Chemical Species Tomography (CST) has been widely applied for imaging of critical gas-phase parameters in industrial processes. To acquire high-fidelity images, CST is typically implemented by line-of-sight Wavelength Modulation Spectroscopy (WMS) measurements from multiple laser beams. The modulated transmission signal on each laser beam needs to be a) digitised by a high-speed analogue-to-digital converter (ADC); b) demodulated by a digital lock-in (DLI) module; and c) transferred to high-level processor for image reconstruction. Although a fully parallel data acquisition (DAQ) and signal processing system can achieve these functionalities with maximised temporal response, it leads to a highly complex, expensive and power-consuming instrumentation system with high potential for inconsistency between the sampled beams due to the electronics alone. In addition, the huge amount of spectral data sampled in parallel significantly burdens the communication process in industrial applications where in situ signal digitisation is distanced from the high-level data processing. To address these issues, a quasi-parallel sensing technique and electronic circuits were developed for industrial CST, in which the digitisation and demodulation of the multi-beam transmission signals are multiplexed over the high-frequency modulation within a wavelength scan. Our development not only maintains the temporal response of the fully parallel sensing scheme, but also facilitates the cost-effective implementation of industrial CST with very low complexity and reduced load on data transfer. The proposed technique is analytically proven, numerically examined by noise-contaminated CST simulations, and experimentally validated using a lab-scale CST system with 32 laser beams.

中文翻译：

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具有成本效益的工业化学层析成像准并行传感仪器

化学物种断层扫描（CST）已广泛应用于工业过程中关键气相参数的成像。为了获取高保真图像，通常通过从多个激光束进行视线波长调制光谱（WMS）测量来实现CST。每个激光束上的调制传输信号需要a）由高速模数转换器（ADC）数字化；b）由数字锁定（DLI）模块解调；c）转移到高级处理器进行图像重建。尽管完全并行的数据采集（DAQ）和信号处理系统可以在最大的时间响应下实现这些功能，但它会导致高度复杂，昂贵且耗电的仪器仪表系统，由于单独的电子设备，很有可能造成采样光束之间的不一致。此外，并行采样的大量频谱数据极大地加重了工业应用中的通信过程，在这些应用中，原位信号数字化与高级数据处理相距甚远。为了解决这些问题，开发了用于工业CST的准并行感测技术和电子电路，其中在波长扫描内通过高频调制对多光束传输信号的数字化和解调进行多路复用。我们的发展不仅保持了完全并行传感方案的时间响应，而且还以极低的复杂度和降低的数据传输负担，促进了具有成本效益的工业CST实施。所提出的技术经过分析验证，并通过受噪声污染的CST模拟进行了数值检验，