Security hologram and associated methods of use and of making

A method for viewing a reconstructed image of a hologram recorded in a recording medium having a surface and containing an integral image, the hologram comprising a first holographic image, which is located and plays back at or near the surface of the recording medium and which is characterized to possess a first image plane and to possess a first center wavelength and a first spectral bandwidth, and a second holographic image, which is located and plays back at a position with respect to the surface of the recording medium that is selected from the group consisting of a foreground position and a background position and which is characterized to possess a second image plane and to possess a second center wavelength and a second spectral bandwidth;

• wherein at least a portion of the first holographic image and at least a portion of the second holographic image together afford the integral image;
• said method comprising:
• providing the hologram comprising the first holographic image and the second holographic image, wherein the second holographic image appears unrecognizable to the human eye under diffuse lighting sources;
• and
• illuminating the hologram with at least partially collimated light from a light source having a spectral bandwidth that overlaps the spectral bandwidth of the first holographic image and the spectral bandwidth of the second holographic image, wherein the image is viewable and recognizable to a human eye and is seen by the human eye as the integral image.

A method for establishing the authenticity of an article containing a hologram recorded in a recording medium having a surface and containing an integral image, the hologram comprising a first holographic image, which is located and plays back at or near the surface of the recording medium and which is characterized to possess a first image plane and to possess a first center wavelength and a first spectral bandwidth, and a second holographic image, which is located and plays back at a position with respect to the surface of the recording medium that is selected from the group consisting of a foreground position and a background position and which is characterized to possess a second image plane and to possess a second center wavelength and a second spectral bandwidth;

• wherein at least a portion of the first holographic image and at least a portion of the second holographic image together afford the integral image;
• said method comprising the steps of:
• (a) providing the hologram on an article to be authenticated, said hologram comprising the first holographic image and the second holographic image, wherein the second holographic image is located at a substantial distance from the surface of the recording medium such that the second holographic image appears unrecognizable to a human eye under diffuse lighting sources;
• (b) illuminating the hologram with at least partially collimated light from a light source having a center wavelength and a spectral bandwidth, wherein the spectral bandwidth of the at least partially collimated light overlaps the first spectral bandwidth of the first holographic image and the second spectral bandwidth of the second holographic image;
• and
• (c) establishing the article bearing the hologram to be authentic only if the integral image is observable by human observation or detectable by an instrument in its entirety upon illumination with the light source in step (b) positioned at least one angle θ with respect to a normal line to the surface of the holographic optical element.

A method for making a hologram, said hologram being recorded in a recording medium having a surface and containing an integral image, the hologram comprising a first holographic image, which is located and plays back at or near the surface of the recording medium and which is characterized to possess a first image plane and to possess a first center wavelength and a first spectral bandwidth, and a second holographic image, which is located and plays back at a position with respect to the surface of the recording medium that is selected from the group consisting of a foreground position and a background position and which is characterized to possess a second image plane and to possess a second center wavelength and a second spectral bandwidth;

• wherein at least a portion of the first holographic image and at least a portion of the second holographic image together afford the integral image;
• the method comprising the steps of:
• a) obtaining a first transparency and at least a second transparency depicting all element(s) that are to be in the hologram;
• b) placing a first photosensitive film suitable for holographic recording between the first transparency and a coherent light source, the first photosensitive film having a surface;
• c) exposing the first photosensitive film with light from the coherent light source to record a first holographic image (1st H1) of the first transparency;
• d) inverting the first holographic image and removing the first transparency;
• e) placing a second photosensitive film suitable for holographic recording between the at least second transparency and a coherent light source, the first photosensitive film having a surface;
• f) exposing the first photosensitive film with light from the coherent light source to record a second holographic image (2nd H1) of the second transparency;
• g) inverting the second holographic image and removing the second transparency;
• h) aligning and bonding the first holographic image to the at least second holographic image to afford a final H1 holographic image in a manner such that said final Hholographic image contains the integral image;
• i) placing a third photosensitive film suitable for holographic recording between the coherent light source and the final H1 holographic image, the third photosensitive film being proximate to the final H1 holographic image;
• and
• j) exposing the third photosensitive film with light from the coherent light source to record a third holographic image (H2) as the hologram.