KB - Thermal Imaging - What you need to know about infrared image size

Question:

What do you need to know about infrared image size. 

Answer:

The infrared resolution of the camera defines the number of pixels in a thermal infrared image in horizontal and vertical direction. 

Usually the resolution of an infrared image is smaller than the resolution of a visual image due to its physical nature and also because of the costs of the infrared sensors,
which may be tens or hundreds times more expensive compared to the sensors used in cameras for visible light like mobile phones or digital cameras.

Typical resolution you will find with thermal cameras are: 120 x 90, 160 x 120, 256 x 192, 320 x 240, 384 x 288, 640 x 480. 

It is necessary to distinguish the resolution provided by the camera detector from the resolution provided by additional image enhancement technologies, like "Super Resolution".

While Super Resolution can provide bigger image size, than the infrared detector size, it is not a 100% replacement of the proper detector size.
Super Resolution only allows to improve existing image by statistically processing multiple images collected by the camera. 
The image received via Super Resolution enhancement will have better look compared to the base image provided by the infrared detector,
but it is mostly improvement in details, and improvement in measurement resolution will be very limited.

Another misconception which may be often observed is related to use of digital zoom. Digital zoom does not allow to get more details from the thermal image and does not increase thermal image resolution.
Digital zoom only allows to zoom into existing details delivered by the infrared detector, for better view or for more precise positioning of measurement tools, like markers on the camera screen.

The infrared resolution of a thermal camera is directly linked to both, how many details you can see in the infrared image, and how small are the details you can distinguish within the infrared image. 

The spatial resolution of a thermal camera, or in other words, what are the small details you can distinguish with your thermal camera at a given distance, is defined by the camera Instantaneous Field of View, or field of view of one pixel.
And this parameter depends not only on the infrared image size, or number of infrared pixels in the image, but also on the field of view provided by the camera lens. 

In this content, the infrared resolution or the infrared image size is not the only parameter, one should pay attention. It should be always considered in connection with the following parameters:

• The application where the camera will be used and this application requires

• The distance, at which the camera will be used

• The field of view provided by the camera lens

You may learn more about how the infrared resolution is connected to other thermal camera parameters, by checking the following knowledge base articles:

• KA - Thermal Imaging - What you need to know about the spatial resolution (IFOV)

• KA - Thermal Imaging - What you need to know about the Field of View

• KA - Thermal Imaging - What you need to know about the operating distance

Below you can find a simple comparison of the part of infrared image depicting several electrical connections in an electrical cabinet, acquired with the cameras with different IR resolution from the same distance.
With the same field of view the thermal camera with a higher infrared resolution allows you to see or distinguish smaller details within the picture.