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How It Works

Measurement Principle

CHRocodile sensors utilize several distinct techniques to perform high speed distance and thickness measurements. Chromatic confocal and interferometric methods are used to measure on nearly all surfaces. Various white and infrared light sources are available to extend the ranges of materials.

 

Which measurement is right for your application?

CHRomatic Confocal Principle for Distance Measurements

A white light source is used to illuminate the surface of a part. The light travels via fiber from the CHRocodile control unit to an optical probe which then spreads the focal length over a discrete number of points creating a full spectrum of light as shown in the graph. Based on the wavelength of the reflected light, a very precise distance measurement can be taken up to 66,000 times per second. The optical probe determines the measuring range, or focal depth of the spectrum. Because of the high numerical aperture of the probes and dynamic range of the sensor, it is possible to measure on nearly all materials.

  • 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 systems available
  • CHRocodile , 2 S, SE, 2 SE, E, LR, M4

CHRomatic Confocal Principle for Thickness Measurements

Using a white light source, the sample is illuminated, and the reflected beams correspond to two distance measurements. Based on the optical properties of the material, it is then possible to determine the physical thickness of the sample. This measurement happens at the speed of light, so is not susceptible to variations from mechanical vibration, or ambient conditions. Because it is a white light measurement, the sample must be somewhat transparent to that light. Optical probes with a high acceptance angle, up to 45°, are available for measurement on rough parts or when conditions limit the ability to control the probe to surface angular relationship. By combining the two distance measurements with the thickness value, it is possible to monitor multiple parameters simultaneously. Some of those values can include surface topography, ovality, roughness or shape.

  • Halogen, Xenon and LED sources available
  • Thickness range from 20 µm to 37mm
  • Color and temperature independent
  • Measurement rates up to 66kHz
  • Easy to integrate inline or with other sensors
  • Multi-channel systems available
  • CHRocodile S, 2 S, SE, 2 SE, E, LR, M4

Interferometric Method for Transparent Thin Films

Using the same white light source as the chromatic method, but with a different optical probe, it is possible to also utilize the spectrometer configuration for the measurement of thin films. When light hits the surfaces of a thin film (between 2µm and 250µm) there is an interference pattern that is returned. By taking a Fourier transform of that signal, it is possible to determine multiple thicknesses at rates up to 66kHz. This measurement technique can be applied to wet or dry materials for the measurement of fluid or film thickness, and even air gaps.

  • Halogen, xenon or LED sources available
  • Transparent or translucent materials
  • Thickness range between 2µm and 250µm
  • Independent of color and temperature
  • Speeds up to 66kHz
  • Easy to integrate inline or with other sensors
  • Multi-channel systems available
  • CHRocodile S, 2 S, SE, 2 SE, E, LR, M4

Interferometric Method for Non-Transparent Materials

Using an infrared source and detector, visually opaque materials such as silicon wafers or black plastic bottles can be measured. Based on the reflected light from the two (or more) surfaces, the interference pattern can be used to determine thickness. If there are multiple layers, those individual thicknesses can also be determined, as well as the total thickness. Since the optical probe contains no electronics or moving parts, it is very robust for inline applications, even in wet, acidic or dirty environments.

  • Multiple SLD sources available
  • Thickness range from 4 μm - 15mm
  • Independent of color and temperature
  • Speeds up to 70kHz
  • Special sensors for rough, doped and thin wafers
  • Small spot diameter
  • Easy to integrate inline or with other sensors
  • Multi-channel systems available
  • CHRocodile IT, 2 IT, TW, DW, LR

CHRomatic Confocal Principle for Synchronized Dual-Sided Thickness Measurements

The highly versatile chromatic confocal principle can be used to measure distance on nearly all substrates. By synchronizing two of these measurements, it is possible to measure the thickness of materials that are completely opaque, such as metals or opaque wafers.

  • Halogen, xenon or LED sources available
  • Unlimited thickness range
  • Independent of color and temperature
  • Speeds up to 66kHz
  • Simultaneous distance and thickness information
  • Small spot size
  • Easy to integrate inline or with other sensors
  • Multi-channel systems available
  • CHRocodile S, 2 S, SE, 2 SE, E, LR, M4
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