| 摘要 |
PURPOSE:To improve a picture reproducibility of a red part of an original by a slit exposure, and also to execute efficiently a laser beam exposure by using multi-layer film filter, and setting the thickness of each layer to a prescribed value. CONSTITUTION:A glass substrate G, the first layer A and an intermediate layer B are provided, and between the first layer A and the intermediate layer B, and between the intermediate layer B and the glass substrate G, multiple film constitution C, D consisting of five layers of alternate multiple layers HLHLH of a high refractive substance H and a low refractive substance L are provided respectively. A high refractive index layer and a low refractive index layer are shown as nH and nL, respectively in the figure, and thickness of the first layer A is lambda0/8 (where lambda0: oscillation wavelength of a laser beam), thickness of the intermediate layer B is lambda0/2, thicknesses of the multiple film constitutions C, D are both alpha0/4, and the wavelength=780nm. In this regard, as for the high refractive index substance and the low refractive index substance, TiO2 (n=2.35) and MgF2 (n=1.38) are used, respectively. |
