US-12626838-B2 - Deploying electric fields

US12626838B2US 12626838 B2US12626838 B2US 12626838B2US-12626838-B2

Abstract

Electric fields are deployed to determine electrical characteristics of an object. A dielectric substrate has a first surface and a second surface, a first set of substantially parallel electrodes are located on said first surface and a second set of substantially parallel electrodes are located on the first surface. The second set is substantially orthogonal to said first set thereby defining electrode crossings. Discontinuities are formed in an electrode at each electrode crossing to electrically isolate electrodes of the first set from electrodes of the second set. An electric bridge is created at each discontinuity to maintain electrical continuity. A selected electrode of the first set is energized two or more times while sequentially monitoring remaining electrodes of said first set. This is followed by energizing a selected electrode of the second set two or more times while sequentially monitoring remaining electrodes of the second set.

Inventors

Noel Samuel CUMMINGS

Assignees

Scanna MSC Limited

Dates

Publication Date: 20260512
Application Date: 20240722
Priority Date: 20230725

Claims (20)

1 . An apparatus for deploying electric fields to determine electrical characteristics of an object, comprising: a dielectric substrate having a first surface and a second surface; a first set of parallel electrodes on said dielectric substrate; a second set of substantially parallel electrodes also on said dielectric substrate, wherein said second set of parallel electrodes is orthogonal to said first set of parallel electrodes; first devices for energizing a selected electrode of said first set of parallel electrodes two or more times and sequentially monitoring two or more remaining electrodes of said first set of parallel electrodes; and second devices for sequentially energizing a selected electrode of said second set of parallel electrodes two or more times and sequentially monitoring two or more remaining electrodes of said second set of parallel electrodes; wherein: said first set of parallel electrodes are mounted on said first surface of said dielectric substrate; said second set of parallel electrodes are also mounted on said first surface, thereby defining electrode crossings; discontinuities are formed in an electrode at each said electrode crossing to electrically isolate electrodes of said first set of parallel electrodes from electrodes of said second set of parallel electrodes; and an electric bridge is created at each said discontinuity, that extends away from a plane of said first surface, to maintain electrical conductivity.
2 . The apparatus of claim 1 , wherein said dielectric substrate is a board and said electrodes of said first set of parallel electrodes and said electrodes of said second set of parallel electrodes are established on said board by an etching process.
3 . The apparatus of claim 1 , wherein said dielectric substrate is flexible.
4 . The apparatus of claim 1 , wherein each said electric bridge is a wire that physically passes over a continuous electrode at an electrode crossing.
5 . The apparatus of claim 1 , wherein: each said electric bridge is formed by a respective bridge conductor on said second surface; and electrical contacts pass through said dielectric substrate, each connecting an end of a discontinuous electrode to an end of a bridge conductor.
6 . The apparatus of claim 1 , wherein all of said electrodes of said first set of parallel electrodes are continuous, such that all of said discontinuities are present in said second set of parallel electrodes.
7 . A method of deploying electric fields to determine electrical characteristics of an object, in which: a dielectric substrate has a first surface and a second surface; a first set of parallel electrodes are located on said first surface; a second set of parallel electrodes are also located on said first surface, wherein said second set of parallel electrodes is orthogonal to said first set of parallel electrodes thereby defining electrode crossings; discontinuities are formed in an electrode at each said electrode crossing to electrically isolate electrodes of said first set of parallel electrodes from electrodes of said second set of parallel electrodes; and an electric bridge is created at each said discontinuity, that extends away from a plane of said first surface, to maintain electrical continuity, the method comprising the steps of: energizing a selected electrode of said first set of parallel electrodes two or more times and sequentially monitoring two or more remaining electrodes of said first set of parallel electrodes; and energizing a selected electrode of said second set of parallel electrodes two or more times and sequentially monitoring two or more remaining electrodes of said second set of parallel electrodes.
8 . The apparatus of claim 7 , wherein each electrode of said first set of parallel electrodes and said second set of parallel electrodes has a normal width defining a track footprint on said dielectric substrate; and each continuous electrode has a reduced width at each electrode crossing to reveal an uncovered region of said track footprint.
9 . The apparatus of claim 8 , wherein an end of a discontinuous electrode extends into one of said uncovered regions of a track footprint.
10 . The apparatus of claim 9 , wherein said reduced width defines uncovered regions of track footprints with trapezoidal shapes.
11 . The apparatus of claim 10 , wherein said end of said discontinuous electrode has a trapezoidal shape.
12 . The method of claim 7 , wherein said dielectric substrate is a board, the method further comprising the step of etching said board to establish said electrodes of said first set of parallel electrodes and said electrodes of said second set of parallel electrodes.
13 . The method of claim 7 , wherein said dielectric substrate is flexible.
14 . The method of claim 7 , further comprising the step of passing a wire over a continuous electrode at an electrode crossing to form a said electric bridge.
