Abstract: An optical device having an optical axis. The device includes at least one surface with at least two meridians, at least one portion of which forms, seen face-on, at least one spiral segment the central point of which is on the optical axis. Each spiral segment defining meridians of different optical powers. The focus obtained extends over a tubular region.

Abstract: A waste comminuting device includes a comminuting housing (1), a rotor (2) provided with a plurality of protruding peripheral knives, stationary counterblades supported by the comminuting housing, the minimal distance separating each knife from each associated counterblade, during the passage of the knife opposite the counterblade, being equal to an operating clearance, called the cutting size. For each knife (3, 4, 5, 6) and for at least one direction of rotation of the rotor, at least two non-aligned counterblades (7 and 11, 8 and 12, 9 and 13, 10 and 14) associated with the knife are adapted so that the distance separating the leading edge (45) of the knife and the leading edge (48, 56) of a counterblade at the moment when the leading edge of the knife opposes the leading edge of the counterblade, is different from one counterblade (7-10) to another (11-14).