In the industrial vision system, the performance of industrial lenses directly determines the imaging quality, which in turn affects the success or failure of the entire vision inspection task. However, in the actual selection process, due to the many parameters involved and the complexity of the application scenarios, many users will fall into some misunderstandings.

I. Resolution Mismatch

1. Lens resolution lower than the camera requirements

Camera resolution increases very quickly, many users in the selection, will give priority to upgrading the camera, but ignored the lens resolution is matched. If the lens resolution is lower than the camera, even if the camera has a high pixel, the final image can not achieve the desired effect. For example, in a high-precision size measurement scenario, if you choose a lens with a resolution of only 1 megapixel with a 5 megapixel camera, the image edges will be blurred and the details will be lost, resulting in a significant reduction in measurement accuracy. In order to avoid this kind of problem, in the selection, need to ensure that the resolution of the lens at least the same as the camera sensor resolution, if possible, you can choose a slightly higher resolution than the camera's lens, to give full play to the performance of the camera.

2. Ignore the actual application of the resolution requirements

Not all applications require ultra-high resolution lens. Some users blindly pursue high resolution, not only increases the cost, but also may bring the burden of data processing. For example, in some of the object surface defects in the macro detection of the scene, only need to identify the larger defects, too high resolution lens to collect a large amount of data, not only take up storage space, but also lead to image processing time is extended, reducing detection efficiency. Therefore, according to the accuracy requirements of specific application scenarios, a reasonable choice of lens resolution.

II. Improper choice of focal length

1. Focal length and working distance mismatch

Focal length and working distance are closely related, improper selection will seriously affect the imaging effect. If the visual inspection system, the required detection of objects farther away from the camera, but the choice of a short focal length lens, the picture will appear distortion, and difficult to clearly capture the details of the object. On the contrary, when the detection object is closer to the camera, the use of a long focal length lens may result in a field of view that is too small to capture the object in its entirety. Selection, according to the working distance, the size of the field of view and other parameters, with the help of calculation formulas or lens manufacturers to provide selection tools to accurately calculate the required focal length.

2. Ignore the limitations of Varifocal Lens

Varifocal Lens seems to be able to flexibly adjust the focal length to meet the needs of different scenes, but in practice, it has certain limitations. Varifocal Lens in the process of varifocal, the image quality may change, especially at the telephoto end, the image may appear to be a decline in clarity, aberration increase and other problems. In addition, Varifocal Lens is relatively expensive and has a large volume and weight. In some scenes with strict requirements for image quality and a fixed working distance and field of view, fixed-focus lenses may be a better choice.

III. Interface compatibility issues

1. Lens and camera interface mismatch

There are many types of lens and camera interfaces, the common ones are C interface, CS interface, F interface, etc. If the lens and camera interfaces do not match, not only can they not be installed, but they may also damage the equipment. If the lens and camera interface does not match, not only can not be installed, but also may damage the equipment. For example, if a C-interface lens is mounted on a CS-interface camera, the lens will not be able to focus accurately due to the difference in interface flange distance, resulting in blurred images. Therefore, before selecting the model, be sure to confirm the interface type of the lens and the camera to ensure compatibility.

2. Ignore the electrical interface compatibility

With the development of industrial vision technology, many lenses with electric varifocal, auto iris and other functions, which requires electrical communication between the lens and the camera. In the selection of such lenses, to ensure that the electrical interface of the lens is compatible with the camera, otherwise these features will not be able to use normally. Some users in the selection, only focus on the optical interface, ignoring the electrical interface compatibility, resulting in the installation of equipment after the function can not be realized, causing unnecessary trouble.

IV. Neglect of environmental adaptation

1. Failure to consider environmental factors such as temperature and humidity

Industrial production environment is complex and variable, temperature, humidity, dust and other factors will have an impact on the performance of the lens. In a high-temperature environment, the lens inside the lens may be due to thermal expansion and contraction and displacement, resulting in changes in focal length; in a high humidity environment, the lens surface is prone to condensation, affecting the imaging quality. If the working environment is dusty, the lens dustproof performance is not good, dust into the lens interior, but also accelerate the lens wear. In the selection, according to the actual working environment, choose the appropriate level of protection and environmental adaptability of the lens, such as high temperature, waterproof and dustproof industrial lens.

2. Insufficient consideration of special environments

In some special industrial scenarios, such as chemical production, food processing, etc., the lens may come into contact with corrosive substances or need to meet specific health standards. If in these scenes, the choice of ordinary lenses, the lens surface may be corroded, affecting the service life, and may even cause contamination of product quality. In this kind of special environment, you need to choose with corrosion resistance, easy to clean and other characteristics of the special lens.

Industrial lens selection is a systematic work, any negligence in any part may lead to selection failure. By fully understanding the parameters, combined with the actual application scenarios, pay attention to the details, you can effectively avoid stepping on the pits, selected the most suitable industrial lens, for the stable operation of the industrial vision system to lay the foundation.