Installing Light Control Hardware
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Cognex MVS-8100C Hardware Manual
Bright Field and Dark Field Illumination
Cognex light modules provide two sets of LED arrays, for both bright field and dark field
illumination. The two sets of LED arrays are shown in Figure 11.
Figure 11. Bright and dark field LEDs on light modules
The light module’s bright field LEDs produce nearly on-axis diffuse illumination. The
bright field LEDs direct the light so that it hits the object at almost the same direction as
the camera lens. Bright field illumination allows the camera to capture the intensity of the
light reflected from the surface of the object.
Dark field illumination directs light at the object from an angle, providing off-axis diffuse
illumination. Dark field illumination is used to inspect the roughness of surfaces that
normally reflect light, such as metal. If illumination in one direction does not produce a
clear image, you can use dark field illumination in multiple directions.
Cognex software is used to vary the ratio of bright field to dark field illumination to obtain
the best image for vision processing.
Light Module Electrical Control
The light control circuitry associated with each camera input port on the MVS-8100C can
provide up to 250 mA at 12 volts (3 watts) to each light module. Power for each port is
fused with a 500 mA PolySwitch resettable fuse.
Each light module will sink up to 125 mA of current. The amount of current is software
selectable in 256 steps from 0 to 125 mA.
Bright field LEDs
Dark field LEDs
