Sierra Olympic Technologies Inc.

Field of View

Which Lens?

In most cases, we have fixed field of view (FOV) lenses.  The Horizontal Field of View (HFOV) is the angle subtended across the horizontal axis of the camera.  In the case of the 320 x 240 cameras, 320 pixels will be imaged across the HFOV.  The wider the FOV, the larger the scene, but the smaller the resolution in angular coverage per pixel.  The same holds true for the 640 x 480 cameras.  Please review the video to see the differences.  With a fixed FOV lens, the only way you can increase the resolution of a particular object you want to see is to get closer to that object.


Size is another issue.  The narrower the FOV, the larger the optic.  Small cameras with small optics will have wide FOV – narrow FOV cameras will have large optics.  Think about a telescope.  The larger the telescope the farther you can see.  It is the same for thermal imaging.


We offer athermalized lenses and manual focus lenses.  An athermalized focus (AF) lens is one which will maintain focus over a wide temperature range.  The lens is either immune to focus shift over temperature, or there are fixtures in the lens that maintain focus over a wide temperature range.  With a manual focus (MF) lens, you will see slight focus shifts as the temperature changes.  This will be apparent at temperature changes of approximately 20 C or more.  You can manually adjust the lens to fix this focus shift, where the athermaized lens does this automatically.  Athermalized lenses are generally larger for a given FOV.