Patent ID: 7147389

Claim:
A focal plane shutter comprising: a shutter blade capable of blocking a light; a blade dowel attached to the shutter blade; and a blade arm which is slidably engaged with the blade dowel to open or close the shutter blade, the surface hardness of said blade arm is in the range of Hv300 to 900, and the surface hardness of said blade dowel is in the range of Hv450 to 1000, the respective surface hardnesses being selected with said ranges such that the surface hardness of said blade dowel is always higher than the surface hardness of said blade arm. said blade arm and said blade dowel being subjected to a chemical polishing treatment, said blade dowel being plated with nickel, chromium, palladium or rhodium, and a material of said blade dowel is one of a free-cutting stainless steel and a carbon tool steel, and a material of said blade arm is a carbon tool steel.