Interferometric Method for Transparent Thin Films (transparent, 2µm to 250µm)
If you have ever seen light reflected through a thin layer of petrol on a puddle of water or bubbles in the bath then you have almost certainly been amazed by the spectrum of colours exhibited. The phenomenon is caused by interference of the white light reflecting from the upper and lower surfaces of the thin layer of petrol or the inner and outer surfaces of the bubbles.
In the interferometric optical probes from Precitec Optronik white light from a variety of sources (halogen, LED, xenon etc) is coupled into an optical fibre in the controller unit and transmitted to the optical probe. The emitted light undergoes reflection from the layers and is collected back into the optical probe, passes back up the fibre where it is collected into an analysis unit. The modulated signal is subjected to a fast Fourier transform to deliver a thickness measurement.
While thickness measurement of materials (glass, plastic etc) can be performed using the chromatic confocal method the interferometric method provides better accuracy and is better at measuring thickness with a varying measuring distance, for example on a production line where the working distance of the sample might change by several mm during measurement. The chromatic confocal method of thickness measurement can operate over a range of 30µm to 35mm but really requires a fixed working distance to ensure maximum accuracy.
Due to the physics behind the mode of operation, the interferometric thickness method is only applicable for layers of thickness between approximately 2µm and 250µm; below this lower limit there are not enough maxima and minima to perform an accurate FFT, above the upper limit there are too many.
The interferometric method of thickness measurement is especially applicable to such applications as the measurement of thin plastic films, layers of varnish on metals or soft gel coatings etc.
- Halogen, xenon or LED sources
- Up to 66kHz measurement rate
- Measurements from a few nanometers to 25 millimeters in range
- Angle to measurement surface: up to 45o
- High lateral resolution: less than 1μm
- Types of materials: glass, metal, leather, paper, liquid
- Integration ready for topography & metrology
- Multi-channel system available
The image on the right shows the CHRocodile C on a custom stand, measuring the thickness of a glass wafer.
The ultra compact CHRocodile C sensor with its robust and integrated design offers high precision distance and thickness measurements.
CHRocodile C is specially suited for industrial inline use and easily integrable into any kind of inspection machine.
The extraordinary high dynamic range and the outstanding signal-to-noise ratio of the CHRocodile sensors ensure the best measuring results on any kind of surfaces.
Thanks to its compact dimensions and excellent performance/price ratio, CHRocodile C is the ideal alternative to classical laser triangulation sensors.
The sensors below require Optical Probes:
The CHRocodile SE and S optical sensors are the fast all-rounder with an excellent cost/performance ratio. They are perfectly suitable for demanding measuring tasks, like non-contact measurement of topography and layer gauge. The senor implements two different measuring procedures and thus provides gauge measurements of 2 µm to 37 mm. The exceptional high dynamic and the excellent signal/noise ratio of the CHRocodile sensors provide the best measuring result on various strongly reflecting and strongly steep surfaces.
Next generation models of CHRocodile sensors offering up to 66.000 measurements/second. With a white light LED they are ideal for non-contact surface profiling and thickness measurements.
The extraordinarily high dynamics range and excellent signal to noise ratio of the CHRocodile sensors ensure the best results on surfaces with differing reflectivity and from different angles. Sensors can be simply switched from chromatic-confocal mode to interferometric mode, and are universally applicable in quality assurance and production.
The proven optical sensor CHRocodile E is perfectly suitable for non-contact measurement of topography and layer thickness. The senor implements two different measuring procedures and thus provides gauge measurements of 1 µm to 37 mm. The exceptional high dynamic and the excellent signal/noise ratio of the CHRocodile sensors provide the best measuring result on various strongly reflecting and strongly steep surfaces.
The proven optical sensor CHRocodile LR is perfectly suitable for non-contact measurement of topography and layer thickness. The sensor implements two different measuring procedures and thus makes gauge measurements of 30 µm to 1200 µm possible and distance measurements with a lateral resolution in the sub-micro meter range. The strong light source and exceptional high dynamic and the excellent signal/noise ratio provide the best measuring result on various strongly reflecting and very slanted surfaces.
The proven optical sensor CHRocodile M4 is perfectly suitable for non-contact measurement of topography and layer thickness. It is designed specifically for industrial inline application with up to 4 channels in a 19″ insertion. Two different types of modules are available: High Sensitivity and High Resolution. Das CHRocodile M4 High Resolution implements two different measuring procedures and thus makes gauge measurements of 1µm to 37 mm possible. The CHRocodile M4 High Sensitivity captures the layer gauge of darker materials (e.g. brown container glass) at the full measuring rate.
For your demonstration please contact Armstrong Optical (44 (0)1604 654220) or CLICK HERE