Frequently Asked Questions
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What is Thermal Imaging?
Technology Overview |
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Light at frequencies below visible red is called infrared. The human eye cannot see infrared frequencies but thermal imaging cameras can. All objects emit infrared energy at ordinary temperatures. The hotter the object, the more infrared energy it emits. |
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The human eye is capable of seeing a small range of frequencies in the Electromagnetic Spectrum that we call visible light. Objects emit visible light only at very high temperatures. |
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How IR Cameras Work |
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Infrared cameras sense infrared energy to See In The Dark. Infrared energy is emitted proportionately to the temperature of an object. As shown in the diagram above, infrared energy from objects in the scene (A) is focused by optics (B) onto an infrared detector (C). The information from the infrared detector is passed to sensor electronics (D) for image processing. The signal processing circuitry translates the infrared detector data into an image that can be viewed on a standard video monitor (E). |
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Advantages |
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See in Complete Darkness |
See Heat and Thermal Energy (e.g.. - People) • See Through Obscurants (Dust, Smoke, etc) |
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Looking Through a Thermal Camera |
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The underlying structure of
this house is visible
in the infrared region.
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Thermal Cameras
allow you to see
through thick smoke.
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With Thermal Cameras
you can see through
the glare of
oncoming headlights.
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Thermal Cameras
provide a dramatic
contrast in a forest.
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With a Thermal Imager
people in water
are clearly visible.
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Solar Loading |
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Thermal Cameras work best at night, because... |
- As the sun shines, objects absorb infrared energy and heat up. At night, these same objects re-radiate the absorbed infrared energy and cool down.IR Cameras see differences in temperature, or thermal contrasts.At some point during the day, a person may blend in with the background because their apparent temperatures are nearly equal.
- Better thermal contrasts usually occur several hours after sunset.
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Image Intensification vs. Thermal Imaging |
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Image Intensification
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Thermal Image
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Image Intensification only magnifies
existing visible light
providing limited applications. |
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Infrared provides a
far richer range of textures
day or night. |
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Thermal Imaging vs i2 |
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Thermal Imager
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I2 Device - Image Intensifier
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- Sees long wave infrared energy or radiant heat emitted by objects.
- Requires a thermal contrast to generate a clear image, two objects of the same temperature and surface finish are difficult to distinguish one from another.
- Does not require or see visible light, and is not affected by shadows or changing light conditions, i.e. no blooming.
- Can see people or objects in dark areas regardless of color, clothing, or shadows. Highlights animate objects in a scene or in foliage.
- Does not provide positive facial recognition.
- Sees through smoke and haze.
- Typically larger and more costly.
- Cannot see through visible glass.
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- Sees visible light that is amplified by a photo cathode tube.
- Requires a visual contrast to generate a clear image, i.e., similarly colored or camouflaged objects are difficult to distinguish one from another.
- Negatively affected by point light sources and shadows. Can bloom or shut down in direct light.
- Difficult to detect camouflaged or still objects. Difficult to find objects in foliage due to low visible contrast.
- Provides positive facial recognition under good conditions.
- Cannot see through smoke and haze.
- Smaller devices and lower cost.
- Sees through visible glass.
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Summary |
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- All objects emit or radiate infrared energy.
- Thermal Imagers detect relative apparent surface temperatures of viewed objects.
- Long wave thermal imagers are passive or non intrusive and do not send out beams or rays. No IR illuminators are required.
- Atmospheric conditions affect the performance of a thermal imager, e.g., clear, rain, fog, snow.
- IR energy is not visible to the human eye and should not be confused with image intensification night vision.
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