Page 355 - Concise Encyclopedia of Robotics

Vision System
does not need to be able to see well in a dark cave. A robot designed for
working in mines, or in pipes, or in caverns, must be able to see in dim
light, using a system that might be blinded by ordinary daylight.
Resolution is the extent to which a machine can differentiate between
objects. The better the resolution, the keener will be the vision. Human
eyes have excellent resolution, but machines can be designed with greater
resolution. In general, the better the resolution, the more confined the field
of vision must be. To understand why this is true, think of a telescope.
The higher the magnification, the better will be the resolution (up to a
certain point). However, increasing the magnification reduces the angle,
or field, of vision. Zeroing in on one object or zone is done at the expense
of other objects or zones.
Sensitivity and resolution depend somewhat on each other. Usually,
better sensitivity means a sacrifice in resolution.Also, the better the resolu-
tion, the less well the vision system will function in dim light. Maybe you
know this about photographic film. Fast film tends to have coarser grain,
in general, than slow film.
Invisible and passive vision
Robots have a big advantage over people when it comes to vision.Machines
can see at wavelengths to which we humans are blind.
Human eyes are sensitive to electromagnetic waves whose length ranges
from approximately 390 to 750 nanometers (nm). The nanometer is a
9
billionth (10 ) of a meter. Light at the longest visible wavelength looks red.
As the wavelength gets shorter, the color changes through orange, yellow,
green, blue, and indigo. The shortest light waves look violet. Energy at
wavelengths somewhat longer than 750 nm is IR; energy at wavelengths
somewhat shorter than 390 nm is UV.
Machines need not, and often do not, see in the same range of wave-
lengths and the human eye sees. Insects can see UV that humans cannot,
but are blind to red and orange light that humans can see. (Many people
use orange “bug lights”when camping,or UV lamps with electrical devices
that attract bugs and then zap them dead.) A robot can be designed to see
IR or UV, or both, as well as (or instead of) visible light. Video cameras
can be sensitive to a range of wavelengths much wider than the range
humans can see.
Robots can be made to see in an environment that is dark and cold,and
that radiates too little energy to be detected at any electromagnetic wave-
length. In these cases the robot provides its own illumination. This can
be a simple lamp, a laser, an IR device, or a UV device. Alternatively, a
robot can emanate radio waves and detect the echoes; this is radar. Some ro-
bots can navigate via acoustic (ultrasound) echoes, like bats; this is sonar.

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