3.1.2 How Binoculars works
The light from the object or target you are looking at enters the binoculars through the Objective lens
system (item 1, fig. 1). Due to the objective lens, the rays are converged to a upside down image. Then
the light rays of the image pass through the prism system (known as the Porroprism) (item 2, fig. 1) , and
are reversed to erect image at the reticle( item 3, fig. 1) just as you see by eyes. This image is magnified
by eyepieces (item 4, fig. 1), so that the observer can now see the distant object.
3.1.3 Reticle Scale (See Fig. 3)
There are vertical and horizontal lines on the reticule 3. Each small division on both vertical and
horizontal lines represents 5 mils and each big division represents 10 mils (one perigon=6400 mils).
3.2 Body assembly (Fig. 2)
The binoculars consists of identical two telescopes. A right side and a left side. Each halve consists
of (1) eyepiece, (2) main binocular body housing the Porroprism assembly and (3) objective. Item (4) is
the connecting shaft holding both halves of the binoculars. Item (5) is a interpupillary scale, its range from
56 mm to 72 mm. Item (6) are diopter adjustment rings, which have diopter index marks. Each graduation
represents one diopter. Item (7) are the rubber fold-down eyecups. Item (8) is the Calculator Dial. Item (9)
is the compass illuminated window. Item (10) is switch for illuminating the compass. Item (11) is the
battery compartment. Item (12) is the dustproof cover for the objective lenses and item (13)is the
dustproof cover for eyepieces.
4. How to use the binoculars
4.1 How to focus the binoculars
4.1.1 Interpupillary adjustment
You must first adjust the binoculars so that each eye piece is adjusted to the distance between your
eyes. This is done by putting the binocular in both hands and bending it until you can see a single circular
image.
Note: the image will not be clear. You will adjust for clarity in the next step. You must first set the
binoculars’s interpupillary to fit your eyes. The setting for your eyes will be indicated on the interpupillary
scale. Note this scale setting for quicker resetting later.