The paper illustrates the results of work carried out towards the development of a computer model for the front end of a 3-dimensional vision sensor based on the optical rangefinder principle. The resultant electro-optical model was found to offer two distinct advantages: first, it helps to design the drive circuit so as to operate the light source within its optimum region in terms of both light output and frequency response and, secondly, it enables the use of a model driven approach during the 3-dimensional data processing stage. This latter, in turn, helps to increase the confidence limit for each set of voxel (or ‘rangepic’) measurements for a given signal-to-noise ratio and, therefore, enables the use of low power light sources such as light emitting diodes in preference to higher power but more expensive laser diodes. The model was developed specifically for a 3-dimensional vision sensor based on the phase measurement rangefinder, but it can be adapted to other 3-dimensional vision sensors which employ light reflectance measurements using light source/detector combinations, such as scanning laser rangefinders.