CCD Selection Guide
the correct CCD for an application requires a knowledge of the wavelength
of the incident photons, the spatial resolution required, the dynamic
range of the scene, the optical connection from the experiment to the
camera, and other experimental details such as experiment time, signal
intensity and trigger issues.
|CCD Size and Type|
Technology delivers cameras with a wide variety of CCD chip sizes.
We supply cameras with CCDs from E2V Technologies, Fairchild Imaging,
Atmel and Kodak. The number of pixels in our cameras typically
ranges from 1024 x 1024 to 2048 x 2048 to 4096 x 4096, but also includes a
wide variety of intermediate and outlying sizes. Depending on the
manufacturer, pixel sizes range from approximately 9 microns up to 24
Most static imaging applications utilize full frame CCDs. These CCDs are available in both front illuminated and back illuminated configurations. Back illuminated devices are used in light starved applications where high detection efficiency (quantum efficiency) is required. They also are used for certain wavelength ranges where the back illumination has higher quantum efficiency for that particular wavelength.
Note that there are other coating options and configurations that can be selected as well. Please discuss your particular need with Retriever Technology.
|Optical Front End|
Retriever Technology provides cameras
with a variety of optical front ends.
Dynamic range indicates how many light
intensity values can be captured in a single scene.
A high dynamic range allows for faint signals to be seen in the
same scene as extremely strong signals.
Typical camera values are:
Well = 120,000 electrons
Noise = 4 electrons
Noise = negligible
gives typical dynamic ranges of = 30,000: 1, or in terms of optical
density = 4.47 OD, which also = 89.5 dB.
Technology has the lowest noise electronics available. Typical
read noise values are 4 electrons at 500 kHz effective Read Rate.
build up thermally generated signal over time. This is called Dark Current, and can be subtracted out
of the image because it is a repeatable phenomenon.
However, there is a noise component in the Dark Current called Dark
Noise, given as:
Current can be greatly reduced by cooling the CCD, typically dropping 50%
for every 5 – 7°C
Read Rate is defined as the speed at which the CCD is read out (clocked). Typical electronic circuitry allows read rates from 20 kHz to 1 MHz. Many CCDs have multiple readout amplifiers (ports), which speed up Read Rate. Total time to read out a CCD is given by:
Time (seconds) = # Pixels / (Read Rate (Hz) * # Ports)