NVG PVS-31 SN: ***78

PVS-31C-MOD Dual-Tube Night Vision Goggles

The PVS-31C is a professional night vision binocular produced by the Canadian company GSCI, which uses Photonis ECHO IIT (image intensifier tubes) and 27mm optics with a clear image and f/1.2 aperture.

Night vision consists of three main parts, the quality of which depends on the overall performance of the device.

1. Image intensifier tube (IIT)
2. Body
3. Optics (lenses)

IMAGE INTENSIFIER TUBE

Image intensifier tube is the most important part of night vision. When choosing, you should be aware that the differences in the specification and performance of individual tubes can differ significantly, so it is necessary to pay attention not only to the manufacturer or generation of the given tube, but also to the specific values that each tube has listed in its datasheet.

The PVS-31C uses a Photonis ECHO Gen2+ tubes.

Photonis is a French manufacturer of image intensifier tubes with 85 years of history, which is generally considered to be the best European IIT manufacturer.

The ECHO Photonis tube is the best-selling high-end IIT generation 2+. ECHO tubes have high performance with a FOM value of 1600 to 2000, fast Auto-Gating, good low-light performance and a good price. The ECHO tubes in this PVS-31C have white phosphor.

When choosing, you should remember that the values between low-end and high-end Gen2+ are very different, while the high-end Gen2+ is comparable in performance to the classic Gen3 tubes at a much lower price. In high-light conditions, Gen2+ tubes are even more efficient, as they have faster auto-gating and thus a lower HALO effect.

For the best assessment of the specific PVS-31C device, here are specific values of the used tubes.

FOM (Figure of Merit): Figure of Merit is simply the tubes Resolution (or line pair per mm) multiplied by it's SNR (Signal to Noise Ratio). FOM=LP/MM * SNR

Resolution: the ability of an image intensifier or night vision system to distinguish between objects close together. Image intensifier resolution is measured in line pairs per millimeter (lp/mm). Typically, the higher the line pair, the better the image resolution.

EBI (Equivalent Background Illumination): is the background noise of the Image Intensifier and mainly comes from the thermal emission of the photocathode. The EBI adds noise speckles to the image. The EBI increases rapidly with temperature and can become a significant source of noise when the IIT is at elevated temperature. Tube manufacturers normally specify EBI at temperature of 21°C.

SNR (Signal-to-Noise Ratio):  A measure of the light signal reaching the eye divided by the perceived noise as seen by the eye. A tube’s SNR determines the low light resolution of the image tube, therefore, the higher the SNR, the better the ability of the tube to resolve objects with good contrast under low-light conditions.

Gain: This is the ratio of brightness of the output of the phosphor screen (what you look at), to the input to the photocathode (what receives the light). it's how many times the light was multiplies before it got to your eyes. The higher the number, the better.

Halo is rings of light that form around concentrated bright light sources when looking through night vision. Halo is typically prevalent with street lights and other similar concentrated light sources. In general, values under 1.0 are ideal, and considered good.

Autogate: autogating is the process of the tubes power supply constantly providing and cutting power to the tube to help protect from high light damage and retain optimal performance of the night vision without blinding the user when exposed to various high light sources. This process happens at high speeds and is constantly working to provide the best image through the tube. This is a very important tube feature to extend the life and performance of your tubes while protecting from high light damage.

BODY

When choosing night vision, you should be aware that many manufacturers do not make any of the night vision parts, they just put the IIT in the already purchased body.

GSCI has been manufacturing custom night vision bodies for over 30 years. GSCI does not make the PVS-31 bodies from plastic, but from high-strength aluminum and brings several features that are not present in the standard PVS-31 bodies.

Adjustable interpupillary distance: each ocular can be swung from side to side to achieve the most comfortable position to match distance between your eyes. The PVS-31 allows to adjust the force that requires to rotate each individual channel to achieve maximum operational convenience.

SFE (Selective Channel Engagement) feature enables to selectively turn off each individual night vision channel when it is swung all the way to the side. It becomes useful when an operator needs to look at distant target through NVG and look with the naked eye at close-range objects. This feature also extends battery life.

Adjusting objective lenses focus: you can adjust focus on each front lens by rotating its focusing ring.

Manual Gain Control is a feature that give the user the ability to manually control the brightness of their system. This is accomplished by rotating a gain knob on the night vision system.

SSF (Stow Safety Feature): allows you to save energy during operation. Moving the device vertically up turns the NVG off, and flipping back to eye level turns the device back on.

The PVS-31C is powered by one AA battery (with AA extender attached) or one CR123 battery (without AA extender) with running time up to 40 hours. Thanks to device's electronics AA or CR123 battery can be inserted any direction (i.e. not observing polarity).

The device has an external power port that allows the NVG to be powered using a USB cable.

LED Indicators:

• Flashing Red LED: IR Illuminator is on. You can be detected by another night vision device.
• Double flashing Red LED: Light overload! The device is exposed to bright light source. After 10 consecutive double flashes, the device shall turn itself off.
• Flashing Yellow LED: Indicates low battery.

The PVS-31 also has the Instant IR-On button located at the front of the device. Press and hold it to temporarily engage IR Illuminator. The purpose is to quickly illuminate the area or send a signal without having to operate the rotary switch button.

OPTICS

The quality of the lenses is also an important parameter, as low-quality optics deteriorate the clarity and brightness, while reducing the overall efficiency of the device. An important parameter is the aperture number, which expresses the ratio of the focal length of the optical system to the diameter of the input lens. The lower the number, the better its brightness.

The PVS-31C uses a 27mm objective lens with an aperture number of f/1.2 and a Field of View (FOV) of 40°.

FEATURES

• ECHO Photonis tube
• High-End Gen 2+
• White phosphor

• Unique GSCI body
• Durable body made of aluminum
• Extra features

• SSF (Stow Safety Feature)
• External power port

• Adjustable Interpupillary distance
• SFE (Selective Channel Engagement)
• Momentary IR-On Button

• Light Overload sensor
• LED indicator

• Manual Gain Control
• Autogated

• IR Illuminator
• Waterproof

STANDARD EQUIPMENT: WHAT’S IN THE BOX

1. Dual-Tube Night Vision Goggles with Dovetail Bracket Installed
2. Rubber Eyecups (2pcs Installed on the device) with Retaining Rings (2pcs)
3. Sacrificial Window (2pcs)
4. Stow Safety Feature (Integrated)
5. AA Battery Extension Adapter (Installed on the device)
6. Rubber Daytime Filter with Training Hole (Installed on the device)
7. Adjustment Kit: Allen Key + Mini-Wrench
8. USB Power Cable
9. Neck Cord
10. Soft Carrying Pouch
11. User Manual
12. 7-Year Warranty with Activation Form
13. Cleaning Kit (3-in-1 Multi-Pen + Cleaning Cloth)

Dimensions: 108 x 105 x 70 mm
Weight: 666 g

ISO 9001:2015 Certified
Manufacturer: GSCI Advanced Photonics, Canada