- 37 -
7.
GLOSSARY
The following terms may have additional meanings. The definitions that follow are in context of
the Starrett Vision Metrology Systems.
Accuracy
The maximum error that the system will produce when measuring a true
standard.
Auxiliary Lens
An accessory lens that may be attached to zoom optics to increase
magnification or increase the field of view.
AV
Automatic Video, an alternative designation for “CNC.”
Axis
A direction which allows movement and along which dimensions can be
measured. In Manual and CNC metrology systems, three mutually-
perpendicular axes are X (left to right), Y (front to back), and Z (bottom to
top). Measurement along the X and Y axes is accomplished by moving
the metrology stage horizontally. Measurement along the Z axis is
accomplished by moving the camera and optics vertically, rather than
moving the metrology stage.
Blooming
A condition where the parts of the video image are distorted by
oversaturated bright regions so objects can be measured larger than
they really are. To avoid blooming errors, observe the video image as
you decrease illumination.
CCD
Charge Coupled Device. The solid-state image sensing element of a
video camera.
CNC
Computer
Numeric
Control. In CNC metrology systems, motion of the
stage and optics is both motorized and computer controlled, making
these system suitable for repetitive measurements in a production
environment. Non-CNC system may also be motorized; control will be
manual by an operator.
Coaxial Light
A light source that is on the same axis as the camera. Surfaces that face
the camera are illuminated brightly, while surfaces angled even slightly
away appear much darker. The result is a high-contrast lighting that can
help sharpen edges for better detection by the Video Probe. By
comparison, light that is not coaxial and shines from different directions
(such as from the Ring Light) results in lower image contrast.
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.
E-Stop
Emergency Stop. A switch with cuts power to the motors. An important
safety feature.
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 that the camera sees and
displays in the video image. “FOV measurement” refers to a measure-
ment that can be done in a single field of view without moving the stage
or camera.
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.
