WO2015060740A1

WO2015060740A1 - 3d-projector with lcd-shutters and dlp as a beam combiner

Info

Publication number: WO2015060740A1
Application number: PCT/RU2013/000925
Authority: WO
Inventors: Vladislav Gennadievich NIKITIN; Nikolay Ivanovich PETROV; Yury Mihaylovich SOKOLOV; Angela Liudvigovna STOROZHEVA; Maksim Nikolaevich KHROMOV
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2013-10-21
Filing date: 2013-10-21
Publication date: 2015-04-30

Abstract

The invention relates to an optical system (100) for projecting polarized images onto a screen (300), comprising a light beam source (103) for generating a non-polarized image beam (105); a beamsplitter (107) for splitting the image beam (105) into a first beam (109-1) having a first polarization on a first optical path and a second beam (109-2) having a second polarization on a second optical path; and a controllable micro mirror matrix (111) for reflecting the first beam (109-1) of the first optical path and the second beam (109-2) of the second optical path in a same direction.

Description

3D-PROJECTOR WITH LCD-SCHUTTERS AND DLP AS A BEAM COMBINER

Technical field

The present invention relates to an optical system for projecting polarized images onto a screen and a method for projecting polarized images onto a screen.

In particular the invention relates to 3D projection systems in which the brightness of the projector is increased.

Background

There are several technologies which are used for creating three-dimensional (3D) images. All of these technologies create a separate picture, for each eye. A viewer uses special glasses for filtering images between the eyes. In 3D-projectors, which are used for creating 3D-images and 3D-cinema, differently polarized filters are used. These filters create images with different polarizations. Alternatively rotating filters with many segments are employed in order to obtain differently polarized images. There are two types of glasses which are used in 3D-technologies, namely active and passive glasses.

Active glasses with liquid crystal display (LCD) shutters are used in digital light processing (DLP) link technologies. A DLP projector creates images with high frequency. DLP-link uses active glasses for each viewer. LCD-shutter glasses shut an image for the one eye and pass the image for the other eye. For the following image the eyes are changed. This technology can use two perpendicular polarizations or polarizations which are rotated in opposite directions. Left and right lenses of the glasses alternate between opaque and transmissive states according to a signal.

Passive polarized glasses are used in other technologies. This technique uses two projectors, which produce images with different linear polarizations. The two polarizations of the projectors are perpendicular to each other. Passive or active glasses are used in these projections systems.

The polarizers used in all types of the aforementioned glasses reduce the brightness for viewer by two times.

Document US 5,239,372 describes a 3D projection system with two projectors. Document US 5,002,387 describes a projection system with a digital light processor as spatial light modulator and glasses with LCD shutters.

Document US 2005/0237487 Al describes a projection system with a color and polarizer wheel.

Summary

It is the object of the invention to provide an improved technique for projecting polarized images onto a screen.

This object is achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

The invention is based on the finding that images projected onto a screen should be rather bright and losses in glasses should be compensated for. Creation of three- dimensional images (3D) should be possible with high brightness using cheap and serviceability devices. The problem of the creation 3D images can be solved by an optical scheme of a 3D projector with a digital light processor (DLP) as a spatial light modulator (SLM) and a beam combiner and a LCD filter.

According to a first aspect, the invention relates to an optical system for projecting polarized images onto a screen, comprising a light beam source for generating a non-polarized image beam; a beamsplitter for splitting the image beam into a first beam having a first polarization on a first optical path and a second beam having a second polarization on a second optical path; and a controllable micro mirror matrix for reflecting the first beam of the first optical path and the second beam of the second optical path in a same direction.

In a first possible implementation form of the optical system according to the first aspect the optical system comprises a first controllable shutter in the first optical path and a second controllable shutter in the second optical path.

In a second possible implementation form of the optical system according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the light beam source comprises light emitting diodes for generating nonpolarized light.

In a third possible implementation form of the optical system according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the light beam source comprises three light sources for generating light with different wavelengths.

In a fourth possible implementation form of the optical system according to the third implementation form of the first aspect, the light beam source comprises a beam combiner for combining the light from the three light sources into the beam.

In a fifth possible implementation form of the optical system according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the optical system is arranged such that the first beam is directed onto a first half of the controllable micro mirror matrix and the second beam is directed onto a second half of the controllable micro mirror matrix.

In a sixth possible implementation form of the optical system according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the optical system comprises an objective for focusing the beam on a screen.

