Quantitative evaluation of optical coefficients of brain tissue such as the absorption coefficient and the reduced scattering coefficient is important for application of light in clinical diagnosis, surgery, and therapeutic procedures for brain diseases. We have investigated a method to estimate the optical coefficients of in vivo brain tissue based on the spectral diffuse reflectance images deduced from a digital red-green-blue image by the Wiener estimation method. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was used to specify the absorption and scattering parameters of brain tissue. The changes in the estimated absorption and scattering parameters during normoxia, hyperoxia, anoxia, and cortical spreading depression indicate the potential applicability of the method by which to evaluate the pathophysiological conditions of in vivo brain.

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The diffuse optical tomography (DOT) technique reconstructs images of optical properties in biological tissue from boundary measurements. Even though its image quality remains far from clinical use, DOT has great potential for diagnostic optical imaging. Its image reconstruction algorithm basically consists of two parts: forward and inverse problems. The radiative transfer equation (RTE) accurately describes photon propagation in biological tissue. Because of its high computation load, the diffusion equation (DE) is often used as a forward model. However, the DE is invalid in the low-scattering and/or highly absorbing regions and near sources. The inverse problem is inherently ill-posed and highly undetermined. The uncertainty of the optical properties of biological tissue also complicates image reconstruction for DOT. Here, we first overview DOT and then describe our approaches for developing accurate and efficient DOT algorithms. Finally, we discuss its future prospects.

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Neruo-marketing, which investigates mind thoughts and emotions by using technologies and methodologies of neuroscience and make good use of the knowledge for products and services, is gathering attentions in recent years. The technologies of mind analysis will be developed progressively in order to create better environment for mind. This is because, as computational power and data accumulation continue to increase Moore’s Law, and technology continues to evolve, humans are faced with an increasing dramatic change in their living environment. Elucidation of the mind needs to be accelerated in order to help people cope with these changes. While, mind investigation involve ethical issue because there is the possibility that the neuro-marketing touch the deepest privacy. This paper introduces the trend in neuro-markeging around the optical topography.

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I produced a miniaturized, multicode, multiband, and programmable light-emitting diode (LED)- stimulator for the wireless control of optogenetic experiments. The LED-stimulator can drive three independent LEDs upon reception of an infrared (IR) signal from a newly developed IR-transmitter. Individual LED photopulse patterns are assigned to as many as 256 different codes of IR signals generated by the IR-transmitter. Using these devices, I remotely controlled the moving direction of a Thy1-ChR2-YFP transgenic mouse by transcranially illuminating the corresponding hemisphere of the primary motor cortex. The IR-transmitter and LED-stimulator will be particularly useful in experiments where free movements or patterned concurrent stimulations are desired, such as testing the social communication of rodents. I summarized optogenetics and available wireless photo-stimulators in this review.

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We propose and demonstrate the laser-induced perturbation of neuronal cells with a focused laser beam. As one approach for realizing the intracellular manipulation of synapses, we evaluated the optical trapping and assembling dynamics of synaptic vesicles or quantum-dot conjugated molecules on neurons by fluorescence analysis. When a near-infrared laser for optical trapping is focused on the synaptic vesicles or molecules, the fluorescence intensity gradually increases with the laser irradiation time, suggesting that the trapping force causes molecular assembly at the laser focus. The molecular dynamics in an optical trap, which is obtained from fluorescence correlation spectroscopy, shows that the motion is constrained at the focus due to the optical trapping force. We also applied a focused femtosecond laser for direct cutting and precise stimulation of a single neuron in the neuronal network. Our methods have the potential to modulate the synaptic transmission of a particular neuron in neuronal networks without any drugs.

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Anoxic depolarization（ AD）, which is caused by ischemia/hypoxia in brain, is known to trigger neuronal cell death. Energy restoration would be needed for preventing the occurrence of AD and resultant cell death. Photobiomodulation therapy, in which low-intensity light with a specific wavelength is used for mitochondria, can enhance energy production in neuronal cells under pathophysiological conditions. In this study, we examined whether visible （665 nm） or near-infrared （808 nm） laser irradiation can control the occurrence of AD in rat brain. At both wavelengths, the onset of AD was significantly delayed in the light-treated hemisphere when compared with that in the non-treated hemisphere （n=8）. The spreading area of AD was also significantly smaller in the light-treated hemisphere than in the nontreated hemisphere. These results suggest that photobiomodulation therapy can control AD in the brain, which is probably due to an increase in ATP by laser irradiation.

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We propose a novel method to study the drying process of tiny ink dots by using the configuration of digital holographic microscopy. Our proposed method enables us to visualize the drying process of tiny ink dots from reconstructed images and to qualitatively evaluate the displacement of ink dots from phase differences. In this experiment, water-based ink was used as a sample and applied to either an OHPsheet or a glass plate by an ink-jet nozzle. We investigated the drying process of ink dots on different plates by the time variations of the reconstructed images of the ink dot surfaces obtained by digital holography.

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We demonstrated all-optical multicasting characteristics using an all-optical triode. The all-optical triode, which is a tandem wavelength converter based on the cross-gain modulation of semiconductor optical amplifiers, enables all-optical signal processing without conventional conversion. The all-optical triode, which has wavelength conversion characteristics, converts the input signal of a single wavelength to the wavelength of four different control signals. This device achieves all-optical multicasting using four channels at the same time. We measured the bit error rate (BER) and the extinction ratio for each wavelength. As the wavelength of the control light becomes a long wavelength from a short wavelength, the extinction ratio decreases and the BER increased. Our experimental results show that all-optical multicasting depends on the SOA gain spectrum corresponding to the wavelength of the control light.

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We observed unexpected modulation in both the spectrum and temporal shape of the amplified signal pulse from a non-collinear parametric amplifier (NOPA). By analyzing the time course of the spectrum, we could prove that the main contribution to the spiky spectrum in the NOPA output is the stimulated Raman process. The modulation is explained by the contribution of the stimulated Raman scattering, induced by a high peak intensity amplified signal pulse, leading to non-ideal pulse compression. This may create a serious problem in the construction of OPA and OPO, particularly for NOPAs used for studying ultrafast processes. The obtained results demonstrate that care must be taken when obtaining the shortest pulse from the NOPA, with reproducible smooth spectral and temporal shapes, by avoiding Raman gain/loss processes.

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We developed a laser Raman spectroscopy technique for the in-situ detection and identification of leaked oils around a transformer to determine whether the leakage originated from its container or an ancillary pipe. This technique successfully identified oil samples using the spectral differences observed in the 1000-3500 cm-1 spectral region. We also demonstrated the Raman identification of oils floating on the water surface as well as oils that were extracted from soils using water. Our results show that laser Raman spectroscopy is a useful method for the in-situ determination of oil leaking from transformers

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