Specifications

Version 1.1 rev Jan 2013
Page 87
iXon Ultra
SECTION 4: HARDWARE
Hardware
4.1 - EMCCD TECHNOLOGY
4.1.1 - What is an Electron Multiplying CCD?
Current trends in photonics are placing unprecedented demands on detector technology to perform at signicantly
greater levels of sensitivity and / or speed. Electron Multiplying Charge Coupled Device (EMCCD) technology has been
designed to respond to this growing need and, in turn, is opening up new avenues of novel experimental design.
EMCCD technology, sometimes known as “on-chip multiplication”, is an innovation rst introduced to the digital
scientic imaging community by Andor Technology in 2000, with the launch of our dedicated, high-end iXon platform of
ultra-sensitive cameras. The EMCCD is an image sensor that is capable of detecting single photon events without an
image intensier (achievable by way of a unique electron multiplying structure built into the chip).
It is readily adjustable in real time through the software, where extremely weak signals may be detected above the read
noise of the camera at any readout speed. This is important, because the traditional problem of combining sensitivity
with speed in standard CCDs is that the two are mutually exclusive, i.e. greater read noise detection limits result from
faster pixel readout.
4.1.2 - Does EMCCD technology eliminate Read Out Noise?
System noise within modern silicon based detectors has two primary sources: dark current noise and read noise. The
higher the noise oor on a detector the less able it is to read out the extremely weak signals associated with ultra low-
light imaging.
With thermoelectric cooling, dark current noise can be reduced to negligible levels. An EMCCD’s ability to multiply weak
signals above the detector’s read noise oor, by applying EM Gain, effectively eliminates read noise at any speed by
reducing it to < 1 e-/p/s.
4.1.3 - How sensitive are EMCCDs?
Two parameters signicantly inuence detector sensitivity, namely Quantum Efciency (QE) and system noise. QE is
a measure of a camera’s ability to capture valuable photons. A high QE results in more photons being converted to
photoelectrons within the EMCCD pixels.
Once converted, the photoelectrons in a given pixel must overcome the detection limit or noise oor of the camera,
which is set by the system noise. EMCCDs deliver superior sensitivity by maximizing QE and minimizing system noise,
through the unique gain control feature. Single photon events are now well within the capabilities of super sensitive
EMCCD technology.