Active damping of high speed scanning probe microscope components
View Patent ↗A technique for actively damping internal vibrations in a scanning probe microscope is disclosed. The excitation of various mechanical movements, including resonances, in the mechanical assembly of an SPM can adversely effect its performance, especially for high speed applications. An actuator is used to compensate for the movements. The actuator may operate in only the z direction, or may operate in other directions. The actuator(s) may be located at positions of antinodes.
1. A method, comprising:
maintaining a feedback loop that maintains a distance relationship between a sample being measured and a support in a sensing system, said feedback loop operating to maintain said distance relationship between said sensing system and said sample that is supported by the support, said maintaining using a first actuator;
measuring momentum-causing actions that are induced to the support structure by actions of components of said sensing system other than said first actuator; and
using a second actuator, separate from the first actuator, to compensate said momentum-causing actions to thereby damp said momentum-causing actions.
2. A method as in claim 1 , wherein said system includes components of an atomic force microscope and where said components other than the first actuator are other components of said atomic force microscope.
3. A method as in claim 2 wherein said measuring comprises measuring in a constant contact type atomic force microscope.
4. A method as in claim 2 , wherein said measuring comprises measuring in a scanning tip atomic force microscope.
5. A method as in claim 1 , wherein said sensing system includes a measuring cantilever.
6. A method as in claim 1 , further comprising using a controller to determine a compensation based on said measuring, and to use said compensation to produce an output to said second actuator.
7. A method as in claim 1 , wherein said measuring and said using are carried out with separate structures.
8. A method as in claim 1 , wherein said measuring and said using are carried out with a single structure that produces an output signal based on motion thereof, and which can move based on an applied signal.
9. A method as in claim 1 , wherein said measuring comprises determining positions of specified movements by said support, and compensating movements at said positions of said positions.
10. A method as in claim 9 , wherein said positions of specified movements are anti-nodes.
11. A method as in claim 1 wherein said using the second actuator comprises using a third actuator that is part of the second actuator and that is oriented in a first direction relative to a direction of motion, and using a fourth actuator that is part of the second actuator and that is oriented orthogonal to said third actuator.
12. A method as in claim 1 , further comprising placing said sample on a removable holder, and wherein said measuring comprises measuring motion on the removable holder.
13. A method as in claim 1 , further comprising further compensating said actuator using a weight.
14. A method as in claim 1 , further comprising attaching a test mass to said second actuator to improve sensitivity of the second actuator to the momentum causing actions.
15. A method as in claim 1 , wherein said momentum-causing actions include one or more of movement, positioning, velocity provision and/or acceleration.
16. A method as in claim 1 , further comprising placing said sample on a removable holder, and wherein said measuring comprises measuring motion on the removable holder.