Blade speed adjustable mechanism and focal plane shutter having the same

摘要

A blade speed adjustable mechanism includes: a board having an opening; a shutter blade opening or closing the opening; a drive lever supported by the board and bringing the shutter blade into an overlapped operation or an expanded operation; a biasing member engaging the drive lever and biasing the shutter blade in an overlapped direction or in an expanded direction; a ratchet member engaging the biasing member and having ratchet teeth; an engagement member holding the ratchet member at a desired stop position and adjusting an biasing force of the biasing member by changing the stop position. The engagement member has a plurality of pawl portions different from each other in length. The pawl portion engages the ratchet tooth to hold the ratchet member at the stop position. A difference in length between the pawl portions is shorter than a distance corresponding to a pitch of the ratchet teeth.