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2 Cascade User Manual
Technology
Introduction
The principal difference between a charge-multiplying CCD and a traditional CCD
is the presence of an extended serial register in the new device (see
Figure 1).
Electrons are accelerated from pixel to pixel in the extended portion of the serial
register (also referred to as a multiplication register) by applying higher-than-typical
CCD clock voltages. This causes secondary electrons to be generated in the silicon
by impact ionization. The degree of multiplication gain is controlled by increasing or
decreasing the clock voltages for this register (gain is exponentially proportional to
the voltage). Although the probability of generating secondary electrons is fairly low
(typically 0.01 per stage), over the large number of stages of a typical multiplication
register, the total gain can be quite high.
This technology combines the ease of use and robustness of a traditional CCD
with the gain capabilities of an intensified CCD in a single device. The
combination of this technology with frame-transfer readout makes the Cascade
cameras excellent choices for experiments where fast framing and low light
sensitivity are required.
Normal Voltage Clock
Standard Serial Register
Frame-transfer Area
Sensor Area
High Voltage Clock
Readout
Amplifier
Output or Sensor Node
Extended Multiplication Register
Readout
Amplifier
Output or Sensor Node
Port #2 (non-multiplication)
For standard, high dynamic range
applications. Available only for
Cascade:512F and Cascade:512B.
Port #1 (multiplication)
For high speed, low light level
applications.
Cascade CCD
Normal Voltage Clock
Standard
Serial Register
Output or
Sensor Node
Frame-transfer Area
Sensor Area
Traditional CCD
Readout
Amplifier
Figure 1. Comparison of Traditional CCD and Cascade CCD Array Structures
Cascade:512F and 512B also offer a non-multiplication readout similar to the one
available in traditional CCD cameras. This makes these more versatile cameras
that can be used for standard imaging applications requiring higher dynamic
range.
System
Components
In addition to the components shown below, the Cascade package also includes
PVCAM
® drivers and QED Capture
™
software.
Camera (with Test Lens) and DATA Cable