| 摘要 |
PROBLEM TO BE SOLVED: To obtain a glass filter which transmits the whole visible region and with which effective tone adjusted to the object of photographing is obtd. without decreasing the color balance, by adding neodymium oxide and praseodymium oxide, adding an inhibitor in a short wavelength region and specifying the design of transmittance at specified wavelength. SOLUTION: Neodymium oxide Nd2O3 and praseodymium oxide Pr6O11 are added as well as an inhibitor for a short wavelength region is added to control the transmittance at 620 nm wavelength to the same or larger than the transmittance at 550 nm and 420 nm wavelength. By adding Nd2O3 and Pr6O11, absorption peaks intrinsic to the oxides are formed near 580 nm and 740 nm wavelengths, and red color is sharply enhanced by the absorption. Further, absorption peaks are formed near 440 nm and 530 nm wavelengths, sharp blue and green colors are also obtd. Or, instead of Nd2O3, holmium oxide Ho2O3 and erbium oxide Er2O3 can be used.
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