In order to understand infrared, it is important to understand something about light. The human eye can detect only a tiny part of the electromagnetic spectrum, called visible light. But there are other forms of light around us such as ultraviolet and infrared. Infrared (IR) light is also a very small part of the entire electromagnetic spectrum and requires a specific device or technology to see it with our eyes.

Infrared light can be split into three categories; near-infrared (near-IR), mid-infrared (mid-IR) and thermal-infrared (thermal-IR). The key difference between thermal-IR and the other two is that thermal-IR is emitted by an object instead of reflected off it. Infrared imaging works two different ways depending on the device or technology used; image enhancement and thermal imaging.

Image enhancement is what most people think of when you talk about night vision. This technology works by collecting tiny amounts of visible light including the lower portion of the infrared light spectrum. This light would be undetectable to our eyes before it is amplified through the night vision device.

Thermal imaging- This technology works by capturing the upper portion of the infrared light spectrum which is emitted as heat by objects. Hot objects such as body heat emit more of this light than cooler objects like trees or buildings. Thermal imaging devices capture this heat and transfer it into an image on a monitor. When viewed in a gray scale, hotter things appear white and cooler things appear black.

[1] Front Lens; [2] Photocathode;[3] Microchannel Plate; [4] High Voltage Power Supply; [5] PhosphorScreen; [6] Eyepiece; [7] Image Intensifier

The objective lens (1) of a night vision device collects light (visible and IR) that can’t be seen with the naked eye and focuses it on the image intensifier (7). The power supply (4) for the image-intensifier tube receives power from two "AA" batteries. Inside the image intensifier a photocathode (2) absorbs this light energy and converts it to electrons. These electrons are then drawn toward a phosphor screen (5). In 2nd and 3rd generation intensifiers the electrons first pass through a microchannel plate (3) that further multiplies them thousands of times. When this highly intensified electron image strikes the phosphor screen (5), it causes the screen to emit visible light. Since the phosphor screen emits this light in exactly the same pattern and contrast as collected by the objective lens, the bright night time image seen through the eyepiece (6) corresponds precisely to the observed scene. These phosphors create the green image on the screen that has come to characterize night vision.

Generation 1

Typically uses an S-20 photocathode and electron acceleration to achieve gain. Gen 1 devices perform best when ambient light (moonlight or starlight) or sufficient IR illumination is available. Geometric distortion (fish-eye effect) is inherent in all Gen 1 devices. Life span of a Gen 1 tube (image intensifier) is approximately 1500 hours of continuous operation.

Generation 2

Usually uses an S-25 (extended red of the electromagnetic spectrum) photocathode plus a microchannel plate to achieve gain. Gen 2 devices provide than better-satisfactory performance at low light levels and exhibit very low distortion. Life span of a Gen 2 tube is approximately 2500-3000 hours of continuous operation.

Generation 3

The most advanced level of night vision technology, Gen 3 uses gallium-arsenide for the photocathode near infrared region of the electromagnetic spectrum) and a microchannel plate for gain. The microchannel plate is also coated with an ion barrier film to prolong tube life. Gen 3 provides very good-to-excellent performance in extreme low light levels. Recent Military Specification quality tubes have no perceptible distortion. Life span of a Gen 3 tube is 10,000+ hours of continuous operation.

At the present US Armed forces are issued Night Vision Devices with expanded sensitivities in the deep IR range. On a limited basis, these technologies are beginning to become available commercially for civilians. JAGER PRO, LLC has access to this equipment to introduce infrared technology into the hog control and hunting industry.

NOTE: Manufacturer data sheets which guarantee a minimum resolution of 64 lp/mm are included with JAGER PRO night vision devices configured with Gen 3 US SELECT "A" image intensifiers.

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). While high quality Gen 3 Image Intensifiers can achieve tube resolution in the 64 to 72 lp/mm range, overall system performance can be dramatically degraded by use of poor quality optics. JAGER PRO, LLC integrates the highest quality optics in its products to insure optimum performance.

IR Illumination

Regardless of generation all image intensifiers require some light to function. In situations where ambient light is insufficient, infrared (IR) illuminators facilitate night operations by providing an independent source of light. Since IR illuminators operate in near infrared range of 700 to 900 nanometers (nm), they are invisible to the naked eye.

Signal-to-Noise Ratio (SNR)

The ratio of light signal to perceived noise reaching the eye. An image tube’s SNR determines its resolution capability. Therefore, the higher the SNR, the better a tube is able to resolve objects with good contrast under low light conditions. The best single indicator of an image intensifier’s performance.

Black Spots

Cosmetic blemishes in the image intensifier which do not affect the performance or reliability of a night vision device. Some number of varying sizes is inherent in the manufacturing process.

Users have difficult choices to make among Generations of technology (Gen 1, Gen 2 or Gen 3) or among competing options within a given generation. Evaluation of night vision equipment usually revolves around four major areas of consideration:

Performance:

Clarity of a night vision device image under varying light conditions. Performance is a product of image intensifier photosensitivity, signal-to-noise ratio, system gain and resolution.

Human Factors:

Issues such as ease of operation, size, weight, technique of employment and use of necessary or optional accessories are critical.

Suitability:

Selecting the right night vision device for the right application. Important considerations are versatility, adaptability, field of view, magnification, weather resistance and ruggedness of the system.

Overall Cost of Ownership:

Users should consider such issues as optional accessories, expected tube life, warranty coverage, ease and likelihood of repair, susceptibility to bright light exposure and availability of batteries.

Contact JAGER PRO for assistance in evaluating night vision equipment.