Abstract

It is well known that the light in the near infrared wavelength range of 0.6 ~ 1.3 μm is very useful for the physiological analysis of the human body.^1,2 Because, the light in these wavelength region shows good transmission characteristics in the tissue of the human body which consists of water, hemoglobin, protein and so on. On the other hand, the silica based imagefiber has been recently developed and applied to the thin endscope in the new medical field such as blood vessel, mammary gland, biliary duct and so on. However, its application for the diagnosis of a human body is now limited to the visible region. In order to apply it to the physiological analysis of the human body, we have investigated the image transmission characteristics of the silica based imagefiber in a near infrared region. The silica based imagefiber with the germanium doped core shows good transmittance not only in a visible region but also in a near infrared region. But, it can be assumed that in a near infrared region, its contrast decreases due to the leakage of LP11 mode, for the usual imagefiber has the cutoff wavelength in this region. On the other hand, it has been reported that the cutoff wavelength can be shifted by changing some parameters of the imagefiber, such as the refractive index difference, the core diameter and so on.³

© 1995 IEEE