Antireflective Lenses

Question 1

For A/R coating to reduce reflections, an A/R coating must meet 2 conditions:

Answer 1

1) path condition - determines what the optical thickness of a single layer coating film must be
2) amplitude condition - amplitude of light waves in the lens material and the film must be equal

Question 2

path condition:

film must be _ of wavelength thick or _ multiples of that

Answer 2

1/4, odd

Question 3

path condition:
when light strikes the single layer coated lens surface, some light will reflect from _ and some from _

this causes _ phase, _ interference, and prevents reflections

Answer 3

coating surface
lens surface

out of, destructive

Question 4

amplitude condition:

requires the amplitude of the light waves in the lens material and film to be _, creating _ interference

Answer 4

equal, destructive

Question 5

amplitude condition:

index of film must be equal to _ of index of material being coated

Answer 5

square root

Question 6

single layer coatings are not 100% effective because:

Answer 6

correct coating thickness for yellow waves is not correct for red or blue (blue and red are reflected more and form purple cast)

Question 7

multilayer coatings (8 layers) work by:

Answer 7

adding more layers of coating, each specific to wavelength and increasing amount of light transmitted that would have normally been reflected

Question 8

multilayer coatings are not placed directly on lens;
first _
then _
then _

Answer 8

primer
hardcoat
adhesion

Question 9

when alternating layers of low and high index materials, it is possible to obtain reflectivity as low as _%

Answer 9

0.1

Question 10

_ is primary material used for AR coatings as in Silica

Answer 10

Magnesium Fluoride (n=1.38)

Question 11

AR is sealed with either _ or _ coating

Answer 11

hydrophobic or oleophobic

Question 12

many new coatings are so efficient in repelling smudges, a temporary _ is applied to prevent slippage during edging

Answer 12

gripper coat

Question 13

multilayer AR coatings are very important for _ lenses as they naturally transmit less light

Answer 13

high index

Question 14

AR coatings are hard and brittle
plastic lenses are soft and spongy
-what supports brittle AR coating?

Answer 14

hardcoat

Question 15

designing AR for the material that it will be placed upon is known as _

Answer 15

substrate matching

Question 16

color that you can see on the lens is called

Answer 16

reflex color

Question 17

multilayer coatings do not have purple cast; most today have _ appearance

Answer 17

blue-green

Question 18

if lens has a reflex color that changes from one section of lens to another, it is an indication of _

Answer 18

even coating thickness

Question 19

reflex color can be any color and still be effective; it also can have virtually _ and still be effective

Answer 19

no color

Question 20

applying an AR coating _ a tinted lens;

therefore required to tint a lens _% darker than desired if AR is going to be applied

Answer 20

lightens

10-15

Question 21

AR coating has what effect on sunglasses?

Answer 21

reduced mirror like reflections from back surface

Question 22

pros of AR:

Answer 22

less reflections
eyes more visible
improved contrast
less halos with night driving
easier to clean/stays cleaner

Question 23

cons of AR:

Answer 23

cost

smudges are more visible

Question 24

AR coatings are _ fragile

Answer 24

thermally, chemically

Question 25

HEV (blue light) _ more easily than other visible light

Answer 25

scatters (not easily focused)

Question 26

blue light is perceived as _ and contributes to _

Answer 26

noise; digital eye strain

Question 27

excessive blue light can damage light sensitive cells in the retina, like _

Answer 27

Macular Degeneration

Question 28

_ is altered by blue light exposure

Answer 28

Circadian Rhythms

Question 29

some blue light is essential for health, benefits?

Answer 29

alertness, memory, cognitive function, elevates mood

Question 30

lack of blue light in fall and winter?

Answer 30

Seasonal Affective Disorder

Question 31

Coating including blue light blocking

Lens that blocks blue light

Answer 31

Prevencia

Blue Tech

Question 32

Lenses that filter HEV light had undesirable yellow cast, now in clear
_ is best option

Answer 32

blue filtering AR coatings

Question 33

product that you should prescribe to all patients that are heavy users of devices

Answer 33

Blue light, AR filters

Question 34

4 major manufacturers of coating equipment

Answer 34

essilor
hoya
satis
zeiss/sola