Study On An Image Acquisition Method For Inner Wall Surface Of Small Diameter-workpiece Based On Conical Reflector

Small size precision workpieces are developing fast and have widely growing applications in industries like aerospace,medical equipment,precision manufacturing.However,defects and scratches on the surface may lead to the breakdown of workpieces while being used.The image detection for small size precision workpieces has long been a widely difficulty.Industrial endoscope is a common solution,but there are many disadvantages such as limited image acquisition area,serious image distortion,inconvenience of image storing and processing,low detection efficiency and a relatively high cost.A new image acquisition method for inner wall surface of small diameter workpiece based on conical reflector is introduced in this research.A conical reflector is placed inside the hole and the reflection image of the inner surface of the hole is captured on it.CCD camera is used to acquire the reflection image that would be used for image processing to get the expansion image of the inner surface.Besides,a 1-axis straight moving motor is used to drive the workpiece with straight motion to acquire reflection images of different sections.Two different new designs of conical reflector structure are introduced to realize the image acquisition for both throughout hole workpieces and non-throughout hole workpieces.Meanwhile,to improve the system positioning accuracy,a calibration method for the system positioning error based on cylindrical calibration object and plane calibration object are introduced.With experiments,the grid corner point coordinates error is dropped by about 70% after calibration.At last,image processing procedures are studied for small-diameter workpiece including image preprocessing,edge detection,image expansion,image mosaicking,etc.Finally a prototype of the detection system is finished which can be used for the complete area color image acquisition for the small workpiece with a 2-5mm diameter hole.The difficulty of image detection for inner surface of small size workpieces can be solved base on the research.The method has simple principles and high feasibility.Image acquired is clear with little distortion and the resolution is up to 10?m level.