Abstract: Apparatus and methods are provided for guarding against unintended exposure to light from a light-emitting device used to direct light to a subject for detection by a light detector. A sensor signal indicative of light detected by the light detector is sampled. An inhibition signal for inhibiting emission of light from the light-emitting device is generated, based at least in part on whether emitted light is expected from the light-emitting device and the comparison of the sampled sensor signal value to a threshold value. The light-emitting device may be monitored for continuous wave operation. A mechanical interlock may be provided having a guard moveable between closed and open positions respectively to cover and expose a port of the light-emitting device.

Abstract: A system for near infrared spectroscopy includes a controller that automates selection of light intensities for one or more light sources. The system may stepwise increase or decrease a current driving a light source until a signal received at a light detector is within a desired range. The system may maintain closed loop control over the intensity of a light source after the intensity has been set. The closed loop control may be based on a signal from a second light detector that senses light from the light source. Current/intensity settings may be established for each of multiple light detectors. In response to selection of a light detector, the corresponding current may be delivered to drive the light source.