The detection of latent fingerprints left at crime scenes usually requires dusting or other physical processing to render them visible. A new optical-coherence-tomography (OCT) method of finding fingerprints leaves them untouched and unaltered, thereby eliminating contamination of the evidence. Satish Kumar Dubey and colleagues at the Indian Institute of Technology Delhi (New Delhi, India) demonstrated that full-field swept-source OCT can be applied as a noninvasive tool to detect latent fingerprints even from poorly reflecting samples that would ordinarily be unnoticed.
The system consists of a superluminescent diode and an acousto-optic tunable filter as a swept source, a Michelson interferometer, and an area detector. To make the system compact, the team modified a conventional OCT interferometer by coating one side of a cube beamsplitter with aluminum oxide and using it as a reference mirror. Unlike the conventional techniques, unwanted reflections are rejected by means of selective filtering of Fourier components. Contact Dalip Singh Mehta at [email protected].