IDEC DATAVS2 Series - Manual (Page 77)

Instruction Manual SVS2 Series
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16.4. ► Lighting Options
Ring light
A technique with many application possibilities. The illuminator is mounted directly on the
sensor and illuminates any object in front of it. A ring light provides diffused lighting over a
small area.
- Advantages: provides correct lighting also for small objects. Reduces shadows on
images with protrusions. Centres the light on the image.
- Disadvantages: with large objects, the corners of the image may lose brightness,
creating a halo of black pixels along the external image edge. With highly reflective
objects, the image may contain a circular glare of reflected light.
Top light
This technique generates even light in a concentrated area. The illuminator is positioned
behind the sensor and if oriented correctly can carry-out very precise inspections.
- Advantages: the light beam is outside the axis respect to sensor optics, allowing the
highlight of specific target areas and not others.
- Disadvantages: difficulty in lighting evenly the entire object, especially in presence of
protruding parts that create unwanted shadows.
Back light
The illuminator is positioned behind the target-object, aimed directly back towards the
sensor, and the resulting silhouette can be inspected for dimension and shape control. The
brightness is low. Typical applications include object sorting according to shape and
dimensions, measurement of spacing between chip leads, inspection of object holes or
cracks.
- Advantages: does not supply surface characteristics. Facilitates the diameter
measurement of round objects. Shows presence or absence of holes.
- Disadvantages: illuminator positioning behind object may result difficult. Does not
analyse object surfaces. The illumination area must be larger than then inspection
area.