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SPA – Surface Profile Analyzer

The Surface Profile Analyzer SPA 25 can measure surface topography and roughness parameters with exceptional speed and resolution. In the following you will learn about the possibilities that surface profile analysis offers and how the white-light interferometry enables the SPA 25 to achieve a height resolution of down to 0.1 nm.

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Surface profile analysis

Utilising the industry leading MountainsMap® Imaging Topography software provides a comprehensive set of tools for the analysis of the studied surface. The SPA 25 can be used to create 3D maps of large surface areas (up to 300 mm x 300 mm with automated sample table) and e.g. detect defects caused by material processing and treatment or the surface roughness can be analysed according to various industry standards like ISO 25178, ISO 4287, ISO 13565, ISO 16610, etc.

Using the SPA 25 in combination with an optical contact angle measuring and contour analysis system of the OCA series provides further insight into surface properties by e.g. determining the surface corrected contact angle according to the Wenzel theory.

With its high resolution even the small particle deposits created by dosing individual picolitre sized ink droplets with a DataPhysics Instruments picolitre dosing system PDDS can be analysed.

Surface profile of deposited and dried silver ink picolitre droplets

Surface profile of deposited and dried silver ink picolitre droplets.

White-light interferometry

The Surface Profile Analyzer SPA 25 utilises the white-light interferometry for studying the surface topography. White-light interferometry is an optical measuring technique and due to the relatively large distance between measuring instrument and test surface there is no danger of damaging the sample compared to profiling systems that rely on some sort of stylus.

The SPA 25 uses Mirau objectives which contain a beam splitter and reference mirror within the light pathway. The light reflected from the sample surface and the light reflected within the objective itself create an interference image. The interference pattern has its highest contrast when the sample is exactly in the focus plane of the objective and becomes less intense closer/further away from the focus plane.

When the distance between sample and Mirau objective is changed the interference pattern changes correspondingly. The SPA 25 changes the distance between sample surface and the objective with a piezoelectric precision scan drive. By sampling various distances and analysing the changing interference pattern the height of every point in the frame can be calculated.

The increased amount of available parallel computation power provided by modern graphics cards enables highly sophisticated evaluation algorithms. Hence the SPA 25 can process up to 500 GByte of image data with each scan and provide a height resolution of down to 0.1 nm using the extended phase shift interferometry (EPSI) scan mode.

A significant advantage of white-light interferometry compared to other optical height resolving methods like focus variation or confocal microscopy is that the height (Z-direction) resolution is independent of the magnification factor of the used objective. The magnification factor only changes the lateral (X-Y-direction) resolution.

Height resolution / system noise for different magnification factors and measurement techniques

Height resolution / system noise for different magnification factors and measurement techniques

SPA 25

The SPA 25 utilises the white-light interferometry technique that features a height resolution of down to 0.1 nm even with small magnification factors. It can be used with either a manual or a motorised automatic sample table. Using a motorised sample table enables software controlled image stitching which combines multiple individual scans hence, larger areas of up to 300 mm x 300 mm can be visualised and analysed.

Main features

  • white-light interferometry measurement technique
  • precision piezoelectric scan drive with gauge control
  • up to 400 μm scan range (z-direction) and 11.3 μm/s scan speed at full resolution
  • USB 3 high speed camera with 1920 x 1200 pixel max. resolution and up to 3000 frames/s with restricted ROI
  • two scan modes:
    • VSI (vertical scanning interferometry) with 1 nm height resolution
    • EPSI (extended phase shift interferometry) with 0.1 nm height resolution
  • Mirau interferometer microscope objectives with different magnification factors
  • manual or automatic sample table
  • control unit with integrated powerful PC:
    • Intel® Core™ I5
    • 16 GB RAM
    • 500 GB SSD
    • NVIDIA® graphics card
    • Microsoft® Windows™ 10 Pro

Software

The SPA 25 is controlled via the SPS 25 Surface Profile Software. It uses the industry leading MountainsMap® Imaging Topography evaluation software to analyse the surface profile. Learn more about the Software for the SPA 25.

Accessories

The SPA 25 can be combined with different automatic or manual sample table as well as various Mirau microscope objectives. Learn more about the available accessories.

SPA brochurefile_download

Measuring head with motorised sample table, joystick and control unit of the SPA 25