Machine vision systems are usually divided into two independent subsystems:
Image Capture;
Image processing and analysis.
Each of them, in its turn, includes a different set of components depending on the requirements of a particular application task. Image processing and analysis subsystem consists of hardware and software components.
Hardware – calculator, built on the basis of a PC or specialized equipment, designed for image processing.
Software – special software containing mathematical algorithms of data processing. These may be classical mathematical algorithms or neural networks. The task of the developer is to choose the types of algorithms and their sequence. However, in order to start processing images, they must first be acquired.
The image capture subsystem consists of one or more cameras, optics, illumination and – most often – a sensor or encoder. Machine vision cameras usually have multiple digital lines for synchronization with sensors, controllers, illuminators, etc.
There are also so-called “smart cameras” that contain all the main components (camera, optics, illumination, calculator) in one housing.
The image – an array of pixel values, or a cloud of points, in the case of multidimensional representations – can be obtained by different equipment: digital camera, thermal imaging camera, laser 3D scanner and others. And the choice may not be limited to one type of device. The way of the solution of the set task, correct selection of components and choice of platform for processing is defined by the developer of the system.
A digital camera can be network (IP), matrix or line camera, color, multispectral, hyperspectral or monochrome, with different resolution and pixel size. Sometimes you have to sacrifice resolution in favor of pixel size, and sometimes a small pixel may be preferable. Depending on the type of camera and the subject under study, the optical subsystem and lighting are selected. It is equally useless to use a good, expensive camera with a mediocre, cheap lens and vice versa. In the article “Choosing a Camera” you can learn more about the main aspects.
In the picture on the right you can see that the resolution available is not enough to read the markings on the surface of the box. So, one of the two components (camera/optics) is selected incorrectly.
Lenses can be of different focal lengths: wide-angle, macro; variable focal length, telecentric, special for “peeking” into the tube (endoscopic) or 360° coverage. Also, when choosing a lens, pay attention to the mount: C, CS, S mount and others.
The illumination can be constant or pulsed. Impulse illumination is often used to take pictures of fast-moving objects in order to be able to work at short shutter speeds and get a clear image regardless of the speed of the object. The type of illumination can be linear, circular, background, structured or it can be a laser. The wavelength of light can be red, green, blue, or from the infrared and ultraviolet range. In addition, various combinations of all of the above options are possible. However, it is worth noting that selecting lighting and its location relative to the object is often a more difficult task than choosing a camera. We will tell you about all the subtleties of light selection in the article “Can’t do without light”.
Choosing the wrong technical solution for getting the image is very difficult, and in some cases impossible, to compensate by the most sophisticated mathematical algorithms.
When selecting all the components of a machine vision system on your own, pay attention to two important points:
Careful matching of all system components is necessary, because the weakest link in a complex technological and functional chain limits overall performance. Using the wrong component (such as a “cheap” lens on a high-quality camera) can compromise the functionality of the entire system.
The right camera, optics and illumination are only a small part. Computing power and specialized software packages are important aspects of a machine vision system, without which proper functionality is impossible. It is essential that the computational capabilities provide the required system performance. A mistake in the choice of computational power will affect the speed of image processing. In addition, the higher the resolution of the camera, the more processing power of the system should be. Therefore it is not necessary to chase megapixels, because most often even a 2 megapixel camera can perform the task.
For selection of machine vision system components we recommend to contact our specialists. To assist you with the selection of equipment, please fill out the questionnaire or click on the “Select Components” button.