科普:机器视觉检测系统中光源的作用及分类
发布时间：
2023-02-10 11:28
在设计整体的机器视觉检测系统方案的时候，关键的任务就是选择好的视觉光源控制器。考虑到每个行业中所检测到的物体形状、光泽和颜色都不尽相同，也就决定了光在物体表面反射的形式也会不同。
In the design of the overall machine vision inspection system, the key task is to choose a good light source. Considering that the shape, luster and color of objects detected in each industry are different, the reflection form of light on the object surface will be different.
如何控制光源反射是机器视觉检测设备光源控制应用的重点所在。能够控制好光源的反射，那么获得的图像就可以控制了。因此，在机器视觉应用中，当光源入射到给定物体表面的时候，明白光源最重要的方面就是要控制好光源及其反映。
How to control the reflection of light source is the key point of light source control application of machine vision inspection equipment. If the reflection of the light source can be controlled, the image obtained can be controlled. Therefore, in the application of machine vision, when the light source incident on the surface of a given object, the most important aspect of understanding the light source is to control the light source and its reflection.
光源可预测：当光源入射到物体表面的时候，光源的反映是可以预测的。光源可能被吸收或被反射。光可能被完全吸收（黑金属材料，表面难以照亮）或者被部分吸收（造成了颜色的变化及亮度的不同）。不被吸收的光就会被反射，入射光的角度等于反射光的角度，这个科学的定律大大简化了机器视觉光源，因为理想的效果可以通过控制光源而实现。
Predictable light source: when the light source incident on the surface of the object, the reflection of the light source can be predicted. The light source may be absorbed or reflected. The light may be completely absorbed (black metal material, the surface is difficult to illuminate) or partially absorbed (causing changes in color and brightness). The light that is not absorbed will be reflected. The angle of incident light is equal to the angle of reflected light. This scientific law greatly simplifies the light source of machine vision, because the ideal effect can be achieved by controlling the light source.
物体表面：如果光源按照可预测的方式传播，那么又是什么原因使机器视觉的光源设计如此的棘手呢？使机器视觉照明复杂化的是物体表面的变化造成的。如果所有物体表面是相同的，在解决实际应用的时候就没有必要采用不同的光源技术了。但由于物体表面的不同，因此需要观察视野中的物体表面，并分析光源入射的反映。
Object surface: if light sources propagate in predictable ways, what makes machine vision's light source design so difficult? What complicates machine vision lighting is the change of object surface. If the surfaces of all objects are the same, there is no need to use different light source technologies in solving practical applications. However, due to the different surface of the object, it is necessary to observe the object surface in the field of view and analyze the reflection of the incident light source.
控制反射：如果反射光可以控制，图像就可以控制了。因此在涉及机器视觉检测系统应用的光源设计时，最重要的原则就是控制好哪里的光源反射到透镜及反射的程度。当观测一个物体以决定需要什么样的光源的时候，首先需要问自己这样的问题：“我如何才能让物体显现？”“我如何才能应用光源使必须的光反射到镜头中以获得物体外表？”
Control reflection: if the reflected light can be controlled, the image can be controlled. Therefore, when it comes to the design of light source for the application of machine vision inspection system, the most important principle is to control where the light source reflects to the lens and the degree of reflection. When observing an object to determine what kind of light source is needed, the first thing you need to ask yourself is, "how can I make an object appear?" "How can I apply light sources to reflect the necessary light into the lens to obtain the appearance of the object?"
影响反射效果的因素有：光源的位置，物体表面的纹理，物体表面的几何形状及光源的均匀性。
The factors that affect the reflection effect are: the position of the light source, the texture of the object surface, the geometry of the object surface and the uniformity of the light source.
光源的位置：既然光源按照入射角反射，因此光源的位置对获取高对比度的图像很重要。光源的目标是要达到使感兴趣的特征与其周围的背景对光源的反射不同。预测光源如何在物体表面反射就可以决定出光源的位置。
Position of light source: since the light source is reflected according to the incident angle, the position of the light source is very important for obtaining high contrast images. The goal of a light source is to make the feature of interest different from the reflection of its surrounding background. The position of the light source can be determined by predicting how the light source reflects on the surface of the object.
表面纹理：物体表面可能高度反射（镜面反射）或者高度漫反射。决定物体是镜面反射还是漫反射的主要因素是物体表面的光滑度。一个漫反射的表面，如一张不光滑的纸张，有着复杂的表面角度，用显微镜观看的时候显得很明亮，这是由于物体表面角度的变化而造成了光源照射到物体表面而被分散开了。而一张光滑的的纸张有光滑的表面而减小了物体表面的角度。光源照射到光源的表面并按照入射角反射。
Surface texture: the surface of an object may be highly reflective (specular) or highly diffuse. The main factor determining whether an object is specular or diffuse is the smoothness of its surface. A diffuse reflective surface, such as a piece of unsmooth paper, has a complex surface angle, which is very bright when viewed with a microscope. This is due to the change of the surface angle of the object, which causes the light source to irradiate the surface of the object and is dispersed. A smooth paper has a smooth surface and reduces the angle of the surface. The light source irradiates the surface of the light source and reflects according to the incident angle.
