Method for checking authenticity of a hologram and a reading device for the performance of the method

US5943131A · kind A · utility

Assignee

• HSM Holographic Systems Muenchen GmbH · DE

Inventors

• Gunther Dausmann · Erding, DE
• Zishao Yang · Erding, DE

Key dates

• Filing date: May 21, 1998
• Grant date: Aug 24, 1999
• Expiry date: May 21, 2018

Classification

• Technology area (CPC G): Physics
• CPC primary: G03H2210/562
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A method for determining the authenticity of a hologram with the following steps: PA1 a) The hologram (1) to be checked is illuminated with a restoration ray (2): PA1 b) The diffraction ray (3) of the first order of the wave field created at the hologram is imaged on a first photo-sensitive element, in particular a CCD target (5), and brought to interference with a first reference ray (7); PA1 c) The diffraction ray (4) of the zeroth order of the wave field created at the hologram (1) is imaged on a second photo-sensitive element, in particular a CCD target (6) and brought to interference with a second reference ray (10); PA1 d) The intensity distributions created at the different photo-sensitive elements (5, 6) are correlated with each other for at least two phase relationships between the restoration ray (2) and the different reference rays (7, 10) to obtain a correlation intensity distribution for the relevant orders of diffraction; and PA1 e) The correlation intensity distributions determined for the relevant orders of diffraction are correlated with each other, particularly subtracted from each other pixel by pixel.