US 12,001,011 B2
Optical element and a method of visually authenticating an object
Yuliy Schwartzburg, Lausanne (CH); Romain Testuz, Lausanne (CH); and Andrea Callegari, Ecublens (CH)
Assigned to SICPA HOLDING SA, Prilly (CH)
Appl. No. 17/917,845
Filed by SICPA HOLDING SA, Prilly (CH)
PCT Filed Apr. 7, 2021, PCT No. PCT/EP2021/059011
§ 371(c)(1), (2) Date Oct. 7, 2022,
PCT Pub. No. WO2021/204844, PCT Pub. Date Oct. 14, 2021.
Claims priority of application No. 20168421 (EP), filed on Apr. 7, 2020.
Prior Publication US 2023/0288697 A1, Sep. 14, 2023
Int. Cl. G02B 26/08 (2006.01); B42D 25/30 (2014.01); B42D 25/405 (2014.01); G02B 1/10 (2015.01); G02B 27/18 (2006.01); G03F 1/68 (2012.01)
CPC G02B 26/0875 (2013.01) [B42D 25/30 (2014.10); B42D 25/405 (2014.10); G02B 1/10 (2013.01); G02B 27/18 (2013.01); G03F 1/68 (2013.01)] 15 Claims
OG exemplary drawing
 
1. An optical element comprising a caustic layer made of a piece of reflective, or refractive transparent or partially transparent, first optical material, and having a light-redirecting surface with a relief pattern,
wherein
the optical element includes a mask layer disposed, respectively, on an optical surface of the optical element or within the optical element, the mask layer comprising a mask pattern and having a variable light transmission coefficient, the mask layer being adapted to at least partially transmit incoming light upon illumination of the optical element with a point-like light source; and
the relief pattern of the light-redirecting surface of the caustic layer is configured to redirect incident light received by the optical element from the point-like light source and form a projected image containing a visible caustic pattern reproducing a reference pattern, wherein
the point-like light source is a source of light whose angular size is sufficiently small that light can be considered to arise from a single point.