KR20110010414A - Stereoscopic image projection device - Google Patents

Abstract

PURPOSE: A stereoscopic image projection device is provided to project images to the same route by forming each left and right side images. CONSTITUTION: A display devices(141a,141b,141c) of a first image forming unit(140) forms a left-eyed image by a first polarized light. A second image forming part(150) forms the right-eyed image with a second polarized light. A polarized light dividing device(160) reflects one of the first and the second polarized light. The polarization splitting device transmits the other one. The polarization splitting device divides the light source(131) into the first and the second polarized light. The polarization splitting device projects the first and the second polarized light to the first and the second image forming part.

Description

Stereo Image Projection Equipment {STEREOSCOPIC IMAGE PROJECTION DEVICE}

The present invention relates to a stereoscopic image projection apparatus for projecting polarization in different directions to the left eye and right eye images.

As the information age evolves rapidly, the importance of a display system that implements a large screen is being emphasized. An example of an apparatus for implementing such a large screen is an image projection apparatus having a function of magnifying and projecting an image. An image projection device refers to a device that implements an image by using light generated from a light source and projects the implemented image. Examples of the image projection device include a projector and a projection television.

Recently, image projection is considered as an interior electronic device to express one's personality, and various design forms are required. In addition, various attempts have been applied to the image projection apparatus to realize a more realistic image. For example, micro projectors using LEDs as light sources and high color projectors using lasers as light sources have been developed.

In addition to the above attempts, consideration may be given to a stereoscopic projection apparatus that projects stereoscopic images closer to reality.

One object of the present invention is to provide a three-dimensional image projection that can increase the brightness than conventional, to implement an image using polarized light.

Another object of the present invention is to provide a three-dimensional image projection with improved optical performance.

A stereoscopic image projection device according to an embodiment of the present invention for realizing the above object is a light source for generating light, a display element for forming a left eye image using the first polarization and converts the polarization direction of the left eye image; A first image forming unit including a reflecting element for reflecting the left eye image having the converted polarization direction toward the incidence path of the first polarization and a second polarization having a different polarization direction from the first polarization direction are used. And a second image forming unit configured to convert the right eye image into the first polarized light and reflect toward the incident path of the second polarized light, and to reflect one of the first and second polarized light and transmit the other one. And the light generated from the light source is separated into the first and second polarized light and incident to the first and second image forming units, respectively. To synthesize and a polarization splitting device is disposed between the light source, a first image forming unit and the second image forming part.

As an aspect related to an embodiment of the present invention, the display elements are provided in plural to form the left eye image using polarization corresponding to three primary colors, respectively, and the reflective element transmits any one of the three primary colors, Is made to reflect. The display device and the reflecting device may be arranged in the same arrangement as the second image forming unit.

As an aspect related to an embodiment of the present invention, the polarization splitting device includes an incident part, a separating part, first and second entrance parts, and an exit part. The incident part is configured to allow the light to be incident, and the separation part reflects one of the first and second polarized light and transmits the other, thereby separating the light into the first and second polarized light. The first and second entrances and exits are passages through which the first and second polarizations advance toward the first and second image forming units, respectively, and the left and right eye images are incident from the first and second image forming units, respectively. It is a passage. An exit part is a path through which the left and right eye images synthesized to face the same optical path are output from the separation part.

In an aspect related to an embodiment of the present invention, the light source is disposed to face the incidence portion, and the first and second image forming portions are disposed to face the first and second entrance portions, respectively. The stereoscopic image projecting value may include at least one of a projection lens and a polarization changing element. A projection lens is disposed on the same optical path facing the exit portion to enlarge the left eye and right eye images. A polarization changing element is mounted on the emission unit, and is configured to convert the first and second polarizations into circularly polarized light.

As an aspect related to an embodiment of the present invention, the light source includes first and second light sources, and the stereoscopic image projection value is synthesized by the light emitted from the first and second light sources, respectively, to the polarization splitting device. It includes a synthesis section to advance. The synthesis unit includes first and second polarizers and a synthetic polarization splitter. The first and second polarizers are formed to polarize the light generated by the first and second light sources with the first and second polarized light, respectively. The composite polarization splitting device includes first and second incidence portions in which the first and second polarizations polarized by the first and second polarization elements are respectively incident and orthogonal to each other, and synthesizes the incident first and second polarizations. It is formed to proceed to the polarization splitting device.

