image: (a) Reconstructed amplitude at wavelength 514.5 nm of a CTF-developed fingerprint on a transparent glass slide and (b) topogram of the CTF-developed fingerprint. The red circles identify level-3 details (pores). The hologram was recorded at a recording distance d = 40 cm using dual wavelengths 514.5 nm and 457.9 nm in the transmission mode. view more
Credit: by Haowen Zhou, Mallik M. R. Hussain, and Partha P. Banerjee
The Holography and Metamaterials (HaM) Lab in the Department of Electro-Optics and Photonics at the University of Dayton has done pioneering work in dynamic and digital holography over its last 10 years of existence. Directed by Professor Partha Banerjee, the lab has worked on a diverse range of topics, starting from photorefractives and self-organization of light, to digital holography, including holographic tomography, integration of holography with 3D virtual reality, dual-wavelength techniques for raindrop and crack characterization, 3D fingerprint recording and reconstruction, 3D characterization of additively manufactured objects, transport of intensity and phase, and combining transport of intensity with holographic reconstruction, correlation of holograms for 3D object identification, etc. In fact, three of the PhDs from the department who worked on digital holography published their own book Analog and Digital Holography with MATLAB on the topic. Many projects have been funded from the US Department of Defense, and projects have opened up collaborations with Tsinghua University, and encouraged students from Huazhong University of Science and Technology and Shanghai University, and Fulbright scholars from Bulgaria to come and work in the lab.
A 2017 article in Laser Focus World, titled Virtual Reality Technology: Digital holographic tomography creates true 3D virtual reality, writes “Partha Banerjee's research group at the Holography and Metamaterials Lab at the University of Dayton (Dayton, OH) is using a Mach-Zehnder interferometer setup to scan different faces of an object and record a series of holograms that all contain both intensity and phase (or depth) information of the illuminated surface. These are then reconstructed and tomographically combined to create a true 3D rendering of the object that is stored in a point cloud. Using commercial Microsoft HoloLens software, the object can then be viewed in full 3D detail for a variety of virtual reality (VR) applications”.
The work on 3D fingerprinting, summarized in this LAM paper (see Figure), and published earlier in Opt. Engr. [Opt. Eng. 56(3), 034117 (2017)], describes the construction and reconstruction of high-resolution topograms of fingerprints using dual wavelength digital holography. Fingerprint analysis is a popular identification technique due to the uniqueness of fingerprints and the convenience of recording them. The quality of a latent fingerprint on a surface can depend on various conditions, such as the time of the day, temperature, and the composition of sweat. In collaboration with the Pennsylvania State University, where latent fingerprints on transparent and blackened glass slides by depositing 1000-nm-thick columnar thin films (CTFs) of chalcogenide glass were developed, we used transmission-/reflection-mode dual wavelength digital holography to construct the topograms of CTF-developed fingerprints on transparent/blackened glass slides. A synthetic wavelength of of 4 μm, was sufficient to resolve pores of depths 1 to 2 μm. This method can be used to measure the level-3 details that are usually difficult to observe with most other techniques applied to latent fingerprints. Continuing effort in this area to bring 3D fingerprinting to commercial use very recently received funding from the Criminal Investigations and Network Analysis (CINA) Center in the Department of Homeland Security.
Journal
Light: Advanced Manufacturing