Abstract: In a video projector for projecting a video picture displayed on a Braun tube, the space between the Braun tube and a lens is filled with a medium having a refractive index substantially equal to those of both the glass faceplate of the braun tube and the material of the lens, and the medium is a silicon resin of the mixture of two liquids which is in liquid phase just after the mixing of two or three or above liquids but cured after lapse of a certain time into a gel state, and the lens is supported by a lens holder so that it can be moved freely along the optical axis within the lens holder.