Security holograms
We describe techniques for recording a holographic image onto holographic recording film, in particular for security holograms. We thus describe a structure having a stack comprising the holographic recording film and a multichannel image generation device under the film. A three-dimensional object (or hologram of a 3D object) is provided, located under the multichannel image generation device. At least a portion of the multichannel image generation device is substantially transparent or absent in a region above the object. A holographic image is recorded in the film by illuminating the stack with laser light. The multichannel image generation device under the film may comprise a volume reflection hologram of a lenticularly generated image. The structure records a hologram of the 3D object in conjunction with a multi-channel holographic image.
1. A modular master hologram stack comprising:
a holder configured for interchangeable support of at least two multichannel image generation devices,
a reservoir to contain refractive index matching fluid between said multichannel image generation devices,
a support for at least one three-dimensional (3D) object or hologram of a 3D object beneath said multichannel image generation devices;
wherein the modular master hologram stack is configured to record a holographic image onto holographic recording film, said holographic image comprising a hologram of a 3D object in conjunction with a multi-channel holographic image, the method comprising:
forming a holographic recording stack by:
positioning said holographic recording film over said multichannel image generation device;
positioning said at least one 3D object or hologram of a 3D object under said multichannel image generation device; and
providing a transparent window in said multichannel image generation device in a region above said at least one object; and then
recording said holographic image in said holographic recording film by illuminating said stack through said holographic recording film with a laser light of at least one wavelength.
2. A modular master hologram stack comprising:
a holder configured for interchangeable support of at least two multichannel image generation devices;
a reservoir to contain refractive index matching fluid between said multichannel image generation devices; and
a support for at least one 3D object or hologram of a 3D object beneath said multichannel image generation devices.
3. A modular master hologram stack as claimed in claim 2 wherein at least one of said multichannel image generation devices comprises a multichannel volume reflection hologram.
4. A modular master hologram stack as claimed in claim 2 further comprising a film holder above said multichannel image generation devices to hold holographic recording film substantially planar and motionless to less than 100 nm for a period of at least one millisecond.
5. A modular master hologram stack as claimed in claim 2 wherein a total height of said stack is less than 1 cm.
6. A modular master hologram stack as claimed in claim 2 wherein said multichannel image generation devices have substantially transparent regions above said at least one 3D object or hologram of a 3D object.