Abstract

In this paper alternatives calculus are proposed intended to simplify the getting of equations given by gravitational lenses characteristics. To do it, an analogy has been done between proposed calculations by classic mechanics and the theory of general relativity with those of opt mechanics and the theory of general relativity with those of optical lenses. This analogy begins from those systems where the deflector, observer and the source are aligned; and when there is not a perfect fect alignment between these. From this situation the necessary conditions are deduced for multiple images formation according to the masses distribution in the gravitational lens.