7
1.4.1.4 Optional 1.8X Extender
The optional 1.8X Extender (available in the SeaFLIR II-C) allows the IR
zoom lens to be increased to 45 through 450mm. The IR still retains the
10:1 zoom capability. Performance characteristics of the IR camera with
1.8X Extender are listed in Table 1-3.
Table 1-3. Infrared Camera - With 1.8X Extender
Parameter Capability
Sensor 320 x 240 pixel InSb FPA
Operating Wavelength 3.4 – 5.0μm
Zoom capability 10x continuous zoom (up to 18x total)
Nominal Field of View (FOV)
1.2 (H) x 0.9 (V) Narrow
12.1 (H) x 9.1 (V) Wide
Effective Focal Length 45mm to 450mm, f/4
1.4.1.5 IR FPA Cooling System
The IR FPA is cryogenically cooled to be sensitive in the 3.4 – 5.0μm
spectral bands. The FPA must be kept at -196C (77°K). A small
internal cooler in the SGA compresses helium gas and allows it to
expand through a specially designed regenerator to achieve cryogenic
temperatures. The cooler is turned on when the system is initially placed
in Standby or ON. When the HCU Power switch is set to Standby or ON
position, it takes 8 to 10 minutes for the cooler to reach cool-down
temperature. Cool-down time is affected by helium gas pressure and the
presence of contaminants (usually from the compressor lubricant). Cool-
down time will increase with use and age of the system. The cooler
needs to be serviced when cool-down time takes 15 minutes or more.
The cooler has a predicted mean time between failures (MTBF) of 1,881
hours under typical ambient temperatures.
1.4.1.6 CCD Camera
The color CCD camera; is used to view objects during daytime, or when
the scene is otherwise illuminated. The camera image is displayed on
the same monitor as the IR image and is fitted with a continuous zoom
lens with a zoom range of 18:1. The CCD camera is selected using the
CCD-IR switch. The CCD Camera characteristics are listed in Table 1-4.
The digital zoom is automatically turned on at the telephoto end of the
18x optical zoom range with a progressive effect from 1 to 4, giving a
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