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What Are the Differences Between Night Vision and Thermal Imaging

night vision vs thermal imaging

So you want the most effective gadget to see through the darkness?

In that case, the comparison between thermal imaging vs night vision is the first that you need to check out. 

While both these technologies are efficient to see in the dark, they differ significantly in terms of technology, capability, and price. And as expected, each has its own set of pros and cons.

Besides, when you want a military-grade tech, you need to consider the price too.

That’s why having a clear idea about this technology is necessary before you make a choice.

This is an in-depth discussion on night vision vs thermal imaging, to help you make the right decision.

Let’s get down to business.

What is Night Vision Technology?

Surely you have seen spy movies where night vision is being used to detect enemies on moonless nights.

Basically, night vision devices were developed for the army and used in World War II by the German army. More extensive use was during the Vietnam War. The various categories of night vision devices were classified into three generations based on the advancement in technology.

Generation 1 Devices

These are the oldest night vision technology that was introduced in the 1950s. They are suited for shorter ranges in half moon conditions and are rated for around 1000 hours of use. Their tubes usually contain some imperfections and are best used with infrared Illuminators.

Generation 2 Devices

These devices are more advanced and have a life expectancy between 2500 to 5000 hours. These devices had Micro-Channel Plate (MCP) in them that resulted in clearer and brighter images in dark conditions. However, all 2nd generation devices aren’t rated the same and can be classified from entry-level to high-end.

Generation 3 Devices

They offer the best image quality and performance. Also, they are the priciest. The life expectancy of these tubes is usually between 7500 to 10000 hours. They are mostly used by the military and law enforcement.

The question is- how do they work?

Night vision mostly works through the process of ambient light amplification. It can be classified into two categories- optoelectronic image enhancement and digital image enhancement.

optoelectronic image enhancement

Optoelectronic Image Enhancement

Older versions of night vision equipment use an optical lens and a special electronic vacuum tube. The device captures and amplifies the ambient visible and infrared light reflected from the surroundings.

An objective lens captures the visible light and some wavelengths from the near-infrared spectrum. The captured photons pass into an image intensifier tube powered by small AA or N-cell batteries.

The first lens in the system, called the objective lens, captures the dim visible light reflected from the subject and some light from the low end of the infrared spectrum. This light, like all light, is comprised of small particles called photons.

Here, the photons are converted into electrons which flow into the microchannel plate. This plate acts as a photomultiplier and multiplies the number of electrons, resulting in the amplification of the electric signal. 

One more thing…

Once the photons are converted into electrons, all color information is lost and we get black and white images.

Finally, the electrons hit a phosphor-coated screen generating a green image that’s much brighter. The user views the image through an ocular lens that can be used for focusing or magnifying.

Why is the image green in color?

Well, the green phosphor screen is used for the luminance effect as green is the best color the human eye can distinguish in the dark.

Digital Image Enhancement

With digital technology, night vision devices have become smaller and lighter. As a result, they have become more versatile. Moreover, images can be viewed from a remote location or stored on an SD card with these devices.

In this case, the ambient light entering the objective lens is converted into a digital signal through a complementary metal-oxide-semiconductor (CMOS) sensor. This signal is enhanced and magnified and finally viewed on an LCD screen.

Actually, the quality of the final image depends on the size of the CMOS sensor. The high-end devices of the current generation can even produce color images instead of the traditional images with an eerie green glow.

night vision light enhanced photography showing us army usa sergeant first f9d0fc
Night vision light enhanced photography showing US Army (USA) Sergeant First Class (SFC) Arnold Stone, 1st Platoon, Bravo Company, 2nd Battalion, 108th New York Army National Guard (NYARNG), wearing his AN/PSV-7D Night Vision goggles while using a hand-held radio to call for a situation report. Soldiers assigned to his Unit are conducting a search to detain suspected insurgents involved in attacks against coalition and Iraqi forces, near Balad Air Base (AB), Iraq (IRQ), during Operation TIGER WOLVERINE, conducted in support of Operation IRAQI FREEDOM.

Best uses of Night vision

Night vision has been used extensively in various fields due to its versatility and durability. Here are a few common uses.

  • Night vision rifle scopes are used for detecting game.
  • They are used in night vision goggles by the military and police to gain a tactical advantage. They are also used in tanks and helicopters.
  • They are used in CCTV cameras for security and surveillance
  • Other uses are for wildlife detection and night time navigation

What is Thermal imaging?

