| 摘要 |
PURPOSE: To increase the focal depth of a distributed index lens array while keeping an optimum radiation efficiency. CONSTITUTION: Four arrays 22 to 25 of distributed index optical fibers are bundled to realize a distributed index lens array 20. In the array 20, 16 fibers contribute to an effective aperture 21, and the effective aperture 21 is approximately symmetrical. When the value of n0√AR where n0 is the axial refractive index of fibers and A is the lens refractive index distribution constant and R is the radius of each fiber is reduced, the focal depth (DOF) of the array 20 is increased. Though the radiation efficiency is reduced then, the optimum radiation efficiency is kept because the effective aperture 21 has a more symmetrical structure. Reduction of the value of n0√AR is achieved by using a weaker standard SELFOC lens array to reduce the constant A. |