In a seventh possible implementation form of the optical system according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the optical system comprises a shutter for controllably rotating the polarization of the reflected first beam and the reflected second beam.

In an eighth possible implementation form of the optical system according to the seventh implementation form of the first aspect, the shutter comprises a first coating area for filtering the reflected first beam in the first polarization and a second coating area for filtering the reflected second beam in the second polarization.

In a ninth possible implementation form of the optical system according to the seventh implementation form of the first aspect or according to the eighth implementation form of the first aspect, the shutter is located in an optical path between the micro mirror matrix and an objective for focusing the beam on a screen.

According to a second aspect, the invention relates to a method for projecting polarized images onto a screen comprising the steps of generating a non-polarized image beam; splitting the image beam into a first beam having a first polarization on a first optical path and a second beam having a second polarization on a second optical path by a beam splitter; and reflecting the first beam of the first optical path and the second beam of the second optical path in a same direction by a controllable micro mirror matrix.

In a first possible implementation form of the method according to the second aspect, the method comprises the step of alternatively shutting the first beam and the second beam.

In a second possible implementation form of the method according to the second aspect as such or according to the first implementation form of the second aspect, the method comprises the step of directing the first beam onto a first half of the controllable micro mirror matrix and directing the second beam onto a second half of the controllable micro mirror matrix.

In a third possible implementation form of the method according to the second implementation form of the second aspect, the method comprises the step of rotating the polarization of the reflected first beam and the reflected second beam by a shutter.

In a fourth possible implementation form of the method according to the third implementation form of the second aspect, the method comprises the step of filtering the reflected first beam in the first polarization by a first coating area of the shutter and filtering the reflected second beam in the second polarization by a second coating area of the shutter.

Brief description of the drawings

Further embodiments of the invention will be described with respect to the following figures, in which:

Fig. 1 shows a schematic diagram of an optical system for projecting polarized images according to an implementation form;

Fig. 2 shows a schematic diagram of the optical system for projecting polarized images according to an implementation form;

Fig. 3 shows a schematic diagram of different polarizations; and

Fig. 4 shows a schematic diagram of a digital light processor.

Detailed description of embodiments of the invention

Fig. 1 shows a schematic diagram of the optical system 100 for projecting polarized images onto a screen 300 according to an implementation form. The optical system 100 can be used in a projector for three-dimensional (3D) images.

A light beam 105 is created in a light beam source 103 by three light sources 115- 1, 1 15-2 and 1 15-3 each having a different wavelength. The light sources 1 15-1, 115-2 and 115-3 use light emitting diodes (LED) or lasers for outputting non-polarized light.

. The light beams from the light sources 1 15-1, 1 15-2 and 1 15-3 are combined and redirected in the same direction by a beam combiner 1 17 of the light beam source 103 so that a polychromatic image beam 105 is created. It is possible to switch between single light sources 1 15-1, 115-2 and 1 15-3 with different wavelengths and an image having different colors can be created.

The non-polarized image beam 105 of the light beam source 103 is separated by a polarizer or a beam splitter 107 into a first beam 109-1 having a first polarization on a first optical path and a second beam 109-2 having a second polarization on a second optical path. The split first and the second optical paths have different directions. Each optical path of the beams 109-1 and 109-2 corresponds to a different polarization.

The first optical path comprises a first shutter 113-1 and the second optical path comprises a second shutter 1 13-2, such as LCD shutters. Each of the shutters 1 13-1 and 113-2 operates with a different polarization and allows switching images at the screen 300 from one polarization to the other. The shutters 113-1 and 113-2 are tilted corresponding to a light polarization in their own optical path. The second optical path additionally comprises a mirror 125 for redirecting the second light beam 109-2 to a digital light processor (DLP) 131 comprising a controllable micro mirror matrix 1 11. The first optical path of the beam 109-1 hits the digital light processor 131 directly.

The first light beam 109-1 and the second light beam 109-2 having different polarizations are redirected by the controllable micro mirror matrix 111 into the same direction. The controllable micro mirror matrix 111 is used as a beam combiner that redirects the beams 109-1 and 109-2 with different polarizations into the same direction.

An objective 1 19 is used for focusing the generated images on the screen 300. A viewer uses passive glasses 121 with different polarizations which divide the projected images with different polarizations for each eye.

