Self calibration for mirror positioning in optical MEMS interferometers

Description

Micro Electro-Mechanical Systems (MEMS) refers to the integration of mechanical elements, sensors, actuators and electronics on a common silicon substrate through microfabrication technology. 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.

Aspects

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 and at least one additional surface offset from the main surface; 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 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; 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 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.

Patenting Status

Patent Granted

Status

Patented

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