Absorptive Lenses Flashcards by Jessica Ward

these are lenses designed to prevent wavelengths from entering the eye reduces the intensity of certain wavelengths that do enter the eye

absorptive lenses

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which UV rays are closest to the visible spectrum

UV-A

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what is the range of the visible spectrum

380nm- 760nm

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Which UV has spectrum of 380-320 nm

UV-A

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which UV has spectrum of 320-290 nm

UV-B

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which UV has spectrum of 290-200 nm

UV-C

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what is the infrared spectrum

760 nm - 1 mm

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which lenses transmit all light roughly equally

crown glass- clear

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what percentage of light is transmitted and why

92% bc of light reflection from the front and back of the lens , which is 4%

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which lenses cause the transmittance curve to shift to the right ; better UV blocker than crown glass but not optimal

CR- 39 clear

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which lens is an excellent UV blocker

polycarbonate

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what three things happens when light strikes a lens

reflection, absorption, and transmission

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reflection equation = amt of light reflection by a lens surface

I(r) =( ( n- n)^2/ ( n + n) ^2 ) x (I)
n* = index of lens
I(r) incident light that strikes front of lens -> complete example problem on slide 18

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what is I on the front and back surface of the lens

I is 1 on the front surface and 0.96 on the back surface because not all the light made it through

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T or F: transmission= incident light - reflection from surface - absorption- reflection from back surface

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as index of refraction goes up…

reflectance goes up

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this law states that for an absorptive material, layers of equal thickness absorb equal quantities of light regardless of the intensity of light

lamberts law of absorption -> example slide 22

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T or F: transmission = I ( incident light ) x q ( number of thicknesses)

T -> ex slide 24

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What is the ultimate transmission

when light passes through a number of lenses

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how is the ultimate transmission found

by multiplying separate transmission of each of the lenses T= T1 x T2 x T3 example slide 28

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what is the term used for the reciprocal of transmission

opacity

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T or F: the equation for opacity is O = 1/ T

T ; ie. slide 30

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how is ultimate opacity

when light passes through a number of lenses , it can be found by multiplying the separate opacities of each of the lenses O= O1 x O2 x O3 -> ie slide 32

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T or F: optical density is Optical Density = -log Transmission
D = -log T

T : ie slide 34

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which types of lenses acts as a filter and can be uniform or neutral ; also which can be selective

absorptive lenses

which type of absorptive lens has the color imparted to the lens by the addition of an absorptive substance

tinted solid glass lenses

which type of absorptive lens has a thin metallic oxide that is deposited on the surface of the lens ; usually the back surface ; requires high temps

glass lenses with surface coatings

these lenses are tinted by dipping into a dye; dye penetrates to a uniform depth

tinted plastic lenses

which tint color has no color distortion for wearer ; and is used to try and negate poor indoor lighting conditions

pink

which tint is used as a bold fashion color

red

which tint is possibly used for shooting glasses, night driving, and poor visibility , enhances contrast of targets against the sky

yellow

which color approximates color sensitivity curve of the human eye ; increases depth perception , maybe golf?

green

which tint is popular for sun lenses and has higher absorption of shorter visible wavelengths

Brown

most popular tint for sun protection ; colors seen in natural state

gray

what is normal transmission for sun lenses

15-30%

what happens if transmission is too high

may not hep average wearer in full sunlight

what happens if transmission is too low

results in visual acuity reduction in dimly lit conditions

how do photochromic lenses work

glass contains silver halide crystals -> lenses darken when exposed to long wavelength UV radiation -> UV transforms silver halide crystals into silver and halogen atoms ; darkening rate is temperature dependent

what are the different types of photochromic glass lenses

photogray II, photogray Extra, photobrown extra, photosun II

which lenses relive glare for pts with severe light intensity and filter out shorter ( blue ) wavelengths

corning photochromic filter lenses- glass

what compounds are used to produce the photochromic effect in plastic

spiropyrans

what type of technology is corning sunsensors and rodenstock

in-mass technology

what type of technology is transitions

imbibed technology

some features of this technology is that molecules never wear out; darkens up to 50 % in the car, scratches don't affect performance; exterior 1.5 mm of lens activated preventing uneven darkenign

in-mass

features of this technology include darkens consistently across the lens regardless of Rx; available in wide range of material and designs

imbibed technology

this type of transitions is a photochromic product for all around; balance between outdoor darkness and indoor; doesn't change behind car windshield; no polarization ; colors are gray, brown, and graphite green

