Imaging Optics
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Light
Light is an electromagnetic energy propagating in space
as a transverse electromagnetic wave. The wavelength range
extends from gamma rays (very short) to radio-waves (very
long). Wavelength determines how much light interacts with
matter and how much of this interaction is seen by human eyes
or by an image sensor. |
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Polarization
Ordinary white light is made up of many waves
vibrating in all possible directions along the axis in which
they are traveling. When all vibrations are blocked in all
directions except those in the horizontal direction, the wave
is said to be horizontally polarized. Similarly, the light
can be vertically polarized. A
polarizer is a material that allows only light
with a specific angle of vibration to pass through.
If
two polarizers are set up in series so that their optical
axes are parallel, light passes through both. However, if
the axes are set up 90 degrees apart (crossed), the polarized
light from the first is extinguished by the second. As the
angle rotates from 0 to 90 degrees, the amount of light that
is transmitted decreases. This effect is demonstrated in the
diagram on the left. The polarizers are parallel at the top
and crossed at the bottom.
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Although light is known to be a wave motion, it is often more convenient
to consider only the paths along which light travels. These paths
are known as rays, and in a homogenous medium (air) they are
straight lines. By using the ray method (geometrical optics), it
is possible to determine the location and brightness of an image. However,
to determine the structure and distribution of light, which can
be affected by phenomena such as polarization, diffraction, interference,
and scattering, the light has to be treated as a wave (physical
optics).
The main task of the optics is to generate an image of an object
at the camera sensor with as little distortion as possible. Optics
can also be used to remove some undesirable information from the
image (filtering, polarizers) or it can be used to modify, direct,
enhance or filter the lighting. The optics may include different
devices – lenses, mirrors, beam splitters, prisms, polarizers, filters,
etc.
The image is the only source of information for the machine vision.
Therefore, the quality of the analysis is dependent on the quality
of the image. And the quality of the image is determined by the
appropriate choice of optics. The software cannot correct for poor
image quality.
For more information, please contact
High-Tech Digital Technical Support.
310-265-8203
support@high-techdigital.com.
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