Transparent Fingerprint Identification System And Algorithm Based On Zinc Oxide Thin-film Transistors

With the popularity of the intelligent electronic equipment,fingerprint identification and face recognition technology are constantly challenged because of the demand for a thinner,lighter device.The increase in the size of the device means that screen-to-body ratio has the highest priority in mobile phones.While the mainstream identity technology occupies a certain space,which is contrary to it.Therefore,on-display transparent fingerprint identification is rapidly developing.Based on a stable and reliable fabrication process of the zinc oxide thin film transistors,three kinds of transparent fingerprint sensors with different circuit structures are fabricated on the glass.The average transmittance is up to 84%,making it feasible to be placed on top of a display while maintaining satisfactory brightness.It is also an approach that takes both the touch interaction and fingerprint recognition.In particular,the ZnO TFTs are used in each pixel not only as select switches but also for pre-amplification of signals,and can work stably under white light.Then we designed a real-time display circuit for testing,and got the 254DPI fingerprint image.This study may open up potential applications of on-display transparent electronics that involve active circuits.The contents and results of this study can be summarized as follows:1.We successfully fabricated the ZnO-TFT with the turn-on voltage,Von,is approxlimately Ov,the on-off current ratio is up to 108 and the gate leakage current,IG,maintains at the pA level,it shows good uniformity,stability and transparency.2.In order to overcome the shortcomings of select switch circuit,we have increate three new circuit to enhance signals.We did some theoretical analysis and simulation to confirm the feasibility of the scheme.3.The transparent fingerprint matrix consist of 50×50,96×96,200×100 units have been successfully fabricated on glass,shows significantly less sensitivity to visible light.A detection circuit is designed,and the output signal of the sensor is displayed real-time by matlab display program.Finally,we got acquisition.4.The difficulty of on-display fingerprint is how to get signal under protective layer.For these three kinds of transparent fingerprint matrix,we have did some experiments and tried the protective layer with thickness of 1?m,8?m and 100?m respectively.The pre-amplifier circuit exhibits significantly enhanced signals and good stability.5.Finally the original image is processed by reprocessing algorithm,including gray equalization,image enhancement,image thinning,binarization,and finally effective feature points are extraced.