Patent ID: 6916101

Claim:
A metallic rotary polygonal mirror comprising: a metallic polygonal mirror substrate made of aluminum or an aluminum alloy; an intermediate layer of TiO 2 formed by vacuum deposition on the substrate; a metallic reflective layer of Cu formed by vacuum deposition on the intermediate layer; and a protective layer including at least a layer of Al 2 O 3 , formed by vacuum deposition on the metallic reflective layer, wherein said protective layer comprises a double layer consisting of a first protective layer and a second protective layer, wherein said first protective layer is a layer of Al 2 O 3 , and said second protective layer is a layer of SiO 2 , and wherein said first protective layer has a layer thickness of from 150 nm to 200 nm, and said second protective layer has a layer thickness of from 10 nm to 20 nm.