Chapter 8  Ensuring Repeatability, Accuracy, and Resolution
Ensuring Accuracy
8-8 Getting Started Guide
8
Figure 8-4. Example of cosine error
To minimize cosine error, follow these guidelines: 
• Take time to carefully check your optic alignment to ensure the laser 
beam is traveling parallel to the machine travel. 
• Watch for irregularities in your linear measurements. If the amount of 
error is steadily increasing, you may have significant cosine error.
• Allow the temperature of the optics to stabilize before making the 
measurement (approximately 5 to 10 minutes).
1
  Laser head
2  Interferometer 
assembly
3  Retroreflector at the 
first measurement 
position
4  Displacement along 
the axis of 
measurement 
5  Retroreflector at the 
second measurement 
position
6  Axis of motion
7  Axis of measurement 
8  Actual displacement 
0
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2
3
4
5
6
8
7