Apparatus to reduce pressure and thermal sensitivity of high precision optical displacement sensors

A method for estimating a parameter of interest in an earth formation intersected by a borehole, the method comprising:

• conveying an optical displacement device into the borehole, the optical displacement device being part of an optical displacement sensor;
• using a light source of the optical displacement sensor to generate an initial electromagnetic beam;
• generating measurement information using an optical displacement device receiving at least one electromagnetic beam comprising at least a portion of the initial electromagnetic beam;
• using at least one detector to receive a part of the at least one electromagnetic beam received by the optical displacement device and provide information relating to the parameter of interest;
• and
• using a closed loop light source control comprising an optical component proximate the optical displacement device such as to experience the same temperature and pressure as the optical displacement device to compensate for changes in temperature at the optical displacement device by adjusting the light source.

A method for estimating a parameter of interest in an earth formation intersected by a borehole, the method comprising:

• conveying an optical displacement device in the borehole;
• generating information from the optical displacement device relating to relative motion between two or more reflective surfaces of the optical displacement device that is indicative of the parameter of interest;
• and
• preventing changes in the information resulting from changes at the optical displacement device in at least one of i) temperature, or ii) pressure, by compensating for the changes at the optical displacement device, by adjusting a light source generating an electromagnetic beam at least partly received by the optical displacement device, the adjusting responsive to information relating to a control optical displacement device proximate the optical displacement device such as to experience the same temperature and pressure as the optical displacement device.