Among the biometric identification methods, fingerprint identification is one of the most widely researched and applied biometric identification technologies. However, the traditional fingerprint identification system is vulnerable to attacks with the use of fake fingerprints, causing security problems. At the same time, when the skin of the finger is worn, wet, stained the efficiency of fingerprint identification will suffer. Optical Coherence Tomography is a non-invasive high resolution imaging technology that can image the subcutaneous depth of 1mm. Therefore, OCT can be used to obtain fingerprints inside the finger to effectively solve the security problem of fingerprint recognition, and at the same time solve the problem of the reduction in the recognition performance when the finger epidermis is damaged by external factors. In this research, OCT technology is used to collect the data of the three-dimensional structure of the fingertip by the aid of the deep learning U-net, SIFT and FLANN algorithm to ensure the reconstruction and recognition of internal fingerprints. The results show that U-net can extract the contour of the subcutaneous papilla layer and reconstruct the 2D internal fingerprint. Then we use Sift algorithm to match and splice the feature points of the internal fingerprints collected by multiple overlapping and establish a large area of internal finger template library. Finally, the FLANN algorithm library is used to extract the minutiae of the tested internal fingerprint and match the fingerprint template to achieve identity recognition. Compared with the traditional algorithm, this method is difficult to imitate and has high security.
A non-interferometric phase retrieval method in the phase-modulated holographic data storage system is proposed. This method can not only avoid phase ambiguity issue with interferometric, but also increase the capacity by reducing media consumption. Iterative Fourier transform (IFT) algorithm is one of easiest non-interferometry methods. We choose to use IFT algorithm due to its compact and stable realized system and simple single-shot operation. Strong constraint conditions such as phase-only and embedded data which are known phase values of the certain positions on the encoded data page are provided to realize accurate and quick phase retrieval in the holographic data storage system.
We demonstrated the phase retrieval process of the recorded 4-level phase pattern in the media experimentally. Besides, we can realize one-time Nyquist frequency recording which is the limitation of recording area by using the non-interferometric phase retrieval method and the periodicity of Fourier frequency spectrum. Therefore, the media consumption can be reduced by 35%. Eventually, we can increase storage capacity by at least 1.5 times.
We have proposed photonic DNA computing as a new parallel computing paradigm, in which optical techniques are used to manipulate information-coded DNA. In this paper, we present a parallel transportation of multiple beads bound with hairpin-structure DNA using a dynamic optical tweezers system which combines a spatial light modulator (SLM) with a diffractive optical element (DOE). This system provides and effective method for parallel manipulations of DNA-bound beads at multiple positions. In the experiments, three
2.8-μm-diameter beads bound with hairpin DNA were trapped and transported in 1 μm of step by switching of the SLM patterns. The results demonstrate that the dynamic holographic optical tweezers system with combination of the DOE and the SLM is useful in spatially parallel processing required for photonic DNA computing.
To overcome the restriction of the density of optical memory systems due to diffraction limit, we have been studying photonic DNA memory, which utilizes photonic technologies and the DNA computing methodology. Our scheme is on the basis of local DNA reaction using laser irradiation and transportation of DNA using parallel optical tweezers with fabricating DNA clusters by attaching DNA onto beads. This paper reports on a new dynamic optical tweezers system, which combines a spatial light modulator (SLM) and a diffractive optical element (DOE) for manipulating DNA clusters. With this combination, real-time programmable manipulation of DNA clusters is achievable in a large spatial range. We also can choose simple patterns for the SLM, and decrease computation cost. In this experiment, a laser beam (633nm wavelength) illuminates a SLM (Hamamatsu Photonics K. K.; PPM8267), which is imaged on an 80-lp/mm transmission-type grating, then the beam is focused with a water immersible objective lens (x 100, NA 1). Simple blazed-phase patterns have different grating constants that are perpendicular to that of the grating are displayed on the SLM. We succeeded in lifting up three 6-micron-diameter polystyrene beads on a glass slide with light spots duplicated by the grating, then transporting the beads in three dimensions simultaneously with changing the grating constants on the SLM. We demonstrated that a same manipulation was implemented at different positions by duplicating a pattern that was generated when only using the SLM. This is usable in implementing a same operation for different data at multiple positions with a single instruction. The promising applications of the method include a nano-scale image memory with encryption.
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