Apparatus is described for obtaining the curves relating area with time in photographic between-lens shutters. A set of separated and illuminated apertures fitted with neutral glass filters passing certain standard fractions of the light is imaged by a lens on film wrapped round a revolving drum, the shutter acting as a diaphragm for the lens. The film is thus exposed in bands along its length. An exposure is made, with the shutter set fully open, for one revolution of the drum. The above apertures are then replaced by a second set without neutral filters, each of these apertures fitting exactly between the spaces previously occupied by two apertures of the previous set. An instantaneous exposure of the shutter is then made during another revolution of the drum, During the whole of this exposure a time scale is impressed on the film by subsidiary apparatus. After development the points at which adjacent bands have the same density are found. These give the times at which the area of opening of the shutter was equal to the standard fractions of its full aperture. Various features of the apparatus are discussed, and particulars are given of the method of calibrating the neutral filters and of tests carried out on shutters for which curves relating area with time could be calculated.

The sound field characteristics in the air gaps of the noncontact ultrasonic motor driven by two flexural standing wave vibration disks were analyzed by finite element method (FEM). Standing wave sound fields with an opposite phase were generated in the two air gaps by a single driving stator. Traveling wave sound fields in the two air gaps are formed as the superposition of the standing wave sound fields generated by two stators whose temporal phases and spatial positions are different from each other. The traveling direction of the calculated sound fields coincided with the rotating direction of the rotor observed in the experiments. The intensity of the sound field generated in the air gap by the single driving stator was measured by detecting the voltage induced in another stator. A gap distance wider than 0.5 mm is required for a high revolution speed because the sound field generated in the gap on the opposite side of the rotor is weak in an air gap narrower than 0.3 mm.

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