A columnar model explaining long-term memory

A hologram provides a useful model for explaining the associative memory of the brain. Recent advances in neuroscience emphasize that single neurons can store complex information and that subtle changes in neurons underlie the process of memorization. Experimental results suggest that memory has a localized character. This finding is inconsistent with the characteristics of holographic memory, because this memory has a delocalized, uniform distribution of refractive index in the recorded medium. The recently proposed columnar memory model has a discrete distribution of refractive index. In this study, we first examined the performance of columnar memory and found that it was comparable to holographic memory. Secondly, we showed that this model could explain the above-mentioned experimental results as well as associative memory

Fiber-based polarization-sensitive Fourier domain optical coherence tomography using B-scan-oriented polarization modulation method

Fiber-based high-speed polarization-sensitive Fourier domain optical coherence tomography (PS-FD-OCT) is developed at 840 nm wavelength using polarization modulation method. The incident state of polarization is modulated along B-scan. The spectrometer has a polarizing beamsplitter and two line-CCD cameras operated at a line rate of 27.7 kHz. From the 0th and 1st orders of the spatial frequencies along the B-scanning, a depth-resolved Jones matrix can be derived. Since continuous polarization modulation along B-scan causes fringe washout, equivalent discrete polarization modulation is applied to biological measurements. For the demonstration, an in vitro chicken breast muscle, an in vivo finger pad, and an in vivo caries lesion of a human tooth are measured. Three dimensional phase retardation images show the potentials for applying the system to biological and medical studies.This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-14-6502. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law

Retardagraphy: a technique for optical recording of the retardance pattern of an optical anisotropic object on a polarization-sensitive film using a single beam

A technique that employs a single laser beam is proposed for recording the retardance of an optical anisotropic object. The retardance pattern is converted into a polarization pattern using a quarter-wave plate and recorded on a polarization-sensitive medium. The recording medium is illuminated by homogeneous polarized light, and the light transmitted by the recording medium is analyzed to reconstruct the recorded retardance pattern

Automatic characterization and segmentation of human skin using three-dimensional optical coherence tomography

A set of fully automated algorithms that is specialized for analyzing a three-dimensional optical coherence tomography (OCT) volume of human skin is reported. The algorithm set first determines the skin surface of the OCT volume, and a depth-oriented algorithm provides the mean epidermal thickness, distribution map of the epidermis, and a segmented volume of the epidermis. Subsequently, an en face shadowgram is produced by an algorithm to visualize the infundibula in the skin with high contrast. The population and occupation ratio of the infundibula are provided by a histogram-based thresholding algorithm and a distance mapping algorithm. En face OCT slices at constant depths from the sample surface are extracted, and the histogram-based thresholding algorithm is again applied to these slices, yielding a three-dimensional segmented volume of the infundibula. The dermal attenuation coefficient is also calculated from the OCT volume in order to evaluate the skin texture. The algorithm set examines swept-source OCT volumes of the skins of several volunteers, and the results show the high stability, portability and reproducibility of the algorithm.This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-5-1862. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law

Development of an Optical Neural Network Module

Introduction The main features of artificial neural networks are the large number of nonlinear processing elements and the massively parallel interconnections among them. Many researchers have studied the hardware required for artificial neural networks and the software for such highly parallel computations. In terms of the hardware, two different approaches have been proposed: VLSI-based neural networks and optical neural networks. The VLSI techniques, in which remarkable progress has been made, are adopted to many artificial neural networks. Compared with the complex 3-D interconnectionsof the human brain, the VLSI techniques have an inherent 2-D architecture with a poor density of wiring between 2-D surfaces. Optical signals, on the other hand, can flow in the 3-D space. Many advantages of applying optics to artificial neural networks have been discussed, and many optical and optoelectronic neural networks have been proposed. The optics, which has inherent parallelism and

Development of an Optical Neural Network Module

Introduction Some efforts to develop optical computing systems have been made in this decade. Many researchers have studied the hardware required for artificial neural networks and the software for such highly parallel computations. In terms of the hardware, two different approaches have been proposed: VLSI-based neural networks and optical neural networks. Many advantages of applying optics to artificial neural networks have been discussed, and many optical and optoelectronic neural networks have been proposed. The optics, which has inherent parallelism and high speed features, offers high potential interconnections in terms of density, capacity, and flexibility. Optical techniques lead to huge parallel operations and interconnections, and provide useful hardware for artificial neural networks. In order to develop a large scale optical neural network computing system, a smaller module is developing at the first step. We present two architectural approaches considered, that is

High Precision Stokes Polarimetry for Scattering Light using Wide Dynamic Range Intensity Detector

This paper proposes a Stokes polarimetry for scattering light from a sample surface. To achieve a high accuracy measurement two approaches of an intensity detector and analysis algorism of a Stokes parameter were proposed. The dynamic range of this detector can achieve up to 1010 by combination of change of neutral-density (ND) filters having different density and photon counting units. Stokes parameters can be measured by dual rotating of a retarder and an analyzer. The algorism of dual rotating polarimeter can be calibrated small linear diattenuation and linear retardance error of the retarder. This system can measured Stokes parameters from −20° to 70° of its scattering angle. It is possible to measure Stokes parameters of scattering of dust and scratch of optical device with high precision. This paper shows accuracy of this system, checking the polarization change of scattering angle and influence of beam size

High Precision Stokes Polarimetry for Scattering Light using Wide Dynamic Range Intensity Detector

This paper proposes a Stokes polarimetry for scattering light from a sample surface. To achieve a high accuracy measurement two approaches of an intensity detector and analysis algorism of a Stokes parameter were proposed. The dynamic range of this detector can achieve up to 1010 by combination of change of neutral-density (ND) filters having different density and photon counting units. Stokes parameters can be measured by dual rotating of a retarder and an analyzer. The algorism of dual rotating polarimeter can be calibrated small linear diattenuation and linear retardance error of the retarder. This system can measured Stokes parameters from −20° to 70° of its scattering angle. It is possible to measure Stokes parameters of scattering of dust and scratch of optical device with high precision. This paper shows accuracy of this system, checking the polarization change of scattering angle and influence of beam size