Sensor Installation
26
Modline 5
3.4
Sensor Optical Characteristics
3.4.1
Optical Resolution
The Sensing Head is sensitive to infrared radiation in the area indicated by the Cone of Vision in the
illustration below.
Figure 11: Cone of Vision and Spot Size Formula
The diameter of the cone at any point will determine the area of measurement at that point. Any part of
the target or other intervening object positioned within the cone will be imaged on the detector.
Anything seen by the detector will become part of the measurement.
When the Sensor is sighted on an object, you are “aiming” or positioning the cone of vision on the object.
When you focus, you are adjusting the optical system elements so the focal point is at the surface of the
object. The measurement area, as seen by the detector, will then be outlined in the reticle. The reticle
only defines the measured area (spot size) in the focused condition.
The formula d = D/F defines the spot size at the focal point. Simply divide the Working Distance (D),
measured from the front of the Sensor to target by the Resolution Factor (F) to determine the Spot Size
(d). Resolution factors for Sensor Model and Lens combinations are provided in the table on the
following page. The focusing range for each lens type is also provided in the table. The focusing range
defines the allowable range for the Working Distance.
For Sensors with the Dirty Window Detector Option, the Working Distance (D) is
calculated by measuring the distance from the front tip of the protruding hood to the
target and then adding 2.6 inches (66 mm).
3.4.2
Lens Focusing Ranges and Optical Resolution Factor
The table below lists Lens Type and Focusing Ranges for the Modline 5 Series 52, 56, 5G and 5R. Two
ranges are shown. The first range is for a Sensor without the Dirty Window Detector Option (DWD)
option. The distance is measured from the front metal surface of the standard Sensor.
d = D / F
where:
d = diameter of cone at focal point
D = distance from front of Sensor to focal point.
For Sensors with DWD Option,
add 2.6 inches (66 mm) for distances
measured from tip of front hood.
F = Resolution Factor of Sensor Model and
Lens combination
Cone of Vision
Focal Point
Sensor
