高穿透深度偏振-自相关门选通成像技术

Polarization-gated imaging is an important tool to image objects hidden in turbid media, which has a strong ability to suppress multiply scattered photons and enables high contrast imaging of objects. However, for imaging of objects deeply hidden in thick turbid media, the polarization-gated imaging is not suitable due to the influence of the strongly scattering and absorbing. In this project, we propose a polarization-autocorrelation gated imaging technique based on a cascade of polarization gate and autocorrelation gate. This method has a high penetration depth and short imaging time, which allows real-time two-dimensional imaging of objects. The study includes:.(1) Investigating the technique of suppression of the depolarization-autocorrelation effect and improving the signal-to-noise ratio by reducing the generation of the multiply scattered photons..(2) Investigating the dependence of the intensity of the sum frequency signal on the scattering orders of the photons. Improving the contrast and penetration depth by selecting the single scattering photons and low-order scattering photons, and filtering the multiply scattered photons..The final goal is to exhibit a polarization-autocorrelation gated imaging system which is suitable for imaging of objects deeply hidden in turbid media such as biological tissues. The system is characterized by a penetration depth more than 3mm, an imaging time less than 1 ms and a spatial-resolution less than 10μm.

偏振门选通成像技术是获取混浊介质中目标物体成像的重要手段，具有较强抑制多次散射光的能力，能够实现目标物体的高对比度成像。然而，由于入射激光被强烈的散射和吸收等因素的影响，偏振门通成像技术不适合用于厚混浊介质内部深层目标物体的成像。为此，本项目提出一种基于偏振门和自相关门级联的偏振-自相关门选通成像技术，该技术具有成像穿透深度大、成像时间短等优点，能够在单脉冲时间内完成目标物体的二维成像。本项目主要研究内容包括：通过研究入射光退偏振-自相关效应的抑制技术，减少多次散射光子的产生，提高成像信噪比；通过研究和频信号强度对不同阶次散射光子的依赖关系，优化选通单次散射光子和少次散射光子，滤除多次散射光子，提高成像对比度和穿透深度；研制适于生物组织等厚混浊介质内深层目标结构观测的高穿透深度偏振-自相关门选通成像系统, 成像穿透深度优于3mm，成像时间优于1ms，成像系统空间分辨率优于10μm。

偏振门选通成像技术是获取混浊介质中目标物体成像的重要手段，具有较强抑制多次散射光的能力，能够实现目标物体的高对比度成像。然而，由于入射激光被强烈的散射和吸收等因素的影响，偏振门通成像技术不适用于厚混浊介质内部深层目标物体的成像。为此，本项目提出一种基于偏振门和自相关门级联的偏振-自相关门选通成像技术，该技术具有成像穿透深度大、成像时间短等优点，能够在单脉冲时间内完成目标物体的二维成像。. 本项目研究了基于飞秒脉冲激光的相关门（超快光克尔门）选通成像技术，通过调控基于二硫化碳的超快光克尔门中门脉冲和成像脉冲之间的相对延时，能够实现混浊介质中目标物体高对比度成像，克服了基于快响应介质材料的光克尔门选通成像穿透深度低的问题；采用Monte Carlo模拟方法研究了单脉冲沿（脉冲前沿或脉冲后沿）和双脉冲沿飞秒激光在散射介质中的传输过程，研究了弹道光子到蛇形光子转变过程与散射介质参数的关系，以及弹道光子和蛇形光子强度随着穿透深度的变化规律，得到了透射成像脉冲的时间分布曲线，加深了对相关门选通成像工作机理的认识；偏振-自相关门选通成像能够实现在混浊介质OD > 10 的条件下，达到成像分辨率优于10 μm的成像性能；利用该系统实现了离体生物组织的成像，有助于对病变组织的检测与诊断，推动生物医学成像技术的发展。.