An example device has optical emitters for emitting incident radiation within a field of view and optical detectors for receiving reflected radiation. Based on the incident radiation and the reflected radiation, a histogram indicative of a number of photon events that are detected by the optical detectors over time bins is generated. The time bins is indicative of time differences between emission of the incident radiation and reception of the reflected radiation. The device further includes; a processor programmed to iteratively process the histogram by executing an expectation-maximization algorithm to detect a presence of objects located in the field of view of the device.