The security printing market has recently seen the number of developments regarding the authentication technology using devices such as smartphones. TOPPAN was no exception and has developed OVD that enables instant covert authentication by capturing the characteristics of its unique viewing angle effect with the flashlight of the smartphone.
TOPPAN has developed a CGH (Computer Generated Hologram) OVD named Illumigram, in which an illegible graphic pattern is observed under normal lighting condition while monochrome three-dimensional image appears when illuminated by a white spotlight source. The 3D image that appear moves around the recorded surface in accordance with the movement of the light source.
With the aim of enhancing this easy and quick authentication, TOPPAN succeeded in giving the Illumigram specific colors to display more sophisticated images for even faster and easier authentication.
The newly developed OVD can show its unique optical effect even more clearly. When the light source is moved, the colored 3D image follows the movement of the light source without changing its stable color. The colored 3D image remains indecipherable when the spotlight source is distant from the OVD.
Multiple color expressions are also available, and multiple 3D images can coexist in each different color. Colors can be selected from the list of developed colors uniquely available. Furthermore, the depth of each 3D image can be designed arbitrarily and can coexist in different depth.
This OVD was achieved by combining our optical calculation method of CGH developed in-house with our proprietary technology to generate and precisely control the nano-level fine structures. The fine structure is provided on the recording surface based on CGH calculations, and the microstructure is designed so that the specific wavelength band of incident light is intensified by the optical path length difference. This changes the spectral distribution of white light and enables the display of a 3D image with selected stable colors. With this method, the fine structure accomplishes both the formation of a dynamic three-dimensional image and its colorization with stable colors simultaneously.
The OVD developed has the features of three-dimensional, dynamic, and stable color display, and its defined visual effect is expected to be implemented for clear determination of authenticity. It is possible to display multiple colors and depths and is expected to expand the design latitude of OVDs.