Patent ID: 6144449
Filing Date: 2000-11-07
Classification: G01B,G01J,G01N,G02B

Abstract:
Low coherence interferometer apparatus for investigation of a sample, in particular for purposes of multi-dimensional imaging, having an interferometer configuration comprising a low coherence light source, a probe head having a light exit opening for irradiating light into the sample, an optical coupler, a reference reflector and a detectorwherein the optical paths between the elements of the interferometer configuration form interferometer arms, namely a light source arm between the light source and the optical coupler, a sample arm between the optical coupler and the sample, a reference arm between the optical coupler and the reference reflector, and a detector arm between the optical coupler and the detector,measuring light is irradiated into the sample via the light source arm and the sample arm and through an interface defining the sample and light reflected from inside the sample is guided to the detector via the sample arm and the detector arm,reference light is-guided from the optical coupler to the reference reflector and therefrom via the reference arm and the detector arm to the detector,the measuring light and the reference light are joined in such a manner that they are both incident on the detector at the same location to produce an interference signal, wherein light reflected at an LCI measuring depth beneath the interface of the sample is selectively detected, andthe optical coupler and the reference arm of the interferometer configuration are commonly integrated in an optical chip, wherein the reference arm has, in addition to the reference reflector, a deflection reflector by means of which the reference light from a first light guide forming a first partial path of the reference arm is reflected into a second light guide forming a second partial path of the reference arm to achieve a sufficient reference light path length in the optical chip, andwherein the deflection reflector is formed at an end surface of the optical chip in such a fashion that the reference light is cross-coupled between the two light guides,positioning means are provided for depth scanning the sample by changing the separation between the probe head and the interface,an optical system is disposed between the probe head and the interface for focusing light irradiated into the sample in a focal plane at a focal depth whose separation from the interface coincides with the LCI measuring depth, andthe optical system comprises focus correction means for matched changing of the focal depth during the depth scan in such a manner that the focal depth and the LCI measuring depth coincide within the depth scanning range of the system.