Research On Portable Raman Spectrometer Control System Based On Array CCD

Because of Raman spectrum reflects the characteristics of molecular structure, it is widely applied to the identification of various kinds of molecules. Although the intensity of Raman scattering is very weak, typically only 10-6 to 10-12 times of the intensity of exciting light, the Raman signal intensity has been significantly enhanced with the emergence and development of SERS and SHINERS technology. Based on these techniques, a portable Raman spectrometer will be widely used in various fields.In this paper, a main control system of a portable Raman spectrometer has been completed which is based the features of Raman spectrum and combined with SERS and SHINERS technology. The whole device consists of the CCD acquisition module, laser light source module and the main control module based on FPGA. This paper mainly introduces the key points when design the drive circuits of high accuracy array CCD and laser, then focuses on the design of the main control system based on FPGA which is composed of the CCD timing design and control program design based on NIOS Ⅱ.In this paper, we design and complete a device includes a stable output narrow FHWM laser light source and a high resolution CCD spectral acquisition system.1. Referred to the demands of excitation light source when designing a Raman spectrometer, in this paper a LML-785.0BF-22 laser diode is used, combined with relative drive circuit and control driver, a laser light source which can provide near infrared narrow FHWM with stable high power output is obtained.2. Then we use the near infrared enhanced array CCD S11510-1106 made by Hamamatsu as the spectrometer photosensitive device, after introduce the drive circuit, a low noise CCD acquisition system is put forward by controlling the timing which makes the CCD-array working in four binning modes. The experiment results have proved that when this CCD is working on 4 binning mode, we can achieve a spectrum acquisition system whose precision is 16bit, dynamic range up to 28000, signal-to-noise ratio is 800:1, and the longest integral time is 400s or more.3. After we fulfill Laser module and CCD module, a control program of Raman spectrometer based on FPGA is completed, it can transmit data to the host computer through USB2.0 module.After experiments and debugging, this system can measure the Raman signal steadily with high dynamic range and signal-to-noise ratio. Future, due to the small volume and simple operation, it is suitable for the on-site inspection, pharmaceutical testing, non-destructive inspection, etc. Finally, this paper summarizes all the work has been done and looks forward to the remains that need to be improved.