Abstract: A camera comprises an image sensor arranged to generate an image signal, and a lens arrangement, which focuses an image onto the image sensor, the focus being variable in accordance with a control signal applied thereto. In the case that a piezoelectric actuator experiencing hysteresis is used to drive movement of the lens arrangement to vary the focus of the image, autofocusing is achieved by applying a control signal to the piezoelectric actuator with a value at an extreme of a predetermined range and subsequently changing the control signal monotonically across the predetermined range to determine a position at which the focus quality is at an acceptable level. Thus, this position may be returned to despite the hysteresis.

Abstract: A switch-mode power amplifier circuit using high power, low distortion waveforms is connected to an electromagnetic load to provide a high degree of control over the load. The circuit comprising a plurality of half-bridge networks having outputs combined at a summation point. The half-bridge networks are switched to provide power outputs sequenced to generate an interlaced output at the summation point which is operably connected to the load so that for a given switching frequency of the networks the operational frequency of the circuit is increased. The sequencing of the half-bridge outputs to generate an interlaced output facilitates the reduction of the switching frequency of individual switching components within the half-bridges while at least maintaining the overall operational frequency of the circuit. For N half-bridges operating at ƒkHz, the overall operational frequency of the circuit is NƒkHz.

Abstract: A switch-mode power amplifier circuit using high power, low distortion waveforms is connected to an electromagnetic load to provide a high degree of control over the load. The circuit comprising a plurality of half-bridge networks having outputs combined at a summation point. The half-bridge networks are switched to provide power outputs sequenced to generate an interlaced output at the summation point which is operably connected to the load so that for a given switching frequency of the networks the operational frequency of the circuit is increased. The sequencing of the half-bridge outputs to generate an interlaced output facilitates the reduction of the switching frequency of individual switching components within the half-bridges while at least maintaining the overall operational frequency of the circuit. For N half-bridges operating at fkHz, the overall operational frequency of the circuit is NfkHz.