A Study Of Calibration Approaches Based On Vision Detection Technology

Visual detecting technology is one of specific application of machine vision; it includes measuring technique, testing technique and so on. Visual detecting system has many merits such as non-contact, fast, high degree of accuracy and so on, which had been extensively applied in industry, agriculture, scientific research, and military. However, any visual detecting system demands calibration. In this dissertation, a new calibration method based on two-dimension visual detecting system is proposed.Staking-out work is a key segment in visual detecting. Generally, a two-dimension image detecting system mainly consists of object measured, optical imaging device, and CCD (CMOS) pick up camera, signal processing circuits, and computer. Optical signal with verge position information or size information is turned into video signal by CCD (CMOS) pick up camera, and transmitted into computer for processing through image processing circuits. So dates of image processing are digital signals and verge position information obtained is expressed according to pixel unit. If real size of object measured is to be obtained, corresponding relation of digital image pixel and real size must be established. Namely calibrate equivalent coefficient of pixel. Compared with the traditional method of calibrating detecting system by using standard parts, this paper uses laser speckle projected on object measured from parallel beam of laser instead of standard parts. Speckle image of the measured object collected by industry pick up camera based on CMOS sensor is transmitted to computer via USB2.0, and then preprocessed by digital image processing technology; finally equivalent coefficient is come out. This calibration method makes the measurement that many sensors are unable or inconvenient to append the measured object become possible. The best merit of this method is calibration at job site, low cost of symtem and convinent use.This dissertation introduces fundamental of calibrating detecting system which use laser beam. System is analyzed detailedly from both hardware and software. Hardware part mainly includes industry pick up camera, laser, and USB2.0,while Software part mainly includes image collecting, image preprocessing,equivalent coefficient calculating and so on.