A compound of formula as well as pharmaceutically acceptable salt thereof, wherein R1 to R5 have the significance given in claim 1, can be used as a medicament. An imaging device in accordance with an embodiment comprises: a light source unit; a light separation unit; a reference unit; a diagnostic unit; a light coupling unit; and a signal processing unit. The floating spring portion includes a contacting portion for being brought into contact with the housing and an operated portion connected to the contacting portion. The timing may be decided such that a time period from receiving the second request packet to sending the second response packet in response to the second request packet is longer than a time period from receiving the first request packet to sending the first response packet in response to the first request packet. A stator is associated with the armature. A portion of the first ring gear is warped toward the second ring gear for periodically reducing the distance between a perimeter of the first ring gear to a perimeter of the second ring gear.