As a new non-destructive imaging technology in the field of biomedicine, photoacoustic imaging technology combines the advantages of pure optical and pure acoustic imaging with good spatial resolution, high sensitivity, and strong penetrating power. In the photoacoustic microscopy imaging system, the acousto-optic coupling prism is a component for optical transmission and ultrasonic detection. It is usually composed of an irregular prism and a spherical concave acoustic lens at the bottom. Because the spherical acoustic lens has a poor focusing effect on the ultrasonic beam, the accuracy of ultrasonic detection is low. In order to solve this problem, we propose an optimization method to eliminate the influence of acoustic lens on the beam transmission. A collimating lens is added to the acousto-optic coupling prism with an aspheric acoustic lens at the bottom of the system. In this paper, Zemax optimizes the curvature coefficient and thickness of the collimating lens to eliminate the deteriorating effect of the aspheric acoustic lens on the beam transmission, and evaluates the optimization effect by analyzing the spot and MTF image. The simulation results show that the collimating lens can eliminate the influence of the aspheric acoustic lens on the beam transmission, so that the optical focus and the acoustic focus can be kept coaxial and confocal, and the detection efficiency of the photoacoustic signal can be improved. This work has theoretical guiding significance for the study of photoacoustic microscopy imaging with large depth of field.
As a new non-destructive imaging technology in the field of biomedicine, photoacoustic imaging technology combines the advantages of pure optical and pure acoustic imaging with good spatial resolution, high sensitivity, and strong penetrating power. In the photoacoustic microscopy imaging system, the acousto-optic coupling prism is a component for optical transmission and ultrasonic detection. It is usually composed of an irregular prism and a spherical concave acoustic lens at the bottom. Because the spherical acoustic lens has a poor focusing effect on the ultrasonic beam, the accuracy of ultrasonic detection is low. In order to solve this problem, we propose an optimization method to eliminate the influence of acoustic lens on the beam transmission. A collimating lens is added to the acousto-optic coupling prism with an aspheric acoustic lens at the bottom of the system. In this paper, Zemax optimizes the curvature coefficient and thickness of the collimating lens to eliminate the deteriorating effect of the aspheric acoustic lens on the beam transmission, and evaluates the optimization effect by analyzing the spot and MTF image. The simulation results show that the collimating lens can eliminate the influence of the aspheric acoustic lens on the beam transmission, so that the optical focus and the acoustic focus can be kept coaxial and confocal, and the detection efficiency of the photoacoustic signal can be improved. This work has theoretical guiding significance for the study of photoacoustic microscopy imaging with large depth of field.
Photoacoustic microscopy imaging is an important imaging method of photoacoustic imaging. It is a new type of biomedical imaging method developed in recent years, which combines the advantages of high contrast of optical imaging and deep penetration of ultrasound imaging. In the photoacoustic microscopy imaging system, the acousto-optic coupling prism is a component for optical transmission and ultrasonic detection. It is usually composed of an irregular prism and a spherical concave acoustic lens at the bottom. Because the acoustic lens has a strong focusing effect on the ultrasonic beam, the depth of field of ultrasonic detection is small. In this regard, this paper constructs a bifocal acoustic lens, which is a biconcave acoustic lens with different radii of curvature, with a small middle focal length and a large edge focal length. However, the acoustic lens will cause the divergence of light. Therefore, this paper uses Zemax to design a collimating lens whose structure is similar to that of the acoustic lens. The concave surface of the collimating lens with different radii of curvature is optimized to achieve the purpose of light convergence. Finally, the resolution of the spot is analyzed to evaluate the optimization effect.The software simulation results show that the double-focus acoustic lens can realize fast large volumetric ultrasonic detection, and effectively improve the detection efficiency of photoacoustic signals. This work has important theoretical guiding significance for the study of photoacoustic microscopy imaging systems for large volumetric ultrasound detection.
Photoacoustic tomography is a new medical imaging technology with the advantages of high resolution, high contrast and high penetration depth. There are three common photoacoustic imaging methods in practical applications: photoacoustic microscopic imaging (PAM), photoacoustic computed tomography (PACT), photoacoustic tomography (PAE). As an important branch of photoacoustic imaging, photoacoustic microscopy combines high contrast of optical imaging with high resolution of ultrasonic imaging. In photoacoustic microscopy, acousto-optic coupling prism is a very important component, which is usually composed of irregular prism and spherical concave acoustic lens at the bottom. Its function is to carry out optical transmission and ultrasonic detection. The ultrasonic depth of field of spherical concave acoustic lens is limited. In order to overcome this defect, researchers propose to use conical concave acoustic lens to produce Bessel sound beam to realize large depth of field ultrasonic detection. But the conical concave acoustic lens affects laser focusing and imaging. In order to solve this problem, we propose an optimization method to eliminate the influence of conical concave acoustic lens on beam transmission. A calibration mirror is added to the acousto-optic coupling prism with conical concave acoustic lens at the bottom, and the deterioration of the cone concave acoustic lens to the beam transmission is eliminated by optimizing the surface shape and thickness of the calibration mirror by Zemax. The optimization effect is evaluated by analyzing the spot. The simulation results show that the optimization method can eliminate the influence of the conical concave acoustic lens on the beam transmission, make the focal point and the focal point keep the coaxial focus, and improve the detection efficiency of the photoacoustic signal. This work is of theoretical significance for the systematic study of large depth of field photoacoustic microscopy.
