Piezoelectric actuators are used in various applications to precisely control and manipulate mechanical movement. In cameras, particularly in certain types of autofocus systems, piezoelectric actuators can be employed to control lens movement for achieving fast and precise focusing. The process typically involves the following steps:
Position Sensing: A position-sensing mechanism, often based on feedback from an optical sensor or an encoder, monitors the current position of the lens element. This feedback is crucial for accurate control and positioning.
Control Circuitry: The position data from the sensor is sent to control circuitry, which calculates the necessary adjustments to achieve the desired focus point based on the camera's autofocus algorithm.
Piezoelectric Actuator: The piezoelectric actuator itself is a device made from piezoelectric materials. These materials generate mechanical displacement (movement) in response to an applied electric voltage. When an electric voltage is applied to the piezoelectric material, it undergoes a deformation or displacement proportional to the voltage. This displacement can be very small, but it's highly precise and controllable.
Lens Movement: The piezoelectric actuator is attached to a lens element or a lens group in the camera's lens assembly. When the control circuitry determines the need for lens movement, it applies specific voltages to the piezoelectric actuator. As a result, the actuator changes its shape, causing the attached lens element to move by a tiny amount.
Focusing: The controlled movement of the lens element alters the focal length of the lens system, enabling the camera to focus on the subject. By continuously adjusting the voltage applied to the piezoelectric actuator, the lens can be moved back and forth rapidly to achieve precise focus. The feedback loop from the position sensor helps ensure accurate positioning.
Fast and Precise Autofocus: Piezoelectric actuators can respond quickly to changes in voltage, allowing for rapid adjustments in lens position. Their high precision and responsiveness make them suitable for achieving fast and accurate autofocus, especially in scenarios where quick focus changes are needed, such as in continuous autofocus during video recording or capturing fast-moving subjects.
It's important to note that different cameras and lens systems may use various autofocus mechanisms, and piezoelectric actuators are just one of the technologies available for achieving lens movement. Other technologies, such as ultrasonic motors (USM) and stepper motors, are also commonly used for autofocus in cameras.