Introduction to X-ray imaging for
industrial applications
Markus Tarin
President & CEO
MoviMED
Agenda
Agenda
• What exactly are “X-rays” ?
• The X-ray tube
• Typical applications
• Methods of detection
• Detector type...
The Electromagnetic Spectrum
Historical Background
• German Physicist
• Discovered x-rays or “Roentgen rays”
on Nov 8, 1895
• During experimentation wi...
First X-ray image
• First X-ray images taken
by Wilhelm Roentgen
• 22nd December, 1895
• Shows the hand of
Wilhelm’s wife ...
The X-ray tube
X-rays
Cathode
Filament
Glass body
Anode with Tungsten target
Electron beam
kV
(keV)
The filament provides ...
X-ray Energy
Definition of X-ray energy:
The term xxx kV (kilo Volt or 1 x 1,000 Volt) refers to the high voltage supplied...
Examples of Energy (eV)
The following are examples of eV energies:
• Visible light photons: 1.5 – 3.5 eV
• Approximate ene...
Typical Applications
• Airport/Homeland Security
• Electronics
• General Inspection
• Petro-Chemical
• Automotive
• Aerosp...
X-ray detection methods
• Image Intensifier
• Scintillator
(Gamma detector)
• Amorphous Silicon
Panel
• X-ray film
• Phosp...
X-ray image intensifier
Image Intensifier
• Commonly found
in industrial x-ray
applications
• Converts x-rays
into photons...
Scintillator
• User for gamma
ray detection
• Could be
coupled to a
photon multiplier
counter
• Uses inorganic
material to...
Amorphous Silicon Panel
• Energy range from
10 to 160 keV
• Resolution about 48
µm (~10lp/mm)
• Standard frame
grabber int...
Challenges in X-ray imaging
• X-ray applications are generally “light starved”
• Signal to noise ratio is usually not very...
Importance of Detector Selection
Why using a standard machine vision
camera for X-ray will not work…
• The light output pr...
Importance of Dynamic Range
Sensor A Sensor B
Pixel Size 7.4um x 7.4um 16um x 16um
Full well capacity 20,000 e 150,000 e
R...
Lens Selection
• Due to the large pixel size
requirement, the sensor size of a
camera is also large.
• F-mount lenses are ...
Example application - BGA
Ball grid array inspection
• Higher density integrated circuits also come
with a higher pin coun...
BGA – X-ray image
• The solder paste is very opaque
to the x-rays and provides a
very favorable contrast ratio.
• The elec...
Image Processing – X-ray
Step 1: Raw x-ray image
BGA – Threshold
Step 2: Threshold type “Moments”
Creates a binary image. Only black
areas are being considered.
BGA - Dilate
Step 2: Dilate
Dilates binary pixels in the object
BGA - Close
Step 3: Close
Closes holes in the blobs
BGA – Particle analysis
Step 4: Particle analysis
Counts objects, measures size and
location. 144 pins found – pass!
BGA defect
• This images show multiple
defects after the soldering
operation of a BGA IC.
• Multiple BGA contacts are
acci...
BGA defect – raw image
BGA defect - Threshold
BGA defect - Erode
BGA defect – Remove particles
BGA defect - result
• The final image
processing step
reveals 7 shorts
• The blobs are
much larger than
the acceptance
cri...
Conclusion
• X-ray imaging is a very useful, non-visible imaging
tool
• A considerable amount of domain knowledge is
requi...
Markus Tarin
President & CEO
MoviMED
15540 Rockfield Blvd., Suite C110
Irvine, CA 92618
USA
Phone: 949-699-6600
email: m.t...
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Introduction to X-Ray Imaging for Industrial Applications

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Introduction to applying X-Ray imaging techniques to industrial machine vision applications. This presentation was given at the "Vision Show" in 2009 in Phoenix, AZ. It provides as overview of possible sensors to convert X-Rays into photons for imaging.

