Datalogic Matrix 120 Product Reference Manual page 92

READING FEATURES
Example:
The FOV for a Matrix 120™ 310-xxx at a reading distance of 100 mm is:
FOV
H
FOV
V
78 MATRIX 120™
Figure 60 - Reading Distance References
= 2 [(100 mm + 8 mm) * tan (41°/2)] ≅ 81 mm
= 2 [(100 mm + 8 mm) * tan (32°/2)] ≅ 62 mm