Viewing Through Fog and Clouds

BRC holds a patent on a unique device and method for seeing through fog and light clouds.  This technique can be applied to any visible imager or video camera that can have its NIR filter replaced with the BRC FogCutterTM filter. Example performance of this device and method are shown below.

This method exploits the optical properties of water by limiting the viewing passband to a water absorption band.  In this way fog droplets absorb rather than scatter the light allowing more distant dimmer objects to be visible.  The limit of the effect is when no light reaches the imager from the objects of interest.  With the addition of machine vision software, the FogCutterTM method essentially doubles the viewing range at whatever density of fog is present. We have fabricated a number of FogCutterTM systems for a variety of applications including an active demonstrator camera system that simultaneously collects images and video showing visible and FogCutterTM performance.

Visible-FogCutterTM Comparison Camera

Most recently we have built a dual-imager video camera to collect side-by-side images in the visible and the FogCutterTM passbands simultaneously. A few sample comparison images are shown here.

This image was taken a little before sunrise. Note the detail at the base of the treeline is more evident in the FogCutterTM image. This is due to the fact that the fog is no longer the brightest source in the image, so, even when the fog is not directly blocking the image, it is driving the automatic gain control of the camera making the dimmer regions of the image too dark to see.
As the sun rises, the fog becomes brighter in the visible image. Within a few minutes after sunrise, the scattered light from the fog completely blocks the view of the far side of the field (compare left side of the visible and FogCutterTM images below).
FogCutterTM image shows a lens flare but distant details can still be seen.