7.
GLOSSARY
The following terms may have additional meanings. The definitions that follow are in the context
of the HDV300 and HDV400 benchtop horizontal digital video comparators.
Accuracy
The maximum error that the system will produce when measuring a true
standard.
Aperture
An optical element which limits the diameter of the optical bundle that can
pass through a specific plane.
Axis
A direction which allows movement and along which dimensions can be
measured. In the HDV300, the X-axis is horizontal from left to right, and the
Y axis is vertical from bottom to top.
Blooming
A condition where the parts of the video image are distorted by oversa-
turated bright regions, making objects appear larger than they really are.
CCD
Charge Coupled Device. The solid-state image sensing element of the
HDV300 video camera.
Distortion
Optical image distortion at the CCD sensor across the maximum field of
view. Expressed in percent for the dimensional error along one axis divided
by the true dimension.
DXF
A computer aided design (CAD) data file format developed by Autodesk,
Inc. and now also used by other companies for the export and import of
CAD data.
Focus
The condition which provides the sharpest image. Achieved by optimizing
the distance between the object and imaging optics.
FOV
Field of View. The region of the metrology stage being viewed by the camera
and displayed on the video monitor.
FOV Measurement
A video measurement performed in a single field of view without moving
the stage or camera.
Illumination, Front
Lighting applied to the object from the same side as the camera so that
surface features can be viewed on the video monitor.
Illumination, Back
Lighting applied from the back of the object so as to create a silhouette
when the object is viewed by the camera.
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.
Mag
Shorthand for magnification.
Magnification, Lens
In a vision metrology system, the image size in the CCD plane divided by
the corresponding object size (0.14X to 4X for HDV300 telecentric lenses).
In an optical comparator, the image size on the projection screen divided by
the corresponding object size (typically 10X to 100X).
Magnification, Image
Image size on the video monitor divided by the corresponding object size.
Same as lens magnification in a properly adjusted optical comparator.
Parcentricity
The condition where a feature remain 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.
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