Vertical Smear Artifact; Smear Reduction - Point Grey Flea3 GigE Technical Reference

Point Grey Flea3 GigE Technical Reference
9.7

Vertical Smear Artifact

When a strong light source is shone on the camera, a faint bright line may be seen extending vertically through an image
from a light-saturated spot. Vertical smear is a byproduct of the interline transfer system that extracts data from the
CCD.
Smear is caused by scattered photons leaking into the shielded vertical shift register. When the pixel cells are full, some
charges may spill out in to the vertical shift register. As the charge shifts in/out of the light sensitive sensor area and
travels down the vertical shift register, it picks up the extra photons and causes a bright line in the image.
Smear above the bright spot is collected during read out while smear below the bright spot is collected during read in.
9.7.1

Smear Reduction

Smear may be minimized using one or more of the following techniques:
Reduce the bright light source.
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Increase the shutter time/lower the frame rate. This increases the amount of time light is collected in the
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photosensors relative to the time in the vertical transfer register.
Turn the light source off before and after exposure by using a mechanical or LCD shutter.
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Use a pulsed or flashed light source. A pulsed light of 1/10,000 duration is sufficient in most cases to allow an
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extremely short 100 ns exposure without smear.
Increase light collimation by using a lens with variable aperture. Note that an effect of closing the iris is a darker
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image.
Use a low smear trigger mode
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all models.
Related Knowledge Base Articles
Vertical bleeding or smearing from a saturated portion of an
image
Revised 10/29/2013
Copyright ©2010-2013 Point Grey Research Inc.
which may reduce the effect of smear. This trigger mode may not be available on
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Knowledge Base Article 88
9 Troubleshooting
87