Teledyne Princeton Instruments PI-MAX 3, System Manual

Page: 240 / 250

240 PI-MAX
®
3 System Manual Issue 2
Gen I Intensifier:
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 0.01 lux. Problems included image distortion,
short-lived components, and large size.
Gen II Intensifier:
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 a
Gen I Intensifier . However has high resolution, no
image distortion, and is small. Can detect images under ambient
light intensity as low as 0.001
lux .
Gen III
Intensifier:
Gen II Intensifier 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

m diameter channels) and
ion-barrier films. 2-3 orders of magnitude more sensitive to light
than
Gen II Intensifier devices. Can detect images under ambient
light intensify as low as 0.0001 lux .
Gen IV
Intensifier:
Introduced in 1999. No ion barrier film and exhibit enhanced QE,
SNR, dynamic range, and high-light-level resolution.
Input Windows:
The intensifier and the CCD array both have input windows.
• MgF2:
High vacuum UV transmission between 100 nm and
200 nm.
• Quartz:
Excellent transmission over 190 nm - 1100 nm.
• Clear glass (BK7):
— Visible
400 nm -700 nm
— NIR
700 nm - 2500 nm)
Anti-Reflection (A/R) coatings may be added to input windows to
reduce signal loss and glare caused by reflection.
Intensifier-CCD
Coupling:
Transmission of the emitted photons is either through a
fiberoptic bundle or with a lens. The drawback to lens coupling is
lower throughput (5% – 10%) and increased stray light in the
camera system. The advantages are that the intensifier can be
removed and the camera can be used as a standard CCD imager
conversely an intensifier can be added to an existing camera.
Fiberoptic coupling results in a throughput of >60%, are capable
of sensitivities approaching single-photoelectron detection, and
have a much better signal-to-noise ratio (SNR) than lens-coupled
devices. Disadvantages are that the fiberoptic bundle is
permanently attached to the CCD array and that the camera must
be operated in a dry, non-vacuum inert environment.