Patent ID: 8023364

Claim:
A hand position detecting device comprising: an optical detection unit configured to detect whether or not light passes through light-passing apertures provided in hand wheels having hands; a hand position detecting unit configured to detect positions of the hands based on passage or non-passage of light detected by the optical detection unit; a darkness detector configured to detect whether or not the hand position detecting device is in darkness; a dark state determining unit configured to determine, when the darkness detector detects that the hand position detecting device is in darkness, whether or not the hand position detecting device has been in darkness for a predetermined time period; and a hand rotation stop controlling unit configured to, when the dark state determining unit determines that the hand position detecting device has been in darkness for the predetermined time period, rotate at least one of the hands to a reference position, stop the one of the hands, and control the hand position detection unit to detect positions of remaining hands at predetermined time intervals.