TEM Aligna 4D - Page 46

Aligna
®
4D User Manual
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 The Output CrossLink Matrix (OCL) allows the actuators to achieve a nearly pure angle
or position movement of the beam. A parallel beam movement, e.g., is achieved by an an-
gle displacement of the first actuator and an angle displacement by exactly the negative
value of the first. Thus the resulting angle movement will be compensated and a pure paral-
lel (position) movement results. Therefore, a position movement requires a combination
movement of both actuator mirrors.
In extension, a combination movement of both mirrors can act as a beam angle movement
around any arbitrary point of the beam.
Due to properties of the opto-mechanical setup a movement of one piezo (let's say the X
piezo of actuator 1) may cause a combination movement even (more or less) also in Y di-
rection. This can be compensated by suitable combination steering signals to all four piezo
actuators. Thus the four regulator channel signals (angle x,y and position x,y) are trans-
formed into four actuator signals by the 4x4 Output CrossLink Matrix OLC.
There is one OCL related to the motorized actuators (called OCLM) and a second one, re-
lated to the piezo actuators (OCLP or simply OCL). Both are independent from each other,
because even the motor and piezo actuators can be separated completely: In some appli-
cations the piezo actuators ("BeamScan OneInch") are located in the vacuum chamber,
close to the target, while the motorized actuators ("Aligna60", e.g.) are located at the laser
table.
 The regulator parameters of the four servo loops (of each beam) have to be aligned fitting
to the mechanical setup to achieve a fast and precise servo loop operation. By applying test
signals to the output channels, and analyzing the system response by recording the input
signals an optimization of the regulator parameters P, I, D, and f
0
is achieved, individually
for each of the four channels.