Title:
MULTILAYERED OPTICAL SECURITY DEVICE
Document Type and Number:
WIPO Patent Application WO/2022/011746
Kind Code:
A1
Abstract:
A multilayered optical security device (100) has a resonant waveguide grating (RWG) layer (110) on an under layer (120) having a hologram. The RWG layer (110) has plural RWGs (601-625) for generating one or more patterns. Each RWG (601-625) has the first and second RWG portions (301, 302), with diffraction gratings (320, 330) of different grating periods, for light coupling-in and coupling-out, respectively. Using the RWGs (601-625) minimizes interference to a holographic image generated by the under layer (120). This advantage is especially useful when the holographic image carries digital data such as in digital holographic encryption where an encrypted hologram is used in the under layer (120). The digital data may contain biometric information such as a fingerprint. In each RWG portion (301, 302) of an individual RWG (601-625), scattering elements (321, 331) in a grating (320, 330) are curved to thereby enhance an angular tolerance in azimuthal angle during observing the patterns by an observer while the individual RWG (601-625) is still selective in elevation angle.
Inventors:
BEN AZIZA ZEINEB (FR)
WANG XIAOHAN (CN)
HAO TING (CN)
ZHU XIULING (CN)
CHAN KENNY (CN)
WANG XIAOHAN (CN)
HAO TING (CN)
ZHU XIULING (CN)
CHAN KENNY (CN)
Application Number:
PCT/CN2020/105230
Publication Date:
January 20, 2022
Filing Date:
July 28, 2020
Export Citation:
Assignee:
HONG KONG APPLIED SCIENCE & TECH RESEARCH INST CO LTD (CN)
International Classes:
B42D25/351; B42D25/30; B42D25/328; B42D25/435; G02B5/18; G03H1/02; G03H1/28
Domestic Patent References:
| WO2015096859A1 | 2015-07-02 |
Foreign References:
| US20180001692A1 | 2018-01-04 | |||
| EP3205512A1 | 2017-08-16 | |||
| US20190009609A1 | 2019-01-10 | |||
| CN201619321U | 2010-11-03 | |||
| CN207704754U | 2018-08-07 |
Attorney, Agent or Firm:
CHINA TRUER IP (CN)
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