Device for detecting interaction with an object

Abstract

A device and method for the detection of the interaction between two or more objects is disclosed. The device utilizes electrical impedance spectra measured from a piezoelectric element attached to one such object. Comparison of such spectra along a range of traverse allows precise estimates of distance to be made. One useful application is the topographical mapping of a surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic representation of the components of this invention, demonstrating a contact object attached to a piezoelectric element, with an electrical connection to a device capable of making electrical measurements of the piezoelectric, such as electrical impedance. In this illustration, the contact object is shown at a distance from another solid object.

FIG. 1B is a schematic of the same invention depicted in FIG. 1A, but in this case the contact object is shown physically interacting with another solid object.

FIG. 2A is an overlay of two impedance spectra gathered from a piezoelectric attached to a contact object when that object is at a distance from a solid surface and in contact with a solid surface.

FIG. 2B is a plot of the difference between the two spectra in FIG. 2B.

FIG. 3A shows the sum of the difference in impedance at five frequencies, as a function of time, between the measured value and a previously calibrated value.

FIG. 3B shows the sum of the difference in impedance at three frequencies, under the same conditions as for FIG. 3A.

FIG. 3C shows the sum of the differences in impedance at one frequency, under the same conditions as for FIG. 3A.

FIG. 4A is an overlay of two impedance spectra gathered from a piezoelectric element attached to a hollow tube when that tube is empty and when it is full of water.

FIG. 4B is a plot of the difference between the two spectra in FIG. 4A.

FIG. 5 is a contour plot of the topography of a surface as measured by this invention when mounted on a precision positioning system.

Claims

1. A device for detecting the physical interaction of two or more objects comprising a contact objecta piezoelectric element attached to said contact object, such piezoelectric element having a measurable change in electrical properties at more than one applied alternating current frequency when the contact object interacts with another object or objectsan operable electrical connection to means for measuring the electrical properties of said piezoelectric element; andpositioning means to move said contact object into contact proximity to a target object or objects.

2. The device of claim 1, wherein said target object is selected from the group consisting of a substantially planar object, a curved object, an object with a patterned or complex surface, and a spatially disposed object.

3. The device of claim 1 wherein the electrical properties to be measured are selected from the group consisting of impedance, resistance, capacitance, reactance, and phase.

4. The device of claim 1 wherein said physical interaction is contact between said contact object and said target object or objects.

5. The device of claim 1 wherein said contact object is selected from the group consisting of a hollow glass cylinder, a hollow glass cylinder having a tapered tip, a solid metal pin, a hollow metal cylinder having a tapered tip, a solid polymer pin, and a hollow polymer cylinder having a tapered tip or combinations thereof.

6. A device for detecting the fluid level in a hollow vessel comprising a hollow substantially round tubular structure adapted to contain a liquid having an inner and an outer walla piezoelectric element attached to the said outer wall of said tubular structure, such piezoelectric element having a measurable change in electrical properties at more than one applied alternating current frequency with a change in fluid level within the vessel, andan operable electrical connection to means for measuring the electrical properties of said element.

7. The device of claim 6 wherein said tubular structure is a capillary tapered at one end.

8. A method of detecting fluid in a hollow vessel comprising providing a hollow substantially round tubular structure adapted to contain a liquid having an inner and an outer wall, said structure having a piezoelectric element attached to said outer wall, and an operable electrical connection to means for measuring the electrical properties of said elementfilling or draining incremental fluid volumes from said tubular structuremeasuring the electrical properties of said piezoelectric element at more than one applied alternating current frequency at each increment, andcorrelating the electrical properties with the fluid volumes so filled or drained.

9. A method of calibrating the detection of the physical interaction of two or more objects comprising attaching a piezoelectric element to a contact object having an operable electrical connection to means for measuring the electrical properties of said elementmounting said contact object on a positioning device whereby the position of said contact object can be directed incrementally in at least one dimension along a substantially rectilinear path of traverseplacing a target object in the path of traverse of said contact objectmeasuring the electrical properties of said piezoelectric element at more than one applied alternating current frequency without interacting said contact object with said target object and recording those propertiesadvancing said contact object along the path of traverse until interaction occurs between said contact object and said target objectmeasuring the electrical properties of said piezoelectric element while said contact object is interacting with said target object and recording those properties.

10. The method of claim 6, wherein said physical interaction is physical contact between said contact object and said target object.

11. The method of claim 6, wherein said physical interaction is a liquid bridge between said contact object and said target object.

12. A method of detecting the physical interaction physical interaction of two or more objects comprising attaching a piezoelectric element to a contact object having an operable electrical connection to means for measuring the electrical properties of said elementmounting said contact object on a positioning device whereby the position of said contact object can be directed incrementally in at least one dimension along a substantially rectilinear path of traverseadvancing said contact object incrementally along the path of traverse in the direction towards said target objectmeasuring the electrical properties of said piezoelectric element at each such incremental positioncomparing the electrical properties with previously calibrated values to determine when interaction between said contact object and target object has occurredon interaction of the contact object and target object, reversing the direction of path traverse of said contact objectretreating from the point of interaction incrementally in smaller increments than the advancing increment, andcomparing the electrical properties with previously calibrated values to determine when interaction between said contact object and target object is no longer occurring.

13. The method of claim 12, wherein said physical interaction is physical contact between said contact object and said target object.

14. The method of claim 12, wherein said physical interaction is a liquid bridge between said contact object and said target object.

15. The method of claim 12 wherein the steps thereof are carried out a plurality of times at different locations on a substrate, whereby to topologically map surface imperfections and determine cant of the substrate.