As an aspect related to an embodiment of the present invention, the three-dimensional image projection device includes a mirror. The mirror is configured to reflect one of the first and second polarizations emitted from one of the first and second polarization elements toward the composite polarization splitting element. The first and second light sources may be parallel to each other, and the first light source may be disposed to face the mirror, and the second light source may be located farther from the composite polarization splitter with respect to the parallel direction than the first light source. have.

The stereoscopic image projection device according to another embodiment of the present invention polarizes the first and second light sources for generating light and the light generated from the first and second light sources with first and second polarizations having different polarization directions, respectively. And a synthesizer for synthesizing the first and second polarizations to form the same path, and forming different images by using the first and second polarizations, respectively, and determining the polarization states of the formed images, respectively. A first and second image forming unit converting the first and second polarizations, and one of the first and second polarizations to reflect and transmit the other and transmitting the first and second polarizations incident from the synthesis unit, respectively. Between the combining unit, the first image forming unit, and the second image forming unit to separate and enter the first and second image forming units and synthesize images formed in the first and second image forming units, respectively. A first polarization separation element is arranged.

As an aspect related to another embodiment of the present invention, the synthesis unit includes a first polarization element and a second polarization separation element. The first and second polarizers polarize the light emitted from the first and second light sources into the first and second polarized light, respectively, and the second polarization splitter synthesizes the first and second polarized light to synthesize the first and second polarized light. The first and second polarizations are respectively incident to the polarization splitter.

The stereoscopic image projecting device according to the present invention configured as described above may project the left and right eye images formed in the plurality of image forming units through the polarization splitter with the same optical path. In addition, it realizes a more excellent stereoscopic image projection value through this.

In addition, the present invention may further increase the brightness of the projected image by using the plurality of light sources and the synthesis unit.

EMBODIMENT OF THE INVENTION Hereinafter, the image projection apparatus which concerns on this invention is demonstrated in detail with reference to drawings. In the present specification, the same or similar reference numerals are assigned to the same or similar configurations in different embodiments, and the description thereof is replaced with the first description. As used herein, the singular forms "a", "an" and "the" include plural forms unless the context clearly indicates otherwise.

1 is a perspective view of a stereoscopic image display system 10 according to an embodiment of the present invention.

The stereoscopic image display system 10 of the present invention includes a stereoscopic image projection apparatus 100, a screen unit 101, and a polarizing glasses unit 102 arranged to realize a stereoscopic image.

The 3D image projection apparatus 100 implements an image by using light generated from a light source and projects the implemented image. The stereoscopic image projection apparatus 100 may be a projector that enlarges and projects an image as illustrated. Hereinafter, the stereoscopic image projection apparatus 100 according to the present invention will be described based on the projector. However, the 3D image projection apparatus 100 is not limited thereto, and may be applied to, for example, a projection device embedded in a projection television.

The stereoscopic image projection apparatus 100 is formed to project together the first and second images 104a and 104b having different polarization directions 103a and 103b. Polarizations having different polarization directions may be referred to as first and second polarizations 103a and 103b, respectively. The first and second polarizations 103a and 103b may be S waves and P waves, or P waves and S waves, respectively. In the following description, the first and second polarizations 103a and 103b are described based on S waves and P waves, respectively.

The first and second images 104a and 104b may be formed to have a binocular parallax forming a stereoscopic image. That is, the first and second images 104a and 104b may be left eye and right eye images, respectively. However, the present invention is not limited thereto, and the first and second images 104a and 104b may be right eye and left eye images, respectively.

The screen unit 101 displays an image enlarged and projected by the image projection apparatus 100 on a screen. The screen unit 101 is disposed at a position crossing the projection direction of the image projection apparatus 100 so that the left and right eye images 104a and 104b are projected. The screen portion 101 may be, for example, a wall surface or an achromatic or silver film. The screen unit 101 may be a polarization maintaining screen, which is formed to maintain a polarized state.

The polarizing glasses 102 are formed of polarizing plates respectively corresponding to polarization directions 103a and 103b having different left and right sides. As a result, left and right eye images 104a and 104b each having binocular disparity arrive at the left and right eyes of the user. Therefore, the user can view the stereoscopic image.

Hereinafter, an example of a stereoscopic image projection value that can implement the stereoscopic image will be described. 2A and 2B are perspective views of the stereoscopic image projection apparatus 100 of FIG. 1 viewed from the front and the rear, respectively.

