Photoacoustic imaging has great potential in the field of biomedical imaging because it is a beneficial combination of the high contrast of pure optical imaging and the high resolution of ultrasound imaging for deep-tissue. By acquiring the photoacoustic signals at multiple locations, we can obtain a two-dimensional or three-dimensional optical absorption distribution image of the biological tissue. However, it is difficult for actual photoacoustic imaging to acquire the photoacoustic signals with enough de...