Research On Auto-zooming & Focusing Visual Sensor And Calibration

Visual sensor system is an integrated system which is composed of CCDcamera as the main sensitive element, integrating modem optical, mechanical andelectrical technology. It involves mechanical, optical, electrical, computer vision,digital image process, and software engineering technology. As a non-contacttesting method, it has been more and more widely researched and applied.As restricted by the condition that camera calibration process is complicatedand with low precision, the existing visual sensors are usually used in the workenvironment where the tested objects have no significant differences, are massproduced and highly repeating, but are rarely used in situation where tested objectsmake a great difference. Based on the research on existing visual sensors, a newvisual sensor is developed to satisfy the need in mechanical parts manufactureprocess, where the tested objects are greatly different. The visual sensor is equippedwith auto-zooming&focusing optical lens, which could adjust the camera focusaccording to the size of tested workpiece, acquiring proper image and improvingtesting precision. When the focus is changed, the relationship between the imageand the real object is acquired automatically, avoiding the complicated calibrationprocess.The basic principle of testing system is introduced, and several commontesting methods based on visual sensors are briefly reviewed.Aiming at the problem of limited testing range and complicated calibrationprocess after focus varied with existing visual sensor testing system, a new auto-zooming&focusing sensor is advanced, and the macro structure and hardwarecomponents design and choosing are introduced in detail. The manual-focusing lensis controlled by a step motor through mechanical rigging, to gain the varied value offocus and realize the auto-zooming&focusing of visual sensor. The softwaresolution of auto-zooming&focusing visual sensor is advanced, and the macrosoftware process of visual sensor function is introduced as well as the process offocusing subprogram.Finally, the calibration of auto-zooming&focusing visual sensor is researched,chiefly the calibration of lens and camera. In lens calibration, the lens focusdetermination and backlash problem of rigging system are analyzed. In cameracalibration, the linear imaging model of camera is established, according to which the camera calibration method is determined; Then taking the aberration of lens intoaccount, the camera non-linear imaging model and corresponding calibrationmethod is briefly introduced; finally, according to the specific requirement, anappropriate camera calibration method is established.