transitions VII

what type of transitions is for pts. in bright sunny conditions; has superior outdoor darkness with a slight indoor tint; moderate activation behind a car windshield ; no polarization; colors are gray, brown, or green

transitions XTRActive

what type of transitions is a photochromic product with variable polarization as the lens darkens; darkens with increasing polarization outdoors; dark outdoors and clear indoors ; doesn't change behind a car windshield and clear to gray only

transitions vantage

what type of trans is designed for pts that spend more time in bright sunlight ; designed to be worn outdoors ; multiple color options

transitions adaptive

what type of lenses have new photochromic technology . have better clearing speed; better fatigue resistance and can be tinted

photofusion lenses

which photochromic lenses claims they are the second largest selling photochromic on the market

corning sunsensor

what are the Photochromatic plastic fashion tints

splitz (sola) changeable fashion tint); and solera (invicta) darkens into a darker fashion tint outdoors

which Photochromatic lenses go from clear to brilliant saturated shades

beloptix 1.60 polarized

T or F; transitions optical is partnering with motorcycle safety equipment manufacturers to produce face shields and visors

what diff face shields is transitions making to be put on helmets

bell transitions face shield, laser lumino trans, and SHOEI trans adaptvie face shield

what is bright light that interferes with optimal vision, produces discomfort

glare

what are the diff types of glare

distracting , discomfort, disability, and reflected

this type of glare caused by lens reflections

distracting

this type of glare is sensation of irritation or pain from sources of light ; light doesn't interfere with resolution

discomfort

this type of glare causes objects to appear to have lower contrast than they would if there were no glare; it increases the brightness of the background and lowers the brightness of the object thereby interfering with the resolution ie. turning on the room lights while trying to watch a slideshow

disability

T or F: light sources with the central 10 degrees of the visual field contribute to disability glare

this type of glare is also know as blinding glare ; glare caused by reflected light sources

reflected glare

how are polarized lenses manufactured

suspending polarized film within the lens mold and casting the lens with the film in place

what are the two axes of a polarizing filter

absorption axis and a transmission axis

this axis blocks all polarized light incident at that axis

absorption axis

this axis transmits all polarized light incident at that axis

transmission axis

how do the axes have to be oriented to each other for polarization

perpendicular

this type of lens eliminates specularly reflected horizontal polarized light; improves VA and restores the natural balance of light intensities; helpful for motorists, fishermen, and skiers

polarizing lenses

what are materials that best polarize light ; they are nonconductors such as glass, pavement, sand, and snow

dielectrics

light reflected from a dielectric is completely polarized at a specific angle of incidence called

Brewsters Angle

What is the equation for Brewsters Angle

tan I= n* n*= index of medium to which the light is incident I= angle of incidence for which the reflected light is most completely polarized example on slide 90

T or F: Polarized lenses reflect horizontal light waves and admit vertical vibrating light waves

what is a well know company for producing polarized resin lenses

NuPolar Lenses

this film is located .4 to .8 mm from the lens front surface ; polarizing axis alignment is critical ; tolerance is 3 degrees

nupolar lenses

this law determines the intensity of light that passes through two perfect polarizers ( 2nd polarizer is called an analyzer)

Malus Law: Io = I cos^ 2 θ theta; angle between transmission axis of first polarizer ( lights initial plane of polarization) and the transmission axis of the second polarizer I= intensity of the light I(o)= light passing through two polarizer series; example slide 102

according to Malus Law, if the two polarizers are 90 degrees apart, the polarizers are crossed , is light transmitted?

according to Malus Law, if the two polarizers are coincident ( transmission axes aligned,) the polarizers are uncrossed and how much light is transmitted

100 %

what are some negatives about glare

glare from natural sunlight can be visually debilitating; glare from natural sunlight has contr. to aviation accidents

pros about appropriate aviation suns

free from distortions and imperfections; transmit 15 % overall light ; don't alter color perception; employ larger lenses in a wrap around design

these sunglasses are not recommended for aviation bc they reduce the visibility of instruments in the cockpit; interfere with visibility through an aircraft windscreen ; mask the sparkle of light that reflects off shiny surfaces of other planes wings etc

polaroid sunglasses

what can be added to the lens that provides advantage of blocking UVA, UVB, and glare , and HEV radiation

melanin

what are two types of combination lenses

transitions drivewear and julbo falcon lens

this type of lens have trans photochromic technology plus; nupolar polarization

drivewear lens

this is a plastic photochromic lens ; reacts only to visible light ; darkness not affectd by windshield ; not affected by temp. ; polarized lens; AR coated

julbo eyewears falcon lens