Method for improving scanning probe microscope imaging by inverse filtering
View Patent ↗In accordance with the invention, an inverse filter is used to improve scanned images from a scanning probe microscope by removing the effect of the scanning system dynamics from the image data. This may be done in-line or as a post-processing operation.
1. A method for using inverse filtering to remove the effect of scanning system dynamics from surface image data comprising:
determining a linear model of a closed-loop response from a surface to a selected output signal of a closed-loop control system for a scanning probe microscope;
determining an inverse transfer function;
determining an appropriate bandpass filter;
determining an inverse filter using said bandpass filter and said inverse transfer function; and
filtering said selected output signal using said inverse filter to obtain filtered surface image data.
2. The method of claim 1 wherein said selected output signal is a controller output signal.
3. The method of claim 1 wherein said selected output signal is an actuator position signal.
4. The method of claim 1 wherein said selected output signal is an optical detector output signal.
5. The method of claim 1 wherein said closed loop control system comprises a MEMS actuator.
6. The method of claim 5 wherein said MEMS actuator comprises a position sensor.
7. The method of claim 1 wherein said inverse filter is a digital filter.
8. A method for using inverse filtering to remove the effect of scanning system dynamics from surface image data comprising:
determining a first linear model of a first closed-loop response from a surface to a first selected output signal of a closed-loop control system for a scanning probe microscope;
determining a second linear model of a second closed-loop response from said surface to a second selected output signal of said closed-loop control system for said scanning probe microscope;
determining a first inverse transfer function using said first linear model;
determining a second inverse transfer function using said second linear model;
determining an appropriate first and a second bandpass filter;
determining a first inverse filter using said first bandpass filter and said first inverse transfer function;
determining a second inverse filter using said second bandpass filter and said second inverse transfer function;
filtering said first selected output using said first inverse filter to obtain first filtered surface image data; and
filtering said second selected output using said second inverse filter to obtain second filtered surface image data.
9. The method of claim 8 further comprising forming a linear combination of said first and said second filtered surface image data wherein said first and said second filtered surface image data are weighted by a first and a second coefficient, respectively.
10. The method of claim 9 wherein said first coefficient is a constant value.
11. The method of claim 9 wherein said first coefficient is time dependent.
12. The method of claim 9 wherein said first coefficient is frequency dependent.
13. The method of claim 8 wherein said first bandpass filter is adapted to emphasize a frequency range over which said first selected output signal provides the best information.
14. The method of claim 8 wherein said first selected output signal is an optical detector output signal.
15. The method of claim 8 wherein said first selected output signal is a controller output signal.
16. The method of claim 8 wherein said first selected output signal is an actuator position signal.
17. The method of claim 8 wherein said first inverse filter is an analog filter.
18. The method of claim 8 wherein said closed-loop control system comprises a MEMS actuator.
19. The method of claim 18 wherein said MEMS actuator comprises a position sensor.
20. The method of claim 8 wherein said closed-loop control system comprises a sensored piezoelectric actuator.