ZYGO KMS-310, Supervisor Manual

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KMS-30/400 Supervisor's Manual 5-31
Set Piezo Autofocus Algorithm
To set the Piezo using the autofocus algorithm (Figure 5-23):
Figure 5-23. Piezo Autofocus Algorithm
2*step
swing
range/2
Starting
position
Pass 3
Pass 1
Pass 2
stepsize = 110 nm
Final
position
stepsize = 'step'
stepsize = 7.324 nm
1. Complete a first pass (pass 1).
Scan from start range/2 through start+ range/2 for the best focus position
(p1). To do this, take a focus reading approximately every 110 nanometers
(if you are using a 30 micron Piezo).
Use Table 5-3 and the following definitions to complete the first pass (p1):
ƒ
Start: initial position at the start of the autofocus procedure
ƒ
Range: a user-specified parameter
ƒ
p1 : the best focus position
Table 5-3. Piezo Autofocus Algorithm
User Parameters 20 micron, 10 bit 30 micron, 12 bit
Min (nm) Max (nm) Min (nm) Max (nm)
Range : total scan distance of
pass 1
1000 20000 10
∅
0
30000
Swing : half the total scan
distance of pass 2
100 15000 10
∅
15000
Step : step size of scan during
pass 2
10 10000 7 15000