A novel optoelectronic interface-circuit design for sensing applications

A novel and commercially viable optoelectronic interface is proposed for sensors measuring optical attenuation. Emphasis is given to commonly neglected background-noise-interference and dynamic-range-limitation problems. A modulated laser-diode, together with optical and electrical filtering, reduces the optical noise to less than a measurable level, even in extremely bright "light-infested" surroundings. In addition, an effective approach is introduced for substantially increasing the sensor's dynamic range. The power of the light-source is monitored in a dynamic intensity-control loop designed to perform "floating-point" measurements according to the attenuation in the optical path. The sensor acquires the combined dynamic ranges of the detector and light-source circuits.