Bayer filter
A Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, and camcorders to create a color image. The filter pattern is half green, one quarter red and one quarter blue, hence is also called BGGR, RGBG,[1][2] GRBG,[3] or RGGB.[4]
It is named after its inventor,
Explanation
The raw output of Bayer-filter cameras is referred to as a Bayer pattern image. Since each pixel is filtered to record only one of three colors, the data from each pixel cannot fully specify each of the red, green, and blue values on its own. To obtain a full-color image, various demosaicing algorithms can be used to interpolate a set of complete red, green, and blue values for each pixel. These algorithms make use of the surrounding pixels of the corresponding colors to estimate the values for a particular pixel.
Different
Demosaicing
Demosaicing can be performed in different ways. Simple methods interpolate the color value of the pixels of the same color in the neighborhood. For example, once the chip has been exposed to an image, each pixel can be read. A pixel with a green filter provides an exact measurement of the green component. The red and blue components for this pixel are obtained from the neighbors. For a green pixel, two red neighbors can be interpolated to yield the red value, also two blue pixels can be interpolated to yield the blue value.
This simple approach works well in areas with constant color or smooth gradients, but it can cause artifacts such as color bleeding in areas where there are abrupt changes in color or brightness especially noticeable along sharp edges in the image. Because of this, other demosaicing methods attempt to identify high-contrast edges and only interpolate along these edges, but not across them.
Other algorithms are based on the assumption that the color of an area in the image is relatively constant even under changing light conditions, so that the color channels are highly correlated with each other. Therefore, the green channel is interpolated at first then the red and afterwards the blue channel, so that the color ratio red-green respective blue-green are constant. There are other methods that make different assumptions about the image content and starting from this attempt to calculate the missing color values.
Artifacts
Images with small-scale detail close to the resolution limit of the digital sensor can be a problem to the demosaicing algorithm, producing a result which does not look like the model. The most frequent artifact is
False color artifact
A common and unfortunate artifact of Color Filter Array (CFA) interpolation or demosaicing is what is known and seen as false coloring. Typically this artifact manifests itself along edges, where abrupt or unnatural shifts in color occur as a result of misinterpolating across, rather than along, an edge. Various methods exist for preventing and removing this false coloring. Smooth hue transition interpolation is used during the demosaicing to prevent false colors from manifesting themselves in the final image. However, there are other algorithms that can remove false colors after demosaicing. These have the benefit of removing false coloring artifacts from the image while using a more robust demosaicing algorithm for interpolating the red and blue color planes.
Zippering artifact
The zippering artifact is another side effect of CFA demosaicing, which also occurs primarily along edges, is known as the zipper effect. Simply put, zippering is another name for edge blurring that occurs in an on/off pattern along an edge. This effect occurs when the demosaicing algorithm averages pixel values over an edge, especially in the red and blue planes, resulting in its characteristic blur. As mentioned before, the best methods for preventing this effect are the various algorithms which interpolate along, rather than across image edges. Pattern recognition interpolation, adaptive color plane interpolation, and directionally weighted interpolation all attempt to prevent zippering by interpolating along edges detected in the image.
However, even with a theoretically perfect sensor that could capture and distinguish all colors at each photosite, Moiré and other artifacts could still appear. This is an unavoidable consequence of any system that samples an otherwise continuous signal at discrete intervals or locations. For this reason, most photographic digital sensors incorporate something called an optical low-pass filter (OLPF) or an anti-aliasing (AA) filter. This is typically a thin layer directly in front of the sensor, and works by effectively blurring any potentially problematic details that are finer than the resolution of the sensor.
Modifications
This section may contain material not related to the topic of the article and should be moved to color filter array instead. (September 2012) ) |
The Bayer filter is almost universal on consumer digital cameras. Alternatives include the
Panchromatic cells
On June 14, 2007,
Another 2007 U.S. patent filing, by Edward T. Chang, claims a sensor where "the color filter has a pattern comprising 2×2 blocks of pixels composed of one red, one blue, one green and one transparent pixel," in a configuration intended to include infrared sensitivity for higher overall sensitivity.[9] The Kodak patent filing was earlier.[10]
Such cells have previously been used in "CMYW" (cyan, magenta, yellow, and white)[11] "RGBW" (red, green, blue, white)[12] sensors, but Kodak has not compared the new filter pattern to them yet.
