Optical projection device and an optical reader incorporating this device
AssigneeThomson-Brandt
InventorsClaude Bricot, Michel Hareng, Erich Spitz
Life of this patent
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Abstract
This invention relates to a projection device of which the optical device having a focal length is variable under the effect of an electrical signal and comprises a hollow transparent lens into which a liquid nematic crystal is introduced. Under the effect of the electrical signal applied between two transparent electrodes respectively arranged on the two inner surfaces of the lens, the index of the liquid crystal for the direction of incidence of the projected beam is capable of varying as a result of the oscillation of the molecules of the liquid crystal, the position of the focussing point of the projected beam varying in consequence.
Claims6
An optical projection device for focussing an optical beam having an optical axis and polarized rectilinearly in a direction .DELTA. perpendicular to said optical axis, comprising a hollow glass lens arranged on the path of said beam, said hollow glass lens having inner walls and comprising two transparent electrodes arranged on said inner walls, supply means for applying to said two electrodes a variable electrical field, said lens containing a liquid nematic crystal having molecules capable of oscillating under the action of said electric field, the index thus presented by said liquid crystal to said beam varying between the ordinary index n.sub.o and the extraordinary index n.sub.E of said liquid crystal.
Dependencies are inferred from the claim text.