PVS-31A, 2376+ FOM

SPEC KEY:

Hand-Select Night Vision includes actual specs of the tube(s) included in your night vision device as listed on the tube manufacturer's data sheet. The data sheet serves as a certificate of conformance to demonstrate that tubes meet or exceed their quality and performance standards.

For a breakdown of L3Harris' various tube options and associated minimum performance, please see our guide to Minimum Specifications and Spots. Guides discussing specs are available under the "Resources" tab

FOM = Figure of Merit

SNR = Signal to Noise (Numeric)

RES (or CR) = Center Resolution (line pairs / mm)

HALO = Halo (mm)

EBI = Equivalent Background Illumination

Provided images through the tubes are captured on a Hoffman Engineering 126A. The digital imaging process can cause slight color and brightness variations between images. White phosphor tubes appear white to the eye. Images may may not depict all cosmetic details in every lighting evironment. Every night vision device has some degree of peppering or small spots at or below .003" (the smallest countable size depicted on a data sheet).

Q: Why do some pictures look more blue vs. green? Is one better? Also, some appear to be brighter than others. 

A: Color differences are primarily caused by taking digital images of tubes and are not reflective of tube performance. Tube pictures are provided to show spots and cosmetic blemishes.  White phosphor tubes will appear white to the eye - not blue or green, though there can be very slight variation among tubes.

Q: Why do some tubes contain dark spots?

A: Spots are caused by the manufacturing process of night vision intensifier tubes. Spots aren't an indication of performance and exist in nearly every tube (though some tubes may exhibit larger spots than others). Military Spot spec tubes permit countable spots (those larger than .003") in zone 2 and zone 3 (the rings outside of the bullseye on a dart board), whereas aviation spot spec tubes only permit countable spots in zone 3 (outer periphery of the tube, furthest from center).

 L3Harris | Minimum Specifications and Spots

Spots

L3Harris Tubes ending with UM or UA (ex. 18UM vs. 24UA) have differing tolerances for dark spots.

• UM (military) tubes permit spots greater than .003" (diameter) in Zone 2 and 3. Spots greater than .003" are not permitted in Zone 1.

• UA (aviation) tubes limit spots greater than .003" to Zone 3 only. This is L3's strictest spot spec.

• Dark spots less than or equal to .003" don't meet the threshold as a countable spot and are commonly referred to as "peppering".  

To reference the Zone regions, you can refer to the image above which shows a tube photographed on a Hoffman Engineering 126A test set. 

Military Spot Spec:

Despite adding up to 6 total (above), L3 tubes are limited to 4 spots max

Aviation Spot Spec: 

Performance

L3Harris unfilmed tubes are available with various minimum performance levels (18, 20, 22, 24).

The higher the performance series number (i.e. 20 vs. 18), the higher the minimum performance.

This performance series is then combined with a spot spec to identify the tube. For example, the 18 performance series, with unlimited FOM ("U"), and Military ("M") spot spec would be 18UM. 

Tube Model Performance summary:

• Center Resolution: 64 lp/mm minimum
• FOM: 1540 minimum
• Halo: 1.0 maximum
• EBI: 2.5 maximum

• Center Resolution: 64 lp/mm minimum
• FOM: 1792 minimum
• Halo: 1.0 maximum
• EBI: 2.5 maximum

• Center Resolution: 64 lp/mm minimum
• FOM: 1920 minimum
• Halo: 1.0 maximum
• EBI: 2.5 maximum

• Center Resolution: 64 lp/mm minimum
• FOM: 2160 minimum
• Halo: 1.0 maximum
• EBI: 2.5 maximum

• SNR: 36 minimum
• Center Resolution: 64 lp/mm minimum
• FOM: 2304 minimum (implied)
• Halo: 1.0 maximum
• EBI: 2.5 maximum
• Aviation Spot Spec (Spots limited to Zone 3 only)

Other:

• SNR: 33 minimum
• FOM: 2376 minimum
• Center Resolution: 72 lp/mm minimum
• Halo: 0.85 maximum
• EBI: 2.5 maximum
• Military Spot Spec (Spots permitted in Zone 2 and Zone 3)

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