Device for displaying colors produced by controllable cholesteric color filters

• US 5,686,931 A
• Filed: 11/03/1995
• Issued: 11/11/1997
• Est. Priority Date: 11/14/1994
• Status: Expired due to Fees

• Current Assignee: Rolic AG (BASF SE)
• Original Assignee: Rolic AG (BASF SE)
• Inventors: Seiberle, Hubert, Schadt, Martin, Funfschilling, Jurg
• Primary Examiner(s): Bayerl, Raymond J.
• Assistant Examiner(s): Vail, Seth D.
• Application Number:
  US08/552,664
• Time in Patent Office: 739 Days
• Field of Search: 345/88, 345/151, 349/5, 349/9, 349/80, 349/97, 349/106, 349/108, 349/115, 349/194
• US Class Current: 345/88
• CPC Class Codes: G02B 5/3016 involving passive liquid crystal elements optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters
• CPC Class Codes: G02F 2201/343 cholesteric liquid crystal reflector
• CPC Class Codes: G02F 2203/34 Colour display without the use of colour mosaic filters
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time

Abstract

Colors are generated in the display device by guiding light through three serially-arranged, electrically controlled color filters. Each filer attenuates one of three colors. The color filters incorporate two cholesteric filters, two λ/4 plates, and one electrically switchable liquid crystal display.

Claims

1. An electrically controllable color display device having compact linear light guidance, which comprises three switchable color filters optically connected in series, each color filter comprising two cholesteric filters, two λ

/4 plates, and one electrically switchable liquid crystal cell with segmented electrodes, each color filter being constructed so as to attenuate one of three different colors in response to electrical control.

2. The display device according to claim 1, wherein a matrix is disposed in front of each filter, the matrix comprising a lens selected from the group consisting of microlenses, holographic lenses, Fresnel lenses, and graded index lenses.

3. The display device according to claim 1, wherein the liquid crystal cells in the color filters are selected from the group consisting of TN-LCD, STN-LCD, ECB-LCD, DAP-LCD, OMI-LCD, polymer-dispersed LCD, polymer dispersed cells, DHF cells, and other ferroelectric cells capable of generating grey values.

4. The display device according to claim 3, wherein the color filter is a ferroelectric cell capable of generating grey values, selected from the group consisting of charge-controlled SSF-LCDs, SBF-LCDs, and anti-ferroelectric LCDs.

5. The display device according to claim 2, wherein the liquid crystal cells in the color filters are selected from the group consisting of TN-LCD, STN-LCD, ECB-LCD, DAP-LCD, OMI-LCD, polymer-dispersed LCD, polymer dispersed cells, DHF cells, and other ferroelectric cells capable of generating grey values.

6. The display device according to claim 5, wherein the color filter is a ferroelectric cell capable of generating grey values, selected from the group consisting of charge-controlled SSF-LCDs, SBF-LCDs, and anti-ferroelectric LCDs.

7. The display device according to claim 1, wherein the display device is a projection display device.

8. The display device according to claim 1, wherein the display device is a projection attachment for a light-room projector.

9. The display device according to claim 1, wherein the display device is a direct vision display device.

10. An electrically controllable color display which comprises three switchable color filters optically connected in series, each filter comprising in order a first cholesteric filter, a first λ

/4 plate, a liquid crystal cell, a second λ

/4 plate, and a second cholesteric filter, each color filter being constructed so as to attenuate one of the three different colors in response to electrical control.

11. The display device according to claim 10, wherein the three different colors are red, green, and blue.

12. The display device according to claim 10, wherein first cholesteric filter is an L-filter which in the presence of a light source transmits R-light from the light source to the first λ

/4 plate which converts the R-light into p-light which is then transmitted to the liquid crystal cell which either polarizes the p-light to s-light or allows the p-light to remain as p-light, the s-light or p-light is then transmitted to the second λ

/4 plate which converts the s-light or p-light, respectively, to L-light or R-light, which is then transmitted to the second cholesteric filter which only allows L-light to be further transmitted.