Research On Design And Imaging Performance Of The Retina-like Sensor

With the rapid development of photoelectric imaging technology, the imagesensors are widely used in the industrial and agricultural production, national defenseand scientific research, and they will be applied in the new areas, but the traditionalrectangular sensors such as CCD/CMOS image sensors have problems in somespecial applications, for example: during the high-speed forward motion imagingprocess, the traditional rectangular sensor with uniform distribution of pixels willproduce a radiant blurred image and effect the effective field of view; during thevideo transmission, the large amounts of data is a challenge to the bandwidth andstorage devices; when using the traditional rectangular sensor with a fisheye lens toachieve the panoramic image, the image distortion will take places. However, theabove problems are very simple tasks for the human eyes, and the researches havepointed out that the human visual system is an intelligent imaging system. Therefore,in recent years, bionic technologies are developed quickly by the effort of theresearchers, and the retina-like sensor is a kind of bionic sensor mimicking thedistribution of photoreceptors in the human retina. The pixels are arranged in differentconcentric rings, and the sensor is divided into two parts: the fovea and the periphery.In the fovea, the pixel size is the same, and it is the smallest one across the wholesensor, while in the periphery, the pixel size grows exponentially toward the border ofthe sensor. Because of its unique pixel layout, the sensor can soften the trade-offbetween the small amount of data, a large field of view and high resolution. Thus, theretina-like sensor is expected to solve the above problems of the rectangular sensor,and the research on it has important application and practical significance.Although the retina-like sensor has the above advantages, there is no criterion todesign its pixel layout. After a lot of literature research, we did not search any reporton the design of pixel layout of the retina-like sensor based on the different visual taskrequirements. The research on the design and manufacture of the retina-like sensor isstill blank in China. Therefore, after thoroughly analyzing and summarizing thedeveloping trends of the retina-like sensor, this thesis is focused on the design of pixelarrangements and the static and dynamic imaging properties of the retina-like sensor. The novel achievements are demonstrated as follows:1) A new retina-like sensor model for compensating motion blur introduced byforward motion imaging is proposed, then three retina-like sensors are designed tomeet different visual task requirements. The determination of pixel arrangement of aretina-like sensor according to visual task requirements is formulated into amulti-objective optimization problem. Then, the particle swarm optimizationalgorithm is used to determine the optimal pixel parameters. The results are robustand approximate to the design criteria;2) In order to analyze the static imaging performance of the space-variantretina-like sensor, the static modulation transfer function(MTF) of the sensor isestablished. According to the definition of the MTF, the ratio of the spectrum of theoutput image and the input image of space-invariant sub-areas is calculated to obtainthe static MTF. The MTF helps to analyze the performance of an imaging systemcontaining a retina-like sensor. Then, the MTF of the retina-like sensor is measuredusing spoke targets with different periods. The measured MTF values are compared tothe theoretical ones and the results show that they are close to each other;3) The dynamic MTF of the retina-like sensor during the forward motion imagingis established according to the property of the forward motion imaging. The statisticalmoments analytical method is used to calculate the motion MTF during the forwardmotion imaging, and the dynamic MTF of the retina-like sensor is derived by thecombination of the static MTF and motion MTF, and the simulating experiment ofoutput image of the sensor during the forward motion imaging process based on thedynamic MTF is carried out, and the Pearson correlation coefficients of the simulatedimages and experimental images are all larger than0.85;4) The rotation imaging process is used instead of the forward-motion imagingprocess, and the imaging sytem of the equivalent forward-motion imaging process isbulit to compare the blur length of the retina-like sensor and rectangle sensorquantively. It truns out that the retina-like sensor purposed in this thesis has thesuperiority of reducing the radiant blur.The design method of pixel arrangements of the retina-like sensor purposed inthis thesis meets the different visual task requirements in order to make full use of the advantages of the sensor, while the analyses of static and dynamic imaging propertiesof the sensor provide theoretical and technical reference for the further design anddevelopment of the sensor.