Projection apparatus

Navigational light simulating apparatus for use in a navigational training system comprising in combination a screen and a projection means for projecting a plurality of movable spots of light onto the screen to simulate a changeable pattern of navigational lights, said projection means comprising a plurality of light spot projectors displaced one from another laterally about a center line of the system extending between the screen and the projection means, wherein each projector comprises an optical system having an optical axis and including means defining an aperture which is controllably displaceable in a predetermined aperture plane, a light source for illuminating the aperture and means for focusing an image of the illuminated aperture onto the screen to form a respective spot of light thereon, said means defining the displaceable aperture comprising a pair of parallel plates mounted adjacent one another and normal to said optical axis, each being opaque to the light from said light source apart from a fine straight transparent line, said lines extending in orthogonal directions and crossing one another at a crossing point defining said aperture, mounting means by which each of said plates is mounted for linear movement in its own plane in a direction transverse the direction in which the respective transparent line extends, and means for independently moving said plates in said respective directions of linear movement, thereby to displace the aperture.