Takashi Tsumanuma

The Ultrathin Silica Based Imagefiber For The Medical Usage

The most suitable structure of the ultrathin silica based imagefiber for the medical usage were investigated by evaluating the image transmission characteristics and the mechanical characteristics. As a result, following facts have been clarified, 1) In the case of NA 0.43, the suitable structural parameters are core-cladding ratio 1.5 and pixel diameter 5 μm. 2) The 0.27 mm diameter imagefiber can stand more than 103 times repeated bending in 10 mm radius.

Specialty fibers for sensors and sensor components

This paper surveys a variety of special fibers which have been developed for the sensor and component markets, based upon the polarization-maintaining and absorption-reducing design. Various types of polarization-maintaining fibers, rare-earth doped fibers, image-transmitting fibers, and other special fibers will be discussed.

Ultrathin single-mode image fiber for medical usage

Miniaturization of silica-based ultrathin imagefibers is needed to serve more medical applications in diagnostic imaging. However, by reducing the pixel element size rapidly, the imagefibers were found to have the characteristics of the single-mode imagefiber. The optical properties of the ultrathin imagefiber with the LP11 mode cutoff wavelength within the visible wavelength region, which is called the single-mode imagefiber, have been studied. The studies found that the property of wavelength selective propagation associated with single-mode ultrathin imagefibers can be applied to the field of biomedical diagnostic imaging as a fluorescence sensor.

Characteristics of an optical fiber for high-power excimer lasers

KrF excimer laser (248 nm) is expected to be the new therapeutic instrument in the medical field. However, there is still not the optical fiber which has enough durability for the high power energy of KrF excimer laser. We have developed the optical fiber for transmitting the light of the high power KrF excimer laser. This fiber consists of the pure silica core with a large amount of OH, and also has been specially treated during fabrication. As a result, the newly developed fiber has achieved to transmit the light of KrF excimer laser efficiently.

Ultrathin fiberscope for stereoscopic vision

Endoscope for stereoscopic vision is in great demand for medical field to diagnose and treat disease parts of patients more precisely. The authors are convinced that the silica based imagefiber is suitable for making a thinner fiberscope for stereoscopic vision. The structure of the fiberscope and the quality of transmitted image have been investigated. It has been found that stereognosis depends on the magnification of eyepiece, distance between left and right objective lenses and the image quality between two transmitting systems. On the basis of these results, the ultrathin fiberscope with silica based imagefibers for stereoscopic vision have been developed. The diameter of fiberscope is only 2 mm with two transmitting systems that consist of two imagefibers with 10000 pixels and lightguide for illumination and objective lenses. This fiberscope for stereoscopic vision can be used for the micro surgery, such as the laparoscopic surgery and the thoracoscopic surgery required for the thin diameter.

New image diagnosis system with ultrathin endoscope and clinical results

The characteristics of the thin silica based imagefiber have been investigated by evaluating the image thrown on the TV monitor. As a result, it has been found that the picture diameter of the imagefiber and the magnification of the eyepiece strongly relate to the image quality of the total system. On the basis of this result, the image system for the diagnosis of breast lesions with thte thin endoscope of only 0.4 mm diameter has been developed. And we have applied this system to 66 ducts and succeeded in observing 61 ducts (92.4%) and could get some clinical information, which would be useful to the early detection of cancer.

New Ultrathin Needle Scope Used For Diagnosis Of Small Parts

The image transmission characteristics of shorter silica based imagefiber has been investigated. It has been found that the image quality strongly depends on the length and the suitable structure to the fiber length exists for the imagefiber. And as a result, it has been clarified that the most part of the unwanted waves can be removed by twisting or bending the imagefiber.

Ultrathin image fiber with hemispherical fiber lens for medical use

The gradient-index rod lenses have been conventionally used as the objective lens of the ultrathin medical fiberscope. In this paper, we propose to apply the new hemispherical fiber lens for the ultrathin fiberscopes. The lens can be fabricated by attaching a silica rod to imagefiber and heating the free end of the rod in arc charge. As the result of our investigation, it has been known that the radius of the hemispherical lens can be controlled by the discharge time. The imagefiber with the hemispherical lens had a diameter of 0.2 mm, 1600 pixels, a working distance of 3 mm and the angle of view of 40 degrees. It has been found by evaluating its image quality that it has the sufficient feature for the practical medical usage. In addition, it has been shown that the end of the imagefiber itself can be transformed to the hemispherical objective lens, and its optical characteristics as a lens can be controlled by changing the elongating length and the preheating condition.

New method of eliminating mesh pattern of image fiber

In order to eliminate the mesh pattern due to pixels of the imagefiber, we have developed and studied the new image processing method. As a result, it has been found that the quality of the processed image is improved in brightness and contrast without blurring.

Silica-based rod lens for the medical fiberscope

The ultrathin fiberscope, in which the outer diameter is under 1.0 mm, has made possible the direct observation of narrow portions within the human body. The fiberscope mainly consists of the imagefiber, the objective lens, and the illumination fiber, and each advance of these devices has brought the reduction of the scope-diameter. We have investigated the silica based rod lens for the following merits: (1) The fiberscope can be sterilized by the (gamma) -ray instead of ethylene oxide gas which has the problem of carcinogenicity, because the silica glass has high radiation resistant characteristics. (2) The silica based rod lens can be spliced with the imagefiber without any adhesive agent by using the arc fusion splicing machine. As a result, the reliability of the fiberscope can be significantly improved. The silica based rod lens with 125 micrometers in diameter was fabricated by drawing from preform rod made by the vapor phase axial deposition method. The characteristics of their images were evaluated by the modulation transfer function method. This paper presents the details of the fabrication technique of the silica based rod lens and its characteristics.