Optical Fog-Penetrating Technology

Optical fog-penetrating technology is developed based on the varying properties of light in different wavebands. Natural light consists of light waves with different wavelengths. Light with wavelengths shorter than 390 nm is ultraviolet light, while light longer than 780 nm is infrared light. The visible spectrum for human eyes roughly ranges from 390 nm to 780 nm.

Light of different wavebands features distinct properties due to varying wavelengths. Fog and smoke interfere with visible light imaging. In contrast, infrared light has a longer wavelength and is less affected by aerosols during propagation. It can penetrate fog, mist and smoke of certain concentrations and achieve accurate focusing — this forms the fundamental principle of optical fog penetration.

Those familiar with day-night switchable cameras are no strangers to optical filters. Such cameras are generally equipped with two filters. One filters out light waves outside the visible spectrum during daytime for clearer, brighter imaging. The other works at night to transmit infrared light and enable infrared surveillance after dark.

Professional fog-penetrating lenses integrate highly targeted filters, which precisely capture light of required wavebands. To adapt to specific environmental conditions, multiple filters for different wavebands are often installed for switchover.

Applications of Fog-Penetrating Filters

Generally speaking, cameras paired with fog-penetrating lenses only need basic day-night switching capability for fundamental imaging performance. As indicated by the working principle, optical fog penetration focuses on capturing and accurately focusing near-infrared light of specific wavebands, a task mostly undertaken by the lens itself. Simply put, lens quality determines the overall fog penetration effect. The primary challenge in fog-penetrating lens development lies in optical design.

However, considering the high cost of dedicated fog-penetrating lenses, some camera manufacturers have explored more cost-effective optical fog penetration solutions. Unlike traditional day-night switchable cameras with two filters, these cameras adopt a four-filter configuration, which not only realizes day-night switching, but also brings extra functions:

1. An additional filter selectively blocks light within the 400 nm–600 nm waveband to achieve strong light suppression.
2. A fog-penetrating filter is added to deliver economical optical fog penetration performance.

This mechanical filter assembly can be controlled automatically by the camera or manually switched. This type of filter absorbs visible light while allowing ultraviolet light and part of near-infrared light to pass through.