An optical instrumentation using dual sensor-dummy against noises

Methods of Alternating Noise Canceling (ANC) were previously developed for the optical instrumentation: one using a dual photo sensor and another using a single photo sensor that could cancel normal mode noise (NMN) on a transmission line, even if the noise was equal status noise. A method using a sensor with a sensordummy resistance was also previously developed using ANC method against NMN not only on a transmission line but also on a sensor line. In this case, the sensordummy resistance had to be adjusted to a suitable averaging value against the changing impedance of the photo sensor. A new method of ANC is developed using a photo sensor and a dual sensor-dummy i.e. an inverse-connected sensordummy. This method doesn't need adjustment for any dummy resistance.<>