  In recent years, with the increasing demand for indoor positioning service,
visible light indoor positioning based on image sensors has been widely
studied. However, many researches only put forward the relevant localization
algorithm and did not make a deep discussion on the principle of the visible
light localization. In this paper, we make a deep discussion on the principle
of the two-light positioning algorithm and the three-light positioning
algorithm based on the image sensor, which includes how these positioning
algorithms work and the errors analysis. Based on the discussion above, we
propose two methods to improve the positioning accuracy, which is rotation
method and dispersion circle method respectively. In our experiment, we have
numerically and experimentally verified the two optimization methods and we
obtained good positioning results. Especially, the positioning accuracy of the
dual-lamp positioning algorithm based on dispersion circle optimization is up
to 1.93cm, while the average positioning error is only 0.82cm, which is
state-of-the-art of the same type of positioning system at present.
