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3D Characterization by Local X-ray Emission Tomography

IP.com Disclosure Number: IPCOM000101195D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Christenson, KK: AUTHOR [+2]

Abstract

Disclosed is a method of inspecting objects by measuring their absorption of X-rays from a local "point" source created within the object by an electron beam. While similar to presently employed X-ray shadowing techniques using a distant source and (typically) a CCD array to gather the image, local X-ray emission tomography (LXT) provides over an order of magnitude improvement in spatial resolution and data acquisition rate.

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3D Characterization by Local X-ray Emission Tomography

       Disclosed is a method of inspecting objects by measuring
their absorption of X-rays from a local "point" source created within
the object by an electron beam.  While similar to presently employed
X-ray shadowing techniques using a distant source and (typically) a
CCD array to gather the image, local X-ray emission tomography (LXT)
provides over an order of magnitude improvement in spatial resolution
and data acquisition rate.

      When an electron beam strikes an object X-rays are produced
within a small volume.  These X-rays radiate out in all directions
and are partially absorbed as they pass through the object (Fig. 1).
The fraction of X-rays that emerge from an object in a given
direction can be used to determine the X-ray's path length (the
object's thickness) in that direction.

      By acquiring these "shadow images" at different orientations
the complete geometry of the object can be determined.  The
deconvolution algorithm is similar to that used in CAT scans.

      If full 3D information is not required, it may be possible to
simplify the process.  For instance, the thickness of the sample
shown in Fig. 2 can be determined with a single detector.  If
necessary, a second detector above the sample may be used to
determine the sample thickness in areas where the thickness is less
than the electron penetration distance.

      Alternately, a coating on the detector (or a thin m...