Patent ID: 8049899

Claim:
A method for measurement of at least one geometric value on a transparent or diffusive object by means of Time Domain Optical Coherence Tomography (TDOCT), comprising the steps of: generating a radiation of short coherence length with a radiation source, splitting the radiation into a measurement arm and into at least two reference arms of a Michelson interferometer, forming reference arm beams are respectively in the at least two reference arms and guiding the reference beams to a rotating path length variation element, producing a change in delay time of the reference arm beams that is a function of a rotation of the path length variation element, bringing the transparent or diffusive object to be measured into the measurement arm, selecting fundamental optical delay times of the reference arms in such a way that an optical delay time difference of the beams in the at least two reference arms corresponds approximately to an optical delay time difference of the geometric value to be measured, and superposing radiation reflected at the transparent or diffusive object and in the reference arms together with interference, and respectively detecting resulting radiation interferences, further comprising the step of: guiding the at least two reference arm beams of the reference arms to one and the same rotating path length variation element at a mutual spatial offset angle, wherein the guiding of the at least two reference arm beams of the reference arms to one and the same rotating path length variation element at a mutual spatial offset angle is done in such a way that the path length variation initially acts in the first reference arm and then in the second reference arm by virtue of the fact that a change in delay time caused by the path length variation element is successively impressed on the fundamental optical delay times in the reference arms as a result of which the radiation interferences defining the geometric value occur with temporal separation from one another.