Omnidirectional scanner
A reader that catches the code however the package is turned, by sweeping the beam in a starburst rather than a single line.
A single-line scanner needs the barcode to cross the beam roughly square on, which at a checkout means somebody has to rotate the box. The fix is a spinning polygon mirror plus a set of fixed mirrors that split the beam into a dozen or so lines at different angles, swept fast enough that every orientation gets covered several times a second. The customer sees a static star in the glass; the code only has to pass fully across any one of those lines.
The in-counter scanner is therefore a mechanically ambitious device, and it exists because somebody in the early 1970s worked out what one second per item costs across a whole chain of stores. The first live scan happened at Marsh Supermarket in Troy, Ohio, on 26 June 1974 — a pack of Wrigley's gum. Today's imager-based readers are omnidirectional by nature: they take a picture and go looking for the code in it, no mirrors involved.