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Double telecentric lens principle and use scope ( Seconds to understand)

by:Fugen      2020-10-13
Industrial camera is an important part of the machine vision system, lens of telecentric lens with its unique performance, is widely used in machine vision applications. This article mainly to introduce the basic knowledge of telecentric lens, from the principle of telecentric lens, application scope, the selection method from three aspects, let the reader friends of telecentric lens have a further understanding. Telecentric lens, the principle of first of all, we from the several problems of telecentric lens. The first question: general lens in the process of imaging, when change the working distance, the image size will be change accordingly, the result is the same focal length lens, corresponding to different object distance, there will be a different magnification, this phenomenon with the human visual system depending almost small similar visual difference. This problem in some applications can be ignored or even use them, but when our visual system is used to perform precision measurement tasks, this feature will become the great obstacles. Second question: ordinary lens there is a range of depth of field, when the measured object is beyond the scope of the lens depth of field, the image will become fuzzy, not clear focus, therefore, the designers design the adjustable JiaoHuan on ordinary lens, when the working distance changes, can adjust the focus plane of the region of interest to see clearly. The question is, if it is to measure the depth of the object itself is beyond a certain range, the lens is always can't see fore and aft ends at the same time, this problem, must be addressed through other way. The third question: with the constant improvement of the resolution imaging chip now, user requirement for accuracy of measurement is becoming more and more strict, ordinary lens is subject to the principle of the optical imaging, best can only do about 10 um, visual inspection areas need higher precision of imaging products. Double telecentric lens is in order to solve these problem arises at the historic moment. Double telecentric lens through aperture is placed in the intermediate position of the optical system, the main light must through the center of the aperture, the object side and side of the main light must be parallel to the optical axis into the lens. Parallel to the incident light to ensure the enough depth range, parallel light from the lens, to ensure the working distance is within the scope of the depth of field changes greatly, the height of the image magnification is not to change. What conditions should choose telecentric lens? According to many years of experience in machine vision product selection, give readers some double telecentric lens selection in terms of reference. When tested object thickness is bigger, need to detect more than one plane, the typical applications such as food, beverage bottle, etc. When put the position of the object to be tested is not sure, probably with lens into a certain Angle. When jumping up and down in the process of tested object to be tested, such as production line up and down vibration lead to changes in working distance. When the belt aperture, object to be tested or three-dimensional objects. When you need to low distortion rate, image brightness is almost entirely consistent effect. Only when the need to detect the defects in the same direction parallel to the lighting can be detected. When need more than precision, such as tolerance to 1 um. Shanghai optical technology co. , LTD, a professional production and sales of accessories, all kinds of machine vision professional trustworthy, if you have any doubt on the selection, please consult our customer service personnel, to provide you with technical guidance, thank you!
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