Aperture correction
The term aperture correction has its origins in the technology of analog television cameras , but is now also used for image generation by digital cameras .
Aperture (opening width) in analog television cameras means the size of the electron beam that is used to generate images in the vidicon . In the case of digital cameras, this means the size of the individual pixels on the CCD chip.
The opening width creates blurring in its edge area . The aperture correction tries to correct this blurring.
In order to prevent aliasing effects during this correction , which for example produce moiré patterns , the transfer function is limited to half the limit frequency according to the Nyquist-Shannon sampling theorem . For this purpose, a spatial low-pass filter is connected upstream of the chip . In order to increase the slope, higher frequency components in the image are raised - the aperture correction. The transition from aperture correction to image sharpening is fluid.
Individual evidence
- ↑ Ulrich Schmidt: Professional video technology - analog and digital basics, film technology, television technology, HDTV, cameras, displays, video recorders, production and studio technology