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Chapter 5 Image Acquisition
NI 17xx Smart Camera User Manual 5-2 ni.com
can be used to calculate the maximum exposure. Assuming the object is
moving horizontally across the field of view, use Equation 5-1 to calculate
the maximum exposure time.
(5-1)
where E
max
is the maximum exposure time without blurring,
R is the rate of motion of the object either horizontally or
vertically,
FOV is the field of view in the direction of motion, and
N is the number of sensor pixels in the direction of motion
For many applications that include moving objects, additional lighting is
necessary to achieve good image contrast due to the short exposure time
required to avoid motion blur.
Additionally, in many environments, the ambient light conditions vary too
significantly to obtain consistent results without adding dedicated lighting.
For example, in a building with windows, the ambient light can vary
significantly with weather. Also, standard fluorescent lighting flickers at a
rate that is perceivable by the smart camera. In these situations, the ambient
light must be overridden with a dedicated light source to ensure
reproducible results.
Acquiring Images
You can configure the NI Smart Camera to acquire images based on
internal timing or an external trigger signal. In both cases, the smart camera
can acquire full frame images at the camera’s maximum frame rate.
If partial scanning or binning are enabled, the smart camera can acquire
images faster than the full frame maximum frame rate. Refer to the
Maximum Frame Rate section for information about factors that affect the
maximum frame rate.
Internal Timing
The NI Smart Camera features two types of internally-timed modes:
free-run mode and fixed-frame-rate mode.
In free-run mode, the smart camera acquires images at the maximum frame
rate allowed by the configuration.
E
max
R
Horizontal
2×
FOV
Horizontal
()N
Horizontal
()⁄
------------------------------------------------------------------------=