Compensation of the effects of uncontrolled light in an imaging system using a controlled light source. Light from the controlled light source reflected by an object and uncontrolled light are detected in a plurality of frequency ranges. Intensity of the uncontrolled light is determined based on the varying sensitivity of an image sensor to light in the different frequency ranges and known emission characteristics of the controlled light source in the frequency ranges. Once the intensity of the uncontrolled light is determined, the total light detected at each point is adjusted to reduce the effects of the uncontrolled light in the resulting imaging data produced by the imaging system.