Eidophor

The Eidophor system ( Swiss patent) was the first method for large-scale projection of television pictures. It was invented in 1939 by Swiss engineer Fritz Fischer at the ETHZ. The development took place first at the Dr. Edgar Gretener AG, which was later renamed to GRETAG AG. Eidophor was applied in the professional field until the late 1980s. The name is borrowed from the Greek and can be translated as " image support ".

When peeling products appeared from the 1990s, cheaper LCD ( liquid crystal display) - and DLP (Digital Light Processing ) - Video projectors on the market, with preparations for the corresponding LCD technology have been made in Switzerland (probably world's first projector presentation with LCD matrix display modest resolution as a light modulator by Peter J. Wild, Brown, Boveri & Cie, 1972).

Principle of operation

Beam path

When Eidophor system the light of a high-power xenon gas discharge lamp over louvred bars mirror is directed into a concave mirror. Compared with the concave mirror is a convex lens or lens that projects all passing through the slits of the bars mirror light beams on the screen. Since the mirror is symmetrical bars, located right in the center of the concave mirror, the light is reflected back into the source and the screen remains dark at first.

Imaging

In order to give rise to an image, the light in the beam path must be distracted, so that it can mirror the bars happen. The concave mirror is part of this, and the anode of a cathode ray tube. On the concave mirror, a thin layer of oil (about 14 microns thick ) is applied, which is scanned by the electron beam and shot in Depending awareness of the video signal varies strongly with electrons. The oil layer deforms thereby locally, which causes a slight deflection of the light. The reflected light rays no longer meet exactly on the mirror bars, but get past it and be from the lens ( converging lens ) projected as a dot on the screen.

The deflection in the deformed oil film is thereby caused by the optical diffraction of a phase grating, or by refraction similar to Schlieren optics.

Color projections may be achieved by the use of three parallel Eidophor systems with appropriate color filters.

Sophisticated Eidophor systems were characterized by an excellent image quality for its time.