Design And Implementation Of HDMI Microscopic Auto-focus Camera Based On Hi3516A

Digital microscope has been playing a more and more important role in the scientific research,industrial vision detection and other fields.But it always needs to manual focus for getting clear image because of the thickness difference of the slice and the height of the sample,and the switching of magnification,which is time-consuming and laborious.Auto focus technique has been widely used in digital camera,video surveillance,mobile terminal and other fields.However,there is a little research on its application in digital stereo microscope and biological microscope.Because of this,the research on microscopic auto-focus camera is greatly useful.This thesis will focus on the microscopic auto-focus camera which achieves focus by moving the image sensor and do comprehensive research on algorithm,hardware,software and mechanical structure,and develop a prototype camera.Firstly,it is a rather complicated process to achieve perfect focus by algorithm.According to the characteristics of evaluation function of sharpness,a new searching algorithm that combines climbing searching method with exhaustive searching method is proposed in this thesis,which improves the accuracy of the existing algorithms.In order to improve the focus speed,the searching strategies of prejudging the direction and adaptive step size is proposed.In order to reduce interference of the local peak of the evaluation function curve,the sliding average preprocessing of the evaluation function curve is introduced,and a new judging standard of peak point is adopted.We identify the changes of scene by monitoring the changes of the regional brightness and focus value,which improves anti-interference,accuracy and stability of auto focus.At the same time,this thesis proposes the focus monitoring algorithm,and achieves the function of continuous auto focus of camera.Secondly,according to the characteristics of optical system of microscope,this thesis is carried on the thorough research and analysis on the internal structure of microscopic auto-focus camera from hardware circuit and mechanical structure design.This thesis proposes a new method which achieves auto focus of digital microscope by adjusting the position of the image sensor.The camera is smaller and more portable than the auto-focus system which adjust the focusing handwheel of microscope,because all mechanical structures of auto focus are integrated inside the auto-focus camera.And the auto-focus camera can achieve auto focus function of different microscope without changing the original system of microscope,which further reduce requirement of the accuracy of the focusing mechanism.Thirdly,on the development of software,our camera is an embedded Linux application.We achieve acquisition,real-time display,encoding,and storage of high-definition image based on media development platform of Hi3516A.We also achieveauto exposure,manual exposure,one push white balance,Gamma correction,wide dynamic range,noise reduction,sharpness,saturation,contrast,anti-flicker and the function of auto focus based on image signal processing platform of Hi3516A.Furthermore,we develop user-friendly graphical user interface using Qt/Embedded tool and the camera can be controlled by a USB mouse.This thesis successfully develop a practical microscopic auto-focus camera that is completely detached from the computer.Lastly,in order to verify advantages of the microscopic auto-focus camera we developed,we test it in stereo microscope and biological microscope respectively.Experiment results show that our camera has a high accuracy and stability of auto focus,and the speed of auto focus meets demands of general application,such as teaching research and laboratory application.