| 摘要 |
PROBLEM TO BE SOLVED: To enhance brightness of a back light used in a liquid crystal panel or the like and reduce consuming power. SOLUTION: A plurality of birefringent members 4 are arranged in a light guide body 3, and when the refraction index of the light conductor 3 is represented by n1 , normal light refraction index of the birefringent member by n0 , and abnormal light refraction index by ne , the condition of ne >n1 >n0 is satisfied. Light incident to the light guide body 3 conducts double refraction when it transmits the double refraction member, an angle incident to the interface of the light guide body 3 of extraordinary light 13 is made larger than a total reflection angle, and the extraordinary light 13 outgoes from the light guide body 3. When ordinary light 16 is repeatedly transmits a birefringent sheet 5, a vibration surface is rotated, and finally the ordinary light 16 outgoes from the light guide body 3 as the extraordinary light. As a result, the brightness becomes twice as strong compared with the conventional back light. |
