Metamerism-based security patterns

A method of performing counterfeit detection on an article having a security pattern, comprising:

• alternating between a first light source and a second, different light source to illuminate the security pattern on the article, wherein the first light source emits first light, and the second light source emits second light, and wherein the first and second light sources are separate from the article;
• and
• causing the security pattern to have different perceived appearances when the security pattern is alternately illuminated with the first and second light sources, wherein the security pattern has a frame surrounding a region, and wherein a perceived depth of the region varies depending upon which of the first and second light sources illuminates the security pattern.

A method of performing counterfeit detection on an article having a security pattern, comprising:

• viewing the article under a first light source that includes a liquid crystal display of a mobile device, and viewing the article under a second, different light source that emits light, wherein counterfeiting is suspected if the security pattern appears the same under both the first and second light sources,
• wherein the security pattern is based on metamerism that causes a region within a frame of the security pattern to be perceived to have different depths when alternately viewed under the first and second different light sources.

Anti-counterfeiting apparatus for printing human-perceivable security patterns on articles, the security patterns based on metamerism, wherein the metamerism causes each security pattern to be perceived differently when viewed under two different external light sources that emit light, wherein the anti-counterfeiting apparatus has a processor to generate the security patterns for printing on the articles, wherein at least one of the security patterns has a frame surrounding a region, wherein a perceived depth of the region varies depending upon which of the two different light sources illuminates the at least one security pattern.

An article bearing a human-perceivable security pattern based on metamerism, wherein the metamerism causes the security pattern to be perceived differently when viewed under two different light sources,

• wherein the security pattern is perceived to have a first pattern when the security pattern is illuminated by light emitted by a first of the light sources having a first spectral distribution with a relatively sharp peak in radiant power in a particular wavelength range, and
• wherein the security pattern is perceived to have a second pattern when the security pattern is illuminated by light from a second of the light sources having a second spectral distribution different from the first spectral distribution, wherein the metamerism is used to hide details of a structure in the security pattern, wherein the structure surrounds a region of the security pattern, and wherein a perceived depth of the surrounded region varies as a light source illuminating the security pattern alternate between the first and second light sources.