An optoacoustic imaging system includes a handheld probe and first and second pulsed light sources having a common output. The first and second light sources generate pulses of light at first and second predominant wavelengths, respectively. The handheld probe includes an ultrasound transducer array having an active end located at the distal end of the handheld probe for receiving an optoacoustic return signal. A sensor measures a portion of the light transmitted along the light path. A data acquisition samples the ultrasound transducer array during a predetermined period of time after a pulse of light from the first light source and during a predetermined period of time after a pulse of light from the second light source. The sampled data is stored. An image processing unit reconstructs a first optoacoustic image based on the sampled data corresponding to a pulse of light from the first light source and reconstructs a second optoacoustic image based on the sampled data corresponding to a pulse of light from the second light source. An energy normalizing unit computes a normalization factor based on a measurement from each sensor in the array and applies the normalization factor to data corresponding to the pulse of light.
