Patent ID: 8270794

Claim:
A light guide for endoscopes constituted by a plurality of bundled optical fibers, for propagating an illuminating light beam, which is focused and caused to enter a light input end facet thereof, to a light output end facet thereof, to emit the illuminating light beam onto a portion to be observed; the light guide comprising: the plurality of optical fibers including bundled plural first multi mode optical fibers and bundled plural second multi mode optical fibers, each of said second multi mode optical fibers having a diameter smaller than a diameter of each of said first multi mode optical fibers; and a transparent member having a sectional shape which is at least as large as the focused spot of the illuminating light beam, provided in close contact with the light input end facets of the first multi mode optical fibers; wherein the optical fibers are connected to the transparent member in a maximally densely packed state, and more than one of the second multi mode optical fibers are connected to each of the first multi mode optical fibers; and a central optical fiber and six peripheral optical fibers which are arranged about the periphery of the central optical fiber are employed as said bundled plural first multi mode optical fibers and as each of said second multi mode optical fibers; and the optical fibers form the maximally densely packed state by being provided such that each of the six peripheral optical fibers is in contact with the central optical fiber, and adjacent peripheral optical fibers are in contact with each other.