Piao Daqing, Zhu Quing
Department of Electrical and Computer Engineering, University of Connecticut, Unit 1157, 371 Fairfield Road, Storrs, Connecticut 06269-1157, USA.
Appl Opt. 2005 Jan 20;44(3):348-57. doi: 10.1364/ao.44.000348.
We introduce a new method, to our knowledge, for direct detection of flow signal intensity by stationary target rejection. In our system, two delay lines are constructed with identical scanning speed and ranging depth. One delay line is used for depth ranging as well as phase modulation, and the other one acts as a full-range retroreflector (FRRR). The signal from this FRRR carries the overall features of local phase modulation, and it is used as the local oscillator for coherent demodulation. With this setup, stationary targets can be rejected at a 4-kHz high-pass cutoff frequency of the filter that follows the demodulator, compared with 20 kHz for conventional fixed-frequency demodulation. This technique features angle insensitivity and provides flow direction as well by implementing standard in-phase and quadrature detection. Besides the direct directional detection of flow signal intensity, flow speed information can be acquired with postprocessing.
据我们所知，我们引入了一种通过静止目标抑制直接检测血流信号强度的新方法。在我们的系统中，构建了两条具有相同扫描速度和测距深度的延迟线。一条延迟线用于深度测距以及相位调制，另一条用作全范围后向反射器（FRRR）。来自该FRRR的信号携带局部相位调制的整体特征，并用作相干解调的本地振荡器。通过这种设置，与传统的固定频率解调的20kHz相比，在解调器之后的滤波器的4kHz高通截止频率下可以抑制静止目标。该技术具有角度不敏感性，并且通过实施标准的同相和正交检测还可以提供血流方向。除了对血流信号强度进行直接定向检测外，还可以通过后处理获取血流速度信息。
