Flexibility for machine vision systems
The short life cycle of products and order-based production set new challenges for production technology. The use of machine vision further faces challenges also in new applications with varying environmental factors, e.g. lighting and temperature, such as in moving machinery and vehicles. The long configuration time of product changes is currently the limiting factor of automation technology. Traditionally, machine vision systems are specially planned to work only for a certain product or for a certain field of view. When looking for the most flexible machine vision application, the ideal solution for flexibility is described in the following.
1. Programmable lighting
It is imperative that lighting can be easily modified to suit a new product or point of imaging. Use of new type of LED light sources, among others, allows flexibility of lighting as various lighting profiles and patterns can be controlled by means light control units or a PC. It is also sometimes necessary to be able to control colours. New light sources include integral memory capacity, into which the desired product-specific lighting pattern, such as the Wisematic CCLS- light source, can be saved. In case there is sufficient cycle time and computing power, the light source can also be controlled with direct feedback from the machine vision system. In this case the light is automatically controlled into a state in which the features to be analysed are the most prominent ones.
2. Software-controlled filter unit
For example, a controllable filter carousel can be installed in front of the lens of the camera for changing a product-specific filtering (for example a colour filter, a polariser or a band pass filter).
3. Flexible machine vision camera and electronically controlled optics
Here we use an OF10 camera unit productized by OptoFidelity as an example. The features of the camera include motorised zoom lens integral with a colour/greyscale camera with automatic focus, aperture adjustment, exposure time adjustment and gain control among others. If the measurement technology makes it preferable not to have the camera control all values automatically, correct values can be saved in advance for various products and then loaded into the camera via software in connection with a product change. As all values of the camera can be controlled via software, the product-specific adjustment of the camera can be achieved remotely by a professionally competent person.
4. Electronically controlled positioning of the camera and light
Various alternatives are available for the movement control. The X-, Y - and Z-movements, for example, can be optimised by means of linear guides. In case angular adjustment is needed as well, a pan and tilt head can be attached to the camera.
5. Control and interface bus for the camera and the peripherals
Lack of standardisation in machine vision components has hindered the connectivity of components. Currently, an Ethernet bus (GigE) allows a reliable data transfer even for long distance data transfers. OptoFidelity Oy has delivered, among others, interface solutions in which GigE bus can transmit pictures and control other actuators. Thus, increasing the number of cameras, if necessary, is as easy as possible. In addition to allowing easily adding new cameras the GigE also allows a new kind of Vision Server architecture. Other implemented commercial bus solutions are IEEE 1394 Firewire and USB bus.
6. Programming environment
It is an advantage for programming, if the image processing, camera programming, movement control and the control of other actuators can be carried out by in the same programming environment. In our experience, e.g. National Instruments LabVIEW offers a wide range of programming tools for fast development of applications.
OptoFidelity is a company specialising in testing solutions for product development of the electronic industry. OptoFidelity also provides machine vision modules and engineering services for system integrators and OEM customers.