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To manage health conditions of farmed fish and other living creatures, a simple method to measure bioelectric signals of the creatures in seawater is expected. A novel method to measure bioelectric signals by utilizing the conductivity of seawater surrounding the entire body of a fish is proposed. As for the proposed method, a needle-type internal electrode is inserted into the fish’s muscle at a certain measurement point, and an external electrode is sunk in seawater. The internal electrode is isolated from the seawater by virtue of being inserted in the fish. Bioelectric signals generated between the external and internal electrodes are then measured. By sharing the external electrode with the internal electrode, it is possible to measure bioelectric signals with half the number of bioelectrodes used by conventional methods. To demonstrate the practicality of the proposed method, two internal electrodes were inserted into different parts (above the gills and near the tail) of three fish (Parajulis poecilepterus, ca. 20 cm fork length) kept in a tank. The proposed method obtained reliable bioelectric signals corresponding to electrocardiograms (ECGs) and electromyograms (EMGs) from each part of the individual fish.

A novel method of noninvasive bioelectric measurement that utilizes the conductivity of seawater covering a person’s whole body is proposed. Concretely, a conductor used as a common electrode is sunk into the seawater, and four special bioelectrodes isolated from the seawater are attached at measurement points on the body. Bioelectric signals generated between the common electrode and special bioelectrodes are then measured. To verify the effectiveness of the proposed method, bioelectric signals of six participants immersed in a bathtub filled with seawater were experimentally measured. The measurement results revealed that the proposed method enables multipoint bioelectric measurement using about half the number of bioelectrodes used by the conventional method on land, and a plurality of bioelectric phenomena can be observed at one measurement point. It was also revealed that compared with the conventional method, the proposed method significantly reduces external electrical noise included in the bioelectric signals by exploiting the shielding effect of seawater. If simple bioelectric measurements in seawater were possible in the manner described above, not only people such as scuba divers but also precious animals living in the sea could be noninvasively treated as measurement subjects.

Volume holographic optical element (VHOE) for imaging under white light illumination is integrated with imaging elements and background noise reduction filter. An integrated VHOE and the band pass filter which is optimized to the VHOE can develop the optical setup for a wearable eye-gaze detection system. An integrated VHOE is fabricated in photopolymer and then the effects of noise reduction filters as a function of the direction of the incident plane wave into an image sensor are evaluated. Experimental results show that the background noise reduction filter should be designed to reduce the incident light with wide direction of the transmitted light.

In order to establish monitoring systems for home health in elderly people including the prevention of mental illness, we investigated the acceleration of teeth in utterance on the assumption that an acceleration sensor can be implanted into an artificial denture in the near future. In the experiment, an acceleration sensor was fixed in front of the central incisors on the lower jaw by using a denture adhesive, and female and male subjects spoke five Japanese vowels. We then measured the teeth accelerations in three (front-to-back, right-to-left and top-to-bottom) axes and conducted frequency analyses. The result showed that high power spectral densities of the teeth accelerations were observed at a low frequency range of 2-10Hz (both the female and the male) and at a high frequency range of 200-300Hz (the female) or 100-150 Hz (the male). The low and high frequency components indicate movements of the lower jaw and voice sounds by bone conduction, respectively. Especially in the top-to-bottom axis of the central incisor, the frequency component appeared to be significant. Therefore, we found that utterance can be efficiently detected using the acceleration in this axis. We also found that three conditions of normal speech, lip synchronizing and humming can be recognized by using frequency analysis of the acceleration in the top-to-bottom axis of the central incisor.

The imaging characteristics of volume holographic imaging elements (VHIEs) are evaluated numerically and experimentally. To evaluate the imaging characteristics of a VHIE, a volume holographic imaging simulator between one-dimensional regions is fabricated. In the simulator, the propagated light in free space and the diffracted light at the VHIE are calculated by numerical Fresnel propagation and Kogelnik's coupled wave theory, respectively. The imaging characteristics of VHIEs for imaging between point sources and between one-dimensional regions are evaluated. Furthermore, we numerically and experimentally investigate the influences of Bragg-mismatched light on imaging characteristics along the direction of the optical axis of a VHIE.

Optical switching elements using controllable defect modes in one-dimensional photonic crystals are proposed. The transmittance in a defect mode is markedly changed by modifying the local structure of the photonic crystals. Such modification is implemented by micro electro mechanical systems (MEMS) or optical manipulation. We present two methods of changing the transmittance in the defect mode. The spectral transmittance and peak wavelength in the defect mode, and the extinction ratio between on and off states are numerically analyzed using plane waves and Gaussian beams. Numerical results show that the extinction ratio is about 40 dB in 43 layers of SiO2 and air with a thickness of 6.8 µm.

We propose a new method for vibration measurement in non-rigid test environment with electronic speckle pattern interferometry (ESPI). The ESPI is useful for non-contact, real-time analysis of vibration. This method needs rigid test environment, however. When the interferometer and a vibration surface are on a non-rigid table or their environments are separated, especially at manufacturing areas, high-amplitude, low-frequency noise fluctuation overwhelms a vibration signal and the amplitude fringes disappear. We use electronic shutter function of a TV camera and reduce exposure time of an image sensor. With the time reduction, we may extract an image from many input images, during whose acquisition time noise fluctuation turns back and its magnitude is so small that the vibration signal goes to be included in the image. We accumulate the images and increase the contrast of the amplitude fringe map. We evaluated usefulness of this method with circular saw vibration. The interferometer and the saw are fixed on a rigid board and the noise fluctuation is electronically superposed on the vibration signal with sine wave. This method is successful for a fluctuation amplitude of 60μm.

Human-eye detection is demonstrated by volume holographic imaging elements (VHIEs) for see-through-type glasses. A VHIE is integrated with imaging function and background noise reduction filter for imaging under white light illumination.

We evaluate the imaging characteristics of an integrated optical imaging element that is used to obtain images from opposite directions in one imaging sensor for a three-dimensional eye-gaze detection system. The element consists of a transmission-type holographic imaging element, a reflection-type holographic imaging element, and a noise reduction filter. In the evaluation of the imaging characteristics, modulation transfer functions of both the reflection-type and the transmission-type holographic imaging elements are evaluated. Results indicate that both holographic imaging elements have enough resolution, even under white-light illumination conditions, for eye-gaze detection. We also demonstrate the simultaneous detection of images by an artificial eye and objects by using the integrated element under white light or sunlight.

Optimization of integrated volume holographic optical imaging element (IVHIE) is investigated. IVHIE can image eye and the scene to be gazed on an image sensor. A filter is attached to the IVHIE to remove the transmitted background scene and then is optimized.

A holographic imaging element (HIE) by use of a transmission-type holographic optical element is evaluated by a numerical simulator. To design HIE and evaluate its imaging characteristics, we fabricate a holographic imaging simulator between one-dimensional arbitrary spaces. In the simulator, two calculation methods that are free space propagation and diffraction at the holographic element are used. The propagated light between the input plane and a transmission-type HIE, or between the HIE and the observation plane is calculated by numerical Fresnel propagation. The diffracted light at the HIE is calculated by Kogelnik's coupled wave theory. By using the simulator, imaging characteristics of a pair of point sources and one- dimensional regions are evaluated.

In a three-dimensional (3D) eye-gaze detection system with an integrated volume holographic imaging element (VHIE) and two image sensors, human eye gaze is detected by analyzing both the reflected images of two eyes of a human and the transmitted images that the human is watching. To make the detection of the reflected images of the eyes more effective, a noise filter for removing the background noise is fabricated and is then attached to the integrated VHIE. The results obtained by the noise reduction technique are presented.