REAR PROJECTION SYSTEM AND REAR PROJECTION SCREEN

• US 20110102688A1
• Filed: 06/04/2009
• Published: 05/05/2011
• Est. Priority Date: 06/11/2008
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: De Boer, Dirk Kornelis Gerhardus
• Application Number:
  US12/994,890
• Publication Number:
  US 20110102688A1
• Time in Patent Office: Days
• US Class Current: 349/5
• CPC Class Codes: G02B 27/0103 comprising holographic elements
• CPC Class Codes: G02B 5/1866 Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02F 1/13342 Holographic polymer dispersed liquid crystals
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: G03B 21/60 characterised by the nature of the surface
• CPC Class Codes: G03B 21/62 Translucent screens
• CPC Class Codes: G09F 19/18 involving the use of optical projection means, e.g. projection of images on clouds projection apparatus per se G03B
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

To provide a rear projection system, which offers a high transparency and a high efficiency of projection, a rear projection system is proposed, comprising: a projector (18), and a projection screen (16) being switchable between a transparent mode and a diffractive mode, wherein the projector (18) is located with respect to the projection screen (16) such that light from the projector (18) is incident at an inclined angle at the rear side of the projection screen (16), the projection screen (16) is adapted to deflect in its diffractive mode the incident light into a limited angle range with respect to the front surface normal of the screen (16).

Claims

1. A rear projection system comprising

a projector (18), and

a projection screen (16) being switchable between a transparent mode and a diffractive mode,

wherein the projector (18) is located with respect to the projection screen (16) such that light from the projector (18) is incident at an inclined angle at the rear side of the projection screen (16), the projection screen (16) is adapted to deflect in its diffractive mode the incident light into a limited angular range with respect to the front surface normal of the projection screen (16).

2. A rear projection system as claimed in claim 1, wherein the projection screen (16) is used as a shopping window.

3. A rear projection system as claimed in claim 1, wherein the angle of incidence between the incident light and the rear surface normal of the projection screen (16) is bigger than 30°

.

4. A rear projection system as claimed in claim 1, wherein the limited angular range extends from −

10°

to 10°

in the vertical direction.

5. A rear projection system as claimed in claim 1, wherein the light from the projector (18) is polarised.

6. A rear projection system as claimed in claim 1, wherein the projection screen (16) comprises:

a first transparent substrate (42) with a first transparent electrode (40),

a composition (48) of a liquid crystal material (50) and a compound material (52),

a second transparent substrate (46) with a second transparent electrode (44), wherein the refractive index of the liquid crystal material (50) being disposed between the first and second substrate (42, 46) is switchable by means of electrical field generated by the first and second electrode (40, 44) to be substantially equal or different to the refractive index of the compound material (52).

7. A rear projection system as claimed in claim 6, wherein the compound material (52) is a polymer.

8. A rear projection system as claimed in claim 6, wherein the composition of the liquid crystal material (50) and the compound material (52) is adapted to form a switchable Bragg grating.

9. A rear projection system as claimed in claim 8, wherein the composition of the liquid crystal material (50) and the compound material (52) is a holographic polymer-dispersed liquid crystal (HPDLC) material.

10. A rear projection system as claimed in claim 8, wherein the composition of the liquid crystal material (50) and the compound material (52) is a polymer liquid-crystal polymer slices (POLICRIPS) material or an electrically manageable polymer liquid-crystal polymer hologram (POLIPHEM) material.

11. A rear projection system as claimed in claim 8, wherein the composition of the liquid crystal material (50) and the compound material (52) is a photopolymerized mixture of monoacrylates, diacrylates and non-reactive liquid crystal material forming a liquid crystal gel.

12. A rear projection screen (116) being switchable between a transparent mode and a diffractive mode, the projection screen (116) comprises:

a first transparent substrate (54) comprising a first transparent electrode (56) and a relief portion with a surface-relief grating (58),

a liquid crystal material (72) located next to the relief portion of the first transparent substrate (54) and filling the surface-relief grating (58),

a second transparent substrate (64) with a second transparent electrode (66), wherein the refractive index of the liquid crystal material (72) could be changed by means of electrical field of the first and second electrode (56, 66) to be substantially equal or different from the refractive index of the relief portion of the first transparent substrate (54).

13. A rear projection screen (116) as claimed in claim 12, wherein the first transparent substrate (54) comprises a support layer (60) made of PMMA and a relief layer (62) made of polycarbonate facing the liquid crystal layer (72).

14. A rear projection screen (116) as claimed in claim 12, wherein the second substrate (64) comprises a support layer (68) made of glass and a rubbed polyimid layer (70) facing the liquid crystal layer (72).

15. A rear projection screen (116) as claimed in one of the claim 12, wherein the surface-relief grating (58) has a grating period of about 1000 nm and a modulation depth in the range of about 100-300 nm.

16. A method for manufacturing a rear projection screen (116) as claimed in claim 12, comprising the steps of:

providing a first transparent substrate (54) comprising a first transparent electrode (56) and a transparent surface portion being prepared for an embossing process,

embossing the transparent surface portion to form a relief portion in the first transparent substrate (54) having a surface-relief grating (58),

depositing a liquid crystal material (72) on the relief portion of the first transparent substrate (54), filling the surface-relief grating (58),

providing a second transparent substrate (64) with a second transparent electrode (66), and

assembling the first transparent substrate (54) and the second transparent substrate (64).

17. The method as claimed in claim 16, wherein the embossing is performed by injection moulding, hot embossing or by continuous film replication.