Study Of Machine Vision Optical Apparatus For Simultaneously Inspecting Double Surfaces Of TEC Components

Machine vision is the equipment for measurement and inspection by replacing the role of human eyes.A conventional machine vision automatic optical inspection(AOI)system usually employ one camera with imaging lens and illuminating source for inspecting one surface of the object.An optical inspecting system with multiple image taking cameras must be employed if multiple surfaces of the object need to be inspected simultaneously.However the system configuration,cost and reliability of such solution are our concern.In this article two novel optical inspection apparatuses were proposed and studied which enable one to inspect two surfaces of thethermoelectric cooler(TEC)components.The commercial image processing software MIL10 is used to analyze the images taken and preliminary experimental inspection results are obtained.Those technical solutions may offer potential advantages of simplified configuration,easy installation and effective cost to the automatic optical inspection systems.In Chapter 1,the current situation of the machine vision,the purpose and significance of this thesis were introduced in details.Meanwhile,the main contents and innovation of this article were also explained briefly.In Chapter 2,the configuration and working principle of AOI systems were described.The AOI system includes software part and optical imaging part and the hardware part divides into camera,lens and illuminating source.The image of the object is collected by optical imaging part,while the software part processes the image of the optical imaging part.In Chapter 3,an optical inspection apparatus was proposed to inspect the top and bottom of object simultaneously.The novelity of the proposed inspection system is that the right angle prism reflector located beneath the glass stage is used to image the bottom surface of the object on top of the stage.The principle of the inspecting system is described as follows: the top surface of the object with illumination is being directly imaged by the telecentric lens onto the left area of CCD sensor while the bottom surface of the object after being illuminated and reflected twice by the right angle prism reflector is also being simultaneously imaged by the same telecentric lens onto the right area of CCD sensor.Hence both the top and bottom surfaces of the object are being imaged onto the same CCD sensor simultaneously.On the other hand,the optical paths for imaging the top and bottom surfaces are not identical using the same imaging lens and CCD sensor,a proper telecentric imaging lens with sufficient large depth of field needs to be selected to address their optical path difference in order to obtain clear images of both top and bottom surfaces of the object.An experimental apparatus was established for the above proposed optical inspecting system.A right angle prism reflector with solpe side length of 3.6mm is elected for this experimental setup.A camera IMC 750 GC with sensing area of 1/2.5',pixel array of 2588×1940 and pixel size of 2.2microns was used together with a telecentric imaging lens DH110-03F50 with field of view around 17×12.8mm and resolution about 100pl/mm.The depth of field of this lens is 6mm.With this apparatus three groups of components were inspected in the experiments.The two images we gained are imaged clearly at the same time,while the two images differ greatly in contrast because of the low reflectivity of the right angle prism reflector,which needs to be improved.In Chapter 4,a new optical inspection apparatus was proposed to inspect the two adjacent surfaces of the object.The principle of the device is similar to that described in chapter 3: the lateral surface of the object with illumination via the beam splitter is being directly imaged by the telecentric lens onto the left area of CCD sensor while the bottom surface of the component after being illuminated by the beam splitter and reflected twice by the right angle prism reflector is also being simultaneously imaged by the same telecentric lens onto the right area of CCD sensor.IMC 750 GC camera and DH110-03F50 lens are used in the experiment since the object to be tested is the TEC components and the inspection accuracy remains unchanged.In addition,a right angle prism reflector with solpe side length of 70.7mm and a beam splitter with the length of 15 mm are used in this experiment.With this apparatus a few groups of Pass and Fail components were inspected in the experiments.From the experimental results,the image obtained is clear and recognizable,but there are some background noises,which needs to be optimized at the later stage.In Chapter 5,an image processing method was used to verify the feasibility of static inspection for the surface defects and dimensions of TEC components according to the characteristics.The method mainly includes image preprocessing,area inspection,surface defect inspection,edge length inspection and other steps.After processing the typical images obtained in Chapter 3 and Chapter 4,the results show that the image processing method is suitable for static inspection of TEC components.The optical principle and technique for simultaneously inspecting double surfaces of the object have been investigated.The optical inspection apparatus has been set-up using a right-angle prism reflector for obtaining the image of bottom surface of the component and the preliminary experimental studies have been conducted.The results show that the proposed techniques allow us to inspect two surfaces of the component with simplified configuration and effective cost.These novel inspecting techniques will find applications in the automatic optical inspection systems for the TEC components.