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Introduction to X-Ray Imaging for Industrial Applications

  1. 1. Introduction to X-ray imaging for industrial applications Markus Tarin President & CEO MoviMED
  2. 2. Agenda Agenda • What exactly are “X-rays” ? • The X-ray tube • Typical applications • Methods of detection • Detector types • Challenges in x-ray imaging • Detector selection • Example application • Conclusion • Q & A Head x-ray – “Homer Simpson”
  3. 3. The Electromagnetic Spectrum
  4. 4. Historical Background • German Physicist • Discovered x-rays or “Roentgen rays” on Nov 8, 1895 • During experimentation with vacuum tubes he noticed a faint glow (fluorescent) on a cardboard covered with “Barium Platinocyanide” • Named the radiation “x-rays” as in “unknown” rays • Wilhelm Roentgen received the Nobel Prize in 1901 for this discovery Wilhelm Conrad Röntgen *03/27/1845 † 02/10/1923
  5. 5. First X-ray image • First X-ray images taken by Wilhelm Roentgen • 22nd December, 1895 • Shows the hand of Wilhelm’s wife with ring
  6. 6. The X-ray tube X-rays Cathode Filament Glass body Anode with Tungsten target Electron beam kV (keV) The filament provides an “electron cloud” which is accelerated by the high voltage potential between the anode and cathode. The electrons collide and rapidly decelerate on the high-density Tungsten anode. The energy decay causes a photon emission. The emitted wavelength is in relation to the energy loss of the electron.
  7. 7. X-ray Energy Definition of X-ray energy: The term xxx kV (kilo Volt or 1 x 1,000 Volt) refers to the high voltage supplied to the x-ray tube. With other words the potential between the anode and cathode. A higher “kV” setting results in a higher x-ray energy output and a shorter wavelength. The current (mA – milli-Ampere - 1/1000 A) is the selected current allowed to flow through the filament of the x-ray tube at the selected voltage. A higher current causes a higher x-ray flux. The term “eV” or more commonly “keV” or “MeV” is the “electron Volt” or the energy given to an electron by accelerating it through 1 Volt. When considering x-rays, the keV or MeV is referring to the output energy of the x- ray photons generated by the x-ray tube.
  8. 8. Examples of Energy (eV) The following are examples of eV energies: • Visible light photons: 1.5 – 3.5 eV • Approximate energy of an electron striking a color television screen (CRT tube): 20,000 eV (20 keV) • High energy medical, diagnostic x-ray: 200 keV • 100W light bulb burning for one hour: 2.2 Trillion TeV !!! (2.2 Trillion Trillion eV) • Kinetic energy of an 1,900lb race car traveling at 230 mph: 28 x 10^24 eV
  9. 9. Typical Applications • Airport/Homeland Security • Electronics • General Inspection • Petro-Chemical • Automotive • Aerospace • Non-Destructive Testing • Medical/Diagnostic Imaging • X-ray Fluoroscopy
  10. 10. X-ray detection methods • Image Intensifier • Scintillator (Gamma detector) • Amorphous Silicon Panel • X-ray film • Phosphor plate scanner (CR) • others
  11. 11. X-ray image intensifier Image Intensifier • Commonly found in industrial x-ray applications • Converts x-rays into photons using phosphor
  12. 12. Scintillator • User for gamma ray detection • Could be coupled to a photon multiplier counter • Uses inorganic material to convert gamma rays into photons in the visible waveband Conceptual overview – Scintillator with detector
  13. 13. Amorphous Silicon Panel • Energy range from 10 to 160 keV • Resolution about 48 µm (~10lp/mm) • Standard frame grabber interface • Easy to integrate • “X-ray camera” • Compact form factor
  14. 14. Challenges in X-ray imaging • X-ray applications are generally “light starved” • Signal to noise ratio is usually not very favorable • Achieving acceptable image quality requires careful selection of optics and camera • X-ray imaging requires a considerable amount of “domain knowledge” • Image contrast depends on many factors (x-ray energy, absorption bands in specimen, type of materials, focus quality of x-ray beam, selection of detector, lens and imaging sensor) • Feature definition may be “fuzzy” or “faint”
