STRUCTURE OF BENDED PART OF LIGHT GUIDE

摘要

PROBLEM TO BE SOLVED: To prevent a bended part from becoming dark. SOLUTION: This light guide 1 guides a beam from one end to the other end using reflection on an inner surface, and leaks a part of the beam to the outside. Plural sheets of reflection mirrors 3 are arranged parallel at a certain interval in the direction linking an inner corner side with an outer corner side in the bended part. When an angle formed between the axis of the light guide 1 and the reflection mirror 3 is defined asθ, and the interval between the reflection mirrors 3 as (d), the width L of the reflection mirror is made to satisfy d×tanθ<=L<=(3d/2)tanθ. The widths of respective reflection mirrors are reduced by using plural sheets of reflection mirrors, and light guide efficiency is kept by securing the above-mentioned value as the width.