Color Lock-in Imaging

In the industrial detections based on machine vision, it is usually difficult to obtain a real image of an object, specially in billet detection, rail abrasion detection, video monitoring, etc, where strong background light exists. Without an effective method, the target image will be merried in the strong background light, making it impossible to get the target image.So obtaining clear target image in the presence of strong background light has become a technical problem. In the process of billet detection, for example, steel billet just came out of smelting is in high temperature conditions so as to send a strong light. It is required to detect the quality of billet production as early as possible in a working line to find possible defections in advance, which requires to obtain faint image signal in strong background light for billet crack, bubble, etc. Additionally, security requirements are also getting stricter now, in video monitoring. For example, sometimes it needs to get car license number and color images of the suspect in the evening when bright lights of the car are turn on but the current video detection techniques are not capable of getting these informations. There is a kind of method, laser lock-in imaging, can effectively obtain the license number but unable to know the useful color information of criminal suspect. So we put forward the color lock-in imaging technique based on the laser lock-in imaging, which can filter the strong background light and can also get more effective information simultaneously.This thesis makes an improvement firstly by a single gray image into a color image based on laser lock-in imaging, performs the experiment under the compile environment of Windows, and the result of the experiment are analyzed compared with conventional techniques. The experimental results verify the ability of color lock-in imaging to obtain the target image from strong background light. Then in the Linux compile environment experiment, the same verification of getting target image under the background of strong light is also verified. The software based on Linux runs faster than Windows. The experimental results show that the color lock-in imaging technique is capable of getting a weak target image from strong background light.Based on laser lock-in imaging technology color lock-in imaging technology is put forward, using common LED as a light source and color CCD image sensor to get the target image. Using the computer to modulate illuminate light source and control color CCD camera at the same time, then to process and display the image obtained. The system is simple, practical, and can not only inhibit the action of the strong background light, but also obtain more effective information of color target image. The technology gives full play to the advantages of lock-in imaging technology and avoids the use of the valuable optical components such as laser to reduce the cost and expand the scope of lock-in imaging technology effectively.