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1.
Appl Opt ; 57(4): 632-638, 2018 Feb 01.
Article in English | MEDLINE | ID: mdl-29400733

ABSTRACT

We study the efficiency of coherent anti-Stokes Raman scattering (CARS) under frequency comb excitation. We calculate the power density of the anti-Stokes signal for two major cases: (1) molecular excitation by frequency comb and cw probe and, (2) both excitation and probing by frequency combs. In the first case, average CARS power varies as an inverse third degree of frequency combs free spectral range (FSR-3); in the second case, it varies as FSR-5. These results were applied to the CARS on blood glucose under frequency comb excitation. It was found that the resulting glucose CARS signal could approach nanowatt (nW) level at FSR=10 GHz.

2.
J Biophotonics ; 11(4): e201700153, 2018 04.
Article in English | MEDLINE | ID: mdl-29027755

ABSTRACT

The work describes features of the compressed sensing (CS) approach utilized for development of a wearable system for wrist vein recognition with single-pixel detection; we consider this system useful for biometrics authentication purposes. The CS approach implies use of a spatial light modulation (SLM) which, in our case, can be performed differently-with a liquid crystal display or diffusely scattering medium. We show that compressed sensing combined with above-mentioned means of SLM allows us to avoid using an optical system-a limiting factor for wearable devices. The trade-off between the 2 different SLM approaches regarding issues of practical implementation of CS approach for wrist vein recognition purposes is discussed. A possible solution of a misalignment problem-a typical issue for imaging systems based upon 2D arrays of photodiodes-is also proposed. Proposed design of the wearable device for wrist vein recognition is based upon single-pixel detection.


Subject(s)
Biometric Identification/instrumentation , Optical Devices , Veins , Wearable Electronic Devices , Wrist/blood supply , Humans , Signal Processing, Computer-Assisted
3.
Opt Express ; 23(25): 32215-21, 2015 Dec 14.
Article in English | MEDLINE | ID: mdl-26699011

ABSTRACT

Through-focus scanning optical microscopy (TSOM) method based on use of a library, which is composed of simulated defocused images of nanosized silicon lines on the top of a monocrystalline silicon substrate, is demonstrated. The images are simulated using Finite-Differences in Time-Domain (FDTD) method taking into account optical aberrations of the experimental setup, which are measured experimentally. Consideration of the optical aberrations allows us to reduce the discrepancy between experimental and simulated defocused images of the samples under study to the value of ≈2%in contrast to ≈10% when the aberrations are not taken into account. It results in ≈5% recognition accuracy for critical dimension (CD) values in the range 40-150 nm.

4.
Opt Express ; 22(12): 14958-63, 2014 Jun 16.
Article in English | MEDLINE | ID: mdl-24977589

ABSTRACT

We present a novel all optical method for nanoscale pattern inspection. This method uses the chromatic aberration in an imaging optical system and a tunable light source. Such an approach allows stable and precise inspection of nanoscale objects based on an analysis of their defocused diffraction patterns without any external mechanical influence on the sample or optical system. We demonstrate the efficiency of a low cost light source tunable in the range of a light emitting diode bandwidth of ~30 nm (FWHM) for providing the required defocusing. The proposed method is tested using calibrated lines (height 50 nm, length 100 µm, critical dimension (СD) value range 40-150 nm with 10 nm steps) on a monocrystalline silicon substrate with demonstrated measurement accuracy better than 10 nm. A comparison of this all optical method with a mechanical scanning inspection system is discussed.

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