A method of actuating a plurality of probes. Each probe may be made of two or more materials with different thermal expansion coefficients which are arranged such that when the probe is illuminated by an actuation beam it deforms to move the probe relative to a sample. Energy is delivered to the probes by sequentially illuminating them with an actuation beam via an objective lens in a series of scan sequences. Two or more of the probes are illuminated by the actuation beam in each scan sequence and the actuation beam enters the objective lens at a different angle to an optical axis of the objective lens for each probe which is illuminated in a scan sequence. The actuation beam is controlled so that different amounts of energy are delivered to at least two of the probes by the actuation beam during at least one of the scan sequences.