A big difference between thermal imaging vs night vision is the difference in technology.

But before taking a look at the technology used for thermal imaging let’s take a quick look at the spectrum of infrared light. 

The Electromagnetic Spectrum

The electromagnetic waves span a wide band ranging from long-wavelength radio waves to very short wavelength gamma rays.

The infrared spectrum lies just beside the visible light spectrum. The infrared waveband can be further classified into four categories.

  • Short-wave infrared, wavelengths between 1.4–3 μm
  • Mid-wave infrared (MWIR), wavelengths between 3–8 μm
  • Long-wave infrared (LWIR), wavelengths between 8–15 μm
  • Far-wave infrared (FWIR), wavelengths between 15–1000 μm

Thermal cameras usually make use of the LWIR category.

How Thermal Imaging Works?

thermal imaging

These devices use infrared scanners that detect heat signatures released by all objects and their surroundings. That allows thermal devices to capture images in complete darkness, without needing any ambient light.

Next, these heat signatures are converted into an image where higher temperatures are marked with a brighter color.

How does that function?

A special lens focuses the incoming infrared light which gets scanned by infrared-detector elements or a sensor array. The thousands of pixels in the sensor convert the infrared energy into a color map or a thermogram.

Then the signal-processing unit uses the information on the thermogram and converts them into electric impulses. Thus the data for display is generated from the captured information. Finally, each temperature is assigned a specific color and is generated as an image on the screen.

The final output and the color range will depend on the intensity of the infrared radiation and the device’s sensitivity. 

Now, the device performance depends on three main factors

Temperature Sensitivity

This factor is a measure of the image quality when you increase the contrast levels. It varies with the object temperature. A camera with better sensitivity will detect better in an environment with low temperatures with poor thermal contrast. It is expressed in terms of milli-Kelvin (mK). 

The cheaper models come with 100 mK sensitivity, whereas the high-end thermal cameras offer around 50mK sensitivity. So you need to pick a camera that’ll be suitable for the temperature range you need.

NETD (Noise Equivalent Temperature Difference)

This is the capability of the thermal sensor to distinguish between tiny temperature differences. The lower the value of NETD of a device, the higher the thermal sensitivity and the image quality. NETD depends on the internal stabilization of the camera and also on the f-stop of the lens.

Resolution

Since thermal technology is more expensive, the resolution of thermal cameras is lower than standard digital cameras. The higher the resolution, the better is the image quality. There are three common resolution types.

  • Low Resolution – 160×120 (19,600 pixels)
  • Medium Resolution – 320×240 (76,800 pixels) 
  • High Resolution – 640×480 (307,200 pixels)
thermal resolution

Best uses of Thermal Imaging

One major use of thermal imaging is in the military, to detect enemy positions and resources on the ground. Let’s take a look at some of the other common uses.

  • It’s used for transport navigation during the night, especially in maritime navigation.
  • No-contact inspection of electrical distribution equipment and electrical circuits is carried out by thermal imaging. It can detect blocked cooling passages and loose contact easily.
  • Plumbers and power line technicians use thermal images for maintenance and solving heat leakage issues.
  • They are used in mechanical equipment and systems to detect leaks, clogs, and overheating issues.
  • Non-destructive testing of various materials, including buildings. Testing of composite materials for the aerospace and automotive industry is also done by using thermography.
  • It’s used in the field of medicine to detect cancer cells, locate the source of arthritis, and issues related to circulation.
  • Firefighters and law enforcement use thermal imaging to see through smoke and fog.
  • Handheld thermal imagers are also used for fun and entertainment.

Thermal vs Night Vision: Pros and Cons

Thermal Imaging

thermal imaging pro

Pros

  1. Thermal imaging can be used in a wide range of light conditions. You can use it on a bright day or a moonless night without impacting the image quality. The contrast level of the image isn’t affected by weather conditions or smoke. 
  2. A thermal camera is simple and effective as it doesn’t require any additional lighting. Also, the overall viewing range is longer which makes them ideal for motion detection. They can also detect the footprints of a person or animal. That makes them very effective for surveillance and tracking.
  3. They can detect human presence without detecting the identity. So they are ideal for zones with high privacy-protection standards. Moreover, they can clearly detect between animals and humans, resulting in fewer false alarms.
  4. The inspection method is extremely safe for equipment that’s very hot and dangerous to touch. Inspection of difficult-to-reach objects like power lines is also possible.
  5. Thermal cameras require minimum maintenance. So they are a value-for-money investment in the long run.

