The Study On Readout Circuit Of Flexible Pyroelectric Infrared Detector

Flexible pyroelectric infrared detector has the characteristics of uncooled,long detection wavelength,low fabrication cost and flexible wearable,and has become a focus in the field of infrared detection.The flexible detector readout circuit which determines the extraction and conversion of the pyroelectric signal is an important part of the detector.Therefore,designing a pyroelectric readout circuit with high signal-to-noise ratio and high voltage response rate is a significant task.A voltage-based and current-type composite readout circuit is designed for the flexible PVDF pyroelectric thin film sensing element which is made in the laboratory in the paper.In order to screen the PVDF film with high pyroelectric coefficient during the experimental preparation and quantize the detection energy for the readout circuit,a pyroelectricity test system based on the modulation temperature of triangular wave and sine wave has been designed,of which the main content is introduced as follow:Firstly,the detection principle of pyroelectric infrared detector based on PVDF flexible sensitive element is analyzed.Based on the equivalent circuit model of PVDF,we have analyzed and compared the structure and characteristics of three kinds of readout circuits which contain voltage type,current type and charge type.And we have explored the source of noise in readout circuits of flexible infrared detectorsSecondly,we have developed a dynamic adjustable readout circuit which composite the voltage type and current type.The voltage type readout circuit is a JFET differential amplification structure,and the differential amplification voltage gain is60dB.We have adopted a transimpedance structure in the current-type readout circuit of which the large feedback resistor is based on a T-type resistor network,and the dynamic adjustable range of the resistance is from 500M?to 100G?.The bias voltage of the current type preamplifier is automatically adjustable according to the feedback of the output signal,and the adjustment range is from 0 to 0.67Vcc.Finally,we have achieved that the energy measurement is form 0.1?J to 1mJ and voltage response rate is bigger than 700V/W in the readout circuit.Thirdly,based on BP neural network PID algorithm,the triangular wave or sine wave temperature controled technology of which the frequency is form 10mHz to 1Hz and the amplitude value is form 0.5°C to 2°C has been acheieved.The error of the temperature control system is less than 0.15°C.Based on the readout circuit of high signal-to-noise ratio and high-voltage response rate designed in Chapter 3,the data acquisition module with STM32F407 as the core,the TEC power driver module,the PT100 temperature acquisition module,and the Matlab and STM32F407 serial port communication module,we have realized the measurement system for pyroelectric coefficient of PVDF film Sample.Finally,the pyroelectric coefficient of the PVDF sample measured by the temperature control of the triangular wave is 10.7?C/K·m~2 and the pyroelectric coefficient is 23.89?C/K·m~2 under the temperature control of sine wave modulation.Through analysis and comparison,the test error of pyroelectric coefficient under the temperature control of sine wave modulation of the system is within 10%.