Holographic displays attract attention for use in telemedicine, prototyping, updatable 3D maps, military imaging, and other applications that require situational awareness1. Also popular in advertising and entertainment, the usefulness of holography is often directly correlated with how long an image can be displayed and how fast and effectively that image can be changed.
Currently available photorefractive (PR) polymer composites used as dynamic holographic recording materials are not sensitive enough to record holograms using low intensity light within a short exposure time, imposing a significant limitation on the potential of holographic display technology. An improved PR polymer component is needed for holographic 3D display technology to advance to the next level. This novel development is the first to demonstrate the following abilities combined: nearly 100% diffraction efficiency, fast writing time, hours of image persistence, rapid erasure, and large area2.
This invention combines a method for forming the sensitized PR polymer composite used to write holograms at near real-time imaging rate. In contrast to currently available, inferior PR polymer composites with less than 100% quantum efficiency (QE), this composite’s rate of greater than 100% enables index pattern impressing within the composite in a shorter time frame, impacting the refresh rate for holographic images. The new PR polymer component is capable of a two-second image refresh rate, the first to achieve a near real-time speed. The PR polymer was chosen to create the largest photorefractive 3D display to date for its ability to be recorded within a few minutes, viewed for several hours without the need for refreshing, and be completely erased and updated without a residual ghost image effect1.
This invention is comprised of three parts: a PR polymer composite, a hologram writing apparatus, and a method for making the polymer.
The PR polymer composite consists of a charge transporting polymer (CTP) matrix and a photosensitizer made of a quantum dot (QD) material (made of graphene, lead selenide, and indium phosphide) with a first band gap coupled with a nanoparticle material (made of titanium oxide, zinc oxide, and zinc sulfide), where the second band gap is greater than the first. The photosensitizer is configured to generate a number of free charges and transfers them to the CTP matrix which responds to an incident photon on the polymer composite.
An apparatus for writing holograms includes a pair of electrodes which are placed on opposite sides of the polymer and applies an external electric field across it. A light modulator receives image data and transmits an object beam which a lens focuses for each 3D perspective view from a first side of the polymer. A reference beam, directed from a second side of the polymer to the first side, interferes with the object beam and impresses an index pattern of the 3D perspective view of the object at each fixed direction.
The PR polymer composite method combines the CTP, a plasticizer, a non-linear optical (NLO) chromophore, and a QD sensitizer in a solvent to form a mixture which is then sonicated, and the solvent is evaporated to obtain the composite. Melt processing the composite occurs between the electrodes to obtain the PR polymer composite.
- Enables largest PR 3D display to date
- Near real-time updating
- Can record within minutes
- Able to be viewed for several hours without refreshing
- Completely erasable
- Military imaging
- 3D mapping
Additional Technology Numbers: 33270