Detector or photomultiplier tube (PMT) gain control over time

An optical system comprising:

• an interference optical system that operates to:
• (i) receive and divide light from a light source into a first light with which an object or sample is to be irradiated and which travels along a sample arm of the interference optical system and a second reference light, (ii) send the second reference light along a reference arm of the interference optical system for reflection off of a reference reflection of the interference optical system, and (iii) generate interference light by causing reflected or scattered light of the first light with which the object or sample has been irradiated and the reflected second reference light to combine or recombine, and to interfere, with each other, the interference light generating one or more interference patterns;
• one or more detectors that operate to continuously acquire the interference light and/or the one or more interference patterns to measure the interference or the one or more interference patterns between the combined or recombined light to obtain data for one or more imaging modalities;
• and
• one or more processors that operate to:
• control a gain for the one or more detectors such that the optical system achieves reliable or consistent measurement(s) for the one or more imaging modalities and/or such that the optical system performs one or more calibrations for the one or more imaging modalities;
• perform a fluorescence calibration using one or more fluorescence signals;
• calculate a background fluorescence signal, determine whether the background fluorescence signal is in an adjustable range or a first set or predetermined range, and determine whether the background fluorescence signal is in an acceptable range or in a second set or predetermined range;
• and
• in a case where the background fluorescence signal is in the adjustable range or in the set or predetermined first range and is in the acceptable range or in the set or predetermined second range, then the one or more processors record the gain of the one or more detectors and the fluorescence signal, and the one or more processors return the optical system to a standby mode and/or a catheter disconnect mode.