What is a Bayer Filter?
A Bayer filter is an array of color filters which is used to alternately arrange the colors red, green and blue (RGB) in a grid. The Bayer filter is commonly used on digital photosensors mainly for the purpose of producing a colored image. Unique to this type of filter is its ability to filter only specific colors such as red, blue and green. These color sensors are used in certain devices or gadgets that capture or produce colored images. Examples of devices that make use of the Bayer filter are picture scanners, video camera recorders and digital cameras.
The Creation of the Bayer Filter
When filtering colors, the green filter is doubled in a Bayer filter mainly because of human physiological considerations. In normal eye physiology, the retina of the eye contains a particular group of cells called cones which are responsible for the perception of color. It has been found out that the human eye structure, specifically the cone, is sensitive to green light in the visual spectrum. With this information in mind, Dr. Bryce E. Bayer, who works at Eastman Kodak, invented the Bayer Filter in 1976 in such a way that half of the filter pattern is solely for green while red and blue gets one-fourth each. Doubling green pixels in a Bayer filter produces an image that is much clearer and tends to project finer details of the image.
What is the Function of a Bayer Filter in a Digital Camera?
In digital cameras, the red, green and blue elements of the photosensors, simply called pixels, becomes the raw output of the Bayer filter. The final image could not be yet seen automatically since a pixel contains only one out of the three colors. In order to get an image in its full and complete color, different demosaicing algorithms are used to fill in the actual colors of the image. These millions of tiny pixels undergo interpolation, turning them into image pixels, which may then produce a complete image. The user has the freedom to choose from different varieties of software algorithms in order to come up with the final output or image.
Bayer Filter vs. Foveon X3 Sensor
Bayer filters arrange the colors either in Red, Green, Green, Blue (RGGB) or Green, Red, Green, Blue patterns (GRGB) in a square, mosaic grid. There are also other available filter alternatives which similarly require demosaicing and they come in the in the forms of the Red, Green, Blue, Emerald (RGBE) filter as well as the Cyan, Yellow, Green, Magenta (CYGM) filter. Another option is the use of the Foveon X3 Sensor. This type of sensor layers the colors Red, Green and Blue in a vertical pattern while the Bayer filter layers it in mosaic form. Although the Foveon X3 Sensor does not require demosaicing, it is more expensive than Bayer filters.