Machine vision systems for nontrivial inspection tasks in automated production processes usually exhibit a high degree of technical complexity. The best machine vision algorithms are useless, however, if the user is unable to operate the system properly. Poorly designed user interfaces quickly lead to the operator being overwhelmed and might endanger the smooth production operation. This results in higher costs because of erroneous inspections, downtime and service that can easily reach a multiple of the inspection system's original purchase price.

The user interface of a machine vision system must be as transparent as possible and as detailed as necessary when it comes to displaying what the system is doing and what means of interaction are available. What is important, though, is that the high degree of internal complexity is shielded by an exemplary and intuitive guidance of the user.

Basically, the user interface has to address two different user types [1]. One of these types is the (usually) highly qualified applications engineer who - besides selecting the cameras and optical components - develops an evaluation strategy necessary for a robust solution of the inspection task and configures the software accordingly during the commissioning of the vision system.

After the successful deployment of an inspection line, an operator takes on the responsibility for the system. This person monitors the automated inspection process and, if necessary, changes inspection parameters interactively. Usually, the operator is responsible for a number of different assembly and inspection stations on a line. The operator's knowledge concerning the system and the software behind it is therefore normally not on the same level as that of the applications engineer who commissioned the system.

The operators' requirements on process data visualization and the means for interaction can vary greatly. For various reasons, some companies regard a minimal interface as sufficient: start the automated inspection process, stop it, and display the most important global results. Other users value the option to change many process and system parameters interactively in a comfortable way during operation and prefer an elaborate display of a number of intermediate results.

In the following, the possible requirements of the shop floor operation (i.e., the user interface in automatic mode) of machine vision software are viewed in detail.

Requirement: Visualization of Process Data

To care for a system productively, operators wish for the following features:

• § Clear arrangement: Visualization of the results, measurement values, and other process data and system states must be clearly structured and well-arranged.
• § Diverse display options should be available for showing camera images and visualizing iconic intermediate results of the evaluation process itself. This includes both freely definable zoom settings as well as configurable parameters for additional information made up of overlaid geometrical drawings and text. Font size and color should be freely configurable.
• § Disturbances in the system or errors during the inspection run should be located and described unambiguously.
• § By visualizing the history of individual measurement values, it should be possible to recognize in time (by visual inspection) whether a production process might be slowly leaving the tolerance range.

Requirement: Interaction

Even in fully automated inspection systems a certain degree of human interaction is needed or desired. For this the following requirements can be stated:

• § Upon deployment, the details and contents of the user interface can be freely configured for each inspection process.
• § Menu structure and labeling of commands may be adapted to an existing company standard. It is clear what action is caused by each menu item.
• § During operation, the level of detail of (process) visualization can be easily switched interactively if necessary, e.g. to display the detail view of the camera position in question for a work piece classified as faulty.
• § Optionally, the system can be operated using keyboard, touch screen or multi touch screens.

Solution: Control Panel and Process View

Irrespective of the purely functional requirements, it is clear to see that users nowadays attach great importance to an "attractive wrapping", i.e. an appealing and modern design of the user interface.

How can such diverse and, in parts, mutually exclusive requirements on a standard software for machine vision be realized?

Ever since the release of the first software version, it has been the successful approach of NeuroCheck to give the user as much freedom as possible when designing his inspection solution and its user interface. With the new software version 6.0, the possibilities for designing the user interface have once more been greatly augmented.

After analyzing a multitude of customer requirements, we decided to divide the software user interface in the automatic mode into two separate output windows: a so-called "Control Panel" and a "Process View" (which is displayed optionally).

The keyboard-oriented Control Panel is the central operating element and is displayed permanently. Commands are entered using the function keys or a menu. The control panel provides a compact and rapid visualization of the inspection process.

Customers wishing for a detailed visualization can display a second, optional window called Process View.

The arrangement and display of the two cooperating windows can be configured at will. For example, the Control Panel can disappear "behind" the Process View window after a certain amount of time to use the maximum available screen area to visualize the inspection process.

Solution: Graphical Development Tools

For the applications engineer to be able to set all the parameters and settings without any programming knowledge, NeuroCheck offers a specially developed graphical interactive design tool (the so-called "Designer") for the Control Panel and Process View integrated into the software.

The Designers enable you to design a window interface interactively from a number of pre-designed output windows (Controls) using Drag&Drop. Graphically attractive controls are available for the visualization of

• § evaluation results for the current inspection piece,
• § intermediate results in the form of images or lists of values,
• § status, diagnosis and result messages of the system,
• § I/O states,
• § statistical information and measurement data series,
• § target values of the peripheral equipment,
• § ...

Buttons for commands and the selection of menus can be added interactively as well. What command is assigned to one of the 12 function keys on a typical PC keyboard, is up to the user. A high degree of operating security at the line is achieved by links to password-protected user profiles.

In the future, system integrators, machine builders and end users using the NeuroCheck platform can fully realize their corporate design. Hundreds of freely configurable color, font and style settings for the controls allow for the implementation of individual designs of the user interface. It is also possible to adapt to the operating philosophy of a PLC manufacturer already familiar in the company, thus reducing the amount of training for the operating personnel.

All user interface designs and menus are saved as XML files and can be transferred between computers.

Also available are a large number of attractive, pre-defined designs for various screen resolutions and applications that come with the software and can be selected with a mouse click.

Conclusion

Due to the new approach and the software tools available, user interfaces optimized for any kind of machine vision application can be easily designed. According to the customer's needs, a customized and safe-to-use system can be quickly delivered. In the end, efficient production is the aim of every customer, a proven operating concept is a vital contribution.

Reference

[1] Cover Story "Modernes User-Interface garantiert hohe Nutzerfreundlichkeit" by Christian Demant, NeuroCheck GmbH, in INSPECT 2/2008.