Characterization of collagen orientation in human dermis by two-dimensional second-harmonic-generation polarimetry

We have proposed an optical probe that can be used to characterize the orientation of collagen fibers in human dermis. A specific probing ability for collagen results from the use of second-harmonic-generation (SHG) light induced by collagen molecules in the tissue. Based on the concept of collagen SHG light, a reflection-type polarization measurement system (named SHG polarimetry) with a probe light spot of 15 microm in diameter has been constructed, and the human reticular dermis has been measured using this system. Resultant data exhibit that the reticular dermis possesses approximately uniaxial orientation of the collagen fibers. Furthermore, we demonstrated a nondestructive measurement of the collagen orientation in the papillary dermis across an epidermis layer. For distribution measurement of the collagen fiber orientation in the reticular dermis, we have extended the SHG polarimetry to one- (1-D) and two-dimensional (2-D) measurement. By the macroscopic 2-D SHG polarimetry, we have observed that the orientation angle and organization degree of collagen fibers vary widely depending on the discrete probing positions in the reticular dermis. Furthermore, microscopic 1-D SHG polarimetry indicated a swell of the orientation angle and a large variance of the organization degree in the collagen fibers in the microscopic region. These results imply that the reticular dermis posses a tangled structure of collagen fibers, which is highly consistent with the result of the anatomical examination of the skin. The proposed method will be a powerful tool for monitoring the microscopic distribution of the collagen fiber orientation in the human dermis.


Microscopic time-resolved two-dimensional imaging with a femtosecond amplifying optical Kerr gate

We demonstrate microscopic time-resolved two-dimensional (2D) imaging that is based on a femtosecond amplifying optical Kerr gate (fs-amp OKG). The contribution of the optical nonlinear effects to the transverse imaging performance and the limit of the transverse resolving power are investigated. The optical Kerr effect in the excited state with amplification, used in the fs-amp OKG, does not deteriorate the quality of the time-resolved image at transverse resolutions up to at least 5.5 microm. We obtain a femtosecond-time-resolved 2D image of a microscopic object with a transverse resolution of 1.7 microm.


Visual demonstration of calcium accumulation in human arteries of upper and lower limbs

To elucidate the calcium content of the arteries in the upper and lower limbs, the authors determined the calcium content of all the arteries in the upper and lower limbs continuously by microwave-induced plasma-atomic emission spectrometry. The subjects were an 87-yr-old man and a 72-yr-old woman. The calcium content was determined both in the arteries of the upper limbs continuously, such as the subclavian arteries and its distal arteries, and in the arteries of the lower limbs, such as the common iliac arteries and its distal arteries. The common finding that the higher accumulation of calcium occurred in the arteries of the lower limbs in comparison to the arteries of the upper limbs and extremely high accumulation of calcium occurred in the common, external, and internal iliac arteries was obtained in the two subjects. The calcium content of the arteries in the upper and lower limbs was visually demonstrated.


Stabilization of femtosecond mode-locked Ti:sapphire laser for high-accuracy pulse interferometry


Three-dimensional shape measurement of a diffusing surface by use of a femtosecond amplifying optical Kerr gate

We propose a system for three-dimensional (3D) shape measurement of a diffusing surface by use of a previously developed femtosecond amplifying optical Kerr gate (fs-amp OKG). The system has an opening time of 459 fs and a maximum transmittance of 185%. It also provides good 3D imaging performance: a transverse imaging resolution of 70 microm, a depth resolution of 100 microm, and a positioning accuracy of 5.9 microm in depth. It is found that the optical Kerr effect and the amplification process in the fs-amp OKG do not cause the quality of a time-resolved image to deteriorate. We prove the effectiveness of the proposed system by measuring the shapes of completely diffusing objects with stepped and spherical surfaces.


Three-dimensional imaging using a femtosecond amplifying optical Kerr gate


自動車用スパークプラグを用いたナノ秒パルス光源の試作と応用

自動車用スパークプラグを用いたナノ秒パルス光源の試作と応用


Accurate stabilization of a 3 mW single-mode output He-Ne laser by intermittent frequency offset locking to an iodine stabilized He-Ne laser


An intermittent frequency offset lock of a transverse Zeeman laser to an iodine stabilized He-Ne laser


Intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser


顕微蛍光分光測光による歯科用前歯人工歯と天然歯の蛍光特性の比較

顕微蛍光分光測光による歯科用前歯人工歯と天然歯の蛍光特性の比較


Optical-frequency-comb based ultrasound sensor

Progress in Biomedical Optics and Imaging - Proceedings of SPIE


Hyperspectral single-pixel imaging with dual optical combs


Scan-less confocal phase imaging with dual comb microscopy


Orientation analysis of collagen fibers in healing tendon by using second-harmonic-generation microscopy


In situ monitoring of collagen fibers in human skin using a photonic-crystal-fiber-coupled, hand-held, second-harmonic-generation microscope


Multi-object investigation using two-wavelength phase-shift interferometry guided by an optical frequency comb

Two-wavelength phase-shift interferometry guided by optical frequency combs is presented. We demonstrate the operation of the setup with a large step sample simultaneously with a resolution test target with a negative pattern. The technique can investigate multi-objects simultaneously with high precision. Using this technique, several important applications in metrology that require high speed and precision are demonstrated.


High-precision 3D surface topography measurement using high-stable multi-wavelength digital holography referenced by an optical frequency comb

High-stable, two-wavelength, digital holography referenced by an optical frequency comb is presented. The technique is demonstrated by using optical waves from an external cavity laser diode phase-locked to a mode-locked Er-doped fiber comb laser light. The mixed beat signal is stabilized at 30 MHz by a sensitive proportional integral derivative controller. The tunable continuous-waves stabilized with frequency uncertainty of 5×10 are employed to investigate large stepped structures.


Real-time line projection for fast terahertz spectral computed tomography

We demonstrated fast terahertz spectral computed tomography by using real-time line projection of a terahertz beam. Two types of cross-sectional images of continuously rotating samples have been measured in only a few seconds. From temporal data, a peak-to-peak sinogram and cross sections have been reconstructed using a filtered backprojection algorithm. Using fast Fourier transform from temporal data, spectral cross sections of the sample have been obtained.


Fiber-based, hybrid terahertz spectrometer using dual fiber combs

We constructed a fiber-based, hybrid terahertz (THz) spectrometer having two working modes, asynchronous-optical-sampling THz time-domain spectroscopy (AOS-THz-TDS) and multiple-frequency-heterodyning THz comb spectroscopy (MFH-THz-CS), by use of dual fiber-laser-based frequency combs. A spectral range of 2THz and dynamic range of 100 was achieved at the single sweep measurement of 200ms in the AOS-THz-TDS mode, whereas the detailed structure of the THz frequency comb was clearly observed in the MFH-THz-CS mode. The spectrometer features compactness, robustness, flexibility, and cost effectiveness, in addition to high spectral resolution in rapid data acquisition, and has the potential to become a powerful tool for practical applications.


Mechanism of elastic softening behavior in superlattice


Stiffened ultrathin Pt films confirmed by acoustic-phonon resonances


Terahertz frequency comb by multi-frequency-heterodyning photoconductive detection for high-accuracy, high-resolution terahertz spectroscopy


Asynchronous optical sampling terahertz time-domain spectroscopy for ultrahigh spectral resolution and rapid data acquisition


Inactivation of SARS-CoV-2 by deep ultraviolet light emitting diode: A review