222 PI-MAX/PI-MAX2 System Manual Version 5.F
Intensifier Types:
Gen I: Obsolete. Developed in the early 1960's. Used electrostatic focusing and
electron acceleration to achieve signal gains up to 150. These intensifiers could detect
images under ambient light intensity as low as .01 lux. Problems included image
distortion, short-lived components, and large size.
GenII: Introduced in the late 1960's and early 1970's. Incorporated MCPs with
resulting signal gain improvement (up to 20,000). Not as efficient as Gen I
intensifiers however have high resolution, no image distortion, and are small. Can
detect images under ambient light intensity as low as .001 lux.
Super Gen II: Gen II devices that employ novel photocathodes with extended
spectral range or high QE in a particular wavelength.
Gen III: Gen II technology with GaAs added as the photocathode coating. Highly
sensitive in the NIR region above 800 nm but relatively insensitive in the blue/green
region. Utilizes high-resolution MCPs (6 µm diameter channels) and ion-barrier
films. 2-3 orders of magnitude more sensitive to light than Gen II devices. Can detect
images under ambient light intensify as low as .0001 lux.
Gen IV: Introduced in 1999. No ion barrier film and exhibit enhanced QE, SNR,
dynamic range, and high-light-level resolution.
Internal Trigger mode: PTG or DG535 mode where gate pulses are delayed from
trigger pulses produced by an internal timer. Delays are programmable in increments
of 10 nsec instead of 1 nsec as they are in External Trigger mode.
Kinetics Mode: An optional PI-MAX mode of operation in which most of the CCD is
mechanically or optically masked, leaving a small section (i.e., window) open to
light. A series of images is rapidly acquired during a single data acquisition period by
repeatedly gating the intensifier. The image is collected in the window while the
intensifier is gated on, and after it is gated off, the image is shifted on the array to
clear the window for the next image. After the entire series is collected, the CCD is
readout. Kinetics mode takes advantage of the fact that shifting on the array is much
faster than performing a readout.
lp/mm: line pairs per millimeter. A measure of resolution based on the ability of the
imaging system to differentiate between two parallel lines. The higher the value, the
finer the resolution.
MCP: MicroChannel Plate. Composed of cylindrical channels through which electrons
from the photocathode travel and generate additional electrons, resulting in electron
gain. At the output of the MCP is a phosphor-coated fluorescent screen that converts
the electrons to photons that subsequently strike the CCD array and generate charge
in the array pixels.
MCP Bracket Pulsing: Available for PI-MAX cameras with Gen II intensifiers. This
technique enhances the intensifier's on/off ratio in UV measurements by
automatically adjusting the on/off switching of the MCP to bracket the photocathode
gate pulse. By switching off the MCP, unwanted UV signal that strikes the
photocathode (even though gated off) is prevented from passing through the MCP to
integrate on the CCD array.
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