Abstract: A surface-wave driven motor comprises a moving member for being displaced, a resilient member having a surface urged against the moving member, a piezo-electric member provided in contact with the resilient member to impart vibration to the resilient member and create an elastic wave in the surface, means having electrode means provided on the piezo-electric member and applying an AC voltage to the piezo-electric member through the electrode means, means for detecting an electrical output produced in the piezo-electric member from an area on the piezo-electric member which is electrically insulated from the electrode means, and means for determining the frequency of the AC voltage on the basis of the detected electrical output.

Abstract: A film rewind device in a camera in which a rewind coupling is automatically engaged with a cassette shaft in response to rewind operation has a rotatable member having a spiral groove on its peripheral wall portion and said rewind coupling at the end of the shaft thereof, the rotatable member being slidable in axial direction and rotatable by rewind operation, and a meshing member meshing with the spiral groove at the initial stage of the rewind operation to thereby slide the rotatable member in axial direction to cause the coupling to engage the cassette shaft. The mesh engagement between the meshing member and the spiral groove is released in axial direction when the coupling engages the cassette shaft, so that the meshing member comes to support the rotatable member so as to block the return of the rotatable member in axial direction.

Abstract: A surface-wave driven motor comprises a moving member for being displaced, a resilient member having a surface urged against the moving member, a piezo-electric member provided in contact with the resilient member to impart vibration to the resilient member and create an elastic wave in the surface, means having electrode means provided on the piezo-electric member and applying an AC voltage to the piezo-electric member through the electrode means, means for detecting an electrical output produced in the piezo-electric member from an area on the piezo-electric member which is electrically insulated from the electrode means, and means for determining the frequency of the AC voltage on the basis of the detected electrical output.