Holographic images are natural and human-friendly stereo images without additional instruments such as eye wear. In daily life, you can find holograms in credit cards and paper currencies for security applications, toys, arts, etc. In these applications, photopolymers and silver halides are usually used, and these holographic images cannot be updated once the images are written. Recently, many researchers have been interested in holographic techniques for their applications to three dimensional (3D) movies like “Star Wars”. Because holograms realize natural 3D images without any eye wear, the application to 3D movies is possible if holographic images can be updated with the time scale of the time resolution of human visions.

So far several updatable holographic materials have been developed with photorefractive polymers. Photorefractive polymers change their refractive indices upon light irradiation under the application of high voltage, and they are one of the most promising materials for dynamic holographic movies. However, the application of the high voltage to the film makes the film preparation harder and more costly. Although photorefractive polymers that do not need any voltage have been reported, the updating speeds of the holographic images still need to be improved to achieve 3D movies.

Recently, Kobayashi and Abe in Aoyama Gakuin University in Japan achieved the real-time dynamic holographic movie of a 3D object by using fast photochromic imidazole dimers. Photochromic compounds are one of the photoswitch compounds that change their colors by UV light irradiation, and photochromic imidazole dimers show very fast photoswitching with a time scale of tens of milliseconds. The holographic movie demonstrated by the authors instantaneously and smoothly follows the motion of the 3D object. This study is the first demonstration of a holographic movie that can instantaneously update the holographic images of the 3D object. This cutting edge research is important to develop further novel dynamic holographic materials by using photochromic compounds and is important to advance holographic techniques for application to 3D movies.

Text kindly provided by the authors of the original manuscript