  15. 15. Importance of Detector Selection Why using a standard machine vision camera for X-ray will not work… • The light output produced by an image intensifier is typically very low • Increasing the x-ray energy to achieve more light output will not necessarily improve the contrast ratio • Using a small pixel size sensor (<7.4um with 8-bit ADC) results in a limited dynamic range • Light starved x-ray imaging competes with detector noise of the camera
  16. 16. Importance of Dynamic Range Sensor A Sensor B Pixel Size 7.4um x 7.4um 16um x 16um Full well capacity 20,000 e 150,000 e Read noise 16 e 15 e Dynamic Range 20,000e/16e = 1,250 150,000e/15e = 10,000 Dynamic Range 62 dB 80 dB Gray levels ADC @ 10-bit - 1024 ADC @ 14-bit = 16,384 (Effective #of bits: 13.3) • Sensor B has a dynamic range 8 x higher than sensor A • X-ray images need to be processed in 16-bit format
  17. 17. Lens Selection • Due to the large pixel size requirement, the sensor size of a camera is also large. • F-mount lenses are often required • The field of view and working distance needs to be matched to the output port of the image intensifier • The lens needs a large aperture (low f#) to capture all available light. Ideally f# < 1.0
  18. 18. Example application - BGA Ball grid array inspection • Higher density integrated circuits also come with a higher pin count • The “BGA” or ball grid array IC package type has little balls as connection leads • The connections are underneath the chip and are no longer visible, after assembly • The solder paste is being placed onto the circuit board, prior to chip placement • The chip is then placed onto the PCB and run through a reflow oven, where the solder paste melts and forms an electric connection between the PCB and the ball contacts • X-ray inspection is the only method to “see through the circuit board and verify that all balls are in contact and that there are no accidental short circuits
  19. 19. BGA – X-ray image • The solder paste is very opaque to the x-rays and provides a very favorable contrast ratio. • The electronics industry frequently uses radio isotopes, emitting gamma rays (MeV energy) • Automatic detection algorithms can be used in this example for verification.
  20. 20. Image Processing – X-ray Step 1: Raw x-ray image
  21. 21. BGA – Threshold Step 2: Threshold type “Moments” Creates a binary image. Only black areas are being considered.
  22. 22. BGA - Dilate Step 2: Dilate Dilates binary pixels in the object
  23. 23. BGA - Close Step 3: Close Closes holes in the blobs
  24. 24. BGA – Particle analysis Step 4: Particle analysis Counts objects, measures size and location. 144 pins found – pass!
  25. 25. BGA defect • This images show multiple defects after the soldering operation of a BGA IC. • Multiple BGA contacts are accidentally soldering together. • The bridged pins or ball contacts are creating a shortcut • The circuit will not function properly
  26. 26. BGA defect – raw image
  27. 27. BGA defect - Threshold
  28. 28. BGA defect - Erode
  29. 29. BGA defect – Remove particles
  30. 30. BGA defect - result • The final image processing step reveals 7 shorts • The blobs are much larger than the acceptance criteria • Their center of gravity does not coincide with the IC package definition
  31. 31. Conclusion • X-ray imaging is a very useful, non-visible imaging tool • A considerable amount of domain knowledge is required to successfully apply this technology • Budgetary estimate for X-ray imaging systems range from $60k to $500k and up. • Exposure to x-ray radiation is potentially dangerous to ones health and safety. • Automated image processing may not always be possible, due to sometime poor defect definition • 16-bit image processing is necessary, due to the need for large dynamic range.
  32. 32. Markus Tarin President & CEO MoviMED 15540 Rockfield Blvd., Suite C110 Irvine, CA 92618 USA Phone: 949-699-6600 email: m.tarin@movimed.com www.movimed.com Q & A

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