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Charged Coupled Device Imaging

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Charged Coupled Device Imaging By Marc Castro 17443948 CCD Imaging Process (3 step process) 1. Exposure Converts light into an electronic charge at discrete sites ... – PowerPoint PPT presentation

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Title: Charged Coupled Device Imaging


1
Charged Coupled DeviceImaging
  • By
  • Marc Castro
  • 17443948

2
CCD Imaging Process
  • (3 step process)
  • 1. Exposure
  • Converts light into an electronic charge at
    discrete sites called pixels, photo sites,
    photodiodes or capacitors.

2. Charge Transfer One of the CCD
architectures is used.
3. Charge to voltage Signal conversion from
analog (electrical charges) to digital
(0s and 1s).
3
How does it look like?
Charged Couple Device
4
What is it?
  • Charged Coupled Device (CCD)
  • an analog shift register, that enables the
    transportation of analog signals (electric
    charges) through successive stages (pixels)
    controlled by a clock signal.
  • Primary uses
  • Memory
  • Delaying samples of analog signals
  • In an array of photoelectric light sensors (image
    sensors)

5
History
  • Invented in 1969
  • Creators Willard Boyle and George E. Smith
  • Location ATT Bell Labs. Currently part of
    Lucent Technologies
  • Motivation the lab was working on the picture
    phone and on the development of the semiconductor
    bubble memory.
  • CCD originally designed as an electronic memory
    device that can be charged by light.

6
CCD Fabrication
  • Made using photolithography techniques.

Individual pixel gate fabricated on a silicon
wafer
Courtesy of Olympus
7
End Product
Don Groom LBNL
8
Capturing Images
The CCD - comprised of many individual signal
capture units (photo sites, capacitors, pixels)
CDD - 2D Pixel Array
9
Capturing Images
How charges are stored
  • CCDs are comprised of pixels (capacitors) which
    are MOS (Metal Oxide Semiconductors).
  • MOS allow electron charges to build up within the
    wells.

10
Capturing Images
  • Light incoming photons falls onto the surface
    of a pixel.
  • (CDD - 2D array of pixel elements)
  • Result- generates free electrons in the silicon
    of the CCD due to the photoelectric effect,
    proportional to the number of photons striking
    it. These electrons collect in little packets.
  • Point- the total charge is proportional to the
    light intensity at that pixel.
  • A brighter image ( higher electrical charge).
  • A darker image ( lower electrical charge).
  • Drawback- only measures intensity. Not
    color!!!
  • CCDs normally have 1 to 5 million packets of
    charge.

11
CCD Scanning Formats
CCDs can be used to collect an image in one of
three ways, either one pixel at a time, one row
at a time, or as an entire area at once.
12
Methods to capture color
  • Method 1 Beam Splitter

Method 2 Bayer Pattern
Courtesy of HowStuffWorks
13
2-D Pixel Array with Bayer Pattern
  • Used over the CCD (color grid over imaging array)
  • Each square (4 pixels) contains
  • One red
  • One blue
  • Two green

14
Transfer image from array.
  • General Idea
  • Control circuit causes each pixel to transfer its
    contents to its neighbor using a clocking scheme.
    The last pixel in the array dumps its charge into
    a charge amplifier, which converts the charge
    into a voltage.
  • The controlling circuit converts the entire
    semiconductor contents of the array to a sequence
    of voltages, which it samples, digitizes and
    stores in some form of memory.

15
Readout Architecture
  • Full Frame
  • Frame Transfer
  • Interline
  • They are the most common

16
Full Frame Architecture
Courtesy of Molecular Expressions
17
Frame Transfer Architecture
Courtesy of Molecular Expressions
18
Interline Architecture
Courtesy of Molecular Expressions
19
Storing the image
  • Analog to digital converter
  • Samples the analog signal and turns the
    information into bytes of (1s and 0s).
  • Charge amplifier converts the charge into
    voltage.
  • Record bytes in a storage medium
  • Memory Cards
  • Hard Drive
  • DVD

20
Applications
  • Digital Photography
  • Astronomy
  • Sensors
  • Electron Microscopy
  • Medical Fluoroscopy
  • Optical and UV Spectroscopy

21
Devices
  • Astronomical Telescopes
  • Scanners
  • Bar code readers
  • Machine vision for robots.
  • Optical character recognition (OCR)

22
Works Cited
  • Tom Harris. How Camcorders Work.
    HowStuffWorks.http//electronics.howstuffworks.com
    /camcorder.html
  • Charge-coupled device. Wikipedia.
    http//en.wikipedia.org/wiki/Charge-coupled_device
  • Building A Charge-Coupled Device. Olympus
    Microscopy Resource Center. http//www.olympusmicr
    o.com/primer/java/photomicrography/ccd
  • Tom Thompson. Charge-Coupled Device.
    ComputerWorld. http//www.computerworld.com/softwa
    retopics/software/multimedia
  • What is a Charge-Coupled Device. Tech-Faq.
    http//www.tech-faq.com/charge-coupled-deivce.shtm
    l
  • Lucent Technologies. CCD-The History of CCDs or
    Charge Coupled Devices. About.com Inventors.
    http//inventors.about.com/od/cstartinventions/a/C
    CD.html
  • Charge-Coupled Device (CCD) sensor. MIR.
    http//www/mir/com.my/rb/photography/digitalimagin
    g/ccd/html
  • Charge-coupled deivce. Whatis.com.
    http//searchstorage.techtarget.com/sDefinition/0,
    ,sid5_gci295633

23
Works Cited
  • Anatomy of a Charge-Coupled Device. Molecular
    Expressions Optical Microscopy Primer Digital
    Imaging in Optical Microscopy. http//micro.magnet
    .fsu.edu/primer/digitalimaging/concepts
  • Eric Meisenzahl. Charge-Coupled Device Image
    Sensors. Eastman Kodak Co. http//engage.advansta
    r.com/jnserver/acc_random
  • Charge-couple device. Answers.com.
    http//www.answers.com/topic/charge-coupled-device
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