Photoacoustic imaging is a new non-destructive medical imaging method in recent years. It combines the advantages of high resolution and rich contrast of optical imaging with the advantages of high penetration depth of acoustic imaging. It can provide safe, high resolution and high contrast tissue imaging. As an important branch of the field of photoacoustic imaging, photoacoustic microscopy can achieve higher-resolution imaging. Therefore, this technology has been widely applied in the field of medicine. However, the limited depth of field limits the speed of volumetric imaging. Therefore, improving the depth of field of photoacoustic microscopy is of great significance. The acoustic lens used to collect the photoacoustic signal is a very important part of the photoacoustic microscopy. The acoustic lens commonly used are spherically focused, where the ultrasonic signal is focused at a single point. This results in a limited and uneven detection range of photoacoustic signals, which reduces the volume imaging speed. Here we design a multi-focus acoustic lens to expand the detection range of photoacoustic signals, and then achieve large depth of field photoacoustic detection. We used COMSOL to simulate the transmission of ultrasonic field of the designed multi-focus acoustic lens, and compare it with the single-focus acoustic lens. The results show that the depth of field of the multi-focus acoustic lens is about 3.4 times that of the conventional single-focus acoustic lens. And the depth of field of the multi-focus acoustic lens can be further adjusted by adjusting the number of focus of the multi-focus acoustic lens.
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