Design Of THz-TDS Rapid Data Acquisition System

Recent years, THz's academic value has received extensive attention worldwide. As one of the earliest development of terahertz technology, terahertz time-domain spectroscopy can simultaneously detect the terahertz wave amplitude and phase information, it is rapidly developing in biomedical, safety inspection, non-destructive testing and communicationmany fields. Recent years many research institutes have been committed THz-TDS technology and Research on instruments of THz-TDS, rapid automated collection is one of the main problems instrumentation applications need to be resolved. Conventional THz-TDS systems have a long detection time and a small amount of collected data. To improve THz-TDS system's detection speed and accuracy, a rapid terahertz time-domain spectroscopy data acquisition and control system based on closed-loop control is presented. The system can perform continuous scanning and data collection with a high speed. When performing step scanning, it can get real-time location information of the optical delay line by the delay line's feedback signal, and thus can complete automatic scanning rapidly. By acquiring multiple data continuously in a single step, the accuracy of acquisition in every step is improved. Experiment results show that the system can take full advantage of the optical delay line to achieve a highest data acquisition speed of 800 KHz. When the step length is 5um, the time of continuous acquisition of 1000 data is only 86.34 ms, which means the system can perform automatic and rapid acquisition of terahertz time-domain pulse signal with high precision.The main contribution and innovation of this paper is concluded below:1. Control system of data acquisition is designed based on the principle of Terahertz time-domain signal production and detection by Photoconductive terahertz time-domain spectroscopy system. Both hardware design and software design of the system are included.2. The control circuit of the data acquisition system is designed. Optical delay line control module, data acquisition module, data storage module and data transmission module are designed according to the demand analysis.3. The software design of the data acquisition system is completed. Automated scanning control algorithm based on closed-loop control is proposed to make full use of the hardware performance of optical delay line control module. The software program of the lower computer and the interface of the upper computer are designed and implemented.4. Experiments and analysis on optical delay line control, data collection and data transmission were completed. Datum collected by continuous scanning and step scanning were both used in the experiments and the results have been analyzed in our work.