A method of ambient light suppression in an imaging system, including illuminating leaves of a multi-leaf collimator (MLC) with a first light of a lighting system inside a housing of the MCL, receiving ambient light inside the housing of the MLC through an aperture of the MLC, and capturing, using an imaging system having optics situated inside the housing of the MLC, an image of the leaves of the MLC illuminated with the first light and the ambient light. The method may further include, suppressing the ambient light in the first image to generate a second image of the leaves of the MLC and detecting a feature of the leaves of the MLC in the second image.