Optical encryption technology using phase-shifting interferometry (PSI) is widely used in many security fields, showing the advantages of parallel processing and the high security due to the information can be encrypted in multiple dimensions. The traditional PSI- based encryption methods are realized by the traditional multi-step phase-shifting algorithms (PSAs), although they are fast and accurate, the phase shifts deviation (PSD) caused by phase shifter detuning often affect the performance of the above methods. In order to solve this problem, a phase-only encryption method combining a normalization and orthogonalization phase-shifting algorithm (NOPSA) is proposed to eliminate the influence of PSD on the effective on decryption. First, the original image is phase encoded and encrypted by a phase key loaded on a liquid crystal spatial light modulator (SLM). Subsequently, the modulated reference light will be overlapped with the object wave to form interference pattern. Finally, the encrypted image hiding can be implemented based on NOPSA. Compared with the current PSI- based encryption methods, its obvious advantage is that when the phase shifts are not accurate or unknown, the proposed method can still achieve high quality encryption and hiding, which broadens the working conditions of PSI- based encryption methods.
A look-up table (LUT) method for solving the problem of phase unwrapping is presented. Considering the effect of noise on the unwrapping process, a concept called “tolerance” is advanced, and an associated algorithm called the “equipartition of tolerance” algorithm is proposed. The proposed algorithm eliminates the need for a high signal-to-noise ratio while retaining the LUT method’s advantages of extended measurement range and high precision. Further, it improves the tolerance of the LUT method and enables reconstruction of discontinuous objects. In simulations and experiments conducted, the proposed algorithm successfully unwrapped the absolute phase of a slope model and a three-step model. The proposed algorithm is significantly more accurate and has better stability and sensitivity than the heterodyne algorithm.
KEYWORDS: Raman spectroscopy, Proteins, Stem cells, Luminescence, Biological research, Principal component analysis, Spectroscopy, Molecular mechanisms, Data analysis, Signal to noise ratio
Mesenchymal stem cells (MSCs) differentiate into islet-like cells, providing a possible solution for type I diabetes treatment. To search for the precise molecular mechanism of the directional differentiation of MSC-derived islet-like cells, biomolecular composition, and structural conformation information during MSC differentiation, is required. Because islet-like cells lack specific surface markers, the commonly employed immunostaining technique is not suitable for their identification, physical separation, and enrichment. Combining Raman spectroscopic data, a fitting accuracy-improved biochemical component analysis, and multiple peaks fitting approach, we identified the quantitative biochemical and intensity change of Raman peaks that show the differentiation of MSCs into islet-like cells. Along with increases in protein and glycogen content, and decreases in deoxyribonucleic acid and ribonucleic acid content, in islet-like cells relative to MSCs, it was found that a characteristic peak of insulin (665 cm−1) has twice the intensity in islet-like cells relative to MSCs, indicating differentiation of MSCs into islet-like cells was successful. Importantly, these Raman signatures provide useful information on the structural and pathological states during MSC differentiation and help to develop noninvasive and label-free Raman sorting methods for stem cells and their lineages.
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