Spectrograph camera adds color inspection to sorting
Color-image measurement is a simple way to increase the reliability of inspection and sorting procedures in many industrial applications. To perform such image analysis, systems integrators can couple color cameras, frame grabbers, and off-the-shelf image-processing software to perform image analysis. A key problem often associated with this type of processing is the time required to capture and analyze color images. To reduce this time, another analysis technique such as imaging spectroscopy can be applied.
Spectral Imaging (Oulu, Finland) uses this method in building a stationary spectrograph module connected to a matrix detector to form a fixed-imaging spectrometer. Dubbed the ImSpector, the C-mount compatible unit can be used to retrofit standard monochrome CCD cameras to a spectral line-imaging camera.
At systems-integrator Orbis (Helsinki, Finland), the ImSpector has been used as the basis for an on-line crate-sorting system for recycled bottles. Based on the 5200/5400 PC-based vision processor from Cognex (Natick, MA) and monochrome CCD cameras from JAI (Copenhagen, Denmark), the ImSpector-based system was first developed using reflective and transmissive light sources. Because the glass bottle surfaces produced strong reflections, the spectral information was inconsistent and inaccurate and color spectrum information could not be determined. For this reason, Orbis chose transmissive halogen light sources to illuminate the bottle crates.
After images are captured by the Cognex 200/5400, the measurement results are captured as a 3-D hypercube. Based on these results, a two-dimensional map of the color is calculated using the spectral information in each image element. To analyze the color spectrum and data, software written using Cognex-supplied tools provides a menu-driven display of the measurements.
In operation, classification is performed by analyzing the measured spectra and comparing it with trained spectra.
