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Requirements for SCAPS USC-1, USC-2 and USC-3 cards:

•Correction File: 2D ucf file from SCAPS.

•Required SCAPS option: FlatLense and Optic3D.

Figure 513: Shape of a 2D Correction File

Settings: For USC cards, enter the following Dialogs Settings → System → Optic:

Figure 514: Settings → Optic Dialog for Z-Dimension

In this dialog the XY field size, the correction file and the Z-dimension can be defined.

Z Dimension: In general changing this setting is not necessary and is only advised to use after instruction of SCAPS or by users with vast knowledge concerning the Z-calibration if the default z range is not sufficient. The Z-Dimension [mm] can be used to define the Z range. The Z range is by default defined symmetrically around Z = 0, with the min/max values fs/2. With Z-Dimension [mm] is it possible to shift and scale the Z-range. Using the Z Dimension, the Z value Z = (Z_Max + Z_Min) / 2 will be correlated to the Focus Distance which is equal to the Distance 2nd Mirror to Focus. The linked values Focus Distance [mm] and Z-value [bit] will stay the same after changing the Z-Dimension.

Find the following Dialog for USC-1 in Settings → System → Optic → Advanced → Z-Correction (Enable) → Advanced and for USC-2 in Settings → System → Optic → Advanced → Correction, Settings → Z‑Correction, Settings.

Figure 515: Z-Correction Settings

Distance mirrors: Distance between the x and y mirror of the scan head in mm. This value is usually given by the scan head manufacturer.

Distance second mirror to focus: Distance between the second mirror to the center of the field in the focus plane.

F-Theta lens: Should be checked if in addition to the 3rd scanner axis, a F-Theta lens is mounted.

2nd mirror is X: Switches x and y values.

F-Theta factor 1st mirror/ F-Theta factor 2nd mirror: These empirical factors can be found following the description in F-theta Factor Calibration. The value '0' corresponds to a perfect telecentric lens while '1' would correspond to no additional lens.

Z Jump Delay [µs]: Due to the fundamental difference of the Z axis it could be necessary to increase the jump delay after a big change in the Z value. The 'Z Jump Delay' is added to the normal jump delay when a jump has a Z dimension greater than 'Z Jump Delay Threshold [mm]'. A value of '0' disables this feature.

Z Jump Delay Threshold [mm]: If a jump has a Z dimension greater than this threshold the 'Z Jump Delay [µs]' is added to the normal jump delay.

Pass Defocus Trough Lookup Table: With this option enabled, the defocus calculation will be done using the values of the lookup table instead of the Z field size. This option is only available for the USC-3. Further information regarding the Defocus is located in the Miscellaneous Pen Settings.

Z Lookup Table: For compensating the non-linearity of the relation z axis position to focus distance, a lookup table can be defined. The lookup table contains the DAC value plus the distance from second mirror to focus when adjusting this DAC value. The points must be ordered ascending by the 'Focus Distance [mm]' value. The lookup table can only be accessed if there is the license FlatLense active.

Number of control points: The number of control points can be between 2 and 32.

Insert control point: Insert a new control point. If no line is selected the control point will be added at the bottom, if a line is selected the point will be added above.

Delete control point: Select a control point and delete it.

XYZ Move: A helper function for finding the proper lookup table values.

Bit Step 1000 / 100 / 10: Define Step Width for XYZ Move.

Recommended calibration procedure:

•Get the correction file from scan head manufacturer and send it to SCAPS (info@scaps.com) for being converted into a UCF file format containing no z values

•Setup hardware to right working distance (z=0 plane).

•Find the right lens size value to get a correct aspect ratio when marking for example a rectangle. 10 mm in drawing have to be 10 mm on marking (in z=0 plane). The lens value defines how many mm are related to the 65536 bits.

•Get the right mirror mounting distance values.

•Within the z calibration dialog, type in values for field size and the 2 distance mirror values.

•For getting the right calibration values for the lookup table

•Best would be having a z stage for calibration of different z heights. The valid DAC range is from -32768 to +32767. Two general ways to generate the lookup table. Either predefining DAC and varying z or the other way around.

•E.g. you create 3 control points and enter following values for DAC.

•Then you search for the focal planes d1, d2 and d3 with the XYZ Move window. For compensating further non-linearities you have to create further control points in the lookup table.

 

Table 66: Example Z lookup table. d1 < d2 < d3

Tilt Compensation: In case of a not perfectly aligned scan head, small tilts in x, y and z can be compensated by using the tilt compensation feature. Please note that z-offset = 0 is not a valid input. (find information on the measurement of the parameters here)

X Offset [mm]: Insert the detected offset in x which should be compensated by the tilt compensation.

Y Offset [mm]: Insert the detected offset in y which should be compensated by the tilt compensation.

Z Offset [mm]: Insert the difference between the z-heights.