1. Charged Coupled Device ImagingBy
Marc Castro

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 (0’s and 1’s).

3. How does it look like?
Charged Couple Device

4. What is it? Charged Coupled Device (CCD) Primary uses:
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: AT&T 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!!!
CCD’s 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 (1’s and 0’s).
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.
“Charge-coupled device.” Wikipedia.
“Building A Charge-Coupled Device.” Olympus Microscopy Resource Center.
Tom Thompson. “Charge-Coupled Device.” ComputerWorld.
“What is a Charge-Coupled Device.” Tech-Faq.
Lucent Technologies. “CCD-The History of CCDs or Charge Coupled Devices.” About.com Inventors.
“Charge-Coupled Device (CCD) sensor.” MIR.
“Charge-coupled deivce.” Whatis.com.

23. Works Cited
“Anatomy of a Charge-Coupled Device.” Molecular Expressions Optical Microscopy Primer: Digital Imaging in Optical Microscopy.
Eric Meisenzahl. “Charge-Coupled Device Image Sensors.” Eastman Kodak Co.
“Charge-couple device.” Answers.com.