| 摘要 |
PURPOSE:To approximate the transmittivity of the 2nd wavelength to an ideal value by providing plural reflecting surfaces which has a low reflection factor to light of the 1st wavelength, a high reflection factor to light of the 2nd close wavelength, and varies in reflection factor monotonously in an intermediate wavelength range and its circumferential wavelength ranges. CONSTITUTION:Normal etalon, etc., are used for reflecting surfaces 2 on the optical polished surface of a substrate 1; and a multilayered film having about 20 layers for obtaining a high reflection factor is vapor-deposited and a film having about 10 layers for compensation is formed to obtain sharp monotonous reflection factor characteristics. The reflecting surfaces 2 are opposed to each other in parallel by using a spacer 3. This multilayered vapor-deposited film has such spectral characteristics that the film has the low reflection factor R1 to the 1st wavelength lambda1 and the high reflection factor R2 to the 2nd wavelength lambda2 and varies in reflection factor monotonously with wavelength, so the transmittivity is almost 100% in a range of the wavelength lambda1 and a waveform range wherein said condition is satisfied is wide. On the other hand, the transmittivity to the 2nd wavelength lambda2 is extremely low because of extremely small transmittivity condition and the high reflection factor R2 and about (1-R2)<2>/4- 2.5X10<-5>. |
