Display devices

• US 4,088,400 A
• Filed: 12/21/1973
• Issued: 05/09/1978
• Est. Priority Date: 12/29/1972
• Status: Expired due to Term

• Current Assignee: Thomson-CSF
• Original Assignee: Thomson-CSF
• Inventors: Hareng, Michel, Leiba, Eugene, Assouline, Georges, Roncillat, Michel
• Primary Examiner(s): Haroian, Harry N.
• Application Number:
  US05/427,304
• Time in Patent Office: 1,600 Days
• Field of Search: 353/20, 353/10, 353/25, 353/102, 353/122, 350/150, 350/275, 350/160 P, 350/160 LC, 350/159
• US Class Current: 353/20
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 2413/02 Number of plates being 2
• CPC Class Codes: G02F 2413/07 All plates on one side of the LC cell

Abstract

An improvement in electro-optical display devices utilizing polarized light is disclosed, in which the linearly polarized light emerging from the display device is picked up by a diffuser and reaches the observer eyes after passing through a linear polarizer. The contrast is thus enhanced and the display can be used in presence of strong ambient lighting. The contrast can be still further improved by arranging at either side of the diffuser two suitably oriented quarter-wave plates.

Claims

1. A display device comprising means for producing a parallel beam of linearly polarized light, and successively positioned for receiving said light;

electro-optical modulating means, first linear polarizer means having a first polarization direction, diffuser means and second linear polarizer means having a second polarization direction.

2. A device as claimed in claim 1, wherein said first and second polarization directions are mutually parallel.

3. A device as claimed in claim 1, wherein that face of said second linear polarizer means which is opposite said diffuser means, has an anti-reflection coating.

4. A device as claimed in claim 1, wherein first and second optical phase-shift means are positioned for receiving said light respectively between said first polarizer means and said diffuser means and between said diffuser means and said second polarizer means.

5. A device as claimed in claim 4, wherein each said first and second optical phase-shift means respectively introduce, between two mutually perpendicular preferred directions of vibration, an optical phase-shift equal to an odd multiple of a quarter wave length;

said wave length being the mean wave length of said polarized light;

said two preferred directions of said first and of said second phase-shift means making an angle of 45°

respectively with said first and second polarization directions.

6. A device as claimed in claim 1, wherein optical projection means are arranged between said modulator means and said diffuser means and facing said first polarizer means to project the image of said modulating means on to said diffuser means.