1. A combined photoacoustic and ultrasound imaging system, comprising: (a) a laser configured to illuminate an object and thereby generate photoacoustic signals emitted from the object; (b) a transducer configured to:(i) transmit ultrasound waves to the object; (ii) receive ultrasound echo signals based on echoes reflected from the object in response to the transmitted ultrasound waves; and (iii) receive the photoacoustic signals generated from the laser illumination; (c) an ultrasound echo signal pathway coupled to the transducer to receive the emitted ultrasound echo signals and configured to produce ultrasound image data; (d) a photoacoustic signal pathway coupled to the transducer to receive the photoacoustic signals and configured to produce photoacoustic image data; (e) a motion processor coupled to the transducer to receive ultrasound echo signals reflected at different times from a same location on the object and configured to produce motion estimator data based on the ultrasound echo signals received at the different times from the same location; and (f) an image processor coupled to the photoacoustic signal pathway to receive the photoacoustic image data and coupled to the motion processor to receive the motion estimator data, wherein the image processor is configured to temporally correct the photoacoustic image data for motion based on the motion estimator data.