OPTICALLY CHANGEABLE PLANE SPECIMEN Russian patent published in 2006 - IPC B42D15/00 G02B5/18 

FIELD: optics.

SUBSTANCE: the optically changeable plane specimen is made of partial elements with diffraction reflecting structures and mirror-reflecting partial elements for formation of two or more images, which at illumination by light falling perpendicularly to the plane specimen may be perceived singly by the observer at an observation distance equal to 30 cm at different angles of view. The partial elements contain achromatically diffracting saw-tooth relief structures with saw-tooth inclination angles relative to the plane of the plane specimen. The relief structures related to various images have different angles of inclination, and the value of the maximum angle of inclination makes up maximum 25 deg, so that the difference of the angles of view for light beams reflected from relief structures at least of two images is less than the difference of angles equal to 30 deg. determined by a duplicator, due to it the copy produced with the aid of a duplicator reproduces at least two images by imposition one on the other.

EFFECT: produced optically changed plane specimen, which provides for an improved protection against copying.

11 cl, 9 dwg