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Instruction
Manual
SCS1
Series
153
H: FOV height
h: image height
Θ
: angle
L: operating distance
f: focal length
13.3. Field of view
The field of view (FOV) is the area acquired by the image sensor which forms the image to inspect.
The FOV and image sensor dimensions condition directly the resolution.
13.4. Operating distance
The operating distance is the distance between the lens’ back-side and the object.
The operating distance is limited by:
-
lenses used have a minimum functioning distance;
-
lenses may have to be positioned close to the object to avoid light variations;
-
physical sensor positioning constraints may exist.
13.5. Focal length
The focal length is the distance between the rear nodal point of the lens (the point where the light
beams leave the rear of the lens) and the image sensor.
If more than one focal length is required for the application, the user has to consider the following:
- Cost: a lens with a shorter focal length is less expensive.
- Depth of focus: the depth of focus (focus tolerance) is the area in front of and beyond the best focus
point in which the image quality remains acceptable. A longer focal length provides less depth of
focus; a shorter focal length provides more depth of focus.
- Distortion: a lens with larger focal length provides a less distorted image.
13.6. FOV inspection / resolution
The inspection area has to be measured, considering a margin for object movements, in order to
determine the FOV dimension.
To check if the FOV is sufficient, the user can proceed as follows:
-
estimate the necessary resolution;
-
use the FOV formula to determine the maximum vertical and horizontal FOV dimensions able to
- maintain the necessary resolution.
FOV formula: necessary resolution x 640 pixel = Max horizontal FOV
Necessary resolution x 480 pixel
= Max vertical FOV
Example:
Inspection area: 300 x 350 mm. Necessary resolution: 1 mm
Max. horizontal FOV
= 1 mm x 640 = 640 mm
Max vertical FOV
= 1 mm x 480 = 480 mm
The FOV constraint calculated (640x480) is the largest inspection area and so a 350x300 FOV can be
accepted.
If the FOV calculated is inferior to the desired inspected area, the user can proceed as follows:
-
use more telecameras;
-
inspect a smaller area;
-
reduce
resolution
requirements.
Lenses
H
L
f
Θ
h
Phone: 800.894.0412 - Fax: 208.368.0415 - Web: www.ctiautomation.net - e.mail: [email protected]
Phone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: [email protected]
Phone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: [email protected]
Phone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: [email protected]