To achieve the vision of ‘Seeing the Depths as Clearly as the Surface’, Voyis is dedicated to creating underwater visuals that eliminate the distortive effects of water. To address the challenge of inconsistent lighting underwater, caused by the absorption of light by water, Voyis imaging systems implement a dual strategy that combines both physical and algorithmic lighting adjustments.
In this continuation of the ‘Color Imaging Series’, Voyis explores how illumination and dynamic range contribute to the advancement of high-quality imaging solutions tailored for various unmanned applications.
understanding the Underwater Imaging Challenge
One of the primary obstacles in underwater imaging is achieving uniform illumination throughout the entire field of view of the camera. This uniformity is essential not only for the aesthetic quality of the image but also for the accurate detection of features across the entire frame, including both the center and the edges. Effective photogrammetry relies on the ability to identify features consistently across the imaging area.
This issue arises from the fact that water absorbs light, and the extent of this absorption varies with distance. Light directed towards the corners of the image must traverse a greater distance through the water, resulting in increased absorption. Consequently, even if the light is evenly distributed, the corners of the image will appear darker.
The accompanying diagram illustrates this concept, showing how light directed to the corners (corner light) travels a longer distance compared to the light illuminating the center (center light).
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Achieving Uniform Illumination and Enhanced Dynamic Range
To tackle the issue of uneven lighting, Voyis imaging systems utilize a dual approach that incorporates both physical and algorithmic corrections. The Nova Recon features LEDs positioned at specific angles, with each side angled outward. This design directs light towards the front and edges of the image, where absorption is most pronounced.This hydrodynamic external lightbar can be mounted on the exterior of an AUV hull at a predetermined distance from the camera module.
Though, it has been observed that this light distribution alone does not achieve perfectly uniform illumination. Therefore, the second component of the strategy involves leveraging dynamic range. Dynamic range refers to the camera’s capability to capture a broad spectrum of light intensities, from very dim to very bright reflections.
Typically, camera images are recorded and displayed with 8-bit brightness levels for each pixel, allowing for 255 intensity levels. In contrast, Voyis employs 12-bit or 16-bit imaging sensors, enabling each pixel to represent 4,096 or 65,536 intensity levels, respectively.
the image comparison below highlights this capability, showing that the darker corners of a raw image can be enhanced without notable quality degradation in its 12-bit format. Conversely, an 8-bit enhancement fails to reveal any features.
An image mosaic integrates these corrected images into a single cohesive visual. The consistent lighting across sequential images ensures that the stitching points are indistinguishable.
Access the complete white paper on Voyis’ website >>
