The Design And Study Of Miniaturized Spectrometer Based On CCD

Spectrometer plays an important role in many domains of science and technology. The traditional spectrometer features complex structure, large volume, and can't realize multi-wavelength measurement simultaneously. It is restricted in many application areas. So miniaturization is the inevitable trend of the development of spectrometer.In this paper, a method on how to design a miniaturized spectrometer based on CCD is introduced. The uses of CCD as spectral detector and optical system based on Czerny-Turner structure reduce the instrument's volume effectively. According to this method, the CCD's controlling timing and the signal sampling system are realized on a mass capacity field programmable gate array (FPGA) chip EP1C3T144C8. By using SOPC technique, NiosII soft-core CPU, UART, DMA function modules, CCD driving circuit and A/D controlling circuit are integrated in this FPGA chip, which makes it possible to control the spectrometer by one chip. The serial communication interface between instrument and computer has been achieved. The software about spectra collection and analyzing, which has achieved many functions such as wavelength calibrating and spectrum displaying, has been developed. At last,the imitating experiment about the design shows that the miniaturized spectrometer which is designed according to this method can achieve multi-wavelengths measurement simultaneously.The following works have been finished during the development:â‘ Using CCD, blaze grating, and two concave mirrors, a small dispersing system based on crossing Czerny-Turner structure has been finished. By analyzing optical system structure, the relation among parameters of these components has been found out in order to fix basic parameters for miniaturized spectrometer.â‘¡A new kind of driving and sampling system for multi-channel detector has been designed by using mass capacity field programmable gate array EP1C3T144C8. In this system, many function modules can be generated by logic cells inside of the FPGA chip, such as the driving pulse of CCD, the driving timing of A/D converter, data sampling and storage system. And the A/D results can be transmitted to computer by the serial port. This new design features less electronic components and high integration.â‘¢The CCD's video signal process circuit has been designed with a rail-to-rail amplifier, which features high speed and high Common Mode Rejection ratio.â‘£Based on Visual Basic 6.0, the spectra processing software has been achieved, which has the functions such as communicating with the lower microprocessor NiosII CPU, wavelength calibrating, data processing, displaying, saving, and printing the spectrum.In this paper, the following innovative ideas are presented:â‘ Using a mufti-channel detector CCD as photoelectric detector, and a flat blaze grating as dispersive component, it can realize rapid scanning in the spectral range from 400nm to 800nm. Rapid scanning takes only 5.12ms to get a spectrum.â‘¡The optical system based on crossing Czerny-Turner structure has reduced the volume of spectrometer greatly, which has satisfied the instrument's miniaturization demand.â‘¢The SOPC technology, that NiosII soft-core CPU, UART, DMA are integrated in one FPGA chip, has been applied during the design in order to increase the system's integration. This can expedite the schedule of hardware designing efficiently and can reduce the area of circuit board.â‘£A protocol, which is used to transfer mass data between PC and the spectrometer via serial port, is put forward. This protocol is very simple and can be realized easily.