Near Infrared Multi Spectral Occlusion Limits in Dense Raw Cotton Tuft Streams
Dense cotton tufts block near infrared light past three millimeters, hiding synthetic contaminants beneath opaque cellulose surface layers during optical sorting.
InGaAs Camera Array
Sensor Function
Short-wave infrared detector using indium gallium arsenide to identify materials that are invisible to standard colour cameras. An ingaas camera array detects transparent or white plastics like polypropylene and polyethylene within a stream of white cotton fibres. The technology relies on the specific light absorption patterns of synthetic polymers compared to natural cellulose.
Detection Capability
Light in the 900 to 1700 nanometre range allows the system to see through the visible spectrum. Because an ingaas camera array operates outside the human eye’s range, it finds contaminants that match the colour of the lint perfectly. This capability is necessary for high-end spinning mills where any remaining plastic would cause yarn breaks or dyeing defects.
The sensors detect the unique chemical signature of the polymer, making the material appear as a dark object against the bright background of the natural fibre.
System Integration
These sensors are mounted across the width of the ducting to provide full coverage of the moving material. Information from an ingaas camera array travels to a processor that coordinates the firing of air valves. Precise alignment between the sensor and the nozzles is required to capture small fragments at high transport speeds.
Performance Boundary
Moisture content in the fibre can affect the accuracy of the reading by altering the light absorption. High humidity levels in the blowroom require the system to recalibrate its sensitivity.