The Donegan replacement lens plate for the OptiVISOR hands-free,
headband binocular magnifier, has an optical-grade, acrylic lens
ground and polished into a prismatic lens, and is available in
multiple dioptric strengths which provide specific magnification
power (X) at specified focal lengths, or distance from object.
This magnifier enhances the size and resolution of an object or
image, and is commonly used for a variety of applications such as
jewelry-making, watch-making, knitting, artwork, electronic
inspection, book-reading, print inspection, and stamp-collecting.
Determining Magnification
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Diopter Magnification Focal Length
(Distance from Object) Sample View 20/20 vision 20" (50.8cm)
2-diopter lens 1.50X 20" (50.8cm) 3-diopter lens 1.75X 14"
(35.56cm) 4-diopter lens 2.00X 10" (25.4cm) 5-diopter lens 2.50X
8" (20.32cm) 7-diopter lens 2.75X 6" (15.24cm) 10-diopter lens
3.50X 4" (10.16cm) The OptiVISOR replacement lens plate is made
of a durable plastic material. It is constructed to interchange
in and out of the OptiVISOR body with ease. The replacement lens
plate comes housed in a protective carrying case, and has a
one-year limited warranty.
Diopter (D) is a technical term for the measurement of the light
curvature and thickness of a lens. A dioptric number and a
magnification number are not the same thing. Diopter strength
represents a specific magnification power (X). For example, a
5-diopter provides 2.5X magnification (at a distance of 8”). The
higher the diopter, the more magnification a lens can provide. As
magnification increases, distance to the object (focal length),
and field of view (diameter, or narrowness of view) decrease.
Magnifiers and prescription eyeglasses have a diopter value, such
as 1.5 or 2. The dioptric strength of an accessory lens, such as
prescription eyeglasses or an eye loupe, must be added to the
dioptric strength of the magnifier to calculate total
magnification.
Magnifiers are devices used to the visual appearance of
an object or image. Magnifiers come in a variety of styles such
as hand-held, headband, standing, clip-on, eye loupe, and those
that hang in a necklace form, or fit in a trouser pocket.
Magnifiers are commonly made of plastic or glass. They can have
one or more lenses with varying magnification abilities, and can
have a binocular configuration with a single lens, or two
separate lenses. They are sometimes used with LED or fluorescent
light sources to help control viewing capabilities. Magnifier
ability is often expressed as magnification at a specific length.
For example, 1.75X at 14” means that when a magnifier is held at
14” from a viewer’s eyes, the object will be magnified 1.75 times
(X) its actual size. As magnification increases, viewing areas
and focal length decrease. Magnifiers sometimes have a diopter
number, expressed as + or - D, which is a measurement of strength
(or power) of the lens. Some magnifiers are marked with a
dioptric number on the lens. A high diopter number has a higher
magnification than a low diopter number. Aspheric magnifiers,
unlike spheric magnifiers, produce a sharp image to the edge of
the lens for less distortion. Magnifiers are widely used in
jewelry inspection and fabrication, watch-making, electronic
inspection, needlework, artwork, reading, print inspection, and
stamp-collecting.
Donegan Optical manufactures and distributes precision visual
devices for hobbyists and professionals in industry, home, office
and crafts applications. The company was founded in 1952 and is
headquartered in Lenexa, Kansas.
What’s in the Box?
* Replacement lens plate for OptiVISOR magnifier
* Fitted carrying case
* Instruction manual
- Replacement lens plate for use with OptiVISOR magnifying visor (sold separately).
- Provides 5-diopter (2.25X) magnification.
- Optical-grade acrylic prismatic lens for improved focus and reduced eye strain.
- 8" focal length for a variety of uses.
- Made in USA.