Recording surface profile of object, for in-line quality control of machine-mfd. part

摘要

The method uses a desensitised interferometer (50) which is illuminated by a light source (30) with a defined wave length to generate a desensitised interference pattern. The interferometer has a defined equivalent wavelength greater than that of the light source. Measurement data for at least one pixel in the field of view of the interferometer is generated by repositioning the object (20) relative to the interferometer. This produces a changed signal which is combined with the equivalent wavelength. The combination is modulated by a signal envelope which restricts each interference effect to a region within an equivalent clearance length. The signal corresponds to the interference pattern and the envelope to a diffraction line contrast for the pattern. By analysis of the measurement data a surface height is determined which corresponds to each of the image pixels.