This invention relates in general to a lamp system for a light projector, and more particularily to a lamp system wherein a main lamp is fixedly located on an optical axis of the projection lens for transmitting full brilliancy thereof and a spare lamp is fixedly located in a location not in alignment with the optical axis and reflecting means are positionable between first and second positions wherein light transmission of the main lamp is not obstructed in the first position, and sensing means, actuating means, and releasing means allow the reflecting means to assume a second position for reflecting light from the spare lamp along the optical axis after failure of the main lamp.
Various types of lamp changing mechanisms for light projectors are known to the prior art. Most of such mechanisms generally employ a sliding or rotating carriage, with a main lamp and a spare lamp mounted thereon, for physically moving the spare lamp into the position formerly occupied by the main lamp upon burn-out thereof. The combined mass of such mechanisms inherently gains sufficient inertia during the transition between the main lamp and the spare lamp such that considerable vibration is experienced in the projector when the spare lamp is stopped in the desired position. Because projectors are usually located a considerable distance from the screen or other surface upon which light is projected, even slight movement of the projector caused by vibration translates into much greater movement of the projected image on the screen, and may even result in a portion of the image being located off of the screen. In commercial applications, where images from more than one projector are superimposed or where dissolving between images is required, even slight movement of the projectors becomes intolerable.
Some prior art projectors also suffer from ineffecient light transmission from the main lamp because reflecting means are used therewith. Light transmission losses of about 15 to 20% are customary when reflecting means are used, due to light scattering, reflection losses and imperfect alignment or adjustment of the reflecting surface.