Polarizing lenses reduce glare caused by reflections from surfaces like water, snow, and highways. They work by blocking horizontally polarized light that is reflected from these surfaces, while transmitting regular light. The lenses contain a special filter made of polyvinyl acetate and iodine that absorbs the horizontally vibrating components of light. Polarizing lenses can be made for prescription lenses by mounting the polarizing filter between layers of hard resin or polycarbonate. They provide benefits like reduced driving fatigue and improved visibility for activities like fishing or at the beach.

1. Polarizing lenses
kamal thakur
2nd year bsc opto

2. Polarizing lenses
Polarizing lenses reduce glare is commonly caused by
reflections from water , snow , highways and metallic surfaces
.

3. •They reduce light transmission
•They reduce reflected glare
•They increase contrast sensitivity

4. How polarizing lenses work
• Light reflected from surfaces such as a flat road or
smooth water generally is horizontally polarized ,
instead of light being scattered in all directions .
Reflected light generally travels in a more
horizontally oriented direction.
Polarized lenses contain a special filter
that blocks this type of intense reflected light ,
reducing glare.

5. • When light strikes a horizontal reflecting
surface , it becomes partially polarized with
the major direction of vibration being in the
horizontal plane .
• If light strikes the surface of a refracting
material , such as water or glass , most of the
light will be refracted as it strikes the surface
of the water and go on into the water. The rest
of the light will be reflected . There is an angle
of incidence of the light striking a surface
where all of reflected light will be polarized .
This angle is called Brewster,s angle.

6. Brewster,s angle
When light strikes a refracting surface , most light is refracted into the
media , and some is reflected . The reflected light is partially polarized until
it reaches a certain angle when it is completely polarized . This angle is
where the reflected light and the refracted light are at right angle to one
another. This angle is called brewster,s angle.

7. Manufacturing of polarized lenses
A filter that absorbs the horizontally vibrating
components of light would be useful . Such a
filter is available for ophthalmic use and is made
from a sheet of PVA (polyvinyl acetate).
The PVA is first stretched to five
times its normal length in one direction . Then
dipped in iodine . The iodine is absorbed into the
chains of molecules in PVA . These darkened lines
create the polarizing filter .

8. The filter may be “sandwiched” between two
layers of Cellulose Acetate Butyrate (CAB) .
This is how thin , plano polarizing
lenses are made.
For prescription lenses , the
polarizing sheet is mounted between hard
resin or polycarbonate material . Alternately ,
it can be mounted on one layer of cellulose
acetate butyrate material and molded directly
into a plastic lens casting process.

9. If the polarizing lens is not oriented along 180-
degree meridian , not all horizontally polarized
light will be absorbed . And if a person is
wearing a polarizing filter and tilts his head to
one side , the filter will not absorb as much of
the horizontally polarized light .

10. Advantages
• Decreased driving fatigue specially during day
time.
• Fisherman can see more with polarizing
lenses because it not only removes reflected
or discomfort glare but enables the wearer to
see below the surface.

13. • Comfort at the beach is increased because
sand and water are both source of polarized
glare marking these lenses especially
appropriate.
• Color is not bleached.

14. Bright snowy rays are not blinding when
viewed with polarizing lenses .

15. • Polarizing lenses are good alternative to
sunglasses because they inhibit U.V radiation.

16. Application
Polarizing lenses are made in most lens style-
not just single vision lenses , but bifocal ,
trifocals and progressive addition lenses as
well.
they are available in glass , photochromic
glass , plastic , photochromic plastic ,
polycarbonate and HI plastic.

17. Methods for demonstrating polarizing
lenses
• It is possible to take two Plano polarizing
lenses and by holding one before the other
with their polarizing axis crossed at 900
eliminate all incoming visible light rays .
• Can be demonstrated by showing a glossy
magazine .