Auto-focus sensor implementation for multi-column microscopes
An array of localized auto-focus sensors provides direct measurement of the working distance between each microscope column in the array and the substrate being imaged below. The auto-focus sensors measure the working distance between each column and the imaging substrate as it passes over a point on the substrate to be imaged. The working distance measurement from the sensors is input into a control system, which in turn outputs the required working distance adjustment to the microscope column. The control system independently adjusts microscope working distance and/or physical distance of an individual microscope column in a multi-column microscope based on auto-focus sensor input. The individual microscope columns in the multi-column microscope can also be used as the auto-focus sensor itself.
1. A system comprising:
a multi-column array of scanning electron microscopes (SEMs);
an array of autofocus sensors in line with the multi-column array of scanning electron microscopes;
a controller; and
a stage configured to hold an imaging sample and to swath in multiple directions.
2. The system of claim 1 , wherein the array of auto-focus sensors is configured to allow for simultaneous measurement of working distance or position between multiple microscope columns and imaging substrates.
3. The system of claim 1 , wherein the controller is configured to implement a feedback control loop that inputs autofocus sensor signals and outputs signals to adjust either column focal distances or column-to-sample working distances required to allow each active imaging column in multi-column microscope to maintain proper focus on the imaging sample.
4. The system of claim 1 , wherein the controller is configured to allow each autofocus sensor in the array of autofocus sensors to independently measure column-to-sample working distances.
5. The system of claim 1 , wherein the controller is configured to allow each autofocus sensor in the array of autofocus sensors to measure column-to-sample working distances in parallel with other autofocus sensors.
6. The system of claim 1 , wherein the controller is configured to allow each column in the multi-column array of SEMs to independently adjust column-to-sample working distances.
7. The system of claim 1 , wherein the controller is configured to allow each column in the multi-column array of SEMs to adjust column-to-sample working distances in parallel with other columns in the multi-column array of SEMs.
8. The system of claim 1 , wherein the controller is configured to allow each column in the multi-column array of SEMs to act as an autofocus sensor to measure effective working distances to the imaging sample in between image scans.
9. The system of claim 1 , wherein a column of autofocus sensors sits in between two columns of SEMs.
10. The system of claim 1 , wherein the controller is configured to move the stage in multiple degrees of freedom.
11. A device comprising:
a multi-column array of scanning electron microscopes (SEMs);
an array of autofocus sensors in line with the multi-column array of scanning electron microscopes;
a controller; and
a stage configured to hold an imaging sample and to swath in multiple directions.
12. The device of claim 11 , wherein the array of auto-focus sensors is configured to allow for simultaneous measurement of working distance or position between multiple microscope columns and imaging substrates.
13. The device of claim 11 , wherein the controller is configured to implement a feedback control loop that inputs autofocus sensor signals and outputs signals to adjust either column focal distances or column-to-sample working distances required to allow each active imaging column in multi-column microscope to maintain proper focus on the imaging sample.
14. The device of claim 11 , wherein the controller is configured to allow each autofocus sensor in the array of autofocus sensors to independently measure column-to-sample working distances.
15. The device of claim 11 , wherein the controller is configured to allow each autofocus sensor in the array of autofocus sensors to measure column-to-sample working distances in parallel with other autofocus sensors.
16. The device of claim 11 , wherein the controller is configured to allow each column in the multi-column array of SEMs to independently adjust column-to-sample working distances.
17. The device of claim 11 , wherein the controller is configured to allow each column in the multi-column array of SEMs to adjust column-to-sample working distances in parallel with other columns in the multi-column array of SEMs.
18. The device of claim 11 , wherein the controller is configured to allow each column in the multi-column array of SEMs to act as an autofocus sensor to measure effective working distances to the imaging sample in between image scans.
19. The device of claim 11 , wherein a column of autofocus sensors sits in between two columns of SEMs.
20. The device of claim 11 , wherein the controller is configured to move the stage in multiple degrees of freedom.