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Camera Format
The size of the image sensor is called the image format. The name
of the format does not correspond to the actual dimension. Historically,
a one-half inch format was the size of the sensing area of a Vidicon
Tube, which is one-half inch in diameter. Most CCD sensors come in
sizes of 1’, 2/3”, 1/2", 1/3” and 1/4".
Different
sensor formats require corresponding lens formats. The
lens format has always to be equal or larger than the sensor format.
C-Mount and CS-Mount CCTV lenses can be used for all area-scan
sensor formats. Mega-pixel line-scan cameras, due to their size,
need a larger image format than C-mount lenses can offer. In this
case, an F-format 35 SLR lens can be used.
Camera
Resolution
Resolution is a measure of the camera’s ability to distinguish
between objects that are close together. It is measured as either
spatial frequency or TV lines. It is effected by different factors
– light level, light spectrum, lens f/number, etc.
A practical test for
determining the resolution for machine vision uses a target with
multiple bars with various spacing between bars. The same target can
be used to check for optical aliasing (elements with high
spatial frequency appear to move), which occurs when the lens is
imaging spatial frequencies that are beyond the camera’s capability.
Camera Anamorphism
– The same type of target can also be used to measure camera
anamorphism, which is a difference in magnification in horizontal
and vertical directions. This is due to a timing error designed in
to achieve a more pleasing picture for TV viewing. The camera
anamorphism can also be measured by using a precise dot target.
For more information, please contact
High-Tech Digital Technical Support.
310-265-8203
support@high-techdigital.com.
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