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Illumination, Back
Lighting applied from the back of the object so as to create a silhouette
when the object is viewed by the camera.
Magnification, Lens
In a vision metrology system, the image size in the CCD plane divided by
the corresponding object size.
Magnification, Image
Image size on the video monitor divided by the corresponding object size.
Same as lens magnification in a properly adjusted vision metrology
system.
Pixel
A picture element. Term used to describe the individual light detectors of a
CCD sensor and the individual light emitters of a video monitor. The spacing
and number of pixels determines the resolution of a video metrology system.
Parcentricity
The condition where a feature remains at the optical center of the video
Image throughout the magnification range of zoom optics.
Parfocality
The condition where the video image remains in focus as the
magnification is adjusted from highest to lowest with zoom optics.
Pixel
A picture element. Term used to describe the individual light detectors
Of the CCD sensor in the camera and also the individual light emitters of
An LCD video monitor.
Resolution
The least significant digit to which a physical quantity can be read. High
resolution does not guarantee high accuracy.
Ring Light
A ring-shaped light source which illuminates the object from the top with
even illumination from all sides.
QDF
Quad Dark Field. Term used with an optional height-adjustable ring light,
where LED intensity is individually adjustable in four quadrants. These
adjustments are used for shadow control.
Quad Ring Light
A ring-shaped light source where quadrants of LEDs can be individually
controlled. This produces illumination from the top and from the sides,
with individually adjustable lighting and shadows from the sides. Further
control of lighting and shadows from the sides is provided by height
adjustment of the quad ring light at the bottom of the video probe to a
point 100 mm (or 4”) lower. In AV300 and AV350 systems, the height
adjustment is motorized using the system’s Z-Track lead screw feature.
Skew
Misalignment of the part with respect to the X and Y axes. This will create
measurement errors unless the part is repositioned or the deskew feature
of the metrology software redefines the measurement axes.
Squareness
The alignment of the camera relative to the motion of the metrology
stage. If the camera is misaligned (out of square), the image will drift
diagonally as the stage position is moved along one axis.
Substage Light
A light source located below the glass platen of the X-Y stage for
silhouette or back illumination.
Telecentric
A lens property where the light from the object stays parallel to the
optical axis across the entire field of view, thereby eliminating optical
distortion. This can only happen if the entrance aperture of the lens is
larger than the field of view, requiring a large and high quality lens.
