Ultra-sensitive x-ray sensors give improved contrast sensitivity
Low-light-level cameras used with phosphors detect very small contrast differences and very small features in x-ray images. I used (1) a silicon-intensifier-tube (SIT) television camera coupled by a fiber optic to a phosphor screen and (2) an integrating CCD camera focused on a phosphor to detect a 0.1% contrast difference and 2-micrometer-diameter wires in a digital image. Flannery, et al., and Kinney, et al., reported spatial resolution as small as 1 micrometer in computer x-ray tomography (CAT scans) using synchrotron x-ray sources and CCD cameras. I thought that these cameras could be used with industrial x-ray sources with microfocal spot sizes to produce x-ray images with spatial resolution as small as 1 micrometer and contrast sensitivity as small as 0.01%. Hence, near-real time x-ray inspection system could be made that have the resolution of x-ray film and 20 times better contrast sensitivity. As a proof of principle experiment, I used an x-ray camera composed of an x-ray phosphor deposited on a fiber optic that is coupled to a night vision camera (SIT). Using a digital subtraction technique and an 8-bit frame grabber, this camera detected wires as small as 2 micrometers in diameter and x-ray attenuations as small as 0.27%. Verhoeven reported 0.14% for a free-standing foil without a substrate. However, some CCD cameras have 64 times more levels of digitization than the frame grabber and can integrate images for as long as 30 minutes before the images are digitized. Hence, I predicted that the CCD camera would also detect wires 2 micrometers in diameter and contrast differences as small as 0.02%, ten times better than the SIT and 20 better than film. Unfortunately, my preliminary experiments with CCD camera duplicate, but do not improve upon, the performance of the SIT. 8 refs., 4 figs.
- Research Organization:
- Los Alamos National Lab., NM (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6473934
- Report Number(s):
- LA-UR-88-3865; CONF-890478-1; ON: DE89003581
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
BACKGROUND NOISE
DIAGNOSTIC TECHNIQUES
DIGITIZERS
ELECTRONIC CIRCUITS
IMAGE PROCESSING
INDUSTRIAL RADIOGRAPHY
NOISE
PROCESSING
PULSE CIRCUITS
RESOLUTION
SENSITIVITY
SIGNAL CONDITIONERS
TOMOGRAPHY
X-RAY RADIOGRAPHY