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Optical Density:
Optical density
(OD) is the logarithm, base 10, of the ratio of the incident light to the
transmitted light: OD=log10
Io/I,
where Io
is the incident intensity and I is the transmitted intensity. If neutral
density filters are placed in series, the optical density of the combination
is the sum the individual density values.
Optical Glass:
Optical
glasses are transparent, usually amorphous, and essentially
homogeneous materials whose manufacturing processes are controlled in such a
way as to create a desired variation in glass material characteristics such
as refractive index, transmission range, dispersion etc.
Optical Path
Length (OPL):
The optical
path length of a light ray passing through a medium of constant refractive
index is the product of the geometrical distance d and the index of
refraction n (OPL=nd).
Principal Plane:
In a lens
system, that surface at which the projections of an entering and exiting ray
intersect.
Reflection:
In optics, reflection is the return of radiation upon contact with a
boundary between two different media. There are two types of reflection:
diffuse (from a rough surface) or direct (from a smooth surface). The
characteristics of reflection at the boundary of a weakly or non-absorbing
media are summarized by Fresnel’s equation.
Relay Lens:
An optical system able to transfer an image from one image plane to another
with appropriate magnification
Resolving Power:
Resolving power is the measure of the ability of an optical component or
instrument to image two closely adjacent object details as two separate
details. In general, the resolving power is given as the angular distance at
which these details appear or as the number of resolvable lines per mm.
Telecentric System:
A telecentric system is an optical system where the aperture stop is located
at the focal point of the objective lens resulting in the chief rays being
parallel to the optical axis, i.e. the exit pupils at infinity.
Total Internal Reflection:
If light is incident on a boundary between two optical media of different
optical densities and is incident from the denser medium, it will experience
total internal reflection. The critical angle for the two materials is
described by Snell’s law as sin
ac=n’/n
where n’ is the index of the denser medium. |
