CCD Image Processing

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• CCD Image Processing

Sierra College
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• Why CCD/CMOS Imaging ???

• It's efficient
• It's quantitative
• It's current

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Images
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Color Images These can be obtained by combining
3 or 4 filtered images
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Color Images
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Astrometrics

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Astrometrics
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• What is a CCD ???

• A solid state device
• Converts light to charge
• Digitizes output

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This is a CCD Camera

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Expand on this!
The CCD Grid
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The number recorded in each square can be
interpreted as a shade of grey
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CCD detectors are made of Silicon
Pixel Structure
Pixel Structure
Pixel Structure
Pixel Structure
Pixel Structure
Pixel Structure
Gate (10v)
Gate (10v)
Gate (10v)
Due to photons
Gate (10v)
Poly-Si
Insulator from Thermal photons
Si O2
Si O2
Si O2
Si O2
Si O2
Electrons (- charge)
Electrons (- charge)
Electrons (- charge)
The voltage "well"
Depletion Zone (neutral charge)
Depletion Zone (neutral charge)
Depletion Zone (neutral charge)
Depletion Zone (neutral charge)
P Type Si ( charge)
P Type Si ( charge)
P Type Si ( charge)
P Type Si ( charge)
P Type Si ( charge)
P Type Si ( charge)
Due to thermal

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Advantage of a CCD
Efficiency
CCDs can have Efficiencies greater than 80
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CCD "Structure"

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• CCD's Specs

• Size (pixels and array)
• Well Depth
• Charge Transfer Efficiency
• Analog to Digital Conversion Resolution
• Read Noise
• Anti-Blooming (not for science)
• Cooling (dark current)

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• CCD's are not perfect!

• Bias map
• Thermal current
• Flat field correction
• Post processing of the images

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• CCD's are not perfect!

• Bias map
• Remove the noise component contributed by the
  electronics controlling the CCD

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• CCD's are not perfect!

• Thermal current
• (Dark subtract)
• Remove the noise component contributed by
  thermionic emission

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• CCD's are not perfect!

• Flat field correction
• Normalize the gain of each pixel to a value of 1x.

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Robotic Observatory Spring 06

• Sensor
• Apogee Instruments ALTA
• 1k x 1k Back Illuminated CCD camera
• Spectrally flat
• Very high performance
• EVEN BETTER

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• What is needed ...

• Match the camera to your scope
• Field size
• Nyquist Sampling Theory
• Pixel size (2 per SMALLEST element)
• USUALLY, will be limited by seeing

Variables in red must be in same units
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• Marching Orders

• Answer Questions 1-5
• Green Book Question Consult CCD
  notes/handoutsWhat are the 3 corrections that
  should be made to all CCDs that will enable you
  to take a better picture?

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The End