Charged Coupled Device

Contents

Introduction

Readout Process

Image Scanning

Image Generation

Final Procedure

Aspects of CCD Behavior

Advantages

Disadvantages

Applications

Introduction

• A Charge Coupled Device (CCD) is a highly sensitive photon detector.

• CCDs are dynamic devices that move charge along a predetermined paths under control of clock pulses.

How CCD is clocked out?

• The upper section shows charge being collected under one of the electrodes. To transfer the charge out of the CCD, a new potential well can be created by holding IØ3 high, the charge is now shared between IØ2 and IØ3 (section 2).

• If IØ2 is now taken low, the charge will be fully transferred under electrode IØ3 (section 3).

• To continue clocking out the CCD, taking IØ1 high and then taking IØ3 low will ensure that the charge cloud now drifts across under the IØ1 electrodes.

• As this process is continued, the charge cloud will progress either down the column, or across the row, depending upon the orientation of the electrodes.

Image Scanning

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.

Image Generation

Final Procedure

• The final process on the CCD is the reading of each pixel so that the size of the associated charge cloud can be measured.

• The CCD is an analogue device, and the analogue voltage values are converted into a digital form by the camera electronics.

Aspects of CCD Behavior

1. Quantum Efficiency

2. Wavelength Range

3. Dynamic Range

4. Linearity

5. Noise

6. Power

Advantages

• Relative simple

• More sensitive than photographic film

• Cheaper to replace if failure

• Modularity-easy upgrades

• Detector costs simple

• No chemical processing is needed

Disadvantages

• Demagnification is a major issue

• Vary with application

• Very expensive

• Relates to potentially lower DQE

Applications

• Astronomical Imaging

• Infrared Detection and imaging

• Signal Processing

• Digital Photography

• Medical Fluoroscopy

CCD Chip

References http://www.mssl.ucl.ac.uk/www_detector/ccdgroup/optheor

y/ccdoperation.html

http://www.microscopyu.com/articles/digitalimaging/ccdintro.html

http://micro.magnet.fsu.edu/primer/digitalimaging/concepts/threephase.html

http://www.sciencedirect.com/science/article/pii/0026271476906065

https://www.noao.edu/meetings/gdw/files/Howell_CCDs.pdf

http://www.science20.com/mei/blog/charge_coupled_device_ccd

Thank you