Cases (casings, housings, covers, etc.) forming the exterior of the main body of the stereoscopic image projection apparatus 100 are formed by upper and lower cases 111 and 112. Various optical parts and electronic parts are embedded in the space formed by the upper and lower cases 111 and 112.

The operation unit 113 may be disposed on the upper case 111. The operation unit 113 is configured to input a control command such as a start, end, zoom-in, zoom-out focusing, etc. by the user, and is operated by the user while having a tactile feeling. Any manner may be employed as long as it is in a tactile manner.

The lower case 112 may include a projection unit 114, first and second air flow units 115a and 115b, an interface 116, and the like. The projector 114 is formed to enlarge an image projected by the 3D image projection apparatus 100.

The first and second air flow units 115a and 115b include a plurality of through holes to allow air to flow into the image projection apparatus. Through this, cooling of the image projection apparatus using forced convection is possible.

The interface 116 may be a path through which the 3D image projection apparatus 100 may exchange data with an external device. Image data corresponding to an image to be projected by the 3D image projection apparatus 100 through the interface 116 may be input from the outside. Referring to the drawings, the interface 116 includes a connection terminal that can be electrically connected to an electronic device capable of supplying video or audio data, for example, a computer, a DVD player, or the like.

3 is an exploded view of the image projection apparatus 100 of FIG. 1, and FIG. 4 is a conceptual diagram illustrating the optical system of FIG. 3.

Referring to FIG. 3, a control circuit board 121 and a power board 122 may be mounted on the lower case 112. The control circuit board 121 may be configured as an example of a controller for operating various functions of the 3D image projection apparatus 100. The power substrate 122 receives the AC power and converts it into DC power required for driving the image projection apparatus 100.

The lower case 112 may be equipped with an optical system 130 in which an optical element such as a lens is arranged to form an image and project the image to the outside. A structure (not shown) on which the optical system 130 may be assembled may be further disposed between the optical system 130 and the lower case 112.

The optical system 130 includes a light source 131, first and second image forming units 140 and 150, and a polarization splitting device 160.

The light source 131 is a device that receives electrical energy and converts the light energy into light energy. The light source 131 may be, for example, an ultra high pressure mercury lamp (UHV Lamp), an LED (LED), or the like. In order to assist the operation of the light source 131, a stabilizer for stabilizing electricity supplied to the light source 131 and a cooling fan for generating forced convection may be mounted in the lower case 112.

The illumination optical element group 132 is disposed adjacent to the light source 131 so that the light generated from the light source 131 is illuminated in a constant direction. The illumination optical device group 132 means that optical devices such as a lens are arranged to form a group in a predetermined arrangement so that light is focused.

The light focused in the illumination optical device group 132 is incident on the polarization splitting device 160. The polarization splitter 160 is adjacent to the illumination optical device group 132 and is disposed between the light source 131, the first image forming unit 140, and the second image forming unit 150. The polarization splitting device 160 is formed to reflect one of the first and second polarizations 103a and 103b (see FIG. 1) and transmit the other.

The polarization splitter 160 may be, for example, a polarizing beam splitter (PBS) device in which the rectangular prisms 161a and 161b face each other at a hypotenuse. The polarization separators 166a and 166b may be mounted on the polarization splitter 160. The polarizing plates 166a and 166b are formed to further improve the polarization states of the S and P waves.

The first image forming unit 140 includes display elements 141a, 141b, and 141c and a reflective element 142.

The display elements 141a, 141b, and 141c form a left eye image using the first polarization 103a and convert a polarization direction of the left eye image.

The display elements 141a, 141b, and 141c are controlled to reflect incident polarization to form an image. In detail, the display elements 141a, 141b, and 141c independently reflect the first polarization 103a in a plurality of cells so as to correspond to the left eye image to be implemented. The display elements 141a, 141b, and 141c may be electrically connected to the control circuit board 121 and controlled by the control circuit board 121.

The polarized light reflected by the display elements 141a, 141b, and 141c is converted into the second polarized light 103b. Referring to the drawings, the display elements 141a, 141b, and 141c are provided in plural to form the left eye image using polarization corresponding to three primary colors, respectively.

The reflective element 142 transmits any one of the three primary colors, and reflects the other. The reflective element 142 reflects the left eye image obtained by converting the polarization direction in the display elements 141a, 141b, and 141c toward the incident path of the first polarization 103a.

