What is the difference between low light night vision device and infrared thermal imaging device ?

Buyers often ask a question when they buy an infrared thermal imager: how far they can see by infrared thermal imager? This is a particularly important issue.For example, thermal imager can see the sun 146 × 106 km away, but we can't say that the detection range of the thermal imager can reach 146 × 106 km. The technical director of MH technology Group told us a Johnson rule. Let's take a look at how to determine the observation range.

Target detection orObservationRangecan typically be divided into detection range, recognition range and identification range. Each of these ranges is defined by Johnson’s criteria according to which the observation range is directly connected to temperature and spatial resolution. John Johnson, a scientist from the Army Night Vision Laboratory, was a pioneer in 1958, conducting experiments to test observers’ ability to identify targets through analog sensors.

A. Detection range, distinguish an object from the background.

Detection is defined as the discovery of a target in the field of view. The distance where the critical size of an observed object can be fit in two or more pixels of a thermal imaging sensor is called the detection range. Detection only means that the object is visible at a certain distance but does not give any information about its characteristics (i.e. the type of object cannot be determined).

B. Identification range, classify the object class (animal, human, vehicle, boat …)

Recognition is defined as: the target can be classified, which can identify the target is tank, truck or person, etc. The recognition of an object means that the type of object can be defined. This means that observer can discern what is being observed i.e. human, animal, car, etc. It is considered that recognition is possible when the critical size of an object can fit into at least 6 pixels of the sensor.

C. Identification range, describe the object in details (a man with a hat, a deer, a Jeep …)

Identification is defined as: the type and other characteristics of the target can be distinguished, such as distinguishing enemy or foe. From the hunter’s point of view, the most useful range is the identification range. Identification means that the observer can evaluate not only the type of object but also its characteristic features (e.g. wild dear male 1.3 m long and 0.8 m high) .For this condition to happen the critical size of an object should fit in at least 12 pixels of the sensor.

A image: Detection – At several kms, 2 targets are detected out of the background

B image: Recognition - a human is walking along the fence

C  image: Identification – 2 males with trousers and jackets are identified – one is smoking.

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