How to Use the Function of Lens Correction?

"Lens Correction" function is used to fix the distortion resulted from Lens characteristics or optical problems. If the lens correction has been completed, but the mark result still hassome problems such asunfocused or ratio inaccuracy, usersneed to adjust these parameters from the "Work Area" page under "Property Table."

Lens Manager

Enter "Lens Manger" form 「File」→「Option」→ 「Scan Head」, see Fig. All lenses users have will be listed here.

NEW: Click this button to add a new lens.

DELETE: Click this button to delete the selected lens.

COPY: Click this button to copy the selected lens.

Assign: Click this button to set the selected lens as the default lens.

Import: Allow users to import lens file.

Export: Allow users to export selected lens file.

Correction…: Select the one lens and click this button to enter the Lens Correction function.

Lens Correction

The system will use math formula to correct the barrel distortion, trapezoid distortion, or parallelogram distortion resulted from lenses and optical devices. Adjust lens parameter properly will make the marking result be the same as the original design.

Fig.2.1 shows the lens setup under normal mode. Fig.2.2 is the lens setup under dot mode.

Mark Area: Working area of the lens.

Use Cor File: Use the correction files from manufacturers or use the file created by using Scale or Grid Methods and then adjust parameters.

Correction file: Select the file name same as the lens name from dropdown menu or select "Import…" item from the dropdown menu to import the correction file such as COR, CTB (from ScanLab), or GCD (from RayLase). If the selected correction file has the same name as the assigned lens, users are able to click "Cor File…" button and do correctionthrough “Using Correction File” function.

Offset: If the working pieces cannot be put in an ideal position, users can modify the design or change the offset value to fix this problem. For example, if the position has 5mm deviation to the right side, then input -5mm in Offset X to correct it.

Scale: If the size of marking result (real size) are different from the original design (theoretical size), user can use the scale function of X and Y to fix it. The unit of scale is percentage (theoretical size / real size * 100, the default value is 100). For example, if real size is smaller, this value should be larger than 100.

Rotate: If the working pieces cannot be put in an ideal position, users can modify the design or input suitable values in these fields to amend it.

Correction: When the barrel distortion, trapezoid distortion, or parallelogram distortion happen, enter the suitable X/Y values to do the correction. Please refer the following description of Distortion Correction.

Advance: Allow users to input different correction values at negative X and Y direction.

PreMark Parameters: Setting the parameters for PreMark.

Speed Mode: Select to use Normal Mode or Dot Mode to Premark.

Power: Laser power percentage for PreMark.

Speed: Laser speed (mm/sec) for PreMark.

Frequency: Laser frequency for PreMark.

Pitch(Under Dot Mode): The distance between dot and dot on the marking route when doing PreMark.

Delay(Under Dot Mode): The waiting time a lens needs to start radiating when move to a dot while doing PreMark.

Pulse Width(YAG Laser): The spending time for each pulse.

PreMark: Click the "PreMark" button, the laser will mark according to the parameters setting above.

Please follow the steps listed below to do the correctionand note that the direction of X and Y means the output port of GALVO motor:

Step 1: Select the lens user want to correct and adjust its focus.

Step 2: Input the value of lens working area. Input the value of scale percentage according to the output voltage ratio of lens and driver. Attention, users need to complete this step first and then start executing PreMark, otherwise the lens would be damaged.

Step 3: When barrel distortion happened, follow the rules of "Distortion Correction" as Table 4.1 to do the correction until four square sides are all straight lines.

Step 4: When trapezoid distortion happened, follow the rules of "Distortion Correction" as Table4.2 to do the correction until four square sides are equal in length.

Step 5: When parallelogram distortion happened, follow the rules of "Distortion Correction" as Table 4.3 to do the correction until four square sides are all vertical.

Step 6: Measure the dimension of marking result. Input the value of scale according to the formula (theoretical size / real size * 100). If the real size is larger than theoretical size, then reduce its value and retry. On the contrary, increase its value and retry.

Step 7: Repeat Step 6 until the theoretical size and real size are equal.

Distortion Correction

Correction of barrel distortion

Correction of trapezoid distortion

Correction of parallelogram distortion

Using Correction File

Correction files are provided by lens manufacturers such as SCANLAB and RayLase for users to do lens correction. Mostly, the results of using these files are acceptable. Users only need to adjust some of the scale parameters.

If require more accurate result or the correction files from lens manufacturers are unable to meet the requirement, users can do advanced correction through using the “Cor File…” function to reach the goal. Before using this function, please make all the parameters as the default values as Fig.3.1.

