A measurement apparatus includes: a projection optical system; an illumination unit; an imaging unit configured to image a target onto which pattern light has been projected by the projection optical system, thereby capturing a first image of the target by the pattern light reflected by the target; and a processing unit configured to obtain information on the shape of the target. The illumination unit includes light emitters arranged around an optical axis of the projection optical system symmetrically with respect to the optical axis. The processing unit corrects the first image by using a second image of the target and obtains the shape information on the basis of the corrected image, wherein the imaging unit images the target object illuminated by the light emitters to capture the second image by light emitted from the light emitters and reflected by the target object.

An optical coherence tomography microscopy apparatus (1) is presented for detecting a three-dimensional image of an optically translucent or reflective sample object (OS), the apparatus comprising an interferometric optical setup including a photo sensor unit (20). A sense signal Si from the photo sensor unit (20) is detected using a detection reference signal. The detection reference signal is derived from a signal indicative for a relative displacement of the sample object (OS) with respect to a reference object.

A Micro-Electro-Mechanical System (MEMS) interferometer provides for self-calibration of mirror positioning of a moveable mirror. The moveable mirror is coupled to a MEMS actuator having a variable capacitance. The MEMS interferometer includes a capacitive sensing circuit for determining the capacitance of the MEMS actuator at two or more known positions of the moveable mirror and a calibration module for using the actuator capacitances at the known positions to compensate for any drift in the capacitive sensing circuit.

A Micro-Electro-Mechanical System (MEMS) apparatus provides for self-calibration of mirror positioning of a moveable mirror of an interferometer. At least one mirror in the MEMS apparatus includes a non-planar surface. The moveable mirror is coupled to a MEMS actuator having a variable capacitance. The MEMS apparatus includes a capacitive sensing circuit for determining the capacitance of the MEMS actuator at multiple reference positions of the moveable mirror corresponding to a center burst and one or more secondary bursts of an interferogram produced by the interferometer based on the non-planar surface. A calibration module uses the actuator capacitances at the reference positions to compensate for any drift in the capacitive sensing circuit.