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Micropart topography is vital to understanding and controlling a component’s use. The technique relies on quantifiable, reproducible, and reliable measurements of a part’s surface topography and dimension. For this process, the Nanovea 3-D noncontact profilometer is ideal. With its chromatic confocal technology, the profilometer can provide reliable data regardless of surface variation, angle, and reflectivity.
In this application, the Nanovea ST400 is used to measure the features of a plastic nozzle plate (figure 1). Several surface parameters can automatically be calculated, including average surface roughness, step height, area, and many.
Measurement principle
The axial chromatism technique uses a white-light source, where light passes through an objective lens with a high degree of chromatic aberration. The refractive index of the objective lens will vary in relation to the wavelength of the light. In effect, each wavelength of the incident white light will refocus at a different distance from the lens—i.e., a different height (figure 2).
When the measured sample is within the range of possible heights, a single monochromatic point will be focalized to form the image. Due to the confocal configuration of the system, only the focused wavelength will pass through the spatial filter with high efficiency, thus causing all other wavelengths to be out of focus. The spectral analysis is done using a diffraction grating. This technique deviates each wavelength at a different position, intercepting a line of CCD, which in turn indicates the position of the maximum intensity and allows direct correspondence to the Z height position.
Results
The Nanovea ST400 3-D profilometer can precisely characterize profile, dimensions, area, and surface roughness. From the 3-D and 2-D images in figures 3–10, the measurement information provided can clearly assist quality control to ensure that components have the intended critical dimensions. This information can be used to investigate a component’s performance and the effect any alteration might have. Special areas of interest could have been further analyzed with an integrated AFM module.
Nanovea 3-D profilometers speeds range from 20 mm/s to 1 m/s for laboratory research or high-speed inspection. they can be can be built with custom size, speeds, and scanning capabilities as well as Class 1 clean room compliance. An indexing conveyor and for inline or online integration is also available.
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