Source Word
focal length
Noun
(optics)
A
measure
of
how
strongly
an
optical
system
converges
or
diverges
light,
the
inverse
of
optical
power.
In
the
simple
case
of
a
single
convex
lens,
it
is
the
distance
along
the
optical
axis
from
the
principal
plane
of
the
lens
to
the
lens's
focal
point
(where,
for
instance,
the
film
would
be
placed
in
a
camera).
For
more
complex
or
multi-element
optical
systems,
focal
length
need
not
correspond
to
any
obvious
measurable
physical
distance.
Japanese Meaning
光学系において光がどれだけ集光または拡散されるかの尺度を示す値。単一の凸レンズの場合、主面から焦点（例えばカメラのフィルムが位置する点）までの距離となり、複雑な光学系では必ずしも目に見える物理的距離に対応しない場合がある。
Sense（1）
(optics)
A
measure
of
how
strongly
an
optical
system
converges
or
diverges
light,
the
inverse
of
optical
power.
In
the
simple
case
of
a
single
convex
lens,
it
is
the
distance
along
the
optical
axis
from
the
principal
plane
of
the
lens
to
the
lens's
focal
point
(where,
for
instance,
the
film
would
be
placed
in
a
camera).
For
more
complex
or
multi-element
optical
systems,
focal
length
need
not
correspond
to
any
obvious
measurable
physical
distance.
（ plural ）
