Abstract: An external projection lens aperture, including a holder; an adjustable aperture mounted in the holder; and a self-centering clamping mechanism mounted in the holder for attaching the holder to an end of a projection lens barrel.

Abstract: A module interposed between a slide tray and a projector provides a user selected random presentation of sequentially ordered slides. The module bottom simulates the tray bottom to align gates of the module and projector. The module top simulates the tray bottom to align gates of the tray and module. A microcontroller controls a lifter foot to keep unwanted slides from dropping into the module gate until the tray had been rotated by a hub assembly to the next desired slide position. The lifter foot then acts to lower a slide through the module to the lifter foot and projector, and return it after projection.

Abstract: An overhead projector comprises two light sources, a first reflection mirror that reflects a light from an illuminating light source of said light sources toward a reflection type light collection lens and a projection lens that projects a light reflected from said light collection lens onto a screen via a second reflection mirror, while said two light sources, said first reflection mirror and said projection lens being arranged parallel and housed together in a longitudinal direction of an overhead cabinet, wherein the light axes of said two light sources are directed toward a center portion of a mirror surface of the first reflection mirror, said two light sources are mounted parallel laterally in said overhead cabinet, and said first reflection mirror is mounted in a manner that said first reflection mirror is rotatable around said center portion of the mirror surface.