Patented by SYNCRO, OPTYSCAN represents the latest film measuring technology on the market. Main advantages versus different technology on the market nowadays:
> NIR technology, based on an interferometer concept avoids any certification.
> Optical has a much smaller measuring spot (1 mm) due to which the accuracy and precision of the measurement is improved and increased versus either IR, X-ray or Beta-ray which have measuring spots between 5 and 20 mm.
> Optical is backscatter so it doesn’t need any receiver.
> Optical doesn’t care if the film is moving up and down or if there is any vibration, the quality of the measurement is kept the same.
> Thanks to the unique installation on the chill roll OPTYSCAN will guarantee a faster response in auto profile control due to its proximity to the die especially during start-up where each meter of film extruded is important.
> Infrared and X-ray need to either change their filter or parameters whenever you change material and are also very sensitive to the environmental conditions, while an optical system doesn’t need any calibration once set up. > Accuracy is down to 0.1 micron.
> Other systems installed after the chill roll, even on a robust frame, will lose accuracy due to the vibration caused by a high line speed while OPTYSCAN thanks to the installation on the casting unit won’t suffered any vibration that will affect the measurement.
> Due to installing directly on to the casting unit, the length of the line can be reduced by about 2-3 meters saving space, frame structure and rolls.
The optical sensor is based on low coherence interferometry. The material is illuminated with a broadband nearinfrared light source; part of this light is reflected at the air/material interface (measurement r1). Part of the light that travels through the material is then reflected due to the material/air boundary (measurement r2) and it goes back toward the receiver. The optical head collects both r1 and r2 and makes it possible to obtain the difference between the two measurements. The resulting optical signal intensity has an oscillatory component with a frequency f, called optical thickness, given by f = 2nd, where d is the thickness and n is the refractive index of the material.
Measuring f and knowing n, the thickness d can be obtained with high accuracy. The refractive index is a characteristic that is wellknown for a large number of plastic materials. The sensor can be used to measure total thickness of materials for which the component r2 has sufficient optical intensity to provide the interference signal, like transparent or semi-transparent materials; coloured material can also be measured under certain conditions. It is also possible to measure materials on metal substrates because the metal base has a reflective behaviour