Klaus Körner, Evangelos Papastathopoulos, Wolfgang Osten
SOME ASPECTS OF CHROMATIC CONFOCAL SPECTRAL INTERFEROMETRY
In this paper, we report on the recent development of a novel low coherence interferometry technique for the purpose of 3D-topography measurements. It combines the well established techniques of spectral-interferometry (SI) and chromatic-confocal microscopy (CCM). It allows for the detection of an object’s depth position, without the necessity of a mechanical axial-scan, and the measurement is performed in a so-called “single-shot” manner. Focusing the white-light with a microscope objective combined with a diffractive optical element leads to an expansion of the axial-range of the sensor beyond the depth-of-focus, limited by the numerical aperture (NA) of the used objective. Confocally filtering the object’s light causes the reduction of the lateral dimension of the area sampled upon the object. Due to the high NA, a high light collection-efficiency is achieved as well. The attained interferometric signals consist of high-contrast wavelets in the optical-frequency domain. The depth position of an investigated point of the object is given by the modulation-period of the wavelets. Therefore, unlike in CCM, position-wavelength referencing is not necessary.