Optoelectronic indicator/warning circuit for detecting and observing the high values of incident optical radiation

Abstract

A useful tool in working with non-visible optical radiation is a monitor/indicator with an alarm, activated when the irradiance exceeds a preset value. In extending this tool to more applications, this paper describes the design and development of a small active lightweight indicator in two versions, for detecting, observing and responding to almost every preset level of the optical radiation, extended from low up to high optical power densities. The monitor/indicator, in the form of a small cylinder or a pencil or a thick card, with low power consumption and linear response, may be used as active warning element on the side of goggles, spectacles, helmets etc., or as an active element for replacing the laser indication passive cards. The indicator's audible and visible output alarms are like the indication output of the ionizing radiation monitors. The alarm is activated if the irradiance exceeds a preset limit, which may be set equal to maximum permissible exposure. The main parts in both versions are a photodetector and a FET-input operational amplifier, in an optoelectronic integrator and an intensity/frequency converter. This circuit reacts with sufficient accuracy in CW or pulsed radiation down to the optical irradiance.