scanning disk

noun Television.
  1. (in mechanical scanning) a disk with a line of holes spiraling in from its edge, rotated in front of a surface so as to expose a small segment as each hole passes before it for transmitting or reproducing a picture.

Origin of scanning disk

First recorded in 1925–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018