CCD Primer

Binning
Bracket Pulsing
CCD Grading
Cosmic Rays
Dark Current
Deep Depletion CCD
Detection Modes
Dual Capacity Mode
Dual Readout Mode
Dynamic Range
Etaloning in CCDs
eXcelon CCD-EMCCD
UV Extension
Fiber Optics
Flat Fielding
Full Well Capacity
Gain
Image Calibration
Imager Architectures
Image Intensifiers
ITO CCD
Kinetics Mode
Linearity
Matching Resolution
MPP Mode
Noise Sources
On-chip Multiplication Gain
Open Poly CCD
Optical Window
PVCAM
Quantum Efficiency
Readout vs Frame Rate
Reducing Dark Current
Saturation/ Blooming
Signal to Noise Ratio
Spurious Charge
XP Cooling

 

Dynamic Range

Dynamic range refers to intrascene performance (i.e., the ability to quantitatively detect very dim and very bright parts of a single image). Because the smallest measurable intensity varies between applications and experimental conditions, CCD manufacturers have adopted a definition for specifying dynamic range that is independent of how the camera is used. This definition is defined mathematically as:

linear full well (electrons)/read noise (electrons)

and is therefore a dimensionless number. The linear full well is a specific measure of pixel well capacity (see saturation and blooming). With a high-performance CCD camera, the read noise (i.e., the noise associated with a single readout event) is minimized to yield the largest dynamic range possible.

As a specific example, consider a Sony® ICX285, which has a full well capacity of 16,000 electrons. At a typical readout rate of 10 MHz, the read noise is 4.5 e-. The dynamic range of this CCD is therefore 16,000:4.5. In order to take full advantage of this dynamic range, cameras incorporating Sony® ICX285 devices usually utilize a 12-bit A/D converter (4096 gray levels).

To extend dynamic range beyond the 12 bits given in the previous example, a camera with a lower read noise or a CCD or EMCCD with a larger full well capacity is required. Full well capacity is related to pixel size. For instance, the e2v CCD97 EMCCD chip (pixel size 16.0 µm), has a capacity of 200 ke- and a read noise of 6.5 e- rms at 1.25 MHz for the non EM port. The dynamic range is thus 30,000:1.