PROJECTOR

• US 3,844,650 A
• Filed: 05/22/1972
• Issued: 10/29/1974
• Est. Priority Date: 05/22/1972
• Status: Expired due to Term

• Current Assignee: Geoffrey C. Nicholson, John E. Collins
• Original Assignee: Geoffrey C. Nicholson, John E. Collins
• Inventors: Nicholson, Geoffrey C., Collins, John E.
• Primary Examiner(s): Prince, Louis R.
• Assistant Examiner(s): Mirabito, A. J.
• Application Number:
  US05/255,616
• Time in Patent Office: 890 Days
• Field of Search: 353/98 350/16LC,117
• US Class Current: 353/122
• CPC Class Codes: G02F 1/133 Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements arrangements or circuits for control of liquid crystal elements in a matrix, not structurally associated with these elements G09G3/36
• CPC Class Codes: G03B 21/132 Overhead projectors, i.e. capable of projecting hand-writing or drawing during action epidiascopic projectors G03B21/08
• CPC Class Codes: Y10S 353/03 Transparent
• CPC Class Codes: Y10S 353/05 Transparency holder accessories

Abstract

A device for projecting a modulated light beam on a viewing screen, wherein modulation is achieved by electronic actuation of an electro-optical assembly utilizing a thin liquid crystal layer.

Claims

1. A projection system comprising, in combination, light source means for providing a light beam, condenser means for condensing said beam and directing tHe condensed beam toward a projection optic, projection optic means for focusing said beam on a viewing screen, beam modulating means between said condenser means and said projection head and comprising an electro-optical element having a continuous thin liquid crystal stratum between a transparent upper plate having an x-array of parallel conductive strips contacting one surface of said stratum and a lower plate having a y-array of parallel conductive strips contacting the other surface of said stratum, and voltage supply means including scanning means for permitting impression of greater than threshold voltage consecutively at each juncture of said x-array and y-array, modulating means for restricting impression of said voltage at specified junctures, and suppressing means for restricting the voltage differential to less than threshold voltage at all but said each junctures.

2. System of claim 1 wherein said modulating and scanning means includes a keyboard for activating said system to produce a single desired projected image from a plurality of available image-producing signals, a buffer, a read-only memory, a clock, a pulse shaper, a shift register, a row driver, a column driver, an output enable connection between keyboard and memory, and a reset strobe connection between shift register and memory.

3. A projection system comprising, in combination, light source means for providing a light beam, condenser means for condensing said beam and directing the condensed beam toward a projection optic, projection optic means for focusing said beam on a viewing screen, beam modulating means between said condenser means and said projection head and comprising an electro-optical element having a continuous thin liquid crystal stratum between a transparent upper plate having at least one conductive surface area contacting one surface of said stratum and a lower plate having opposing conductive surface areas comprising a raster of small thin closely spaced metallic reflectors contacting the other surface of said stratum, and voltage supply means for supplying a voltage differential between selected opposing conductive surface areas of said plates and greater than the threshold voltage for said liquid crystals.

4. System of claim 3 wherein is included an electron gun for providing an electron beam capable of imparting a negative charge to any one of said reflectors, and control means for modulating said beam in accordance with a desired display and for causing said beam to scan successively all of said reflectors.

5. System of claim 3 wherein said reflectors are supported on a photoconductive subsurface.

6. System of claim 5 wherein is included means for impressing a light-image on said subsurface to render the thus exposed areas conductive, and means for establishing a potential difference between the reflectors at said conductive areas and the said upper plate conductive surface area.