What Is A Fresnel Lens?
A Fresnel lens for purposes
consists of a flat plastic lens with concentric grooves on one surface and a flat surface on the other side.
Originally invented by Augustine Fresnel. The original Fresnel lenses were used
to magnify the lighthouse beacon light. A Fresnel lens is thinner and lighted then a ordinary convex magnifier lens.Wikipedia
After the age of about
forty you will experience a problem viewing small print and tasks involving close detail work. This eye condition
is called presbyopia and a page size magnifier can help.
Magnifier glass power
and work distance: Select a magnifier with a power that will allow you
to perform your task at a comfortable distance.
The high power magnifier may not be the best magnifier for you. Our large magnifier selection can help those with presbyopia and macular degeneration
Field Of View: The size of the area being magnified when viewing through a magnifier lens. The higher the power
of the magnifier the smaller the field of view.
Diopter: Diopter is a measurement that is used to calculate the power of a magnifier
lens. The higher diopter will provide higher magnification. Diopter is expressed as "D"
Power: Power is how large an object or print increases as you look through a lens. Magnifier power
is expressed as "X"
Focal Length: Measurement from the center of the lens to to the object and be in focus
Focal Range: The distance
from the magnifier lens to the object
Fresnel Magnifier : A flat magnifier consisting of concentric circles.
Visual impairment (or vision impairment) is a decreased ability to see to a degree that causes problems
not fixable by usual means, such as glasses or medication. Our low vision magnifiers can be of help.
Rules Of Magnification.
- The higher the power
of the lens, the closer you must get to the object being viewed and the smaller the field of view.
- As the power of a lens
increases the diameter of the lens decreases.
- Diopter is a term used to determine the power(magnification}of a lens. The terms are
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The National Federation of the Blind
National Library Service for the Blind and Physically Handicapped
National Eye Institute
American Action Fund for Blind Children & Adults
National Eye Health Education Program