Measure surface roughness optically

Surface topography and its structural details like surface roughness is traditionally inspected using tactile stylus-based profilometers (stylus instruments) by guiding a probe tip over a workpiece surface and detecting each vertical deflection by the surface texture. With this method, the information about the surface topography including surface details like roughness is obtained along a 2D profile. It is questionable to which extent profile-based information could describe surface characteristics and provide function-oriented information.

Roughness explained
Webinar June 5th, 11am CEST

How to interpret, manufacture & measure roughness acc. to ISO 21920 & ISO 25178: What is roughness, how to define it? What is relevant in ISO 25178 and what does the new standard ISO 21920 mean? 

Join the webinar on Thursday, 5th of June 2025 and learn about…

  • ... the basic concept of measuring roughness in 2D + 3D
  • ... understand and apply measurement settings the right way
  • ... orientation and what changes with ISO 21920
  • ... where optical areal profiling speeds up while revealing more insights of your workpiece
     

Register now for free

Inspecting surface defects and scratches produced by tactile profilers of nearly the same size 70 nm
Inspecting surface defects and scratches produced by tactile profilers of nearly the same size 70 nm

Optical vs tactile surface roughness and texture measurement

If the surface has randomly distributed features, the result for the roughness parameter is strongly influenced by the measuring position. In many cases, profile-based surface description is insufficient to provide information about functional behavior of the surface. Profile based surface characterization allows only limited information about the cause of poor functionality and so includes limited information for quality control purposes.

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How to quickly measure surface roughness in 3D

This video shows how to measure and characterize surface roughness on mechanical engineered components, e.g. polished surfaces using non-contact optical surface profilers like the TopMap whitelight-interferometers. Choose your magnification, benefit from motorized turret and the automatic Focus Finder for areal 3D roughness measurement and evaluation. Manage and load your individual and predefined measurement recipes for simplified quick starts of 3D roughness evaluation and easily report and share your insights on roughness evaluation e.g. according to ISO 25178 and more.

Surface roughness measurement with cross section on organic material like leather for automotive interior parts
Surface roughness measurement with cross section on organic material like leather for automotive interior parts
Micro roughness with cross section of a wafer surface
Micro roughness with cross section of a wafer surface
Surface roughness with nm resolution of a ground metallic workpiece
Surface roughness with nm resolution of a ground metallic workpiece
Macro view of fine structures (surface roughness) measured with a large field of view up to 34 x 45 mm
Macro view of fine structures (surface roughness) measured with a large field of view up to 34 x 45 mm
Surface roughness measurement with cross section on organic material like leather for automotive interior parts
Surface roughness measurement with cross section on organic material like leather for automotive interior parts
Micro roughness with cross section of a wafer surface
Micro roughness with cross section of a wafer surface
Surface roughness with nm resolution of a ground metallic workpiece
Surface roughness with nm resolution of a ground metallic workpiece
Macro view of fine structures (surface roughness) measured with a large field of view up to 34 x 45 mm
Macro view of fine structures (surface roughness) measured with a large field of view up to 34 x 45 mm

Areal 3D surface roughness measurement data

Three-dimensional, areal topography measurement is not subjected to those limitations. Not only does it provide an image of the surface that makes it easier to understand, but areal measurements also enable a function- and structure-oriented evaluation. Furthermore, 2D profiles can easily be extracted from the areal measurement data which can again be evaluated according to the common rules of profile-based roughness evaluation. In contrast to a tactile roughness measurement, optical 3D roughness measurement is non-contact and non-reactive thus avoiding any damage or influence on sensitive surfaces by the measurement procedure.

Areal surface roughness measurement data provides an easy and complete view of an entire surface. In contrast, a profile measurement contains only a limited section of the entire surface and is less intuitive.

Scheme of areal evaluation of surface roughness acc. to ISO 25178-1,-2,-3
Scheme of areal evaluation of surface roughness acc. to ISO 25178-1,-2,-3
Scheme of line profile evaluation of surface roughness according to ISO 4287, 4288 and ISO 3274
Scheme of line profile evaluation of surface roughness according to ISO 4287, 4288 and ISO 3274

ISO for profile and areal surface evaluation

The measurement chains for the areal or profile-based surface evaluation are described in ISO 25178 or ISO 4287, they differ from each other with some details.

Further applications

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