Reseach On Key Technology In TDI CMOS Image Sensor For Optofluidic Microscope

Portable medical devices have become a research focus in intelligent medical systems and telemedicine.With the advantage of portability,real-time detection and ease of system integration,optofluidic microscope attracted a wide spread attention in the field of biological cell detection.Optofluidic microscope is based on micro-fluidic and image sensor,and the CMOS image sensor determines the image quality.Therefore,it is important to study the key technologies in high-speed and high-precision CMOS image sensor.In this thesis,time delay integration?TDI?CMOS image sensor is applied to optofluidic microscope,and research on key technologies such as improving image resolution and high-speed column-parallel analog-to-digital converter?ADC?.The following is the main contents of this thesis:1.A method for optofluidic microscope super-resolution imaging is proposed,which is oversampled using a TDI CMOS image sensor.It is necessary to study the number of the TDI stages and the frequency of the oversampling,because they determine the relationship between the sub-pixel image and the original image,so it is necessary to study the number of the TDI stages and the frequency of the oversampling.The Matlab simulation results show that,the grayscale mean gradient drops to approximately 0.67^M/2 times and the signal-to-noise of the image increased by M^1/2 times,while the oversampling frequency of the TDI CMOS image sensor becomes M times.2.A column-parallel fully differential input ADC is proposed for converting the differential output of the accumulator,it can improve the anti jamming capacity of signal without additional circuits.Top plates of the two sampling capacitors are used for sampling differential inputs,and the bottom plates are connected to differential ramp for conversion.The differential ramp is generated by current steering strcuture.The proposed ADC is fabricated in SMIC 0.18?m CMOS process.The pitch is 16?m,area of the 64-column is 1.0mm×3.0mm and area of the ramp generator is 1mm×0.7mm.The clock frequency is 20MHz,simulated SFDR and ENOB are 87.92dB and 9.84-bit with the input frequency of 1.32 kHz at 19.49 kS/s sampling rate,respectively.Measured results show that the ADC has a DNL of-0.7/+0.6 LSB and INL of-2.6/+2.1 LSB.3.A two step successive approximation register?SAR?Single-Slope?SS?ADC is proposed for the high-speed,high-accuracy TDI CMOS image sensor.The SAR is used for high bits to increase conversion rate,and SS is used for low bits to decrease area.At the same time,the mismatch error and segmentation error are calibrated.The proposed 12-bit ADC with high 6-bit SAR and low 6-bit SS is fabricated in UMC 0.11?m CMOS process.The chip test results show that,SNR,THD,SFDR and ENOB are 49.25dB,-62.83dB,65.66dB and 7.86-bit with the input frequency of 1.03 kHz at 20 kS/s sampling rate,respectively.Compares the simulation performance of the ADC before and after calibration,DNL and INL are decreased from-0.8/+0.7LSB and-1.7/+0.5LSB to-0.2/+0.2LSB and-0.33/+0.23LSB,respectively.SFDR has increased by 24dB to 89.57dB,THD has reduced by 19dB to-87.67dB,and ENOB has increased1 bit to11.86-bit.4.In order to improve the sampling precision of column-parallel ADC in TDI CMOS image sensor,an improved bootstrap switch for column-parallel circuit is proposed.A source follower to reduce the on-resistance and improve the reliability of the circuit.The body effect compensation circuit is used to decrease the on-resistance change varies with the input.Besides,a control switch is added to the column-shared bias circuit to avoid the unnecessary power consumption.The proposed switch is implemented in UMC 0.11?m CMOS process.Simulation results show that,the on-resistance is decreased about 28.6%,the resistance changes within 1.2%in the input range,ENOB is increased about 1-bit.However,the area is only increased 15%.The measured results after manufacturing show that the SNR,SFDR and ENOB are 85.8dB,71.1 dB and 11.5-bit with the input frequency of 1.97 MHz at 20 MS/s sampling rate,respectively.In this thesis,the key technologies of TDI CMOS image sensor for optofluidic microscope have studied.A super-resolution imaging method has been proposed,and the ADC and its critical circuits to meet the application requirements are studied.This work will lay a solid foundation for the realization of portable optofluidic microscope.