A Micro-Electro-Mechanical System (MEMS) apparatus, comprising; a MEMS interferometer configured to produce an interferogram, the MEMS interferometer comprising: at least one mirror optically coupled to receive and reflect light, a first mirror of the at least one mirror having a non-planar surface, the non-planar surface comprising a main surface (1602, 1804, 2002) and at least one additional surface offset from the main surface (1602, 1804, 2002), wherein the main surface (1602, 1804, 2002) is centered on the first mirror at an optical axis of the interferometer and is configured to produce a center burst (1702, 1904, 2102) of the interferogram, and wherein the at least one additional surface is located near an edge of the first mirror and is configured to produce the secondary burst (1706, 1902, 2104) of the interferogram; and a MEMS actuator coupled to a moveable mirror of the at least one mirror to produce a displacement thereof, the MEMS actuator having a variable capacitance; a memory maintaining a table mapping stored capacitances of the MEMS actuator to respective stored positions of the moveable mirror; a capacitive sensing circuit coupled to the MEMS actuator, the capacitive sensing circuit being configured to: sense a first measured capacitance of the MEMS actuator at a first reference position of the moveable mirror corresponding to a center burst of the interferogram produced as a result of movement of the moveable mirror; and sense a second measured capacitance of the MEMS actuator at a second reference position of the moveable mirror corresponding to a secondary burst of the interferogram produced as a result of the moveable mirror and the non-planar surface; and a calibration module configured to use the first measured capacitance at the first reference position and the second measured capacitance at the second reference position to determine a correction amount to be applied to the stored capacitances in the table. at least one mirror optically coupled to receive and reflect light, a first mirror of the at least one mirror having a non-planar surface, the non-planar surface comprising a main surface (1602, 1804, 2002) and at least one additional surface offset from the main surface (1602, 1804, 2002), wherein the main surface (1602, 1804, 2002) is centered on the first mirror at an optical axis of the interferometer and is configured to produce a center burst (1702, 1904, 2102) of the interferogram, and wherein the at least one additional surface is located near an edge of the first mirror and is configured to produce the secondary burst (1706, 1902, 2104) of the interferogram; and a MEMS actuator coupled to a moveable mirror of the at least one mirror to produce a displacement thereof, the MEMS actuator having a variable capacitance; sense a first measured capacitance of the MEMS actuator at a first reference position of the moveable mirror corresponding to a center burst of the interferogram produced as a result of movement of the moveable mirror; and sense a second measured capacitance of the MEMS actuator at a second reference position of the moveable mirror corresponding to a secondary burst of the interferogram produced as a result of the moveable mirror and the non-planar surface; and