The growth of optically variable features on banknotes

Lancaster, Ian; Mitchell, Astrid

doi:10.1117/12.549893

Cited by 16 publications

(20 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Perhaps the best known optically variable devices (OVD's) are diffractive surface relief microstructures of the type used in, for example, CSIRO's Exelgram TM diffractive Optically Variable Device (OVD) technology. [11][12][13] OVDs of this type are typically mass produced by embossing the diffractive structure into hot stamping foil, followed by vacuum-coating of the embossed film with a thin layer of a reflective metal. The key security feature underpinning these OVD's and, indeed, all OVDs is, as the name implies, the variability of the image with changing angle of view or changing angle of illumination by a light source.…”

Section: Embossed Optically-variable Overt Imagesmentioning

confidence: 99%

New applications of modulated digital images in document security

et al. 2006

View full text Add to dashboard Cite

In previous work we have demonstrated that selective masking, or modulation, of digital images can be used to create documents and transparent media containing covert or optically variable, overt images. In the present work we describe new applications and techniques of such "modulated digital images" (MDI's) in document security. In particular, we demonstrate that multiple hidden images can be imperceptibly concealed within visible, host images by incorporating them as a new, half-tone, printing screen. Half-toned hidden images of this type may contain a variety of novel features that hinder unauthorized copying, including concealed multiple images, and microprinted-, color-, and various fadeeffects. Black-and-white or full color images may be readily used in this respect. We also report a new technique for the embossing of multiple, covert-or optically variable, overt-images into transparent substrates. This method employs an embossing tool that is prepared using a combination of electron beam and greytone lithography. Two approaches may be used: (i) a double-sided "soft" emboss into curable, transparent, lacquer layers, and (ii) a single-sided "hot" emboss in which multiple, dithered images consisting of distinctly-sloped microprisms are impressed into the substrate. Technique (ii) requires a novel, electron-beam-originated master dye.

show abstract

Section: Embossed Optically-variable Overt Imagesmentioning

confidence: 99%

New applications of modulated digital images in document security

et al. 2006

View full text Add to dashboard Cite

show abstract

“…The normal optically variable thin film filters are designed and fabricated by using all dielectric layers or metal-dielectric layers [12]. Compared with all-dielectric structure, metal-dielectric multi-layer structure has higher saturation and fewer layers.…”

Section: Introductionmentioning

confidence: 99%

Metal-dielectric metameric filters for optically variable devices

Xiao

Chen

Deng

et al. 2016

Optics Communications

View full text Add to dashboard Cite

“…The present trend consists of integrating these two effects into one device 7,8 , although in the case of ISISs, there is still much opportunity for innovation. Currently, 78 authorities utilise DOVIDs and 120 use OVI on their currency 9 .…”

Section: Introductionmentioning

confidence: 99%

Use of metameric filters for future interference security image structures

2006

View full text Add to dashboard Cite

In the present work, we describe innovative approaches and properties that can be added to the already popular thin film optically variable devices (OVD) used on banknotes. We show two practical examples of OVDs, namely (i) a pair of metameric filters offering a hidden image effect as a function of the angle of observation as well as a specific spectral property permitting automatic note readability, and (ii) multi-material filters offering a side-dependent color shift. We first describe the design approach of these new devices followed by their sensitivity to deposition errors especially in the case of the metameric filters where slight thickness variations have a significant effect on the obtained colors. The performance of prototype filters prepared by dual ion beam sputtering (DIBS) is shown.

show abstract

The growth of optically variable features on banknotes

Cited by 16 publications

References 0 publications

New applications of modulated digital images in document security

New applications of modulated digital images in document security

Metal-dielectric metameric filters for optically variable devices

Use of metameric filters for future interference security image structures

Contact Info

Product

Resources

About