Surface force apparatus based on a spherical lens

Patent metadata

Field	Value
Publication number	US-11054320-B2
Application number	US-201916675727-A
Country	US
Kind code	B2
Filing date	Nov 6, 2019
Priority date	Sep 10, 2015
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A force detector and method for using the same include a lens and a cantilever below the lens. A laser above the lens is configured to emit a beam of light that reflects from a surface of the lens and the cantilever. A processor is configured to determine a force between the lens and the cantilever based on interference between the light reflected from the surface and the light reflected from the cantilever.

First claim

What is claimed is:

1. A force detector, comprising:
a lens;
a cantilever disposed below the lens;
a laser disposed above the lens, configured to emit a beam of light that reflects from a surface of the lens and the cantilever; and
a processor configured to determine a force between the lens and the cantilever based on interference between the light reflected from the surface and the light reflected from the cantilever.

2. The force detector of claim 1 , wherein the lens is formed from a lens base material and has a coating on the surface of the lens formed from a first material to be tested.

3. The force detector of claim 1 , wherein the cantilever comprises a cantilever base material and has a coating formed from a second material to be tested.

4. The force detector of claim 1 , further comprising a motor configured to move the lens and to track changes in lens position.

5. The force detector of claim 1 , wherein the processor is further configured to determine a deflection of the cantilever based on a change in lens position and a change in a distance between the lens and the cantilever.

6. The force detector of claim 5 , wherein the processor is further configured to

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h

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p

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π

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,

determine the change in distance between the lens and the cantilever according to where Δh is the change in distance, Δp is the change in phase of interference rings in an image, λ is the wavelength of the emitted light, and n 0 is the index of refraction of the medium between the surface of the lens and the cantilever.

7. The force detector of claim 1 , wherein the lens has a spherical surface with a radius of at least lcm and a surface roughness of 2 nm or less.

8. The force detector of claim 1 , wherein the cantilever has a thickness of at least 10 μm.

9. The force detector of claim 1 , wherein the lens is in contact with the cantilever and progressively moved away from the cantilever's resting position, such that a force of adhesion causes a deflection in the cantilever and wherein the processor is further configured to repeatedly measure an adhesion force between the lens and the cantilever until the cantilever breaks contact with the lens.

10. The force detector of claim 9 , wherein the processor is configured to determine the force of adhesion based on a last measured deflection before the cantilever breaks contact with the lens.

11. A method for force detection, comprising:
emitting a laser beam, such that light reflects from a surface of a lens and a cantilever positioned below the lens;
determining a force between the lens and the cantilever with a processor, based on interference between the light reflected from the spherical surface and the light reflected from the cantilever.

12. The method of claim 11 , wherein the lens is formed from a lens base material and has a coating on a lens surface formed from a first material to be tested.

13. The method of claim 11 , wherein the cantilever comprises a cantilever base material and has a coating formed from a second material to be tested.

14. The method of claim 11 , further comprising moving the lens according to a known position change.

15. The method of claim 11 , wherein determining the force further comprises determining a deflection of the cantilever based on a change in lens position and a change in a distance between the lens and the cantilever.

16. The method of claim 15 , wherein determining the force further comprises determining the change in distance between the lens and the cantilever according to

Δ
⁢

⁢
h

=

Δ
⁢

⁢
p

2
⁢

⁢
π

⁢

(

λ

2
⁢

n
0

)

,

where Δh is the change in distance, Δp is the change in phase of interference rings in the captured image, λ is the wavelength of the emitted light, and n 0 is the index of refraction of the medium between a surface of the lens and the cantilever.

17. The method of claim 11 , wherein the lens has a spherical surface with a radius of at least lcm and a surface roughness of 2 nm or less.

18. The method of claim 11 , wherein the cantilever has a thickness of at least 100 μm.

19. The method of claim 11 , further comprising:
moving the lens into contact with the cantilever;
moving the lens away from the cantilever's resting position, such that a force of adhesion causes a deflection in the cantilever; and
repeatedly measuring an adhesion force between the lens and the cantilever until the cantilever breaks contact with the lens.

20. The method of claim 19 , wherein measuring the adhesion force comprises retaining a last measured adhesion force based on the deflection before the cantilever breaks contact with the lens.

Assignees

• IBM

Inventors

• Ellis Arthur W
• Haight Richard A
• Hannon James B
• Tromp Rudolf M

Classifications

• G01L1/24 Primary

  by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis {using infrared, visible light, ultraviolet} · CPC title

• G01B11/161

  by interferometric means · CPC title