Thermal Imaging & Night Vision Systems
MSS Defence provides a decision analysis for thermal imaging and night vision systems for medium and long range observation It provides decision support for deciding which night vision or thermal imaging products are the most effective and economic for various hand-held uses. This example focuses on 2 types of use: short range (<300 meters) and long range (>1.000 meters).
Night vision equipment is used when there is insufficient visible light to see. Night vision devices operate through a process involving the conversion of ambient light photons into electrons that are then amplified by a chemical and electrical process and then converted back into visible light. Infrared light sources can be used to augment the available ambient light for conversion by night vision devices, increasing in-the-dark visibility without actually using a visible light source.
Thermal imaging cameras detect radiation in the infrared range of the electromagnetic spectrum and produce images of that radiation. Since infrared radiation is emitted by all objects above absolute zero thermography makes it possible to see one’s environment with or without visible illumination.
All weather capability
Ease of use
Both technologies are limited by resolution. Or better, the image is “pixalized”. The longer the observation range, the lesser pixels will be distributed over the target.
This pixalization is defined by the sensor pixel density in combination with the lens magnification. With night vision the pixel density is defined by the resolution of the image intensifier tube (ITT). With thermal imaging this is defined by the pixel density of the thermal sensor.
Generally speaking night vision images are better for identification because they intensify existing light and produce a much more detailed picture with various shades of light and dark. Thermal imaging images are more black and white and provide lesser detail but are more suitable for detecting people because contrast between are more visible.
Let’s compare 3 commonly used systems
- 8×50 night vision binoculars with XXX tube
- Thermal imaging binoculars with 100mm lens and 384×288 sensor
- Thermal imaging binoculars with 100mm lens and 640×480 sensor
How many pixels on target for observation purpose:
- For detection you need to have 3 pixels on target.
- For recognition you need to have 8 pixels on target.
- For identification you need to have 15 pixels on target.
- For actionable intelligence you need to have 20 pixels on target.*
The pixel width at a distance of 1.000 meters of the systems is:
- 8×50 night vision binoculars with XXX tube à 0,56 meters
- Thermal imaging binoculars with 100mm lens and 384×288 sensor à 0,32 meters
- Thermal imaging binoculars with 100mm lens and 640×480 sensor à 0,19 meters
* Actionable intelligence, observation of a person, this image shows approximately 20 pixels on target:
Comparison of the three systems:
8×50 night vision binoculars with XXX tube:
With this system, when observing a person of 1,8 x 0,5 meters, you have approximately 3 pixels on target, which is sufficient for detection only.
Thermal imaging binoculars with 100mm lens and 384×288 sensor:
With this system, when observing a person of 1,8 x 0,5 meters, you have approximately 9 pixels on target, which is sufficient for detection and recognition.
Thermal imaging binoculars with 100mm lens and 640×480 sensor:
With this system, when observing a person of 1,8 x 0,5 meters, you have approximately 22 pixels on target, which is sufficient for detection, recognition, identification and actionable intelligence.
The picture is more or less comparable with the picture above.
Decision support comparison table. To decide on which system to use on the 1.000 and 300 meter distances we present 2 tables with multiple systems.
All weather capability
Night vision devices need a minimum of ambient light in order to perform. These devices amplify existing light. In normal daylight conditions visibility can be limited by a number of factors like smoke or fog. The same will happen when using night vision devices.
Thermal imaging devices are not using light but register differences in heat radiation. These devices need no light at all. When observing objects with no heat differences, for example a car parked against a “cold” building, as there are no radiation differences, there will be no distinctive picture. The perception is that thermal imaging devices will see through smoke and fog. This is not always true, results may vary and depend on factors like weather condition, wind, humidity, air pressure, air temperature and object temperature.
Ease of use
Night vision devices are easy to use. These have in most cases only an “on/off” button for operation. These devices have a fixed magnification and only need to manually focused on a given distance. These devices have maximum time before failure of 10.000-15.000 hours. The effectiveness of the tubes will degenerate after being exposed to bright lights. So called “autogated night vision devices” are not affected by exposure to bright lights, these devices more or less adjust.
Thermal imaging devices are a bit more complicated. Although anyone that can operate a video camera should be able to operate such a device. These devices need to be manually focussed although there are products that have automatic focus. These devices need to be powered on by a push button. Magnification (electronic zoom) can be selected by a push button. And most devices have a calibration button. Most devices have a video or picture capture option that can be operated by a push button as well. And most devices have a “menu option” with which selections can be made (brightness, black/white hot, contrast etcetera). The most sensitive part of a thermal camera is the (germanium) lens. The lens should be handled with care. The lens can be damaged by looking into extremely bright light sources (like the sun).
Most of the thermal imaging and night vision devices are completely sealed to IP67 standards and are not maintainable by the operator or end-user. The units only need to be cleaned once in a while. Of course, as there are sensitive electronics and optics in each unit, the units should be handled with care.
It’s impossible to make high-end optical products with a minimum of weight. High quality “glass” optics have a certain weight. A very light weight optical product generally does not have the quality of a light weight one. The higher the specifications, the more optics are integrated and the higher the weight.
In the following table you can find the indicative costs of the various products.
Now we will perform a “layman term” analysis for decision support. What is the best performance cost ratio or “what is the best value for money”? For both distances (1.000 meters and 300 meters) we will compare the various systems that meet the recognition criterion. Performance will be measured by the number of pixels on target. The costs will be measured with USD. Or: “what are the costs per pixel on target?”
Distance of 1.000 meters:
The most valuable system is a bit “overspecified”, the yellow and green marked systems meet the recognition criterion whilst the 3 last systems are underspecified.
The yellow and green marked systems are the systems to decide from.
When the criterion weight is important then the green marked system is the system of choice.
Distance of 300 meters:
The yellow marked systems meet the recognition criterion. All other systems are more or less overspecified.