Chemical Colour Imaging: the evolution of machine vision
Machine vision technology has gone through a constant development process over the past decades. Starting with monochrome cameras, which use differences in contrast for defect detection, imaging technology has advanced to increasingly precise colour cameras revealing even the smallest colour deviation. Chemical Colour Imaging (CCI) takes this technological evolution to the next level. The software technology developed by the Graz-based company Perception Park makes complex hyperspectral data on a molecular level usable for machine vision. The „Perception“ field of research includes a clearly understandable analysis and visualisation of relevant information in large data volumes.
Advanced 3D colour imaging systems generate high-precision spatial images of the scanned objects. However, the systems are designed for surface analysis and reach their limits when the test objects show a different molecular structure or are subject to transformation processes. The first case applies to the separation of plastics, whereas in the food industry the ripeness of fruit and possible mould play an important role.
Unique chemical fingerprint
Objects leave a unique „fingerprint“ with their highly complex spectral information through chemical and molecular properties which can be identified only by deploying hyperspectral cameras.
However, hyperspectral camera technology has not yet been widely applied in the industrial environment. “Until now, the use of hyperspectral systems has only been accessible to experts in spectroscopy and chemometry“, explains Markus Burgstaller, CEO at Perception Park. “Many trials fail because most of the colour processing systems of existing machines are not able to integrate hyperspectral cameras practically. As a result, each application has to be redeveloped from scratch and implemented based on hyperspectral camera technology, which is often not feasible in an economical way.”
CCI as holistic approach
Chemical Colour Imaging (CCI) has closed this gap and allows - for the first time – the analysis of chemical properties by means of real-time image processing. The advantages of spectroscopy and the benefits of machine vision have been merged in a holistic approach.
"The core element of CCI is the extraction of two-dimensional feature data - the chemical colour images - from complex, multi-dimensional hyperspectral data. Hyperspectral cube data are described by colour images holding spatial information together with spectroscopic information coded by colour. By adapting a hyperspectral camera with a real-time processing core, Chemical Colour Imaging turns the camera system into an easy-to-understand and intuitive configurable “chemical colour camera”. The chemical colours reflect the molecular properties of the scanned objects“ , explains Markus Burgstaller.
The advantages of spectroscopy regarding selectivity are extended by the spatial information supplied by imaging systems. A particular benefit is the fact that there is no classification but a targeted reduction of spectroscopic information in order to facilitate the interpretation of chemical properties.
Perception Park has developed the Perception System, a generic, configurable data processing platform providing encapsulated scientific methods of hyperspectral analysis intuitively accessible to everyone. The abstraction of highly complex spectral information through chemical features makes handling of the cameras accessible and interpretable for the user, even without profound expert knowledge of spectroscopy and chemometry.
„Due to the generic approach new applications do not need to be programmed from scratch. In fact, users are able to develop and configure own applications independently, without expert know-how in chemometry, spectroscopy or hyperspectral data processing”, explains Mr Burgstaller. Once configured, the Perception system runs in „stand-alone mode“ just like an adapter between camera and machine. The user can select a familiar machine vision format based on chemical colour imaging for interfacing.
Wide range of possible applications
Chemical Colour Imaging is typically applied to industrial purposes by solution providers such as mechanical engineers. For them, CCI means greater independence from external technology suppliers and, thus, greater independence regarding bespoke applications. Since a Perception system allows easy configuration of applications without new programming effort for each adjustment, existing applications can be modified easily and quickly.
This has particular advantages for the food processing industry, where the sorted products quickly change, (for example due to maturation) thanks to shorter development and modification cycles. Figure 1 shows a typical application in the food processing industry.
In addition to the food industry Chemical Colour Imaging systems are especially suited for recycling, mining and the pharmaceutical industry. A specific application in the recycling industry is the automated separation of plastics (see figure 3). For example, CCI is used to detect and separate plastic parts made from polyethylene (PE) and polypropylene (PP) according to their chemical combination.
Chemical colour information as well as monochrome information can be processed by the user’s vision system. Thus, a hyperspectral camera may be integrated into a sorting machine which has already been using colour sorting. Moreover, CCI allows the user to combine molecular information and colour information of the scanned objects in order to fine-tune the sorting quality.
Even in the medical field there are initial tests using CCI technology: „We have already managed to capture a human hand and visualise the blood vessels inside using CCI and a hyperspectral system“, explains Markus Burgstaller (see figure 4).
All-in-one system available
Thanks to the cooperation of Perception Park and STEMMER IMAGING hyperspectral technology is now available as a modular system for industrial users without expert know-how in the field of spectroscopy and chemometry. Perception Park has developed a generic, intuitive, configurable data processing platform providing encapsulated scientific methods of hyperspectral analysis. The Perception Studio software platform is the basis of the hyperspectral systems available from STEMMER IMAGING and supplemented by hardware components such as the appropriate industrial CMOS and InGaAs cameras, illumination, lenses and frame grabbers as well as vision computers to create all-in-one CCI systems.
The innovative hyperspectral solution works in real-time while processing more than 200 million spectral points per second. Cameras from various manufacturers can be connected using the standard CameraLink and GigE interfaces. STEMMER IMAGING has been distributing the CCI systems since January 2016.