1. A velocimeter apparatus, comprising: a heterodyning unit that receives and heterodynes Doppler-shifted optical beams that have been scattered from a target, producing respectively corresponding heterodyned optical beams at respectively lower frequencies than the corresponding Doppler-shifted optical beams; a digital camera positioned relative to said heterodyning unit to receive the heterodyned optical beams, said digital camera converting the heterodyned optical beams into respectively corresponding sequences of digital values; and a digital data processor coupled to said digital camera for producing in response to said sequences of digital values a velocity image associated with the target.