3-D measuring systems for challenging measuring tasks

In addition to measurement using confocal measuring technology (structured illumination), measurements and assessments can also be undertaken according to the working principle of focus variation, depending on the measuring task. For more demanding measuring tasks, the 2-in-1 scan module for confocal and focus variation measurements is available.The module is integrated both in the flexible measurement system Confovis DUO Vario and in the lead and surface measuring system.

Structured Illumination Microscopy (SIM) and Focus variation in one scan head

Confovis has developed and patented the measuring technology for structured illumination based on confocal microscopy. Essentially, this measuring process entails a grid being mapped to the sample and recorded in a phase-delayed manner. The contrast of the mappings has reached its exact maximum if the surface of the sample is in the focus position. In order to establish the topography of the sample, the focus is moved in relation to the surface. Throughout this, optical sections are generated. It is from these that the 3D point cloud is subsequently compiled.

Confocal measuring technology for roughness measurements

  • Resolution down to 3 nm
  • Measuring results that are virtually free of artefacts
  • Flat measurement for high measurement speed and recording the entire relevant structure
  • Extensive 3D data exclusively with realistic measurement points (no compensation for measuring points on the part of the software)
  • Optical scanning with a high degree of accuracy (cf. tactile devices)
  • Only slight coherency and speckle effects (depending on technology)

When using focus variation, the limited depth of focus is utilised to generate optical sections in the area of the sharp image. It is only in the area of the sharp image that the contrast is at its maximum level.

The height information required for 3D imaging is acquired using the variation in focus height. The sections are subsequently compiled to form the 3D point cloud.

Focus variation for form measurements

  • High flank angles can be measured
  • Contour and form measurements are quick and simple
  • Touchless measurement (optical method) can be used throughout the entire process chain

    Two measurement principles via one optical beam path

    Merging measuring date in one global coordinate system

    The confocal structured illumination measuring method can also be used to measure highly reflective surfaces at a high resolution. Steep edges are measured with the focus variation method because better results can be achieved with the illumination provided by the annular light emitter along the cutting edge. This is why the combination of both measurement methods are the solution for capturing important geometric dimensions (wedge angles, cutting edge radius) and high-resolution roughness measurements.

    The confocal structured illumination technique allows for high-resolution measurements for areas in which roughness must be measured.
    Analysis of cuttung edge of an indexable insert with structured illumintion microscopy
    The focus variation method can be used to measure edges with angles of inclination. Data density is here not high enough for roughness measurements.
    Measuring an indexable insert with focus variation
    Cutting edge measurement with focus variation and confocal metrology. The two point clouds were compiled in the global coordinate system. In this way the customer benefits from the advantages of both measurement priciples.

    Measuring the finest roughnesses – with high-precision confocal measuring technology

    When it comes to measuring roughness, confocal measuring technology has an advantage, as it offers optical scanning with a high level of accuracy. In the process, the Confovis measurement systems can achieve a height resolution of 3 nm (in line with VDI 2655) and a lateral resolution of 267nm (according to Rayleigh) in confocal mode, subject to the illumination wavelength.  The following example shows that, with confocal measuring technology (Structured Illumination Microscopy), a reliable measurement is possible and a significantly better resolution can be achieved on the surface of the roughness standard KNT4070/03 from Halle measured here.

    The following example of a usual milling cutter (item:YG-1, E5E50060) shows that no comprehensive tool analysis is possible with one measurement principle alone. For the determination of roughness values in the flute, only the high-resolution confocal measurement technology provides reliable measurement values. The focus variation principle is ideal for measuring forms and contours, but not for roughness measurements.

    Extended tool analysis at an example of a screw tip

    When measuring micro tools such as screw taps or for small milling tools, the user uses the work piece's axis of rotation in connection with the global coordinate system in order to use the best measurement method to measure each of the relevant areas with a high level of precision and without compromises.