The second image forming unit 150 forms a right eye image using the second polarization 103b different from the first polarization 103a and converts the right eye image into the first polarization 103a. It reflects toward the incident path of the second polarized light 103b. Referring to the drawings, the second image forming unit 150 includes display elements 141a, 141b, and 141c and a reflective element 142 of the first image forming unit 140 and the first image forming unit 140. May be arranged in the same arrangement. Through this, a more concise optical system 130 may be configured.

The left and right eye images, which are formed in the first and second image forming units 140 and 150, respectively, and are reflected toward the polarization splitter 160, are recombined by the polarization splitter 160. The synthesized left and right eye images are projected to the outside to form a stereoscopic image.

Hereinafter, a process of forming an image and a process of projecting the image in the optical system will be described in more detail with reference to FIGS. 5A and 5B. 5A is a conceptual diagram illustrating a process of forming an image in the optical system of FIG. 3, and FIG. 5B is a conceptual diagram illustrating a process of projecting an image in the optical system of FIG. 3.

The polarization splitter 160 separates the light generated by the light source 131 into the first and second polarizations 103a and 103b and enters the first and second image forming units 140 and 150, respectively. In detail, the polarization splitter 160 reflects the S wave to the first image forming unit 140 and transmits the P wave to the second image forming unit 150.

The polarization splitter 160 includes an incident part 162, a separation part 163, first and second entrances 164a and 164b, and an exit part 165.

The light source 131 is disposed to face the incident part 162, and the light generated from the light source 131 is incident to the polarization splitter 160 through the incident part 162. Referring to the drawings, the incident part 162 may be one surface of a rectangular prism 161a (refer to FIG. 4) disposed close to the light source 131.

The separation unit 163 reflects one of the first and second polarizations 103a and 103b and transmits the other, thereby separating the light into the first and second polarizations 103a and 103b. Referring to the drawings, the separating unit 163 may be a polymer coating layer that reflects S waves formed on the hypotenuse of the rectangular prisms 161a and 161b and transmits P waves.

The first and second entrances 164a and 164b may be one surface of the rectangular prisms 161a and 161b which are disposed to be orthogonal to each other. The first and second image forming units 140 and 150 are disposed to face the first and second entrances 164a and 164b, respectively. In the first and second entrances 164a and 164b, the first and second polarizations 103a and 103b travel toward the first and second image forming units 140 and 150, respectively. The left and right eye images are respectively incident from the second image forming units 140 and 150.

Referring to FIG. 5A, S waves incident on the first image forming unit 140 are separated into three primary colors by the reflective element 142.

The reflective element 142 separates the S-waves incident on the first image forming unit 140 into blue, green, and red, and proceeds the blue, green, and red display elements 141a, 141b, and 141c, respectively. It is arrange | positioned between 141a, 141b, and 141c. The reflective element 142 may be, for example, an X (X) dichroic prism, and reflects blue and red in the X (X) plane and is made to transmit green.

Referring to FIGS. 5A and 5B, the display elements 141a, 141b, and 141c respectively reflect blue, green, and red polarization to form three primary colors to form a blue, green, and red liquid crystal on silicon (LCOS) display device. 141a, 141b, and 141c. However, the present invention is not necessarily limited thereto, and the display elements 141a, 141b, and 141c may be micro liquid crystal (LCD) devices, digital micromirror devices (DMDs), and the like.

Among the blue, green, and red reflected by the display elements 141a, 141b, and 141c, blue and red are reflected again, and green is transmitted. That is, the reflective element 142 reflects the left eye image of which the polarization direction is changed toward the incident path of the S-wave.

The P-wave incident on the second image forming unit 150 forms the right eye image through the reflective element 152 and the display elements 151a, 151b, and 151c which are configured in the same manner as the first image forming unit 140, and polarized light. The direction of the right eye image converted is reflected toward the incident path of the P wave.

Referring to FIG. 5B, P waves and S waves emitted from the first and second image forming units 140 and 150 respectively enter the polarization splitter 160 through the first and second entrances 164a and 164b. Done. As the P wave is transmitted and the S wave is reflected by the separator 163 of the polarization splitter 160, the left and right eye images travel in the same optical path.

The emission unit 165 is a portion from which the left and right eyes images synthesized to face the same optical path from the separation unit 163 of the polarization splitter 160 are emitted, and a rectangular prism 161b disposed far from the light source 131. It can be one side of).

Referring to FIG. 5B, the emission unit 165 may be equipped with a polarization changing element 171. The polarization changing element 171 is formed to convert the first and second polarizations 103a and 103b into circularly polarized light, and may be, for example, a λ / 4 plate that changes linearly polarized light into left circularly or rightly polarized light. . Through this, the image projection apparatus 100 may project left and right eye images polarized by left circular polarization or right circular polarization.

