CCD Primer

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


High Performance Image Intensifiers

High Speed Gating
Gating is probably the most important advantage of the PI·MAX. Gating allows the detection of low light level signals in the presence of interfering light sources of much greater energy by temporal discrimination.

Principle of Operation
The intensifier consists of a photocathode, a microchannel plate, and a phosphor screen. A fraction (called the quantum efficiency, or QE) of the photons incident on the photocathode is converted into electrons. Single photoelectrons are converted into electrons by the microchannel plate (MCP), which acts as a distributed electron multiplier. The electrons released from the MCP then strike the fluorescent screen (phosphor) and cause it to emit far more light than was incident on the photocathode. In the traditional configuration, the voltage between the photocathode and the input of the MCP is used to switch the intensifier on and off. If the photocathode is electrically biased more positively than the MCP, electrons will not enter the MCP and the intensifier is gated off. If the photocathode is negatively biased, electrons will be accelerated toward the MCP and the intensifier is turned on.

MCP bracket pulsing
Another feature that contributes to the PI·MAX extraordinary flexibility is provision for MCP bracket pulsing. Traditionally, intensified detectors discriminated against background signal by gating the photocathode. Although this technique yields very high peak Off/On ratios in the visible, background signal can still prove troublesome in low-duty factor measurements, particularly in the UV region.The PI·MAX allows bracket pulsing of the MCP in addition to the photocathode gating, to gain higher rejection (106:1) in UV measurements.

MCP Gating
The ability to gate the MCP on and off gives rise to an additional technique, known as MCP gating, which addresses the need to have the same QE as that of slow-gate tubes, but with shorter gate widths. The lower resistance of the two sides of the MCP allows the MCP to be gated more quickly than a slow-gate photocathode. This technique gives gate widths of <10 ns (better than slow-gate tubes), but does not compromise the QE of the system.

Photocathode Spectral Range
Princeton Instruments offers a selection of Gen II and Gen III fimless intensifiers, covering the entire visible and NIR spectral region. Gen II intensifiers are available with red enhanced, blue enhanced, and compromise red-blue enhanced photocathodes. Intensifiers with MgF 2 windows are also available with response in the 120-700 nm range. PI selects image intensifiers for minimum noise, negligible corona, highest gain, and longest operational and shelf life. In addition, because of our close relationships with most of the major intensifier manufacturers worldwide, we can usually provide state of the art custom photocathodes. For special requirements contact our office or your representative.

Effective Quantum Efficiency (EQE)
To calculate the effective quantum efficiency of the image intensifier tube the noise factor of the intensifier must be taken into account. GEN II and GEN III filmless intensifier have a typical noise factor of 1.6. If you move the mouse cursor over the QE plot you will see the typical Quantum Efficiency of the selected intensifier.

Gen III filmless intensifiers for high sensitivity
Princeton Instruments offers intensified CCD cameras with generation III GaAsP intensifiers for very high sensitivity.  The intensifiers are fiber optically
coupled to a variety of high resolution CCDs with 512 x 512, 1024 x 1024 and 1024 x 256 formats. The Gen III filmless intensifiers allow greater than 50% QE and sub-nano second gate times (500 nsec). This improved performance is ideal for ultra-fast gated applications such as plasma diagnostics, fluorescence lifetime imaging microscopy and planar laser induced fluorescence.