Optical system for use in a surgical apparatus

Claim 1

An optical system to be disposed between a source capable of emitting a divergent beam of light and a target, said optical system including first optics for focusing said beam of light, wherein at the upstream focal point of said first optics, said beam produces an image which is at least substantially circular in section, but wherein due to the divergent nature of the beam of light, produces an image at the downstream focal point of said first focusing optics which has a section of oblong shape, wherein said optical system successively comprises, in the direction of propagation of said beam, downstream of said first optics, first shaping means disposed near the focal point of said first focusing optics, said first shaping means obscuring a variable part of said beam, and second focusing optics, with the result that, for any relative displacement of the target and said optical system wherein said target is within about one focal length of said second focusing optics, the area of said beam removed by said first shaping means is adjustable so as to obtain, at the level of the target, a section of beam which remains at least substantially circular, wherein said first shaping means are constituted by a diaphragm disposed transversely to the direction of propagation of the beam, said diaphragm including a slot, the width of said slot uninterruptingly varying between zero and the largest dimension of the oblong section of the beam at the location of said first shaping means, and said optical system further comprises means for displacing said diaphragm relative to the rest of said system transverse to the direction of propagation of the beam.