| 摘要 |
PURPOSE:To compensate an optical path so that the optical path of projection light is aligned when incident light varies in wavelength by forming a prism reflector or prism coupler of plural glass materials which differ in Abbe number. CONSTITUTION:The prism reflector 11 consists of two kind of glass materials M1 and M2 which differ in Abbe number and the side of the glass material 2 is formed in a triangular shape on the bottom surface of the prism reflector 11. The glass material Ml is formed in a trapezoid shape covering the glass material M2 and has a luminous flux incidence surface 13 and a luminous flux projection surface 14 and a border surface at the border of the glass materials M1 and M2. Then, when incident light beams L1 and L2 having wavelengths lambda1 and lambda2 are made incident on an incidence point A at an angle theta 1 of incidence, they are refracted at incidence points B and C on the glass material M2 to form an intersection D. The two light beams L1 and L2 which are reflected by the bottom surface at the intersection D are both projected at an angle theta1 of projection and the projection optical paths of the wavelengths lambda1 and 22 can be aligned with each other. Consequently, variation of the optical paths of the projection lights can be compensated and the stability of the parallelism between the projection lights can be improved. |
