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RGB "Bayer" Color and MicroLenses
Bayer color filter array is a popular format for digital acquisition of color images [1]. The pattern
of the color filters is shown below. Half of the total number of pixels are green (G), while a
quarter of the total number is assigned to both red (R) and blue (B).
G R
G R
B
G B
G
G R
G R
B
G B
G
In order to obtain this color information, the color image sensor is covered with either a red, a
green, or a blue filter, in a repeating pattern. This pattern, or sequence, of filters can vary, but
the widely adopted “Bayer” pattern, which was invented at Kodak, is a repeating 2x2
arrangement.
Photographs & Text adapted from Photobit
When the image sensor is read out, line by line, the pixel sequence comes out GRGRGR, etc.,
and then the alternate line sequence is BGBGBG, etc. This output is called sequential RGB (or
sRGB).
Since each pixel has been made sensitive only to one color (one spectral band), the overall
sensitivity of a color image sensor is lower than a monochrome (panchromatic) sensor, and in
fact is typically 3x less sensitive. As a result, monochrome sensors are better for low-light
applications, such as security cameras. (It is also why human eyes switch to black and white
mode in the dark).
MicroLenses