CHRomatic Confocal Principle for Thickness Measurements (transparent, up to 37mm)
The chromatic confocal measuring technique uses light from a variety of sources (halogen, LED, xenon etc) coupled into an optical fibre and delivered from the control unit to the optical probe via the fibre. With no moving parts or electronics, the optical probe comprises a series of lenses that exploit a feature of optics – axial chromatic aberration. The optical probe uses the chromatic aberration in such a way that each wavelength is focused at a different distance from the optical probe with blue closest and red furthest away and a colour continuum between.
The distance from the blue focus to the red focus is the measuring range of the optical probe. A surface within the measuring range will cause light of a wavelength determined by its distance from the optical probe to be reflected back into the optical probe, transmitted back to the control unit and analysed with a spectrometer. The wavelength measured by the spectrometer is then translated into a z-axis distance – the distance from the optical probe. The term chromatic confocal is used as judicious use of spatial filters mean that only reflections of light originating along the optical axis will be focussed onto the input aperture of the spectrometer. Reflections from regions other than the optical axis will be focussed either before or after the input aperture and will therefore not be analysed.
In the case of glass or transparent materials within the measuring range, light of different wavelengths (colour) will be reflected from both the first and second surfaces of the container, resulting in two signals being observed by the spectrometer. The wavelength difference (distance) between these two signals corresponds to the thickness of the material. The overall measuring range is used to name the optical probes; for example, the 12mm probe has a separation between the blue and red focus of 12mm in air, which corresponds to a maximum thickness measurement of approximately 18mm in glass (air distance x refractive index).
With reference to the analysis of the return signal, Precitec Optronik has developed a range of highly sensitive control units resulting in the accurate analysis of the wavelength signals. The width of the signals greatly affects the resolution with which a thickness measurement can be determined but high quality optics and a precisely configured sensor combine to achieve sub-micron resolution even at high speeds.
Halogen, Xenon and LED sources available
Thickness range from 20µm to 37mm
Color and temperature independent
Measurement rates up to 66kHz
Easy to integrate inline or with other sensors
Multi-channel systems 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.