SOLA Dec. Lenses: 65x75x8 dec.
SOLA Dec. Lenses: 80 x 8 dec.
SOLA Dec. Lenses: 80 x 9 dec.
SOLA Dec. Lenses: 85x65 x 8 dec.
SOLA Dec. Lenses: 76 x 8 dec.2.2
SOLA Dec. Lenses: 80 x 10 dec.
SOLA Cylindrical lens: 90 x 60 x 7.5 dec.
Decentered Lenses:
The prism of a simple plano lens when viewed along
its axis is, by definition, ZERO. Unwanted prism is
introduced when the lens is viewed from a direction
other than parallel to the optical axis. This is the
case, for example, when the lens has a non-zero wrap
angle.
The essential property of a plano prism is that it
deviates, or changes the direction of, light passing
through it.
This deviating power of the filter is called Prismatic
Power
- is the measure of the displacement of an object
when a filter is placed between the eye and the object;
- convenient unit of measurement is the prism dioptre,
. 1
correspond to the displacement of 1 cm of the object
at a distance of 1 m from the eye;
- its value depends on the thickness of the filter,
the horizontal inclination of the filter (wrap angle)
with respect to the visual axis and the vertical;
- wrap angle determines the horizontal prism (BASE
IN or OUT) and the tilt determines the vertical prism
(BASE UP or DOWN)
Decentered Lenses:
OC Shift
- Introducing a prismatic power into the lens that
compensates for OC placement due to the glazing of
the lens into a wrap frame by continuously changing
the thickness of the lens.
- Decentered lenses move the optical centre (OC) away
from the geometrical centre (GC). The distance measured
in mm from the two centres is the decentration
and the resulting lens is said to be decentred.
- At the OC the prismatic effect is zero. The prismatic
effect increases as the distance from the OC to the
incident ray increases.
Decentered Lenses:
Dec. Lenses: Wrap Frame
Angles
|
6
Base Frames
|
|
Standard
Lenses
|
up
to 10°-11°
|
|
8
Base Frames
|
|
Standard
Lenses
|
up
to 10°
|
|
15.7mm
dec. lenses(Cr-39)
|
between
11° to 27°
|
|
21mm
dec. lenses
|
between
14° to 25°
|
|
27mm
dec. lenses
|
between
20° to 30°
|
|
9
Base Frames
|
|
24mm
dec. lenses
|
between
17° to 27°
|
