Vortex-beam photoacoustic microscopy for enhancing the depth of field

Photoacoustic imaging technology is a new functional imaging method in biomedical application field. It is based on photoacoustic effect. 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 be used for noninvasive detection of structural, functional and molecular abnormalities in biological tissues, Multi scale information of micro and macro world is detected. Photoacoustic microscope is a micro imaging device based on photoacoustic effect. It can measure the amplitude and phase of photoacoustic signals generated at different positions on the solid surface, so as to determine the optical properties, thermal properties, elasticity or geometric structure of samples. However, the traditional optical resolution photoacoustic microscopy imaging system usually uses strong focused Gaussian beam, which has long imaging time and weak penetrating ability, so it is difficult to achieve fast imaging of solid inner surface. The vortex beam has the characteristics of spiral wavefront structure, circular distribution of light intensity, definite orbital angular momentum and phase singularity. Based on the above characteristics, vortex light has high directivity, wide frequency band and wide bandwidth, which can be used for deep and efficient penetrating imaging of inner surface. In this paper, Matlab is used to generate the ideal and transmitted vortex light phase diagram and spot, and then k-wave simulation software is used to build the virtual simulation platform of vortex photoacoustic microscopy imaging system. In the MATLAB simulation, the vortex light beam irradiates on the vascular cells to image the vascular tissue. The results show that vorticity light has better penetrating ability and faster imaging speed than Gaussian light. This study is helpful to detect the deep structure and properties of vascular cells by using vortex light, and put forward a new idea for the deep fast imaging of solid surface.