Technical Data 
16  Rev. D7 Jul 2017  Marathon MM 
3.2 Optical Specifications 
In all cases, make sure the target completely fills the measurement spot, see section 6.1.1 Distance to 
Object, page 26. 
The actual spot size for any distance, when the unit is at focus distance, can be calculated by using the 
following formula. Divide the distance D by your model’s D:S number. For example, for a unit with D:S 
= 300:1, if the sensor is 2200 mm (86 in.) from the target, divide 2200 by 300 (86 by 300), which gives you 
a target spot size of approximately 7.3 mm (0.29 in.). 
 
Figure 1: Spot Size Chart 
All target spot sizes indicated in the optical diagrams are based on 90% energy. 
3.2.1 Variable Focus 
* Optical Resolution is achieved for each focal point in the focus range 
Mean Time Between Failures (MTBF)  10,000 operations (at Tamb = 23°C/74°F)