Abstract: A multiplicity of preferably coherent light sources are disposed along a common axis and are separated from one another by interposed opaque shields in the form of disks of progressively increasing diameters transverse to that axis. Each source confronts an associated screen with an annular light-receiving zone, which (except in the case of the last screen) may be integral with the respective shields, illuminated by light from all the preceding sources. The light sources may be individually modulated by external signals, e.g. oscillations derived from sound waves, to provide a visual pattern thereof.