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If you are using an F-Theta lens for marking on different z-heights, the x- and y-coordinates have to be corrected if you are not marking on z=0.

This is done by "F-Theta Factors". Please follow the following steps to calibrate the F-Theta correction.

 

Calibrate F-Theta Factors:

 

For the calculation of the F-Theta factors, the small program ‘F-Theta Factor Calculator’ is necessary.

 

Figure 93: F-Theta Factor Calculator

 

F-Theta Factor 1st mirror:

 

Create a job with two crosses.

A cross in the middle of the working area (X = center, Y = center and Z = 0) and another cross close to the X limit of the working area along the X-axis (X = center + 0.40 * field size, Y = center and Z = 0) and mark this job.

The distance between the crosses must be 0.40*field size. If not, probably the field size is incorrect.

Mark the two crosses like above, but both at the same positive Z height, close to the Z limit. The positive Z limit is "Distance 2nd mirror to focus [mm]" minus "maximum of Z lookup table Focus distance [mm]".

Measure the distance between the crosses.

Use the marking result Z=0 as Target value and the marking result with the positive Z-height as measured value for X [mm].

 

F-Theta Factor 2nd mirror:

 

Repeat the marking with these two crosses along the Y-axis (X = center, Y = center + 0.40 * field size).

Measure the distance between the crosses.

Use the marking result Z=0 as Target value and the marking result with the positive Z-height as measured value for Y [mm].

 

 

Figure 94: Job in SAMLight for Measurement to calculate F-Theta factor values.

Use the measured values to calculate the F-Theta factor 1st mirror and second mirror.

For that, the values from SAMLight are required.

 

Figure 95: Transfer of values: from SAMLight to calculator and back.

Apply the corrected F-Theta Factor to SAMLight.

To test the new calibrated F-Theta Factor repeat the test. The F-Theta Factor is optimal, when the ‘Target Position’ and the ‘Measured Position’ are identical.