3.6.4 Object sizes
As the distance from the device increases, the laser beam expands. As a result, the
diameter of the light spot on the surface of the object increases.
Figure 4: Beam expansion
1
Expanded laser beam
2
Optical axis
Required values for calculating the light spot size and minimum object size:
•
Light spot size on the device cover: 7 mm (rounded up)
•
Light spot divergence per single pulse: 0.49 deg (8.6 mrad)
•
supplement HDDM/HDDM+ (1 measured value consists of several overlapping
single pulses): 5.8 mrad for devices with 0.33° angular resolution; 17.5 mrad for
devices with 1° angular resolution
Formula for calculating the light spot width:
(Light spot divergence [mrad] + supplement [mrad]) * distance [mm] + light spot size
on the device cover [mm] = light spot width [mm]
Calculation example light spot width at a distance of 4 m, with supplement 5.8 mrad:
(8.6 mrad +5.8 mrad) * 4,000 mm +7 mm = 64.6 mm
Formula for calculating the height of the light spot:
Light spot divergence [mrad] * Distance [mm] + Light spot size at the device cover
[mm] = Light spot width [mm]
Example calculation of the light spot height at a distance of 4 m:
8.6 mrad * 4,000 mm +7 mm = 41.4 mm
Formula for calculating the minimum object size:
2 * supplement [mrad] * distance [mm] + light spot height [mm] = minimum object
size [mm]
Calculation example minimum object size at a distance of 4 m, with supplement
5.8 mrad:
2 * 5.8 mrad * 4,000 mm + 41.4 mm = 87.8 mm
NOTE
For reliable measurement, an object needs to be hit several times. Therefore, the object
either needs to be larger than the minimum object size, or both the LiDAR sensor and
the object must not be moving.
PRODUCT DESCRIPTION 3
8025144//2021-07-21 | SICK O P E R A T I N G I N S T R U C T I O N S | TiM55x/56x/57x/58x
15
Subject to change without notice
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