Think holograms and some famous movies come to mind. But the technology that makes those 3D images look so real is also used in everyday objects too, like credit cards, driver’s licenses, and plenty of security tools.
A hologram is a representation of a surface. Initially they were made based on a real object using laser technology that recorded 3D objects and transferred the images to a photographic medium, like silver halide. By virtue of this cumbersome process, holographs took a while to find their way to more diverse industries than film.
Once it became possible to create a hologram using computers with dedicated software, the graphical output, now known as a computer generated hologram (CGH) could be transferred to glass and other types of materials. But even more important, was that the newly created CGH did not depend on a real object being present the way the original holograms did. Theoretically, using the right mathematical calculations and a knowledge of what an ideal surface should look like, it was possible to create a representation of a surface that was nearly perfect even though the object was not right in front of you. This made CGH a natural extension of interferometry.
CGH and Interferometry
Interferometry has been used for a long time to measure all types of optical components by comparing one surface to another, with one of those surfaces being of very high quality. Usually, it is referred to as the reference. More and more of the small devices we depend upon every day include aspheres, which are a type of lens known to be challenging to manufacture and challenging to measure using standard interferometry.
So why use them? The advantages of an asphere over spheres and cylinders include:
- Focus is sharper
- Fewer optical elements are necessary
- Aperture sizes can be larger
- Spherical aberration, distortion, and mild astigmatism effects are reduced
- Weight is less
- Provides wider design flexibility
Ultimately, these advantages lead to a higher performing, more precise imaging system – no matter what device it’s in – from a camera phone, to night vision goggles, to machines that make computer chips, and much, much more.