Confocal microscopy employing pressure controlled adaptive lenses

Adaptive lenses offer advantages like fast tuning speeds up to the kHz regime and motionless axial scanning. Hence, they have become a valuable tool for axial scanning in optical systems. A variety of adaptive lenses have been proposed, with membrane fluid lenses being the most promising approach because of their potential to be transferred from the laboratory to commercial applications. However, these lenses usually contain a piezo-based actuation mechanism. Hence, axial scanning employing piezo-based adaptive lenses faces hysteresis behavior. To compensate for the hysteresis behavior, these lenses can be equipped with a sensor that measures the differential pressure between the interior and exterior of the lens. A controller for the actuation voltage of the lens is used to tune the differential pressure instead of the actuation voltage. In this contribution, we demonstrate the compensation of the hysteresis behavior in axial scanning of a confocal microscope. Further, we present strategies for minimizing the influence of environmental conditions (such as temperature, humidity and atmospheric pressure) on the focus stability of a confocal microscope.