Projection lenses 114a are disposed in the projection paths of the left and right eye images. The projection lens 114a is disposed on an optical path in which left and right eye images are synthesized while facing the exit unit 165, and enlarges the left and right eye images. The projection lens 114a may be classified into a projection unit 114 (refer to FIG. 2A), for example, in which respective magnification projection lenses are arranged at predetermined intervals.

As described above, the polarization direction is transmitted to the plurality of image forming units through the polarization splitting unit 160, respectively, and the left and right eye images respectively formed by the plurality of image forming units are identical to each other in the polarization splitting unit 160. According to the projection, a compact optical system can be implemented, and a three-dimensional image projection apparatus with better optical performance is realized. In detail, since left and right eye images may be simultaneously projected, disturbance of a stereoscopic image due to a projection time difference between the left and right eye images may be alleviated.

6 is a conceptual diagram illustrating an optical system 230 applied to another embodiment of a stereoscopic image projection apparatus according to the present invention.

Referring to this figure, the optical system 230 of the stereoscopic image projection apparatus includes first and second light sources 231a and 231b for generating light. Light generated by the first and second light sources 231a and 231b is focused through the first and second illumination optical element groups 232a and 232b.

The synthesis unit 280 is disposed between the light sources 231a and 231b and the polarization splitting element 260. The combining unit 280 polarizes the light generated by the first and second light sources 231a and 231b to the first and second polarizations 203a and 203b having different polarization directions, respectively, and proceeds in the same path. The first and second polarizations 203a and 203b are synthesized. Referring to this figure, the first and second polarizations 203a and 203b become S waves and P waves, respectively.

The combiner 280 includes first and second polarizers 281a and 281b and a synthesized polarization splitter 282.

The first and second polarizers 281a and 281b are formed to polarize the light generated by the first and second light sources 231a and 231b into the first and second polarizations 203a and 203b, respectively. The polarizers 281a and 281b are combined with a polarizing beam splitter (PBS) and a half wave plate (HWP) to change unpolarized light into first or second polarized light 203a or 203b. Can be an element. The polarizing elements 281a and 281b may be PCS elements, for example.

The synthetic polarization splitting element 282 is disposed such that the first and second polarizations 203a and 203b are incident respectively. In detail, the composite polarization splitter 282 includes first and second incidences of the first and second polarizations 203a and 203b polarized by the first and second polarizers 281a and 281b and orthogonal to each other. Comprising portions 282a and 282b, the incident first and second polarizations 203a and 203b are synthesized to advance to the polarization splitting element 260.

The composite polarization splitting element 282 is formed to reflect one of the first and second polarizations 203a and 203b and transmit the other, for example, a polarizing beam arranged such that rectangular prisms face each other at a hypotenuse. Splitter). In detail, the synthetic polarization splitter 282 reflects the S wave to the polarization splitter 260 and transmits the P wave to the polarization splitter 260.

The polarization splitting element 260 is disposed between the combining unit 280, the first image forming unit 240, and the second image forming unit 250, and the S and P waves synthesized by the synthetic polarizing separator 282 are Separated from the polarization splitter 260, the light is reflected and transmitted toward the first and second image forming units 240 and 250, respectively.

The first and second image forming units 240 and 250 form different images, for example, a left eye and a right eye image, using S and P waves, respectively, and convert the polarization states of the formed images into P and S waves, respectively. To convert. Images respectively formed by the first and second image forming units 240 and 250 are recombined by the polarization splitter 260 and are projected by the same optical path. As described above, the 3D image projection apparatus 200 in which the brightness of the image projected by the optical system 230 using the plurality of light sources 231a and 231b is further increased.

Referring to the drawing, the first and second light sources 231a and 231b may be disposed in parallel to each other, and the 3D image projection apparatus 200 may include a mirror 290. The mirror 290 reflects any one of the first and second polarizations 203a and 203b emitted from one of the first and second polarization elements 281a and 281b toward the composite polarization splitter 282. It is formed to be.

The first light source 231a is disposed to face the mirror 290. That is, the mirror 290 is disposed between the first light source 231a and the composite polarization splitting element 282. The second light source 231b is positioned farther from the composite polarization splitter 282 in the parallel direction than the first light source 231a. Through this, when synthesizing the light focused in the first and second illumination optical device group (232a, 232b), the movement path of the light can be the same.

