Foveons

Foveons are a type of digital image sensor technology developed by Foveon Inc. Unlike conventional CMOS or CCD sensors that use a single photodiode per pixel to capture light intensity, Foveon sensors employ a unique three-layer structure. Each layer is designed to capture a different primary color: red, green, and blue. The layers are arranged vertically, with the top layer sensitive to blue light, the middle layer to green, and the bottom layer to red. This arrangement is inspired by the structure of the human eye's fovea, which is responsible for sharp central vision.

The light passes through the layers sequentially, with each layer absorbing a specific wavelength. As light penetrates deeper into the silicon, its wavelength changes, allowing for color separation at different depths. This approach eliminates the need for color filters, which are typically used in other sensor designs and can lead to a loss of resolution and color accuracy. The direct capture of RGB data at each pixel location is Foveon's main distinguishing feature.

Sensors based on Foveon technology are known for their potential for high color fidelity and sharpness, often referred to as "true color" capture. Because there are no color filter arrays, aliasing artifacts, which can occur when an image is downsampled or scaled, are generally reduced. However, Foveon sensors have historically faced challenges related to read noise, processing speed, and manufacturing complexity compared to more mainstream sensor technologies. Despite these challenges, Foveon sensors have been used in certain digital cameras, notably by Sigma, where their unique imaging characteristics are valued by photographers seeking specific image quality.