15 . The method of claim 7 , further comprising the steps of: etching bridge conductors on said second surface of said dielectric substrate; and passing an electrical contact through said dielectric substrate to connect an end of discontinuous electrodes to an end of a said bridge conductor.
16 . The method of claim 7 , wherein a plurality of electrodes of said first set of parallel electrodes are selected and sequentially energized.
17 . The method of claim 16 , wherein a plurality of remaining electrodes of said first set of parallel electrodes are sequentially monitored in response to respective energizations of an additional energizing electrode, to produce respective output signals.
18 . The method of claim 7 , wherein a plurality of electrodes of said second set of parallel electrodes are sequentially selected and energized.
19 . The method of claim 18 , wherein a plurality of remaining electrodes of said second set of parallel electrodes are monitored in response to respective energizations of an additional energizing electrode, to produce respective output signals.
20 . The method of claim 7 , further comprising the steps of: sampling monitored output signals a plurality of times; and digitizing each resulting sample.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority from United Kingdom Patent Application number 2311406.9, filed on Jul. 25, 2023 the whole contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to an apparatus and a method for deploying electric fields and, in particular, to deploying electric fields to determine electrical characteristics of an object. BACKGROUND OF THE INVENTION The sensing of the electrical permittivity of an object is disclosed in U.S. Pat. No. 8,994,383. A sensor is described that includes a dielectric layer that presents a surface defining the base of a volume in which a test object may be placed and an electrically active layer beneath the dielectric layer, comprising a first set of electrodes that extend in a first direction and a second set of electrodes that extend in a second direction that is perpendicular to the first direction. The electrodes are electrically isolated by deploying the first set on the first surface of the dielectric material and the second set on the second surface of the dielectric material. By selecting one of the sets, energizing a selected electrode of that set and monitoring one of the remaining electrodes of that set, data may be obtained relating to the permittivity of the material. A similar operation may be repeated during which the same electrode is energized but a different electrode is selected to be monitored; such that resulting electric fields penetrate the object to a greater or a lesser degree compared to the first iteration. As described in U.S. Pat. No. 10,753,898, an object can be scanned by an external electric field by placing the object on a support platform. A dielectric membrane in proximity to the support platform may include input lines and output lines, and a strobing circuit may apply input voltages to the input lines while a sampling circuit receives output voltages from the output lines. A processing device compares selected output signals against a reference signal to produce voltage control data. A voltage adjustment circuit adjusts the input voltage from a first intensity to a second intensity in response to the voltage control data. Apparatus of this type may be deployed as a security device for scanning the shoes worn by passengers before they board an aircraft for example. Scanning may be performed using the first set of electrodes on the first surface of the dielectric material, followed by using the second set of electrodes mounted on the second surface of the dielectric material. However, experiment has shown that the results obtained from the two scanning procedures are different. In applications such as shoe scanning, this can create difficulties in terms of identifying the data that is actually correct. Furthermore, problems may arise in terms of adjusting input voltages if different scanning procedures are producing different results. A known printed circuit board A1 of a dielectric material is shown in FIG. 1. On the first surface of the circuit board A1, material has been etched away to reveal a first array of electrodes A11 to A18. Electrodes are also etched on an underside second face of board A1, identified as A19. Surface A19 is also shown in FIG. 1. This includes a second array of electrodes A21 to A28. The second set of electrodes A21 to A28 is substantially orthogonal to the first set of electrodes A11 to A18. This arrangement may be used for two-dimensional scanning, during which a selected electrode of the first set is energized and a selected electrode of the second set is monitored. This procedure is repeated for all possible electrode combinations and the results obtained may be used to present an image of an object that is being scanned. As is known in the art, this technique may be used for scanning many different objects and the present inventor has performed experiments in relation to the scanning of shoes, as worn by passengers about to enter an aircraft or other protected area, for example. In order to gain a better understanding of the material composition of the object under investigation, is also known to perform layering procedures with respect to a single array of electrodes. Thus, layering may be performed with respect to the first set of electrodes A11 to A18 and then repeated with respect to the second set of electrodes A21 to A28. A cross section of the first set of electrodes A11 to A18 is shown in FIG. 2, when performing a layering operation. The electrodes are mounted on the board A1 and a ground plane B1 is present to shield the device from external electrical noise. During a layering procedure, it is possible for the first electrode A1 to be energized and the second electrode A12 to be monitored. On the next cycle, the first electrode A11 is again energized but this time the third electrode A13 is monitored. This is followed by the first electrode A11 being energized again with the fourth electrode A14 being monit