not described alternative mechanical systems to the one described above for the motion of the dichroic filters 31 may also be manufactured using gear systems e g a worm screw or a belt connected to a pulley and any other common mechanisms known in the state of the art also the number of flat filter sets according to the present invention may change i e using only two sets of filters each one with a determined number of sectors such to correct a coloured light beam through one or more tubular walls having one or more colour corrections on their surface in particular free air circulation is provided inside the projector to avoid overheating of the components housed therein moreover since the sectors of the diaphragms with dichroic filters are not perpendicular to the light beam intercepted by them all the heat reflected by the rays not flowing through the dichroic filters will be prevented from being sent back to the innermost side of the projector adding to its overheating according to another advantage of the present invention light beams of different colour shades can be generated thanks to differentiation of the basic colour and driving independence of the various filters forming the diaphragms interposed on the light beam path moreover a simultaneous use of the tubular wall surrounding the lamp.