Kodak's Bayer filter made one monochrome sensor see color

Early color video cameras often split light into separate sensors or used sequential filters, adding optics, alignment problems and cost. In 1975 Kodak researcher Bryce Bayer patented a simpler answer: put a color mosaic directly on top of one solid-state sensor.

The trick was not a symmetric RGB grid. Bayer's patent made luminance-dominant elements occur at every other position, implemented as the now-familiar 2x2 Bayer pattern with two green samples for every red and blue sample.

That bias matched human perception: green carries much of perceived brightness and edge detail. Camera software could demosaic the sparse color samples into full RGB images, while manufacturers kept the camera rugged, compact and cheap.

Sample luminance twice as often as color

It solved the color-registration problem by keeping all color samples on one imaging plane.

It spent twice as many sites on green, where the eye extracts most image sharpness.

The pattern was regular enough for simple reconstruction algorithms and sensor manufacturing.

It turned color capture from an optical alignment problem into a repeatable filter-layout problem.

When a signal has unequal perceptual value, spend scarce samples on the part users notice most and reconstruct the rest computationally.

The Bayer color filter array became the default architecture for digital cameras and camera phones. Later alternatives such as Foveon and custom phone mosaics challenged pieces of it, but the two-green 2x2 layout remains the normal starting point for single-sensor color imaging.