Cons

  1. A big disadvantage of thermal cameras is they are costly. The reason is, the components of the optics and the detecting system are expensive. This makes them a higher initial investment for users.
  2. Thermal images can’t be captured through materials like water or glass. Water blocks most infrared waves while glass reflects them. They can’t see through concrete walls either.
  3. Image interpretation is difficult for an object with erratic temperature changes or surroundings with differing emissivities. Extreme cold temperatures can also affect image quality.
  4. The fact that thermal imaging can’t detect a person’s identity makes them unusable in some high-security zones. So the chances of identifying an individual with malicious intentions aren’t there.

Night Vision

Pros

  1. They are very useful for improving nighttime vision for drivers and reduce accidents
  2. Being a less expensive technology it’s an affordable choice for hunters and recreational users.
  3. The image quality is more natural than thermal devices. This makes them better choices for delivering a sharp and clear image.
  4. Digital night vision devices can be used during day and night and offer good durability as well.
  5. A good quality device offers excellent battery life which makes them a dependable choice for outdoor use.
  6. Unlike thermal devices, they can be used to see through glass.

Cons

  1. Night vision can only work when there’s some ambient light present. Many night vision scopes require an additional infrared illuminator to act as a flashlight for providing better images. 
  2. Low-end night vision devices don’t work well in extreme brightness.
  3. These devices can’t detect human or animal presence through trees or bushes. That can be a problem when hunting or driving. They can’t identify camouflage either.
  4. Dusty, foggy, or smoky conditions aren’t suitable for the use of night vision. These conditions will result in poor image quality.
Night Vision

What to Choose for Seeing at Night?

Let me say this straight. Considering all the features, thermal imaging is the best choice when you need a 24-hour imaging option without depending on ambient light.

That said, you can’t rule out night vision as there are many other factors involved as well.

One important factor is your budget. Thermal imaging still is a costly technology while night vision is more affordable. However, it also depends on the features that you want. If you want live-view, built-in wi-fi capabilities, or zoom-in features in a rifle scope, you have to pay more.

Next, you also need to consider the purpose of use. For inspection, detection, and seeing through bushes and crops, thermal is a good choice. However, if you want a detailed and natural image, night vision is a better option.

The other thing is night vision devices are usually more lighter and durable. But many modern thermal devices and equally sturdy and durable.

Night Vision vs Thermal Scopes for Coyote Hunting

When it comes to night vision vs thermal for hunting, there are a few things to consider.

For locating your prey in heavily wooded areas and through thick brush, thermal devices work well. Night vision is best for detecting coyotes in wide-open areas with less foliage. 

However, night vision doesn’t work well when the prey is standing still or through the fog. On the other hand, when you want the image to have more details for proper shot placement, thermal devices aren’t the best option. 

Also, thermal imaging isn’t good for image identification in some cases. For example, distinguishing between a coyote and a domestic dog can be difficult through a thermal device.

Moreover, calibrating a thermal rifle scope needs to be done carefully.

On the whole, night vision works great for coyote hunters on a budget.

FAQs

Will Night Vision pick up infrared?

Absolutely. That’s why they are used with infrared illuminators

What is the difference between infrared and thermal?

As mentioned, most thermal devices work in the long-wavelength IR energy belt. But active IR systems used for illumination work within the short IR energy belt.

Can thermal vision see through walls?

They can detect the heat given out by the wall itself. But you can’t see what is behind as the wall absorbs infrared waves.

Why does thermal imaging work better at night?

The fact is, thermal energy works better in completely dark environments as they detect heat, without depending on ambient light.

Thermal Imaging vs Night Vision: Conclusion

What’s the bottom line?

As you can see, there’s no clear-cut winner when it comes to thermal vs night vision. Both technologies have their advantages and disadvantages. Also, the choice depends on the type of use, environment, and budget.

Thermal imaging is great for a variety of purposes. But even though night vision is an older technology it still has plenty of advantages.

Now that you know all the details about night vision vs thermal vision, it’ll be easier for you to make the right choice.

Time for you to take the next step.

About Kim Goodwin

Kim Goodwin holds a Master's in thermal engineering from the University of Rhode Island. At Thermo Gears, she reviews most equipment that uses thermal imaging technologies.