Optical displacement sensor arrangement and method of operation

A method of operating an optical displacement sensor arrangement, wherein the optical displacement sensor arrangement comprises a light source;

• a light detector;
• and a reflective moveable member, wherein the reflective moveable member is moveable relative to the light detector, the method comprising:
• generating light from the light source and directing the light onto the reflective moveable member;
• the reflective moveable member reflecting the light;
• the light detector detecting the light reflected by the reflective moveable member, wherein said light is indicative of movement of the reflective moveable member;
• generating measurement data representing movement of the reflective moveable member based on the light detected by the light detector;
• determining a change in a signal indicative of a rupture of the reflective moveable member;
• and
• in response to determining said signal change, changing a power level of the light source.

An optical displacement sensor arrangement comprising a closed optical sensing system, the closed optical sensing system comprising:

• a light source;
• a light detector;
• and
• a reflective moveable member, wherein the reflective moveable member is moveable relative to the light detector;
• wherein the light source is disposed to direct light onto the reflective moveable member such that the light is reflected by the reflective moveable member;
• wherein the light detector is arranged to detect the light reflected by the reflective moveable member, wherein said light is indicative of movement of the reflective moveable member;
• and
• wherein the closed optical sensing system is arranged to generate measurement data representing movement of the reflective moveable member based on the light detected by the light detector;
• the optical displacement sensor arrangement being further arranged to:
• determine a change in a signal generated therein indicative of a rupture of the reflective moveable member;
• and
• in response to determining said signal change, change a power level of the light source thereby reducing or preventing leakage of the light from the closed optical sensing system.