For Digital and Analog Video Cameras, the basic principles are the same.
Light reflected off an object is gathered by the camera lens.
The lens then focuses the light on the Beam Splitter (Prism).
The Beam Splitter splits the collected light into red, green and blue beams.
These Beams are directed toward their respective CCDs (charge-coupled devices).
The CCDs transform the RGB light into electrical RGB signals.
These signals are amplified, processed and then reconverted into video pictures, as seen in a camera viewfinder.

Light to Video Signal