Electronic Design Of Short-Wave Infrared Low Noise Spectrometer

Many ground objects have rich spectral characteristics and high spectral reflectance in the short-wave infrared band,which makes the short-wave infrared widely used in earth observation.For example,the on-orbit site vicarious calibration method requires the calibration instrument and the satellite simultaneously and synchronously measure the target object with uniform surface spectral characteristics,so as to correct the output of the satellite remote sensing detector.In this paper,the electronic design of the short-wave infrared low noise spectrometer is developed for the observation of the weak signal of the 1600 to 2500 nm continuous spectrum,and spectrometer was applied to the site vicarious calibration.The paper analyzes the noise source of spectrometer and puts forward some performance indexes such as signal to noise ratio.In order to meet the requirements of low noise,four short-wave infrared detectors are investigated,and their performance parameters and spectral response curves are compared,Hamamatsu's G11478 InGaAs line array detector is selected.The optical system adopts the flat field concave grating to split light,design the relevant optical path,and reduce the stray light.The overall design of electronics is divided into the detector measurement and temperature control module and the master control module.The detector measurement module design the driving circuit of G11478 detector;Detector output analog signal processing circuit,including differential amplifier,low-pass filter and programmable gain circuit;And A/D acquisition circuit.Based on the microprocessor STM32F103RET6 of ARM Cortex-M3 core,embedded software design is carried out for the driver,automatic gain and digital average acquisition of detector signals.Since the dark current and other noises of the InGaAs detector are easily affected by temperature,the temperature control module is designed,which is divided into the three-stage thermostatic system to stabilize the environmental temperature of the detector and the two-stage refrigeration system to refrigerate the detector.According to the detector characteristics and environmental conditions,the three-stage thermostatic system selects Thermo Electric Cooler TEC1-12706 as the actuator,designs the MOSFET bridge switch circuit to drive TEC 1-12706,and designs the environmental temperature measurement circuit as the feedback.The two-stage refrigeration system is designed with a large current circuit to drive the two-stage TEC in the G11478 detector,and the temperature measurement circuit of the detector is designed as the feedback.In order to achieve high precision temperature control,the digital incremental PID algorithm was applied to the microcontroller STM32F103RBT6,adjusts the output of the drive circuit according to the temperature feedback.The master control module is designed with STM32F103ZET6 as the core and combined with the peripheral hardware circuit to realize the various working functions and operation process of the spectrometer.The temperature control module was tested,and the results showed that the environmental temperature of the detector was stabilized at 20?,and the accuracy was better than ±0.5?.The temperature of the detector was cooled at-20?,and the accuracy was better than ±0.1 ?.Experiments verified that the method of temperature-controlled refrigeration and average filtering algorithm can effectively reduce the output noise of the detector.The performance test of spectrometer was carried out in the laboratory.The integrating sphere radiation light source was used to simulate the solar spectral signal.In the 1600?2500 nm band,the signal-to-noise ratio(SNR)of the detection instrument is greater than 200,the nonlinearity is better than 0.49%,and the instability is better than 0.54%.The functional test of the spectrometer prototype was carried out outside Hefei to verify that the instrument could measure the 1600?2500 nm continuous spectrum signals of the object.