDP) proportional to?
-stimulus eccentricity (peripheral vision)
-lateral displacement (foveal vision)
What does chromatic difference of position induce?
Wavelength dependent spatial phase shifts
What doe wavelength dependet spatial phase shifts affect?
Image contrast (visual performance)
What does chromatic phase shifts affect?
-judgement of hue, saturation, and brightness
-luminance contrast in the image
What does the amount of phase shifts produced by a given amount of image displacement depend on?
The orientation and frequency of the grating
When dies maximum phase-shift occur?
When high-frequency grating are oriented perpendicular to the direction of displacement of the image
When does zero phase shifts produced occur?
When the grating is parallel to the direction of displacement
What happens when two chromatic components of white sinusoidal grating having the same contrast and luminance are shifted by 180 degrees?
They would cancel each other out leaving zero luminance contrast
Hoe muysch eccentricity is seen when there is 1mm of displacement of the external pupil?
15 degrees of eccentricity
Why do limitations in foveal vision occur with displaced aperture?
Ocular chromatic aberrations due tot clinical assessment of visual functions using a misaligned optical instrument with respect to the visual axis
What is the effect of transverse chromatic aberration on visual acuity?
VA drops from 20/20 to 20/60 when test instrument is displaces 3mm from visual axis
Transverse chromatic aberration increases linearly with ________
Eccentricity
What is chromatic diploid?
When a point emitting two wavelengths produce a double retinal image
What is chromo stereopsis?
A stereoscopic illusion where differently colored objects located at the same viewing distance appear to be at different distances
What color objects appear closer when lined up in the same plane? Red or blue?
Red appears up front (in a normal pupil)
What is chemostereopsis an effect of?
TCA combined with binocular vision
What is the combined effect of longitudinal and transverse chromatic aberration?
All points in the retinal image will suffer -> except if you are aligned along achromatic axis
LCA reduces image contrast by ___________ the image while TCA reduces contrast by inducing ____________
Blurring, phase shifts
Which reduces contrast more? LCA or TCA?
TCA
What happens when chromatic aberrations AND monochromatic aberrations are corrected?
significantly improves contrast sensitivity -> improved by a factor of 3.2-5
What happens when only monochromatic aberrations are corrected?
Contrast sensitivity of the eye is improved by a factor of 2
