| 摘要 |
PROBLEM TO BE SOLVED: To provide a light absorbing filter capable of attaining required transmissivity and a low reflection factor for the light with wavelengthλ=780nm e.g. SOLUTION: The reflection factor R of a light absorbing filler with the thickness t=20nm (≈λ1/40) of a 3rd SiO2 layer 4 laminated adjacently to an Al layer 3 becomes a minimum value (about 1.8%) at wavelength 1:800nm, and even at the required wavelengthλ=780nm, the reflection factor R becomes about 2.4%. When the thickness (t) of the 3rd SiO2 layer 4 is thinned, the reflection factor R is reduced, the wavelengthλcausing the minimum value is also reduced, and in the case of a light absorbing filter with t=4nm (≈λ/200), the reflection factor R at the required wavelengthλ=780nm becomes a minimum value close to about 0%.
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