视觉检测系统中工业镜头的选择五要素
发布时间：
2023-02-10 11:30
工业相机、图像采集卡、照明光源、分析软件和工业镜头是组成机器视觉检测系统的重要元件，其中关键的元件还是工业镜头。视觉检测系统若想完全发挥作用，选择工业镜头前必须要考虑到以下五个要素：
Industrial camera, image acquisition card, lighting source, analysis software and industrial lens are important components of machine vision inspection system, among which the key component is industrial lens. If the visual inspection system wants to play a full role, the following five factors must be considered before selecting industrial lens:
1.运行环境
Operating environment
机器视觉检测系统的工作环境不同所选用的工业镜头会有所区别。因为物体的反射系数、光线、温度、振动和污染物等都会影响镜头的正常工作。若是在高温环境下，可能因为镜头里光学元件的热膨胀出现问题。并不是所有的镜头都可以适应温度变化，在检测热物体时，使用工作距离比较长的镜头，也就是说我们要根据视觉检测系统的工作环境选择适合的镜头。
The working environment of machine vision inspection system is different, and the industrial lens selected will be different. Because the reflection coefficient of the object, light, temperature, vibration and pollutants will affect the normal operation of the lens. If it is in a high temperature environment, it may be due to the thermal expansion of the optical elements in the lens. Not all lenses can adapt to temperature changes. When detecting hot objects, use lenses with long working distance, that is to say, we should select the appropriate lens according to the working environment of the visual inspection system.
2.检测物体类别和特性
Detection object category and characteristics
镜头对于物体特征的解析能力依赖于特征的对比是否强烈。确定系统解析度、或者物体解析特征的方法，可以使用诸如伦奇刻线法这样的解像力方法。镜头在指定光线条件下辨识特定宽度的线耦或者点距的能力，决定了它的解析度。解析度通常被模块转换功能（MTF）以图像的方式显示出来。
The ability of lens to analyze object features depends on whether the contrast of features is strong. In order to determine the resolution of the system, or the analytic characteristics of an object, we can use the image force method such as lunge's method. The resolution of the lens is determined by its ability to identify the line coupling or point distance of a specific width under the specified light conditions. Resolution is usually displayed in the form of images by the module conversion function (MTF).
3.景深或者焦距
Depth of field or focal length
景深效果（DOF）是指由于物体移动导致的模糊。DOF是完全在焦距范围内的物体深度，是保持理想对焦状态下物体允许的移动量，从焦距前后移动。当物体的放置位置比工作距离近或者远的时候，它就位于焦外了，这样解析度和对比度都会受到不好的影响。出于这个原因，DOF同指定的解析度和对比度相配合。当景深一定的情况下，DOF可以通过缩小镜头孔径（也就是增加F/#值）来变大，同时也需要光线增强。
Depth of field effect (DOF) refers to blurring caused by moving objects. DOF is the depth of the object completely within the focal length range, and the allowable movement of the object under the ideal focusing state, moving forward and backward from the focal length. When the object is placed closer or farther than the working distance, it is out of focus, which will affect the resolution and contrast. For this reason, DOF matches the specified resolution and contrast. When the depth of field is fixed, the DOF can be increased by reducing the aperture of the lens (i.e. increasing the F / #) value, and light enhancement is also required.
4.加载
Loading
很多相机镜头需要平稳加载，但是当物体和镜头之间的距离受到限制，改变镜头与图像之间的距离，就可以改变工作距离。加载限制，包括用于艰苦环境的保护外壳，必须具有足够的柔性，可以根据工作距离进行调整。
Many camera lenses need to be loaded smoothly, but when the distance between the object and the lens is limited, changing the distance between the lens and the image can change the working distance. The loading limits, including protective enclosures for harsh environments, must be flexible enough to be adjustable according to the working distance.
5.检测距离
Detection distance
当图像在焦距范围内的时候，物体和照相机镜头前端的距离。它限制了视觉系统以及和视觉系统一起工作的设备所需要的空间。在极限范围内，通过镜头重新对焦，可以改变工作距离。
The distance between the object and the front of the camera lens when the image is in focus. It limits the space required by the vision system and the devices that work with it. Within the limits, the working distance can be changed by refocusing the lens.
由此可见，合适的镜头选择对于机器视觉检测系统发挥着非常重要的作用。
Therefore, appropriate lens selection plays a very important role in machine vision detection system.
视觉检测系统,机器视觉检测技术