Chapter 5
Image Sensor
©
National Instruments Corporation
5-3
NI 177x Smart Camera User Manual
For example, if the working distance of your imaging setup is 100 mm, and
the focal length of the lens is 8 mm, then the field of view in the horizontal
direction of a NI 177x Smart Camera using the VGA sensor is
(5-2)
Similarly, the field of view in the vertical direction is
(5-3)
Based on the result of Equations 5-2 or 5-3, you can see that you might
need to adjust the various parameters in the FOV equation until you achieve
the right combination of components that match your inspection needs.
This might include increasing your working distance, choosing a lens with
a shorter focal length, or changing to a high resolution camera.
Image Sensor Spectral Response
The spectral response curve describes the relative sensitivity of the sensor
to different wavelengths of light. If you are imaging a dim scene, this
information can be useful when selecting a light source to use in your
application as the camera is most sensitive at its peak responsiveness. It
also helps determine if your application might require filters to remove
undesired wavelengths of light from the scene.
Refer to Appendix A,
, to find the normalized spectral
response curves for each image sensor.
Gain
Gain is a multiplier applied to the analog signal prior to digitization.
Increasing the gain increases the amplitude of the signal. Gain allows you
to trade off between making smaller signals more visible at the cost of
increased noise and no longer being able to differentiate between larger
signals. For most applications, the NI 177x Smart Camera default gain
setting optimizes the balance between small signals and large signals.
FOV
horizontal
0.0074 mm 640
×
100 mm
×
8 mm
---------------------------------------------------------------------
59.2 mm
=
=
FOV
vertical
0.0074 mm 480
×
100 mm
×
8 mm
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44.4 mm
=
=
