Development of Portable Fiber-Optic Laser Doppler Velocimetry Sensor for Measurement of Local Flow Velocity of Blood and Opaque Multi-Phase Fluids

为了测量血液和多相流体等不透明流体中的局部速度场，研制了一种新型光纤激光多普勒测速传感器。在目前的研究开发过程中，阐明了以下几点：在获得几种不同稀释率的牛血液和白色颜料与水的混合物中的激光消光特性后，利用现有的光纤传感器测量了放置在旋转圆盘上的环形开放通道中稀释后的牛血液的流速。它的拾音器由一个直径2mm的分布式折射率透镜组成，该透镜连接在两根平行连接的纤维的尖端。虽然传感器能够精确测量20%稀释血液的局部速度，但它无法测量较厚血液的速度，因为使用的血液被认为比体内完整血液的质量更差。传感器头有…更多的改进；首先，其尖端的形状为具有斜截锥，以减少头部对流动的干扰，并减少从头部尖端散射的不希望的光。其次，采用直径为1mm的较小的DIL透镜代替直径为2mm的DIL透镜，使其插入到皮下注射器的针头内。第三，采用单光纤系统代替双光纤系统，提高了对不透明流体的灵敏度。第四，在光纤和DIL透镜之间使用一种经紫外光硬化的粘结剂，以减少不需要的散射光。结果，半透明悬浮液的最大可测浓度增加到原来的4倍。通过将改进后的传感器头插入注射器针头内的硅胶模型血管中，测量高浓度白色颜料悬浮液作为模型血液在管中流动。结果准确地得到了表征稳定层流发展的旋转抛物面的速度分布。因此，可以得出结论，直接将传感器头插入血管，在体内测量血管中的局部血流速度是很有成功前景的。少

In order to measure the local velocity field in opaque fluids like blood and/or multi-phase fluids, a new fiber-optic laser Doppler velocimetry sensor has been developed. In the course of the present research for the development the followings have been elucidated :After obtaining the characteristics of laser light extinction in bovine blood of several different dilution rates and in mixtures of white pigment and water, the flow velocity of diluted bovine blood contained in an annular open channel which is placed on a rotating disc has been measured by using the present fiber optic sensor. Its pickup consists of a distributed index lens of 2mm in diameter attached at the tip of two fibers being joined side by side in parallel. Although the sensor is capable of making a accurate measurement of local velocity of diluted blood up to 20%, it cannot measure the velocity of thicker blood, because the blood used is considered to has worse quality than intact blood in vivo.The sensor head has … More been improved ; Firstly, its tip is shaped to have an obliquely truncated cone in order to decrease a disturbance of flow by the head and also to diminish undesirable light scattered from the tip of the head. Secondly, a smaller DIL lens of 1mm in diameter is adopted instead of the 2mm- diameter DIL lens to make it inserted inside of the needle of a hypodermic syringe. Thirdly, a mono-fiber optical system is adopted instead of the dual-fiber optical system to increase the sensitivity for opaque fluid. Fourthly, a bonding agent of being hardened by ultraviolet light is used between the fiber and the DIL lens to diminish an undesirable scattered light. As a result, the maximum measurable concentration of the semi-opaque suspension fluid is increase to be four times greater than the original one.By inserting the improved sensor head incorporated inside the syringe needle into a modeled blood vessel of silicone rubber, a high concentration suspension fluid of white pigment as a model blood flowing in the tube has been measured. As a result, the velocity distribution of a paraboloid of revolution characterizing the developed steady laminar flow is accurately obtained. Hence, it can be concluded that the prospect of success is good to measure the local blood velocity in blood vessel in vivo by directly inserting the sensor head into the vessel. Less