| 摘要 |
PROBLEM TO BE SOLVED: To widen a wavelength range wherein demultiplexing or multiplexing is possible within the visible range, to improve the steepness from a reflection band to a transmission band, and to make incidence angle dependency small by providing a center layer consisting of a low and a high refractive index layer having their chemical film thicknesses specified and a couple of adjusting layers consisting of a low and a high refractive index layer. SOLUTION: The polarization beam splitter is formed by joining an optical base 1, having the center layer 3 having the low refractive index layer of fluororesin with optical film thicknessλ/4 and a refractive index 1.2 to 1.4 and a high refractive index layer with optical film thicknessλ/4 and a refractive index 2.0 to 2.4 laminated by turns and the couple of adjusting layers 4 consisting of the low refractive index layer and high refractive index layer formed of fluororesin across the center layer 3 (where the center layer 3 and adjusting layers 4 are called a polarization splitting film 6), with a transparent base body 2 having a reflection preventive film 5 with an adhesive 7. Here, the optics film thicknessλ/4 is ndcosθ=λ, where (n) is a refractive index, (d) is mechanical film thickness, andθis an angle of incidence.
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