In this implementation form shutters 1 13-1 and 113-2, like LCD shutters, are used in each optical path for switching the beams 109-1 and 109-2 with different polarizations. A controllable digital micro mirror device 1 1 1 is used as a spatial light modulator and for combining the beams 109-1 and 109-2 with different polarizations. Images can be created with different polarizations on the screen 300. A viewer uses passive polarizer glasses in order to see different images for each eye.

Fig. 2 shows a schematic diagram of the optical system 200 for projecting polarized images on a screen 300 according to a further implementation form. Three light sources 215-1, 215-2 and 215-3 of a light beam source 203 create three light beams with different wavelengths, for example in red, green and blue (RGB) colors. The light sources 215-1, 215-2 and 215-3 use light emitting diodes (LED) or lasers for outputting non-polarized light. The single light beams from the three light sources 215- 1, 215-2 and 215-3 are redirected and combined into a single image beam 205 by a beam combiner 217.

The non-polarized image beam 205 of the light beam source 203 is separated by a polarizer or a beam splitter 207 into a first beam 209-1 having a first polarization on a first optical path and a second beam 209-2 having a second polarization on a second optical path. The first and the second optical path run in different directions. The first polarization of the first optical path and the second polarization of the second optical path are perpendicular with respect to each other. Consequently, after the beam splitter 207 two optical paths exist and each optical path corresponds to a different polarization.

The second optical path additionally comprises a mirror 225 for redirecting the second light beam 209-2 to a digital light processor (DLP) 231 comprising a controllable micro mirror matrix 211. Each of the two light beams 209-1 and 209-2 illuminates a different half of the digital light processor 231. Each half of the digital light processor 231 is illuminated by beams 209-1 and 209-2 with different polarizations from different optical paths. The digital light processor 231 creates images for each eye at a same time.

The digital light processor 231 redirects the first and the second light beam 209-1 and 209-2 into a same direction to a filter or a shutter 221, e.g. a LCD filter, with a polarizing coating 223-1 and 223-2. The first half of the polarized coating 223-1 transmits one polarization and the second half of the polarizing coating 223-2 transmits the other polarization.

An objective 219 focuses the generated image on the screen 300. Again, a viewer uses passive glasses 227 with different polarizations which divide the images with different polarizations for each eye. Each glass transmits a different perpendicular polarization.

In this implementation form a controllable digital micro mirror device 21 1 is used as a spatial light modulator and for combining beams 209-1 and 209-2 with different polarizations. The filter 221 is located after the digital light processor 231. The . filter 221 creates two halves of the image with different polarizations of each of the halves. In the next moment polarizations of the corresponding halves are changed. If images created at these moments are combined, two images with different polarizations are obtained. If a viewer uses passive polarized glasses 227 different images at each eye can be seen.

Fig. 3 shows different polarizations. In one moment the digital light processor 231 creates frames which consist out of the two halves of the image with different polarizations. Consequently, the first half of the digital light processor 231 creates an image for the right eye and the second half of the digital light processor 231 creates an image for the left eye. Accordingly, a viewer with glasses 227 sees a half image at each eye. In the following moment the digital light processor 231 again creates an image consisting out of two halves with different polarizations, but instead the first half of the digital light processor 231 creates an image for the left eye and the second half of the digital light processor 231 creates an image for the right eye.

The filter 221 rotates the polarization of the incident beams 209-1 and 209-2 depending on a voltage at the shutter. Consequently, in the first moment the filter 221 does not rotate a polarization, whereas it in the next moment does. The filter 221 and the digital light processor 231 operate with high frequency so that human eyes cannot see a difference between the projected images, when the filter 221 rotates the polarization. In summary for each eye a different full screen image is achieved so that a man can see a three-dimensional effect.

If this optical scheme is used in 3D-projectors brightness of the projector is increased up to two times. The light power from the three light sources 215-1, 215-2 and 215-3 can be used continuously in time.

Fig. 4 shows a schematic diagram of a digital light processor 231 demonstrating the principle of the digital light processor 231 as a beam combiner. The digital light processor 231 comprises a controllable micro mirror matrix 21 1 having a plurality of micro mirrors 233. Each of the micro mirrors 233 can be independently moved between the two angular positions +a and -a with respect to the plane of the digital light processor 231.

