Performance Data of Cameras and Sensors Can Be Closely

There appears to be obvious demand! “Especially during conversations at the VISION trade fair in Stuttgart, I found out that camera data in machine vision technology are often unclear”, said Dr. Gerhard Holst, Head of Research & Development at PCO AG. “At Awaiba we often have customers who ask about user-specific sensor design. They compare their requirements with published performance data of standard sensors. Data such as sensitivity, SNR (signalto-noise ratio), spatial noise and temporal noise are often confused or incorrectly interpreted since every manufacturer has his own definitions“, said Martin Wäny, Chairman of the Standardisation Working Group 1288 for Camera and Image Sensor Data.

In order to provide users with greater transparency in future as the number of different sensors increase and camera functions in machine vision (MV) become increasingly more complex, the European Machine Vision Association (EMVA) established the Standardisation Initiative 1288 which unites leading manufacturers, distributors and end users. Attempts at standardisation will be made all over the world. “This is also demonstrated by the fact that manufacturers involved in the development of the standard are represented for the most part by their products throughout the world”, said Patrick Schwarzkopf, Head of the Machine Vision Group in the German Engineering Federation (VDMA).

Products certified according to EMVA Standard 1288 will be presented for the first time during Vision 2005, International Trade Fair for Machine Vision and Identification Technologies, which will be held in Stuttgart from 8th to 10th November 2005. First-class experts will answer questions during this event. “Sensitivity is one of the most important characteristics when choosing a camera“, said Dr. Friedrich Dierks, Head of Software Development Components at Basler AG, “in order to determine whether it is suitable for a particular application.

To date, it has only been possible to obtain a clear comparison by testing cameras from several manufacturers.

This was very expensive and time-consuming for our customers. Thanks to the standard, it is now possible to carry out a quick and simple comparison by reading the datasheets contained in EMVA Standard 1288“. Dr. Dierks uses an example to demonstrate how this functions best: “First of all, it is necessary to determine how much light is available. The next step is to find out the required image quality. This is defined by the SNR and can be roughly estimated between ‘sufficient: SNR 10:1’ and ‘excellent: SNR 40:1’. If both are known, it is possible to determine by looking at a diagram defined in the standard which camera is suitable and which isn’t. The diagram shows the SNR in the form of the number of photons.”

Standard 1288 will be introduced on a modular basis, grow gradually and will therefore always describe new aspects of the camera. “The first module will definitely be published at the end of the third quarter of this year and the next one will follow around the second quarter of 2006”, said Wäny. According to Dr. Holst, a modular method makes sense because otherwise discussions would go on for another ten years. That would be too late. The standard can therefore also be taken into account more easily in quality control. “In view of the considerable expense involved in the preparation of a module”, added Dr. Dierks, “gradual implementation was the best way to quickly achieve results which would then no longer change when new modules were added. This would protect the investments by manufacturers in measuring instruments”.

The expenditure of a manufacturer in recording products according to standard 1288 depends a great deal on how his current quality controls are carried out. “The transition to the standard is not so problematic for our company because we already carry out very complex quality controls”, said the PCO expert. “I estimate“, added Dr. Holst, “that 75 % of our measurements are already well-suited. Our cameras are primarily used for scientific measurements, for example in flow measuring techniques, speed measurements in liquids or wind tunnels. During Vision 2005 we will present some products covered by Standard 1288“. Basler AG will also present a large number of cameras based on EMVA standard 1288 at Vision 2005. “We have continuously invested in series tests”, said Dr. Dierks, “which means that the investments were primarily limited to the implementation of additional software in the CTT (Camera Test Tool). Companies intending to carry out quality assurance to a similar extent to Basler AG must invest both time and money”.