Photoacoustic tomography is a new medical imaging technology with the advantages of high resolution, high contrast and high penetration depth. There are three common photoacoustic imaging methods in practical applications: photoacoustic microscopic imaging (PAM), photoacoustic computed tomography (PACT), photoacoustic tomography (PAE). As an important branch of photoacoustic imaging, photoacoustic microscopy combines high contrast of optical imaging with high resolution of ultrasonic imaging. In photoacoustic microscopy, acousto-optic coupling prism is a very important component, which is usually composed of irregular prism and spherical concave acoustic lens at the bottom. Its function is to carry out optical transmission and ultrasonic detection. The ultrasonic depth of field of spherical concave acoustic lens is limited. In order to overcome this defect, researchers propose to use conical concave acoustic lens to produce Bessel sound beam to realize large depth of field ultrasonic detection. But the conical concave acoustic lens affects laser focusing and imaging. In order to solve this problem, we propose an optimization method to eliminate the influence of conical concave acoustic lens on beam transmission. A calibration mirror is added to the acousto-optic coupling prism with conical concave acoustic lens at the bottom, and the deterioration of the cone concave acoustic lens to the beam transmission is eliminated by optimizing the surface shape and thickness of the calibration mirror by Zemax. The optimization effect is evaluated by analyzing the spot. The simulation results show that the optimization method can eliminate the influence of the conical concave acoustic lens on the beam transmission, make the focal point and the focal point keep the coaxial focus, and improve the detection efficiency of the photoacoustic signal. This work is of theoretical significance for the systematic study of large depth of field photoacoustic microscopy.
The study of the relationship between the spectral characteristics of the photoacoustic signal and the shape and size of the absorber has important practical significance for image reconstruction. Using the commercial finite element simulation software COMSOL Multiphysics, a two-dimensional simulation model based on finite element was designed, which studied the relationship between the spectral characteristics of the photoacoustic signal and the shape and size of the absorber. In this study, the model consists of three parts: 1) water layer; 2) short pulse laser source (wavelength of 840nm); 3) gastric tumor tissue. The laser point source is located in the middle of the upper water layer. Simulate the propagation of light in the water layer by solving the diffusion equation. The temperature changes in biological tissues are obtained by solving the biothermal equation. When the absorber is irradiated by Gaussian pulses, due to the extremely short time, the absorber can be regarded as adiabatic expansion after absorbing energy, thereby generating ultrasonic waves. Using the finite element analysis method, the complex situation of photoacoustic imaging is transformed into the coupling of multiple physical fields and the numerical calculation of partial differential equations to obtain the photoacoustic signal. Fitting the simulation results shows that the spectral characteristics of the photoacoustic signal change regularly with the size of the absorber. The size of the absorber obtained in this paper has a power function relationship with the spectral intercept. The larger the size, the larger the spectral intercept, and the growth rate increases with the increase of the size. The size of the absorber and the spectral slope also have a power function relationship. The slope of the large spectrum is smaller, and the rate of change of the slope decreases as the size increases. At the same time, analyzing the photoacoustic spectrum of absorbers of different shapes also shows that absorbers of different shapes have their own characteristics. This research is helpful to understand the relationship between spectral characteristics and the shape and size of the absorber, and has certain theoretical guiding significance for image reconstruction.
Photoacoustic tomography is a new medical imaging technology with the advantages of high resolution, high contrast and high penetration depth. There are three common photoacoustic imaging methods in practical applications: photoacoustic microscopic imaging (PAM), photoacoustic computed tomography (PACT), photoacoustic tomography (PAE). As an important branch of photoacoustic imaging, photoacoustic microimaging combines high contrast of optical imaging with high resolution of ultrasonic imaging. In photoacoustic microimaging system, acoustooptic coupling prism is a very important component, which is usually composed of irregular prism and spherical concave acoustic lens at the bottom. Its function is to carry out optical transmission and ultrasonic detection. The ultrasonic depth of field of spherical concave acoustic lens is limited. In order to overcome this defect, researchers propose to use conical concave acoustic lens to produce Bessel sound beam to realize large depth of field ultrasonic detection. But the conical concave acoustic lens affects laser focusing and imaging. In order to solve this problem, we propose an optimization method to eliminate the influence of conical concave acoustic lens on beam transmission. A calibration mirror is added to the acoustooptic coupling prism with conical concave acoustic lens at the bottom, and the deterioration of the cone concave acoustic lens to the beam transmission is eliminated by optimizing the surface shape and thickness of the calibration mirror by Zemax. The optimization effect is evaluated by analyzing the spot. The simulation results show that the optimization method can eliminate the influence of the conical concave acoustic lens on the beam transmission, make the focal point and the focal point keep the coaxial focus, and improve the detection efficiency of the photoacoustic signal. This work is of theoretical significance for the systematic study of large depth of field photoacoustic microimaging.
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