Abstract: In general, in one aspect, the invention features a method that includes transforming interferometry data acquired for a test sample using a low coherence imaging interferometry system to a frequency domain and, at a plurality of frequencies in the frequency domain, reducing contributions to the transformed interferometry data due to imperfections in the imaging interferometry system thereby producing compensated interferometry data. The errors are reduced based on variations between interferometry data acquired using the low coherence imaging interferometry system for a calibration sample and model interferometry data corresponding to data acquired for the calibration sample using a model interferometry system.

Abstract: In general, in one aspect, the invention features an apparatus that includes an interferometer having a main cavity and an auxiliary reference surface, the main cavity including a partially reflective surface defining a primary reference surface and a test surface. The interferometer is configured to direct a primary portion of input electromagnetic radiation to the main cavity and an auxiliary portion of the input electromagnetic radiation to reflect from the auxiliary reference surface, wherein a first portion of the primary portion in the main cavity reflects from the primary reference surface and a second portion of the primary portion in the main cavity passes through the primary reference surface and reflects from the test surface. The interferometer is further configured to direct the electromagnetic radiation reflected from the test surface, the primary reference surface, and the auxiliary reference surface to a multi-element detector to interfere with one another to form an interference pattern.

Abstract: In general, in a first aspect, the invention features apparatus that include an interferometer having a main cavity and an auxiliary reference surface, the main cavity including a primary reference surface and a test surface. The interferometer is configured to direct a primary portion of input electromagnetic radiation to the main cavity and an auxiliary portion of the input electromagnetic radiation to reflect from the auxiliary reference surface, wherein a first portion of the primary portion in the main cavity reflects from the primary reference surface and a second portion of the primary portion in the main cavity reflects from the test surface. The interferometer is further configured to direct the electromagnetic radiation reflected from the test surface, the primary reference surface, and the auxiliary reference to a multi-element detector to interfere with one another to form an interference pattern.