Absorptive Lenses Flashcards
these are lenses designed to prevent wavelengths from entering the eye reduces the intensity of certain wavelengths that do enter the eye
absorptive lenses
which UV rays are closest to the visible spectrum
UV-A
what is the range of the visible spectrum
380nm- 760nm
Which UV has spectrum of 380-320 nm
UV-A
which UV has spectrum of 320-290 nm
UV-B
which UV has spectrum of 290-200 nm
UV-C
what is the infrared spectrum
760 nm - 1 mm
which lenses transmit all light roughly equally
crown glass- clear
what percentage of light is transmitted and why
92% bc of light reflection from the front and back of the lens , which is 4%
which lenses cause the transmittance curve to shift to the right ; better UV blocker than crown glass but not optimal
CR- 39 clear
which lens is an excellent UV blocker
polycarbonate
what three things happens when light strikes a lens
reflection, absorption, and transmission
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
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
T or F: transmission= incident light - reflection from surface - absorption- reflection from back surface
T
as index of refraction goes up…
reflectance goes up
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
T or F: transmission = I ( incident light ) x q ( number of thicknesses)
T -> ex slide 24
What is the ultimate transmission
when light passes through a number of lenses
how is the ultimate transmission found
by multiplying separate transmission of each of the lenses T= T1 x T2 x T3 example slide 28
what is the term used for the reciprocal of transmission
opacity
T or F: the equation for opacity is O = 1/ T
T ; ie. slide 30
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
T or F: optical density is Optical Density = -log Transmission
D = -log T
T : ie slide 34
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
T
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
T
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
T
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?
no
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
