Subpixels
A subpixel (such as a “sub- pixel ” or “subpixel”) describes the internal structure of a pixel . As a rule, the term subpixel is associated with a higher resolution than can be expected from a single pixel.
In reality, a pixel can also consist of several smaller pixels. A screen pixel can consist of 3 smaller pixels, for example, from whose individual color the color of the "large" screen pixel is generated. OLED displays are a good example of this .
Application in digital image processing
If photos are taken with a digital camera, for example a CCD camera , the result is images with a certain number of pixels. A quite common number of pixels in smartphones in 2018 is 12 million pixels. This means that images with 4000 × 3000 pixels can be displayed.
If a person is recorded in full format in a 4000 × 3000 pixel image, it is possible with suitable software to determine the eye relief in the face to an accuracy better than one pixel. In such a picture, a pixel corresponds roughly to about 0.5 millimeters, i.e. H. a person with a length of 1.8 m (1800 mm) occupies about 3600 pixels in height. The mean eye relief of people is around 65 mm, corresponding to 130 pixels. The size of the pupil in daylight is between 2 and 4 millimeters, corresponding to 4 to 8 pixels.
In the simplest case, the position of the two eye pupils is now determined by a circular fit around the usually black eye pupils. The geometric center of gravity of a “black” eye pupil fitted in this way is then often not exactly in the center of an image pixel. This results in a positional accuracy or distance accuracy in the subpixel area.
Subpixel rendering
The basic colors , often the three colors red, green and blue of liquid crystal screens , computer monitors or television sets , which make up a pixel, are also referred to as subpixels . Since the subpixels in this type of device are usually arranged directly next to each other, it is possible to increase the horizontal resolution through targeted control of the subpixels. For the eye, this can lead to texts on screens that are easier to read, for example. Examples of this can be found in the main article Subpixel Rendering .
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- ↑ E. Bray et al. (2018) Characterizing subpixel spatial resolution of a hybrid CMOS detector.