Flashcards in Diffractive Optics And Iridescence Deck (33):
An optical device that blocks alternate zones is called a ___________
A diffraction grating that creates inwardly bending spherical diffracted wave forms a _________
The focal length of the plate is give by...
Fresnel zone plate blocks wave that contribute to destructive interference at the diffraction maximum, making the image formation much ________
Instead of blocking these waves, they are ________________.
Phase shifted by 180
After phase shift of 180, the phase shifted waves would be ___________ with the axial wave, and would contribute to the constructive interference at the diffraction maximum, making the image much _________.
What is this called?
Phase plate or phase reversal zone plate
A zone plate with kinoform shaped grooves is referred to as a ______________
What is the benefit of the kenoform shaped grooves on an ophthalmic diffractive lens?
It makes it much thinner
A single refractive lens with a phase plate embedded on one side of its surfaces
The original bulk of the dashed lens is reduced, leaving a thin lens whose surface slopes match the original lens. This example has __________
Equal step heights
A Fresnel lens with ______________. A fresnel lens is always a mono-focal lens.
Equal zone widths
What does the power in the M=0 come from?
The base curve power
1st order in contact lens
0th order in contact lens
Local grating _________ determines ray direction (add power). Spacing gets progressively smaller from center to its edge
Local step _____ determines "diffraction efficiency" of light. (Determines how much light put into the add portion)
Allocation of energy into each diffraction order
When m=0, focal length of _________ is infinite (zero power)
What is the diffraction efficiency for multifocal
40% from 0th order
40% from +1 order
Efficiency for trifocals
Divide 80% by 3
Expected VA for multifocal
Cant get 20/20 all around
Unwanted patterns onto the retina which affect the visual performance by obscuring relevant retinal image
What are the two types of dysphotopsia
Positive and negative
Bright artifacts onto the retina
Ex. Arcs, rings, streaks, halos, and glares
Blockage of light onto the retina
Ex. Shadows, dark spots
Fresenel's lens increases the luminosity of the lighthouse lamp by a factor of _____
The smaller fresnel lens orders, the 4th though the 6th orders, were often situated where?
Lakes and harbors
Biological color effects: physics
-delivers color due to interference, diffraction and scattering
Natural diffraction grating on a component found on the insect exoskeleton
Mollusk outer surface of shell
-fine scale grooves
-parallels grooves, smooth and even
-diffraction color is strong
Inner surface of mollusk shell
-diffraction color is weak
Iridescence in shell
Higher orders (3-8) get overlapped
-this causes iridescence
-depend son groove density and surface quality