Once finding that still need to adjust these values after finishing lens correction, users can come back to this dialog box to modify them.

New/Edit Correction File

If it’s the first time entering the "Cor File…" function after creating a new lens, users will need to select one correction method from Scale Method and Grid Method, see Fig. 3.2. Please note that each lens can only choose one method.

Method: Select Scale Method or Grid Method. Please refer to the following description.

Import Cor File: Import an existing correction file and do advanced correction. There are three usable file types: COR, CTB, and GCD.

File Path: The path of the imported correction files.

Scale Method

The traditional lens correction method is using linear way to correct the distortion. However, some of distortions are not completely linear. In this situation, users can use the Scale Method to divide the lens into several areas and adjust each area by different percentage, see Fig.

The left side of Scale Method window is correcting area for users to enter values to get a correction file. The right side is operating area; users can measure the result according to settings of left side or reset the settings of correcting area.

Operating Area: On the top of this area is the Premark parameters.

Reset: The purpose of this function is to reset the setting of correcting area, or import a correction file to do correction.

Import Cor File: Import the correction file provided by the manufacturers for correcting area. The value of correcting area will be reset if press "OK" without clicking "Import Cor File".

File Path: The path of correction file.

Correcting Step

Step 1: Select a Scale (K) value which is close to the voltage ratio of lens and driver. Then select correct rings from the list. The more correct rings users select the better accuracy they will get.

Step 2: Click the "PreMark" button to execute marking.

Step 3: Measure the axis length and then enter the value in the field. (Since the value of X-axis and Y-axis may be different, please enter the shorter one.) If the real value is 109.11mm, it will be better to enter 110mm.

Step 4: Click the “Input Data” button for next step, see Fig.

Step 5: Click the "PreMark" button to see the mark result.

Step 6: Edit the values of A, B, C, and D in the fields separately and then click the "PreMark" button again to see the mark result. If necessary, repeat these steps until achieving the goal. Click "Back" button and then "Exit" button to save the file and exit.

Reset Params: Reset all correction data as the default values.

Grid Method

Instead of using a formula, this method measures the real position of correct dots directly. More correct dots will get more accurate result.

Operating Area: On the top of this area is the Premark parameters.

Mark Type: To use the function, users must click "Input Data" at "Correcting Area" first.

Correct Dots: Select correct dots from the list. More correct dots will get more accurate result.

Algorithm: Select "BiSpline" or "BiLinear" algorithm.

Mark Line: The laser will mark grid line when choosing “Mark Line”.

Mark Point: The laser will mark grid point when choosing “Mark Point”. Users can also set the diameter and fill pitch of the grid point from the field below.

Output Texts: If checked the “Output Texts” checkbox, the representing numbers will appear next to the grid point or line, see Fig.

Correcting Step

Step 1: Select the scale (K) value which is close to the voltage ratio of lens and driver output from the drop down menu. Then select the correct dots.

More correct dots will get more accurate result.

Step 2: Click the “PreMark” button to execute marking.

Step 3: Measure the axis length and then enter the value in the field. (Since the value of X-axis and Y-axis may be different, please enter the shorter one.) If the real value is 109.11mm, it will be better to enter 110mm.

Step 4: Click the “Input Data” button for next step, see Fig.

Step 5: Click the “PreMark” button to see the mark result. Select from the drop down menu to set correct dots. More correct dots will get better accuracy.

Step 6: Edit the positions of X and Y in the fields separately and then click the “PreMark” button again to see the mark result. If necessary, repeat these steps until achieving the goal. Click “Back” button and then “Exit” button to save the file and exit.

Reset Params.: Reset all correction data as the default values.

From File…: Users can create a *.txt file as a correction file and using this function to import that file as the coordinates of X and Y.

Work Area

The size of f-theta lens will affect the working area. If it is not properly adjusted, center drifting and distortion might be caused. Adjust the parameters carefully, and the marking result will be extremely similar to the users’ design.

Lens: Users can select the lens they want to use from here.

Correction/ Lens Manager: This button is used for lens correction or lens management.

Scale X/Y: If the scale is too small, please enter a number larger than 100 (because unit is percentage); on the contrary, please enter a value smaller than 100.

X Offset / Y Offset: If the position of marking result has 5mm shift to the right side, users can enter -5mm in the X column. The other situations are the same.

Rotate: Set the angle of the marking result to fit the marking platform when the platform or work piece cannot be placed appropriately.

Galvo Direction:

X reverse / Y reverse / XY exchange

Provides X reverse, Y reverse, and XY exchange for users to apply when they need to adjust the axis’ direction of working area.