Browse Prior Art Database

X-Ray Axial Tomographic System Employing X-Ray Film for Industrial Applications

IP.com Disclosure Number: IPCOM000046824D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 28K

Publishing Venue

IBM

Related People

Pickar, PB: AUTHOR

Abstract

The present system allows one to observe defects in a thin slice of the object being studied without any interference from adjacent layers. Tomographs of adjacent layers can be added together to give the sum of the whole object. The applicability of a tomographic system depends upon the linear attenuation coefficients of the material to be studied. In the medical case, the linear attenuation coefficient of the various parts of the body may differ by only 0.5%. The linear attenuation coefficients of defects and ceramics (as well as other industrial materials) are quite different than the biological system.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 55% of the total text.

Page 1 of 3

X-Ray Axial Tomographic System Employing X-Ray Film for Industrial Applications

The present system allows one to observe defects in a thin slice of the object being studied without any interference from adjacent layers. Tomographs of adjacent layers can be added together to give the sum of the whole object. The applicability of a tomographic system depends upon the linear attenuation coefficients of the material to be studied. In the medical case, the linear attenuation coefficient of the various parts of the body may differ by only 0.5%. The linear attenuation coefficients of defects and ceramics (as well as other industrial materials) are quite different than the biological system. In the industrial case, with respect to ceramics or other materials, the shape of the object and the linear attenuation coefficient (as a function of X-ray wavelengths) can be accurately determined and, thus, provide significant information as to the type of back projection methods to be used (e.g., spatial back projection algorithms, summation back projection, etc.). The present system involves the summation back projection method. In the medical computer-assisted tomography scanner, the patient is held firmly fixed while the X-ray source and electronic detectors (mounted on a common gantry) rotate about the patient in angular steps. In the present case, the micro-focus X-ray source is held in a fixed position while the object and sensor (photographic film) on their respective tables rotate synchronously. When looking for defects on the order of five microns, a resolution of the same magnitude is required. This requires a micro-focus generator with a focal spot of that size. Similarly, the grain size of the photographic film used also effects the resolution to be observed. Consequently, fine grain (one to three microns) high contrast film is used. Referring to the figure shown, the present system comprises: 1. Micro-focus X-ray generator with a variety of targets to give different wavelengths (absorption

coefficient of materials is a function of

wavelength). Resolution of tomograms depends upon

focal size.

2. Collimator to restrict magnitude of fan-out beam

from X-ray source.

3. Slit systems to define thickness of fan-out beam

(will deter 4., mine the thickness of the layer or

slice being studied).

5.

6. Rotating object table.

7. Object being studied.

8. X-ray beam parallel to X-ray film.

9. Rotating table of stainless steel to hold film

(film held) flat by small magnets.

10. Photographic film.

11. Motor for driving tables (6 and 9) synchronously.

12. Belt drive connecting both tables.

13. Track holding the whole assembly. This track is

1

Page 2 of 3

slotted, which permits changes in magnification by

moving the two tables closer or further apart. In the present tomographic system, photographic film is employed for the...