FIELD: physics.
SUBSTANCE: image forming apparatus has an image forming lens unit, comprising at least one lens having a defined effective aperture and at least one optical element associated with said at least one lens and configured to provide high depth of focus of said apparatus. The optical element is configured as a non-diffraction optical element which affects phase and sets phase shift through spatially separated optically transparent sections of phase shift with low spatial frequencies, differently affecting phase of light passing through and forming a given pattern. The position of at least one section of phase shift on the optical element within the plane of the effective aperture of the lens is defined by at least the size of said aperture so as to ensure maximum optical transfer function during defocusing of the image forming apparatus.
EFFECT: providing an optical method of increasing depth of focus.
34 cl, 44 dwg