When micro mirror 233 is in the "-a" position the beam 209-2 with S -polarization is redirected to the screen 300. When micro mirror 233 is in the "+a" position the beam 209-1 with P-polarization is redirected to the screen 300. Consequently an angle between two beams with different polarizations is smaller than 4a, i.e. between points BCD. For a digital light processor 231 with a=12°±l° a value of 4a equals to 48°±4°. Consequently, an angle between points FCD and BCF is smaller than 2a±2°=24⁰±2°.

The optical scheme for a 3D projector has three light sources with three different colors. After the beam combiner a single image beam with different colors results. The beam splitter divides the non-polarized image beam onto two optical paths. Two beams with the same color but with different polarizations are obtained.

The optical system has the advantage that serviceability is increased because an optical scheme of the projector without any moving parts, such as a rotating wheel, is used. Passive polarizer glasses are used which can be produced with lower effort than active glasses with LCD shutters. Brightness of the projected images can be increased nearly by two times. The optical system and the method can be used for the creation three-dimensional images at a cinema theatre or somewhere else.

From the foregoing, it will be apparent to those skilled in the art that a variety of methods, systems, and the like, are provided. Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present inventions has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the inventions may be practiced otherwise than as specifically described herein.

Claims

1. An optical system (100) for projecting polarized images onto a screen (300), comprising:

- a light beam source (103) for generating a non-polarized image beam (105); - a beamsplitter (107) for splitting the image beam (105) into a first beam (109-1) having a first polarization on a first optical path and a second beam (109-2) having a second polarization on a second optical path; and

- a controllable micro mirror matrix (11 1) for reflecting the first beam (109-1) of the first optical path and the second beam (109-2) of the second optical path in a same direction.

2. The optical system (100) according to claim 1, wherein the optical system (100) comprises a first controllable shutter (1 13-1) in the first optical path and a second controllable shutter (113-2) in the second optical path.

3. The optical system (100) according to one of the preceding claims, wherein the light beam source (103) comprises light emitting diodes for generating non-polarized light.

4. The optical system (100) according to one of the preceding claims, wherein the light beam source (103) comprises three light sources (115-1, 115-2, 115-3) for generating light with different wavelengths.

5. The optical system (100) according to claim 4, wherein the light beam source

(103) comprises a beam combiner (117) for combining the light from the three light sources (115-1, 115-2, 115-3) into the image beam (105).

6. The optical system (200) according to one of the preceding claims, wherein the optical system (200) is arranged such that the first beam (209-1) is directed onto a first half of the controllable micro mirror matrix (211) and the second beam (209-2) is directed onto a second half of the controllable micro mirror matrix (211).

7. The optical system (200) according to one of the preceding claims, wherein the optical system (200) comprises an objective (1 19, 219) for focusing the beam on a screen (300).

8. The optical system (200) according to one of the preceding claims, wherein the optical system (200) comprises a shutter (221) for controllably rotating the polarization of the reflected first beam (209-1) and the reflected second beam (209-2).

9. The optical system (200) according to claim 8, wherein the shutter (221) comprises a first coating area (223-1) for filtering the reflected first beam (209-1) in the first polarization and a second coating area (223-2) for filtering the reflected second beam (209-2) in the second polarization.

10. The optical system (200) according to claim 8 or 9, wherein the shutter (221) is located in an optical path between the micro mirror matrix (211) and an objective (219) for focusing the beam on a screen (300).

11. A method for projecting polarized images onto a screen (300) comprising the steps:

- generating a non-polarized image beam (105);

- splitting the image beam (105) into a first beam (109-1) having a first polarization on a first optical path and a second beam (109-2) having a second polarization on a second optical path by a beam splitter (107); and

- reflecting the first beam (109-1) of the first optical path and the second beam (109-2) of the second optical path in a same direction by a controllable micro mirror matrix (1 11).

12. The method according to claim 11, wherein the method comprises the step of alternatively shutting the first beam (109-1) and the second beam (109-2).

13. The method according to claim 11 or 12, wherein the method comprises the step of directing the first beam (209-1) onto a first half of the controllable micro mirror matrix (211) and directing the second beam (209-2) onto a second half of the controllable micro mirror matrix (211).

14. The method according to claim 13, wherein the method comprises the step of rotating the polarization of the reflected first beam (209-1) and the reflected second beam (209-2) by a shutter (221).

15. The method according to claim 14, wherein the method comprises the step of filtering the reflected first beam (209-1) in the first polarization by a first coating area (223-1) of the shutter (221) and filtering the reflected second beam (209-2) in the second polarization by a second coating area (223-2) of the shutter (221).