This is a Siemens star, a pattern used to calibrate optical equipment – to see how well the lens (or raster, or driver, or whatever) can see. Although actually, this graphic is not merely the Siemens star. As described in the (German) book in which it appears, Digital Imaging Methods, this is a power density spectrum (or power spectral density) of a Siemens star. The text adds the helpful note: at the center of the image edges, the spatial frequency is 1024 line pairs per image height.
A “power spectral density” is a graph showing different energy-levels of a signal spread out over time. The signal can be frequencies of lightwaves (used to ID visible stars in astronomy) or it can be wavelengths of electric pulses, or even the pitch (frequency) or volume (amplitude) of sound. If I’m playing guitar over a set amount of time, certain notes (frequencies) will show up way more often than others, so we’d be able to show which notes are hit every few seconds, which ones are hit once or twice every couple of songs, and which ones are too high, too low, or too sharp or too flat to show up at all.
In this case, we’re looking at the black and white rays of this Siemens star as a diffraction image, a filtered picture that’s broadcast on a digital screen.