Spectra Precision Focus 30 Service Manual page 36

Distance meter unit F30
The Distance meter unit (EDM) is a direct reflecting distance meter based on the phase shift method.
The optical Transmitter unit transmits a modulated light beam to the target. The optical Receiver unit
detects the returning light reflected from the target. The Receiver unit measures the phase difference
between transmitted and received light and calculate the distance.
Location of Distance meter unit
Fig. 3-8 Location of Distance meter unit
Transmitter
diode
Technical specification
• Light source: Laser diode 660nm
• EDM beam divergenz horizontal: 0,4mrad
• EDM beam divergenz vertical: 0,3mrad
• Principle:
• Accuracy Prism mode 2mm + 2ppm
• Accuracy DR mode
Focus 30/35 Service Manual
Reference
fiber
Transmitter
prism
EDM Mirror 1
Phase shift
3mm + 2ppm
3 - 10
Theory of Operation
Receiver
diode
EDM Mirror 2
P/N 79000035_SM, Version 1.5
Chapter 3
Greywedge with
internal/external
Switching motor
Receiver
fiber