KMK 7.4: Aberrations of Lenses and Corrective Lens Designs

What type of lens should you Rx to correct curvature of field?

-Percival form lenses (base curve is based on tscherning ellipse which gives a flatter base curve)

Distortion is determined by the location of the...?

-aperture stop

Minus lenses lead to what kind of distortion?

-barrel -most minus in the center

Both curvature of field and radial astigmatism can be corrected by...?

-choosing the correct base curve (primarily Oswalt) -choosing focal point lenses (fully correct the residual astigmatism)

What is curvature of field?

-intertwined with oblique/radial astigmatism -plane object forms a curved image with decreased image quality as the distance increases *hyperopes can accommodate to clear up the aberration

Longitudinal chromatic aberration is ____________ related to abbe value

-inversely

Coma occurs only for _______ axis point sources

-off axis *correct this with aspheric lenses (aspheric lenses modify the lens surface without changing the power)

Oblique/radial astigmatism is the result of...?

-on and off axis light coming through the lens

Spherical aberration is created by what type of points?

-on and off axis points -marginal rays bend more than paraaxial rays *use an aspheric lens to correct

What is used to correct for distortion?

-orthostatic doublet

Plus lenses lead to what kind of distortion?

-pincushion -more plus in the center

Lateral/transverse chromatic aberration is related to ____________

-prismatic effect

T/F shorter wavelengths bend more as they pass through an interface or optical system than do longer wavelengths

-true -all wavelengths are not focused at the same location so the image will vary in location (longitudinal chromatic aberration) and size (lateral chromatic aberration)

If you have a material with a low Abbe value what are 3 things you can do to minimize the effects of chromatic aberration?

-use shorter vertex distances -use monocular PDs -include sufficient pantoscopic tilt

What is the formula for longitudinal chromatic aberration?

CA=F/v(abbe number)