The stereoscopic image projection value is not limited to the configuration and method of the embodiments described above, but the embodiments may be configured by selectively combining all or some of the embodiments so that various modifications can be made.

1 is a perspective view of a stereoscopic image display system according to an embodiment of the present invention.

2A and 2B are perspective views of the image projecting device of FIG. 1 viewed from the front and the rear, respectively.

3 is an exploded view of the image projection apparatus of FIG.

4 is a conceptual diagram illustrating the optical system of FIG. 3.

5A is a conceptual diagram illustrating a process of forming an image in the optical system of FIG. 3.

5B is a conceptual diagram illustrating a projection process of an image in the optical system of FIG. 3.

6 is a conceptual diagram showing an optical system applied to another embodiment of a stereoscopic image projection apparatus according to the present invention.

Claims (13)

A light source for generating light; A display element for forming a left eye image using first polarization and converting a polarization direction of the left eye image, and a reflecting element for reflecting the left eye image in which the polarization direction is converted toward an incident path of the first polarization; 1 image forming unit; A second image forming unit configured to form a right eye image by using second polarization having a different polarization direction from the first polarization, and convert the right eye image into the first polarization to reflect toward the incident path of the second polarization; And One of the first and second polarized light is reflected and the other is transmitted, and the light generated from the light source is separated into the first and second polarized light and incident to the first and second image forming parts, respectively. And a polarization separator disposed between the light source, the first image forming unit, and the second image forming unit to synthesize the reflected left and right eye images. The method of claim 1, The display device may be provided in plural to form the left eye image using polarization corresponding to three primary colors, respectively. And the reflecting element transmits any one of the three primary colors and reflects the rest. The method of claim 1, The second image forming unit, And the display element and the reflective element are arranged in the same arrangement as the second image forming unit. The method of claim 1, The polarization splitting device, An incident part to which the light is incident; A separation unit for reflecting one of the first and second polarizations and transmitting the other one to separate the light into the first and second polarizations; First and second entrances to which the first and second polarizations advance toward the first and second image forming units, respectively, and the left and right eye images are incident from the first and second image forming units, respectively; And And a light emitting unit configured to emit the left and right eye images synthesized to face the same optical path in the separating unit. The method of claim 4, wherein And the light source is disposed to face the incidence part, and the first and second image forming parts face the first and second entrance parts, respectively. The method of claim 4, wherein And a projection lens disposed on the same optical path facing the exit part to enlarge the left eye and right eye images. The method of claim 4, wherein And a polarization changing element mounted on the emission unit and configured to convert the first and second polarizations into circular polarizations. The method of claim 1, The light source includes first and second light sources, And a synthesizer for synthesizing the light generated by the first and second light sources, respectively, and proceeding to the polarization splitting device. The method of claim 8, The synthesis unit, First and second polarizers configured to polarize the light generated by the first and second light sources with the first and second polarizations, respectively; And The first and second polarized light polarized by the first and second polarizers respectively have first and second incidence portions incident and orthogonal to each other, and the incident first and second polarized light are synthesized to separate the polarized light. Three-dimensional image projection apparatus comprising a synthetic polarization separating device to advance to the device. The method of claim 8, And a mirror for reflecting any one of the first and second polarizations emitted from one of the first and second polarization elements toward the composite polarization splitting device. The method of claim 10, The first and second light sources are parallel to each other, and the first light source is disposed to face the mirror, and the second light source is positioned farther from the composite polarization splitter with respect to the parallel direction than the first light source. Stereoscopic projection device characterized in that. First and second light sources for generating light; A synthesizer which polarizes the light generated by the first and second light sources into first and second polarizations having different polarization directions, and synthesizes the first and second polarizations to proceed in the same path; First and second image forming units for forming different images using the first and second polarizations, respectively, and converting the polarization states of the formed images into the second and first polarizations, respectively; And One of the first and second polarizations is reflected and the other is transmitted, and the first and second polarizations incident from the synthesis unit are separated from each other and incident to the first and second image forming units. And a first polarization separator disposed between the synthesis unit, the first image forming unit, and the second image forming unit to synthesize the images formed by the first and second image forming units, respectively. The method of claim 12, The synthesis unit, First and second polarizers configured to polarize the light generated by the first and second light sources with the first and second polarizations, respectively; And And a second polarization splitting device disposed such that the first and second polarizations are incident to each other so that the first and second polarizations are synthesized and proceed to the first polarization splitting device.

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