| 摘要 |
PURPOSE:To fully heighten the utilizing efficiency of excitation light, and to perform a read with high sensitivity by a small output of excitation light source, by forming a multilayer film filter in which a reflectance to the excitation light increases corresponding to the increase of its incident angle, on the surface at a side where the excitation light is projected, of a recording body. CONSTITUTION:Excitation light 7 is made incident on an accumulative type fluorescent material plate 2 with the incident angle of almost 0 deg.. Therefore, the excitation light 7 transmits a multilayer film filter 2C excellently with the permeability of almost 90%, and arrives at an accumulative type fluorescent material layer 2B, then excites an accumulative type fluorescent material. The excitation light 7 is reflected to some degree on the surface of the accumulative type fluorescent material layer 2B, then being returned to the multilayer film filter 2C side. Above reflection is irregular reflection, therefore, reflected light 7a is made incident on the multilayer film filter 2C with various kinds of incident angles. The light with a large incident angle made incident on the multilayer film filter 2C out of such reflected light 7a, is reflected with the high reflectance by the filter 2C, and is returned again to the accumulative type fluorescent material layer 2B side, then excites the accumulative type fluorescent material.
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