1. Autocollimator Calibration
Calibration : interpretation of output from Autocollimator Controller
What we have:
Output from controller i.e. numbers that quantify the lateral displacment (Δx, Δ y) caused by tilts in arbitrary unit
What we search:
A coefficient that transform the lateral displacment arbitrary unit in µm

2. The idea Autocollimator Calibration Generate a tilt of a known angle…
…measure it…
…calibrate the output!

3. Generate a tilt of a known angle
Autocollimator Calibration
Generate a tilt of a known angle
Response spring
Rotating rail
Micrometric translation
Micrometric translation stage +
Rail arm =
Known angle
autocollimator

4. Procedure Autocollimator Calibration Step of T.S. 20 μm Min angle
Δθ = 0,0571 mrad
i.e. Δy=100 a.u. read  Δy = 56.5 μm
Lateral displacement
Δy = 32 µm
Average of conv coeff:
0, μ/a.u.
Error:
0, μ/a.u.
ACCURACY [%]
12,06248
Average Δy read
74 measure of 20 μm step
Δy = 56,783 a.u.
Why this error?

5. Autocollimator Calibration
Focal length
Rail length
Positioning (per step)
Data Acquisition (per step)
Average on100 meas
St. dev. on 100 meas
Difference between the two Y values
Shift Angle
Linear Shift
Average of
Conversion Coeff
Difference between the two next angles

6. Using Theodolite+ large mirror
Autocollimator Calibration
Next Step +
Reduce Min. angle Δθ
Improve Accurancy
Using Exapod
Using Theodolite+ large mirror