picture element (Pixel)
A pixel is the smallest component of a computer image or a screen and, in the case of color representation, consists of a color triple with the three primary colorsred, green and blue. A digital representation is composed of a large number of individual pixels. The number of pixels and their distance from each other, the dot pitch, determine the resolution of the image. Incomputer graphics, pixels can be individually activated in terms of hue, color saturation and brightness.
In pure black-and-white representations, a pixel is encoded with 1 bit/pixel, in grayscale with 4 to 8 bits/pixel, and in color representations with a color depth of 4, 8, 16 or 24 bits/pixel.
Normally, a pixel is square with an aspect ratio, the Pixel Aspect Ratio( PAR), of 1:1. In the various television standards, however, the PAR ratio differs from 1:1. In terms of representation, a pixel is two-dimensional. By adding the third dimension, a pixel becomes a voxel, a volume pixel.
In image sensors for digital cameras and camcorders, the number of pixels is the characteristic value for the graphic resolution. The specified number of pixels is the effective resolution available. Depending on the image sensor concept, it corresponds to the number of photocells or is only a quarter of it. Since digital cameras have several million pixels, it is common practice to specify the pixel number in megapixels( MP) and even in gigapixels( GP) for high-resolution special photography.
The miniaturization of CCD sensors and CMOS sensors and the increase in image resolution mean that pixels are becoming smaller. Their size is at edge lengths of 1.7 µm and 14 µm. Consumer cameras with an image resolution of 8 MP to 12 MP already have pixel sizes of 1.7 µm edge length and about 3 q µm pixel area. Typical pixel edge lengths of commercially available image sensors are 1.7 µm, 2.2 µm, 3.5 µm, 4.6 µm, 6.5 µm, 7 µm, 10 µm and 14 µm. Since the light- active pixel area is extremely small with small pixel sizes, they have a relatively high signal-to- noise ratio in low light conditions.