Abstract: According to one aspect of the invention, there is provided a method for controlling a monitoring device including a plurality of light emission units (or sources) and a plurality of light reception units (or detectors), comprising the steps of: causing the plurality of light emission units to sequentially generate optical signals in a mutually exclusive manner according to a time division scheme; and with reference to a distance between an m-th light emission unit of the plurality of light emission units that generates an optical signal to be measured and an n-th light reception unit of the plurality of light reception units that detects the optical signal to be measured, dynamically controlling a measurement circuit gain that the n-th light reception unit uses to detect the optical signal generated by the m-th light emission unit.