MIRROR DRIVE DEVICE CAPABLE OF HIGH-SPEED FORWARD AND BACKWARD DRIVING OF MIRROR

摘要

A mirror drive device in which the speed of forward and backward movement of a mirror is increased while reducing a power amount required therefor without affecting a finder image and a focus distance of an image viewed through a finder. A mirror-down cam is cam-engaged with a drive shaft provided in a mirror holder, and causes the mirror holder to enter a finder observation position of a photographing optical path. A mirror-up cam is cam-engaged with the drive shaft, and causes the mirror holder to retract from the photographing optical path. A down spring urges the mirror holder toward the finder observation position with low necessary and sufficient pressure. A motor transmits rotation to the mirror-down cam and the mirror-up cam via a shift gear train. The rotation axes of the mirror-down cam and the mirror-up cam are arranged in positions different from each other.

主权项

1. A mirror drive device that drives a mirror between a first state in which the mirror enters a photographing optical path and a second state in which the mirror retracts from the photographing optical path, comprising:
a mirror holder having a driven portion and configured to hold the mirror; a first cam member configured to be cam-engageable with the driven portion; a second cam member configured to be cam-engageable with the driven portion; and a drive source configured to drive the first cam member and the second cam member, wherein in a case where the drive source has started to drive the first cam member and the second cam member from the first state, the driven portion and the first cam member are brought into cam engagement with each other, wherein before the mirror is placed in the second state, in a case where the drive source reduces a speed at which the first cam member and the second cam member are driven, the cam engagement between the driven portion and the first cam member is released, and the driven portion and the second cam member are brought into cam engagement with each other, wherein in a case where the mirror is placed in the second state, the driven portion and the first cam member are brought into cam engagement with each other again, wherein in a case where the drive source has started to drive the first cam member and the second cam member from the second state, the cam engagement between the driven portion and the first cam member is released, and the driven portion and the second cam member are brought into cam engagement with each other, wherein before the mirror is placed in the second state, in a case where the drive source reduces the speed at which the first cam member and the second cam member are driven, the cam engagement between the driven portion and the second cam member is released, and the driven portion and the first cam member are brought into cam engagement with each other, and wherein in a case where the mirror is placed in the first state, the driven portion is not brought into cam engagement with either of the first cam member and the second cam member.