| 摘要 |
An optical filter element having high isolation and reduction in reflection loss for input light beams. The optical filter element is used with a transparent substrate having a surface that includes a first area and a second area. The optical filter element has a target wavelength range. The optical filter element includes a first dielectric multilayer film arranged in the first area of the transparent substrate. A second dielectric multilayer film is arranged in the second area of the surface of the transparent substrate. The second dielectric multilayer film has a reflectance of a predetermined value or less for a light beam having a wavelength in the target wavelength range. A portion of the second dielectric multilayer film and a portion of the first dielectric multilayer film are laminated each other.
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