表面形状：一个球形表面反射光源的方式与平面物体不近相同。物体表面的形状越复杂，其表面的光源变化也随之而复杂。对应一个抛光的镜面表面，光源需要在不同的角度照射。从不同角度照射可以减小光影。
Surface shape: a spherical surface reflects light in a different way from a planar object. The more complex the shape of the object surface is, the more complex the light source changes on the surface. Corresponding to a polished mirror surface, the light source needs to irradiate at different angles. Illumination from different angles can reduce the light shadow.
光源均匀性：不均匀的光会造成不均匀的反射。均匀关系到三个方面。第一，对于视野，在摄像头视野范围部分应该是均匀的。简单的说，图像中暗的区域就是缺少反射光，而亮点就是此处反射太强了。不均匀的光会使视野范围内部分区域的光比其他区域多。从而造成物体表面反射不均匀（假设物体表面的对光的反射是相同的）。
Uniformity of light source: uneven light will cause uneven reflection. Uniformity concerns three aspects. First, for the field of vision, it should be uniform in the camera field of view. Simply put, the dark area in the image is the lack of reflected light, and the bright spot is that the reflection is too strong here. Uneven light causes more light in some areas of the field of view than in others. As a result, the surface reflection of the object is uneven (assuming that the reflection of light on the surface of the object is the same).
均匀的光源会补偿物体表面的角度变化，即使物体表面的几何形状不同，光源在各部分的反射也是均匀的。
A uniform light source can compensate for the angle change of the object surface. Even if the geometry of the object surface is different, the reflection of the light source in each part is uniform.
光源技术的应用：光源技术是设计光源的几何及位置以使图像有对比度。光源会使那些感兴趣的并需要机器视觉分析的区域更加突出。通过选择光源技术，应该关心物体是如何被照明及光源是如何反射及散射的。其中包括六种照明技术：通用照明，背光，同轴（共轴），连续漫反射，暗域及结构光。
Application of light source technology: light source technology is to design the geometry and position of light source to make the image have contrast. Light sources highlight areas of interest that require machine vision analysis. By choosing the light source technology, we should pay attention to how the object is illuminated and how the light source reflects and scatters. It includes six lighting technologies: general lighting, backlight, coaxial (coaxial), continuous diffuse reflection, dark field and structured light.
选择光源：，一旦选择了照明技术，接下来就是选择何种光源的问题了。光源应该照明形状的需要，需要有足够的均匀度，且稳定性能要好。在机器视觉设备应用中选择光源应该考虑下面的有关光源的特性：
Choose the light source: once the lighting technology is selected, the next question is what kind of light source to choose. The light source should have enough uniformity and good stability. In the application of machine vision equipment, the following characteristics of light source should be considered when selecting light source:
光谱特征：光源的颜色及测量物体表面的颜色决定了反射到摄像头的光能的大小及波长。白光或某种特殊的光谱在提取其他颜色的特征信息时可能是比较重要的因素。当分析多颜色特征的时候，选择光源的时候，色温是一个比较重要的因素。例如，卤灯更多表现为黄色，相比氙灯显现蓝色。
Spectral characteristics: the color of the light source and the color of the measured object surface determine the size and wavelength of the light reflected to the camera. White light or a special spectrum may be an important factor in extracting the characteristic information of other colors. When analyzing multi color features, color temperature is an important factor when choosing light source. For example, halogen lamps are more yellow than xenon lamps in blue.
效率：有些光源效率很高，相对于能量的消耗，其散发出更加多的光能，例如荧光灯。而钨灯，产生相当多的热量，能量消耗也很大。效率不高的光源产生局部过热，浪费很多。一般，光源的温度越高，其寿命就会缩短，其消耗的能量就相对较高。
Efficiency: some light sources are highly efficient and emit more light energy than energy consumption, such as fluorescent lamps. Tungsten lamp, however, produces a lot of heat and consumes a lot of energy. Low efficiency light source produces local overheating and wastes a lot. Generally, the higher the temperature of the light source, its life will be shortened, and its energy consumption will be relatively high.
寿命特性：光源一般需要持续多小时的使用。一个寿命为1000小时的光源，在两班运转的情况下，只能持续一个星期左右。更换光源灯泡的维护就必须了。LED光源是比较流行的光源，其可以连续工作很长时间，大约可以连续操作100,100小时。对多数光源，随着光源的老化，光源释放的能量会减少，根据光源类型的不同，光能减小可能速度比较慢，也可能很快很明显。光能输出的变化可能也影响着光谱特性。当光源的老化速度影响到图像处理结果的时候就可以注意光源的变化了。
Life characteristics: the light source generally needs to last for more than hours. A light source with a life of 1000 hours can only last for about a week in two shifts. Replacement of light source bulb maintenance is necessary. LED light source is a popular light source, which can work continuously for a long time, about 100, 100 hours of continuous operation. For most light sources, with the aging of the light source, the energy released by the light source will be reduced. According to the type of light source, the light energy reduction may be slow or fast and obvious. The change of light output may also affect the spectral characteristics. When the aging speed of light source affects the result of image processing, we can pay attention to the change of light source.
机器视觉检测设备中光源控制器属于消耗品，使用一段时间之后需要更换， 所以选择性能良好，价格低的光源控制器才能够节约企业生产成本。
The light source controller in machine vision inspection equipment belongs to consumables, which needs to be replaced after a period of use. Therefore, the light source controller with good performance and low price can save the production cost of the enterprise.
机器视觉检测