Fujifilm "EXR" color filter array
Fujifilm's EXR color filter array are manufactured in both CCD (
Fujifilm "X-Trans" filter
The Fujifilm X-Trans CMOS sensor used in many
One of main drawbacks for custom patterns is that they may lack full support in third party
Quad Bayer
On March 26, 2019, the Huawei P30 series were announced featuring RYYB Quad Bayer, with the 4x4 pattern featuring 4x blue, 4x red, and 8x yellow.[21]
Nonacell
On February 12, 2020, the
See also
References
- US patent 3971065, Bryce E. Bayer, "Color imaging array", issued 1976-07-20 on web
Notes
- ^ Jeff Mather (2008). "Adding L* to RGBG". Archived from the original on 2011-07-13. Retrieved 2011-02-18.
- ^ dpreview.com (2000). "Sony announce 3 new digital cameras". Archived from the original on 2011-07-21.
- ISBN 0-9581888-5-8.
- ISBN 3-540-40243-8. Archivedfrom the original on 2019-01-09. Retrieved 2016-09-23.
- .
- ^ "Patent US3971065 - Color imaging array - Google Patents". Archived from the original on 2013-08-11. Retrieved 2013-04-23.
- doi:10.1088/1742-6596/536/1/012021.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - ^ John Compton and John Hamilton (2007-06-14). "Color Filter Array 2.0". A Thousand Nerds: A Kodak blog. Archived from the original on 2007-07-20. Retrieved 2011-02-25.
- ^ "US patent publication 20070145273 "High-sensitivity infrared color camera"". Archived from the original on 2017-02-22.
- ^ "US Patent Application 20070024879 "Processing color and panchromatic pixels"". Archived from the original on 2016-12-21.
- S2CID 61954103.
A variety of CFA patterns can be used, with various arrangements of red, green, and blue (RGB) or of cyan, magenta, yellow, and white (CMYW) colors.
- ^ Sugiyama, Toshinobu, US patent application 20050231618, "Image-capturing apparatus" Archived 2017-02-22 at the Wayback Machine, filed March 30, 2005
- ^ "Fujifilm X-Trans sensor technology". Archived from the original on 2012-04-09. Retrieved 2012-03-15.
- ^ Diallo, Amadou. "Adobe's Fujifilm X-Trans sensor processing tested". dpreview.com. Archived from the original on 21 October 2016. Retrieved 20 October 2016.
- ^ "Adobe Improves X-Trans Processing in Lightroom CC Update: Promises More to Come". Thomas Fitzgerald Photography Blog. 17 June 2015. Archived from the original on 21 October 2016. Retrieved 20 October 2016.
- ^ "Sony Releases Stacked CMOS Image Sensor for Smartphones with Industry's Highest 48 Effective Megapixels". Sony Global - Sony Global Headquarters. Archived from the original on 2019-09-05. Retrieved 2019-08-16.
- ^ a b "How Tetracell delivers crystal clear photos day and night | Samsung Semiconductor Global Website". www.samsung.com. Archived from the original on 2019-08-16. Retrieved 2019-08-16.
- ^ "IMX294CJK | Sony Semiconductor Solutions". Sony Semiconductor Solutions Corporation. Archived from the original on 2019-08-16. Retrieved 2019-08-16.
- ^ "Product Releases | News & Events | OmniVision". www.ovt.com. Archived from the original on 2019-08-16. Retrieved 2019-08-16.
- ^ US pending 20200280659, "Quad color filter array camera sensor configurations"
- ^ "Part 4: Non-Bayer CFA, Phase Detection Autofocus (PDAF) | TechInsights". techinsights.com. Archived from the original on 2019-08-16. Retrieved 2019-08-16.
- ^ "Samsung's 108Mp ISOCELL Bright HM1 Delivers Brighter Ultra-High-Res Images with Industry-First Nonacell Technology". news.samsung.com. Archived from the original on 2020-02-12. Retrieved 2020-02-14.
External links
- RGB "Bayer" Color and MicroLenses, Silicon Imaging (design, manufacturing and marketing of high-definition digital cameras and image processing solutions)
- eLynx image processing library, Big set of Bayer mosaic manipulation source code licensed under the GPL.
- Efficient, high-quality Bayer demosaic filtering on GPUs
- Global Computer Vision
- Review of Bayer Pattern Color Filter Array (CFA) Demosaicing with New Quality Assessment Algorithms
- Digital Camera Sensors